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Current and future threats to plant biodiversity on the Cape Peninsula, South Africa
Abstract
The biodiversity of the Cape Peninsula (49127 ha in extent) has been considerably affected by various factors since European settlement in 1652. Urbanization and agriculture have transformed 37% of the original area of natural vegetation. Lowland vegetation types have been worst affected, with almost half of the transformation occurring in one of the 15 recognized vegetation types. Vegetation at high altitudes has been little affected by urbanization and agriculture, but alien trees and shrubs are now threatening biodiversity in these areas. Of the area not affected by urbanization and agriculture 10.7% is currently under dense stands (>25% canopy cover) of alien plants and another 32.9% is lightly invaded. Dense stands of Acacia cyclops, the most widespread invader, cover 2510 ha, 76% of the total area under dense alien stands. This paper assesses the impacts of these factors on aspects of the plant biodiversity of the area, namely, the distribution of major vegetation types and of endemic, rare and threatened plant taxa and of taxa in the Proteaceae (a prominent element in almost all communities, taken as an indicator of overall plant biodiversity).
Possible future impacts on biodiversity are assessed by considering the effects of several scenarios involving increased urbanization and changes to alien plant control strategies and further spread over the next 50–100 years. The worst-case scenario for urbanization sees the area under natural vegelation reduced to 12163 ha (39.3% of its extent in 1994, or 24.8% of its original extent). Under this scenario almost a quater of the 161 endemic, rare and threatened (‘special’) taxa are confined totally to urban areas; 57.4% of the known localities of these taxa, and 40.1% of the remaining localities of Proteaceae taxa are transformed. Dense alien stands currently affect 29.8% of the localities of special taxa known from herbarium records and 8.4% of these taxa currently occur only in areas at present affected by aliens. Clearing all dense stands would result in 62.9% of special taxa having less than half of their known localities affected (49.1% at present). Under this scenario, 92% of Proteaceae taxa have more than 75% of their localities unaffected by aliens. If clearing is confined to specific areas (the Cape Peninsula Protected Natural Environment or all publicly-owned land) and the aliens spread further outside these areas, the area of natural vegetation remaining shrinks (to 82.4% of the current extent if control is confined to public land). The further losses in biodiversity associated with these scenarios are described. If control programmes collapse and all potentially invadable land is occupied by dense alien stands, only 407 ha of natural vegetation would remain (1.5% of the current extent).
The probability of the various scenarios materializing is discussed. To minimize further losses in biodiversity it is essential that: (1) a major initiative is launched immediately to clear (firstly) the 10184 ha of lightly invaded vegetation and then the 3313 ha of densely invaded vegetation; (2) no urban development be permitted within the boundaries of the Cape Peninsula Protected Natural Environment; (3) a systematic programme of prescribed burning (linked to the alien control programme) is initiated; and (4) contingency measures are implemented to improve the status of seriously threatened taxa, habitats and vegetation types.
... Despite limited understanding of the consequences of invasion on grazing potential, there has been increasing interest, research emphasis and expenditure on invasive alien species and their management over the last decade. The initiation of the Working for Water Programme in 1995 ( Van Wilgen et al, 1996;) saw invasive alien plants receive considerable publicity, and millions of Rands are spent annually on the control of these species. While the justification and continued emphasis of this alien clearing programme is on water resource conservation, the clearing operations managers are interested in determining whether clearing activities have any other ecosystem and natural resource benefits which could lend further support to their alien clearing activities. ...
... Whereas some species invade severely disturbed sites such as cultivated land and are referred to as ruderal and agrestal weeds (Swarbrick, 1991; To date, about 161 are now classified as invasive, and 68% of these are woody species (Nyoka, 2003). This invasion problem is anticipated to increase in its severity and as well as in geographical extent, as human-mediated disturbance makes ecosystems more susceptible to invasion by alien species (Vitousek, et al., 1986;van Wilgen et al., 1996;. ...
... The fynbos biome has been regarded the most heavily invaded of all biomes in the country (Richardson et al., 1997;Rouget et al., 2003). Here the principal invaders are trees and shrubs including Acacia, Hakea and Pinus species (Richardson et al., 1996). The highest levels of invasion are found in riparian zones across all biomes . ...
I investigated the impacts of the invasive wattle species (Acacia mearnsii, A. dealbata, A. decurrens), on the ecological function and productivity of rangelands in South Africa and their ability to sustain livestock production. More specifically, this study set out to: (1) assess grazing areas at a national scale; (2) identify evidence of progressive impacts of these species on livestock production across a selection of magisterial districts; (3) determine the effects of A. mearnsii density on growth form dominance of indigenous plant species, and highlight how this translates into impacts in forage quality and quantity; (4) determine the effects of A. mearnsii invasion on soil resources and conditions (key determinates of ecological function) required to support grazing production; and finally (5) determine to effects that clearing operations have had on the provision of grazing resources.
My results indicate that the level of overlap between wattle invasion and areas with a high grazing potential, at the national scale, is relatively low (2.9%). However, at a magisterial district scale, areas with a high grazing potential have a moderate (approximately 35.1% high grazing potential area under wattle invasion for highest invaded district) level of invasion. Scattered and moderate levels of invasion currently dominate or characterise these species invasion patterns. Both light and dense A. mearnsii invasions reduce grazing capacity. Dense invasion had the most severe effect reducing grazing capacity from 2 ha, required to support one large stock unit, to 8 ha. The clearing of this species was found to improve grazing capacity within 5 years. The reduction in grazing capacity following invasion was largely due to reduced basal cover and herbaceous biomass. The clearing of invaded sites was found to increase both basal cover and herbaceous biomass to pre-invasion levels. Acacia mearnsii invasion was found to affect certain soil properties. Under an A. mearnsii canopy, plant litter, carbon content of the soil and nitrogen concentrations were all found to be elevated. Overall, this study demonstrates that Acacia invasions have a significant effect on grazing resources at a local or site scale, and that for the eastern region of South Africa, these effects are ultimately scaled up to a district level. This is likely to have important financial and human well-being repercussions. However clearing and restoration programs are clearly able to reverse or mitigate these effects. This study therefore lends support to or complements other ecosystem service provision arguments for clearing alien invasive species.
... Sin embargo, la invasión además puede afectar significativamente la biodiversidad y procesos ecológicos nativos, generando así problemas de conservación (e.g. D' Antonio & Vitousek 1992, Richardson et al. 1996, Rodríguez 2001. Ambos hechos se han observado desde hace bastante tiempo (Darwin 1859, Elton 1958, sin embargo, investigaciones más exhaustivas se han incrementado sólo en las últimas décadas. ...
... Por otro lado, la alta concentración de población en las regiones mediterráneas ha significado la introducción de una gran diversidad de especies vegetales alóctonas, tanto en forma accidental, como para fines ornamentales, agrícolas y forestales (Groves & di Castri 1990). Esto ha generado una creciente invasión de especies alóctonas hacia zonas naturales, especialmente sitios aledaños a centros poblados (Groves & di Castri 1991, Richardson et al. 1996, Arroyo et al. 2000, Etienne 2001). En particular, la invasión de especies alóctonas arbóreas ya ha sido bastante documentada en diversos ecosistemas mediterráneos (Richardson et al. 1996, Richardson 1998, Etienne 2001, y más aún, ya se han detectado algunos problemas de conservación como consecuencia de ésta, tales como cambios en la composición de las comunidades vegetales, reducciones en la tasa de regeneración de especies arbóreas nativas y la alteración de la fisionomía del paisaje (di Castri et al. 1981, Groves & di Castri 1991, Richardson et al. 1996, Richardson 1998, Etienne 2001). ...
... Esto ha generado una creciente invasión de especies alóctonas hacia zonas naturales, especialmente sitios aledaños a centros poblados (Groves & di Castri 1991, Richardson et al. 1996, Arroyo et al. 2000, Etienne 2001). En particular, la invasión de especies alóctonas arbóreas ya ha sido bastante documentada en diversos ecosistemas mediterráneos (Richardson et al. 1996, Richardson 1998, Etienne 2001, y más aún, ya se han detectado algunos problemas de conservación como consecuencia de ésta, tales como cambios en la composición de las comunidades vegetales, reducciones en la tasa de regeneración de especies arbóreas nativas y la alteración de la fisionomía del paisaje (di Castri et al. 1981, Groves & di Castri 1991, Richardson et al. 1996, Richardson 1998, Etienne 2001). En consecuencia, la invasión de árboles alóctonos en la zona mediterránea de Chile podría afectar más aún el precario estado de conservación en que se encuentran los pocos remanentes naturales de este tipo de ecosistema en el país. ...
In this paper the assemblage of alien tree species inhabiting in the Río San Ramón watershed is described. This watershed is located at East border of Santiago, central Chile. Particularly, we documented the flora of alien tree species, the invasion state (not naturalized, naturalized, invader), abundance and population structure of each species. In addition, we related richness and abundance of each species with the way of access into the watershed (planted or natural immigration) and characterized species distribution through the abiotic habitats and resident vegetation patches. During 2003, a cense of all the individuals of alien tree species observed in the watershed was carried out. Fifteen alien tree species were observed. From these, eight species may be considered as invaders, two species as naturalized, and five species were planted but no natural regeneration was observed. Invader species had different abundance, being Ulmus minor the most abundant. Most of the invader species had natural regeneration and small-size individuals. The species that have become invaders, especially those that are the most abundant, were not planted in the watershed. On the other hand, the alien species had a similar environmental distribution, principally on the wettest habitats and on open sites without woody vegetation. These results suggest that the invasion process would be continuous, and that biotic and abiotic environment might be playing a role on the invasion of alien trees in central Chile, and that this role would be similar among species.
... Within South Africa's Cape Floristic Region (CFR), invasive alien plants (IAP) pose one of the largest direct threats to biodiversity and ecosystem services (Richardson et al. 1996;Gaertner et al. 2009;Le Maitre et al. 2011). the region's flora in 2009 found more than 1000 native plant species were threatened by IAPs (Raimondo et al. 2009). ...
... The dominant alien taxa in TMNP comprise woody alien species from the genera Acacia, Pinus and Hakea. For our purposes only Acacia species are considered as they are the most common alien plants in the PA (Cheney et al. 2018) and arguably pose the greatest threat to TMNP's biodiversity (Richardson et al. 1996;Higgins et al. 1999). ...
In many protected areas in South Africa, invasive Australian Acacia species pose on-going management challenges, perpetuating high long-term management costs. Due to limited availability of resources, conservation actions need to be prioritised within and across Protected Areas (PA). We draw on comprehensive datasets spanning over 20 years from the Table Mountain National Park to model long-term outcomes of clearing Acacia species at different levels of management clearing efficacy. We test a 50 year outlook based on current and 38 incremental levels of management efficacy, ranging from 5 to 100%, to assess under which scenarios a management goal of reducing Acacia density to below 1 plant per hectare for the 22,671 ha protected area is achieved. With the current clearing resources and maximum clearing efficacy (100% control), it would take between 32 and 42 years to attain the management goal. The modelling revealed two main drivers of Acacia persistence. Firstly, germination of seeds added to the seedbank from standing plants made a significantly larger contribution to future clearing requirements than fire stimulated seed germination or the existing (pre-management) seedbank. Secondly the relationship between the number of hectares and management units that could be treated and the efficacy of the treatment was non-linear. When clearing efficacy was decreased from 100% to the current project minimum target of 80% efficacy, the goal was not achieved in all areas, but the area that reached a density of <1 plant per hectare was significantly reduced to 53% of the PA for the simulated 50 years. Results emphasize the need to differentiate between increasing financial resources and increasing efficacy. While increasing financial resources allows for increased effort, this is of little value for Acacia management in the absence of an increase in clearing efficacy, as low quality implementation perpetuates the need for large budgets over time. Conversely, improving efficacy allows for decreased budget requirements over time, allowing fund re-direction to additional areas of alien species management such as the early detection and rapid control of newly introduced species.
... For example, Monterey pine (Pinus radiata) occurs in commercial plantations around Cape Town and it is very popular among hikers, cyclists and tree enthusiasts. However, the species is also highly invasive in the region (Richardson and Brown 1986) and poses a substantial threat to the biodiversity in the adjoining Table Mountain National Park (Richardson et al. 1996). The public and conservationists can thus have divergent perceptions of the benefits and impacts of Monterey pine in Cape Town, and managers face the challenge of integrating such divergent views regarding the species' benefits and impacts. ...
... Although the species is widespread, it is not highly invasive and is being monitored and is tolerated where appropriate. In contrast, P. radiata, which occurs in commercial plantations that are popular for the same reasons as E. diversicolor, is highly invasive (Richardson and Brown 1986) and poses a substantial threat to the biodiversity of Table Mountain National Park (Richardson et al. 1996). Hence, the City of Cape Town planned to systematically remove the species from plantations and protected areas. ...
It has been suggested that existing frameworks for guiding management of invasive species in rural areas and protected areas are inadequate for dealing with invasions in urban settings. A framework for selecting appropriate goals for managing invasive species in urban areas was developed by Gaertner et al. in 2016. This framework groups species into three management approaches (control priority, active engagement, and tolerance) depending on their real or perceived benefits and their potential to generate negative impacts.
This study tests the practical application of the framework using the example of Cape Town. We assess the suitability of the framework to support decision-making for managing invasive species in urban ecosystems using a questionnaire-based survey of members of the public, and an e-mail-based survey and a workshop with invasion biology researchers and managers. Specifically, we (1) determine the differences in perceptions regarding the benefits and impacts of invasive species between the public, managers and researchers; (2) investigate how consistently managers and researchers group invasive species into the three management categories; and (3) identify, with the help of managers and researchers, issues linked to the framework and give suggestions to overcome the identified issues.
We found no clear pattern in the perceptions of the public, managers and researchers regarding perceived benefits and negative impacts. Instead, the answers were widely scattered among all groups for most of the species that were considered. However, using the framework leads to a higher consistency among managers in placing the species into management categories, compared to invasive species grouping without guidance of the framework.
We conclude that decision-support frameworks can assist managers in placing invasive species into management categories. However, even more specific guidelines on the use of invasive species management frameworks in urban areas are needed.
... Invasive non-native plant species, many of which were introduced from other colonial regions , are a signifi cant problem in the region, where they proliferate and suppress local biodiversity, and use considerably more water than indigenous plant species. The problem is extensive; for example, in 1996, 24 % of the Table Mountain National Park was invaded by non-native plant species (Richardson et al. 1996 ). In terms of prevention, the South African National Biodiversity Institute ( SANBI ) hosts an "Invasive Aliens Early Detection and Rapid Response Program" 1 that seeks to identify and address invasive non-native plants before they become a problem. ...
... This is likely to infl uence wild fi re season, frequency and intensity. The intensity and season of a fi re has implications for biological processes of recruitment and regeneration (Cowling et al. 1996), and changes in fi re regime will have repercussions for biodiversity. Plant species in the Cape may be adapted to summer drought, but prolonged periods of drought or shifts in rainfall seasonality could to lead to declining numbers or possible extinctions (Yates et al. 2010 ). ...
The city of Cape Town, South Africa’s most southwestern city, sits on a peninsula in the heart of the geographically restricted Cape Floristic Region, which is home to exceptional biodiversity. Within the city boundary are some 3,350 plant species, 190 of which are endemic to the city itself. Like all South African cities, Cape Town continues to grapple with development discrepancies that persist from unjust apartheid governance in the past and present-day challenges of urban sprawl. The population of the city is 3.7 million. Extreme poverty, with nearly 17 % unemployment, and extensive informal settlements characterize much of the City and stand in stark contrast to wealthy suburbs with freestanding homes. For the populace of Cape Town, the natural environment presents both considerable ecosystem service advantage with, for example, a flourishing tourism industry and provisioning opportunities for the urban poor, but also a significant hazard with, for example, exposure to flooding in winter from a high water table. The value of ecosystem services is an emerging concept in the environmental management arena, and environmental and conservation issues are still seen as separate to other areas of city development, and tend to receive a lower prioritization. South Africa has good environmental legislation, but this is sometimes weakly enforced due to conflicting demands, fiscal constraints, and/or lack of implementation mechanisms. Climate change predictions for the region suggest likely biodiversity impacts, but how these will play out remain unknown. An emerging interest in the role of ecosystem services in broader City management and novel conservation approaches involving civic interests all show considerable promise for the conservation of urban biodiversity in the city of Cape Town.
... The fynbos biome (Mediterranean-climate type shrublands) in which TMNP is situation, has a rich history of botanical study Gelderblom et al. 2003), however invasions by alien plants have become an increasingly important component thereof (van Wilgen 2012). By the mid-1990s IAPs were already considered as one of the key threats to TMNPs ecosystem integrity (Richardson et al. 1996). ...
... In an assessment of threats to the biodiversity of the region in 1996, dense patches of invasive plants were shown to be impacting on a third of the known localities of threatened taxa, with only about 10 % of the sites occurring only within areas already invaded (Richardson et al. 1996). ...
Protected areas in Africa are global conservation icons, attracting millions of tourists a year. However, these areas are being threatened by a growing human population making increasing demands on the natural capitol being conserved. Moreover, global environmental change, of which biological invasions are a key concern, pose significant threats to the function of ecosystems and their constituents. Other than in a few regions, primarily in South Africa, little is known about alien plant invasions in protected areas across the continent. In order to present a first approximation of the threat of plant invasions to protected areas across Africa, we present the information we could find by drawing on published literature, grey literature and personal observations. We also present six case studies from prominent protected areas across Kenya, Tanzania and South Africa. These case studies aim to illustrate what is known in different regions and the key concerns and management approaches, thereby providing examples that may facilitate shared learning. Where information is available it suggests that some species are likely to be widespread, impacting severely on indigenous species diversity. If protected areas are to be successful in carrying out their mandate of biodiversity conservation, and increasingly, revenue creation, long-term management of invasive plants is essential. However, in developing countries, which characterise much of Africa, resources are severely lacking. Where funds are available for conservation these are often channelled to other aspects of protected area management, such as anti-poaching. Protected areas in Africa include a number of unique attributes that can provide natural laboratories for research on basic ecological principles of invasions, while the research can, in turn, contribute directly to the needs of the protected area agencies.
... Of these, at least A. falciformis and A. viscidula already qualify for categorization as invasive. Several mapping exercises have documented the massive scale or wattle invasions nationally (e.g.Rouget et al., 2004) or regionally (e.g.Richardson et al., 1996: Rouget et al., 2003. Le Maitre et al.(2000) estimated that wattle invasions covered 643,000 ba in 2000. ...
This chapter reviews the history of introductions, plantings, usage, naturalization and invasion of Australian Acacia species (‘wattles’) for African countries and several islands that are considered part of Africa in biogeographical or geological contexts. Although many more species have been introduced, our review focussed on 48 species that feature explicitly in discussions about wattles in 45 countries and islands/archipelagos. The history of introductions, plantings, naturalization and invasion is well documented for South Africa, where 40 Acacia species are known to be present, three species are commercially important, several species are important to rural and urban populations for fuelwood and other uses, and 16 species are currently regulated as invasive alien species in national legislation. Less detailed information is available for the rest of the continent. Introductions to South Africa were made mainly for dune stabilization, to create a forestry industry, and for ornamental horticulture, and were largely government-orchestrated. In most other parts of Africa, wattle introductions were mostly for other purposes - to address desertification and soil conservation, for reforestation of degraded ecosystems, for use in diverse forms of agroforestry, to supply fuelwood, for tannin production, and for human food. The interplay of drivers of wattle introductions has changed radically, and sometimes very quickly, over time across the continent. Whereas the implications of wattle introductions for native biodiversity and ecosystems received no attention a century ago, these concerns are now much more important in most areas. Trajectories for wattles in Africa will be affected by changing markets, global change, invasion debt, the effectiveness of management of invasive wattles, the emergence of problems with insect pests and diseases, and by changing requirements for timber, charcoal, fuelwood and food products.
... The exceptionally high level of species diversity and endemism, together with having one of the highest concentrations of threatened plants in the world, has led to the recognition of the CFR as one of the 'hottest hotspots' of biodiversity globally (https://whc.unesco.org/en/list/1007/). Habitat loss (due to infrastructure development, urban expansion, crop cultivation, timber plantations and mines), habitat degradation (by overgrazing and inappropriate fire A Critically Endangered Proteaceae in the Cape Florisitic Region threatened by an invasive pathogen management) and the impacts of invasive alien plant species have all been identified as major threats to the biodiversity of the CFR (Richardson et al. 1996;Bomhard et al. 2005;Manning & Goldblatt 2012). Importantly, climate change is also likely to be a major future threat (Bomhard et al. 2005). ...
BACKGROUND: Sorocephalus imbricatus (Thunb.) R.Br. is a range-restricted species endemic to the Cape Floristic Region (CFR), South Africa. It is currently classified as Critically Endangered in accordance with the IUCN criteria. Like many other species endemic to the CFR, S. imbricatus is subjected to several major threats including habitat loss, habitat degradation and the impacts of invasive alien species. Sorocephalus imbricatus was recently identified as a species requiring improved representation in ex-situ collections. During field work undertaken to collect germplasm for this purpose, a concerning number of dead and dying plants were observed. OBJECTIVES: To determine the cause of rapid death of individuals in a remnant subpopulation of S. imbricatus. METHOD: A field visit to a subpopulation of the only extant population, Elands-kloof, was conducted to examine the symptoms associated with S. imbricatus mortality, and to collect samples for isolation and identification of putative pathogens. RESULTS: Dead and dying plants showed clear symptoms of root and collar rot, with Phytophthora cinnamomi Rands recovered from all samples. The collections highlighted the severe impact of P. cinnamomi on S. imbricatus, with the size of the subpopulation being reduced from 62 to 37 individuals (a 40% reduction) between October 2021 and May 2022. CONCLUSION: This study describes, for the first time, rapid mortality of the Critically Endangered Proteaceae species, S. imbricatus, likely caused by the invasive pathogen P. cinnamomi. This concerning discovery highlights the urgent need for greater recognition of the threat P. cinnamomi poses not only to S. imbricatus, but to the broader floristic diversity of the CFR. Importantly, it illustrates a need for a substantial body of work to be undertaken to address a significant lack of knowledge regarding the relative threat that P. cinnamomi poses to species of the CFR.
... Mourelle & Ezcurra, 1996;Kadmon & Heller, 1998;Kadmon & Danin, 1999;Gimaret-Carpentier et al ., 2003); assessing conservation threats and priorities (e.g. Lozano et al ., 1996;Richardson et al ., 1996;Kress et al ., 1998;Anderson, 2003;Krupnick & Kress, 2003;Loiselle et al ., 2003); and as an important component of the determination of species' conservation status (e.g. Briggs & Leigh, 1996;IUCN, 2001). ...
Banksia hookeriana
Meissn. (Proteaceae) is a fire-killed shrub endemic to the northern
sandplains of south-western Australia that could be described as endangered based
on its small geographical range (< 5000 km
2
) and area of occupancy (
∼
500 km
2
).
Impacts on the species’ geographical range by land clearance for farming and
mining, and by altered fire regime, were investigated using three lines of evidence:
records of herbarium collections, a comprehensive field survey of extant populations,
and air photo and satellite images revealing the recent history of land clearance
and fires. These show that the species’ range has contracted by up to 40% in area and
26% latitudinally through the loss of outlier and range limit populations since 1960.
In addition, 22% of remaining native shrubland on the Eneabba sandplain has been
lost over this period through clearing for farming and mining, representing further
habitat loss for
B. hookeriana
.
Detailed investigation of
B
.
hookeriana
herbarium collections (
n
= 46) revealed
important errors that artificially affected the geographical range of the species and
emphasized the importance of close examination of all data captured from collection
records. Recorded locations occurred hundreds of kilometres outside the current
geographical range of the species in areas with different climate and substrate. Incorrect
species identification of herbarium specimens further extended the apparent geographical
range of the species. On the other hand, credible records indicated the loss
of the species from localities at the limits of its range. Overall, a disconcertingly high
proportion of records contained errors that may be difficult to identify without close
examination of the original collections and detailed ground-truthing. Were these
records to be used to model climate envelopes, identify potential habitat where the
species might occur, or might migrate to either as pests or under climate change
scenarios, or to analyse evolutionary or ecological theory (for example) — as is now
becoming commonplace — large errors may ensue.
Keywords
Fire frequency, land clearance, range estimation, herbarium records.
... The remaining undeveloped (untransformed by urbanization and agriculture) land (32 847 ha) on the Cape Peninsula defined the study area. This study used digital maps of the natural vegetation types (mapped on orthophotos at 1:10 ϫ 10 3 scale; Cowling et al. 1996); alien plant distributions (mapped on orthophotos at 1:10 ϫ 10 3 scale; Richardson et al. 1996), major roads (1:50 ϫ 10 3 topographic sheets; Surveyor General), potential alien plant distribution , the distribution of native plant species, rare and threatened plant species, and endemic plant species, and the priority species score (Trinder-Smith et al. 1996b). The potential alien plant distribution is based on a logistic regression model of the environmental preferences of the alien plant species; the data used for the logistic regression were all sampled at a spatial resolution of 50 m ϫ 50 m (see . ...
... For the purpose of this simulation model only Acacia species are considered as they are the most common alien plants (Cheney et al., 2018), occupying up to ten times the area and occurring at densities of up to 250 times of other genera in the park (C. Cheney, unpublished data), thus posing the greatest threat to park biodiversity (Richardson et al., 1996). ...
Conservation managers are required to make decisions in complex and uncertain contexts. To strengthen the robustness of conservation decisions, several approaches have been proposed to facilitate stakeholder engagement in the setting of conservation objectives and priority actions. While such processes have led to the formulation of several invasive alien plant management strategies to achieve specific objectives, the long-term consequences and trade-offs inherent in these strategies have not been tested. The performance of five of these strategies over 50 years was tested in the protected area context using empirical data from Table Mountain National Park, South Africa. A simulation model based on data for invasive Acacia species in a fire-driven ecosystem, focused on the interaction between strategy performance and clearing efficacy in achieving a management goal or reducing Acacia density to below 1 plant per hectare. At near perfect levels of clearing efficacy, all strategies converged towards reaching the management goal, while at lower efficacy levels the strategies diverged in their ability to achieve desired outcomes. Despite working across the largest area, strategies that focussed on clearing low density invasions, maintained the least area in a maintenance state over time. In contrast, strategies that focussed on a mix of post-fire, low density areas and high altitude areas cleared less area annually, but maintained a much larger area in a maintenance state. At higher levels of efficacy, strategies that return to previously worked areas were more successful than a post-fire strategy. Strategies that focused solely on securing water, performed poorly in maintaining low overall density of aliens. However, the influence of efficacy was significant and substantial and a much larger difference in area reaching the management goal was achieved by varying efficacy than varying strategy. As such, improving quality of work and implementation will have a far greater effect than which areas are prioritized or how this prioritization is done. While acacias are likely to persist in the long-term, improving work quality coupled with correct strategy selection will ensure continued gains in the area under maintenance and improved return on investment over time.
... Acacia saligna) planted mainly along the coast for dune stabilisation, have spread widely into natural vegetation (figure below) where these species outcompete and replace natural vegetation leading to homogenisation and a decrease in native biodiversity (Rebelo et al. 2011). For example, P. radiata that occurs in commercial plantations in and around Cape Town is highly invasive (Richardson and Brown 1986) and poses (continued) Box 11.2 (continued) a substantial threat to the biodiversity of TMNP (Richardson et al. 1996). Acacia saligna also reduces avian species richness in urban and peri-urban areas of Cape Town (Dures and Cumming 2010). ...
As in other parts of the world, urban ecosystems in South Africa have large numbers of alien species, many of which are invasive. Whereas invasions in South Africa’s natural systems are strongly structured by biotic and abiotic features of the region’s biomes, the imprint of these features is much less marked in urban ecosystems that exist as islands of human-dominated and highly modified habitat. Surprisingly little work has been done to document how invasive species spread in South African urban ecosystems, affect biodiversity, ecosystem services and human well-being, or to document the human perceptions of alien and invasive species, and the challenges associated with managing invasions in cities. This chapter reviews the current knowledge of patterns, processes, impacts and management of invasions in South African urban ecosystems. It highlights unique aspects of invasion dynamics in South African urban ecosystems, and identifies priorities for research, and key challenges for management. South African towns and cities share invasive species from all taxonomic groups with many cities around the world, showing that general features common to urban environments are key drivers of these invasions. There are, however, several unique biological invasions in some South African urban settings. The pattern of urbanisation in South Africa is also unique in that the imprint of Apartheid-era spatial planning is striking in almost all towns and cities and is aligned with stark disparities in wealth. This has resulted in a unique relationship between humans and the physical environment (e.g. very different assemblages of alien species in affluent compared to low-income areas). New ways of approaching invasive alien species management are emerging in South African towns and cities, but better facilitating mechanisms and protocols are needed for dealing with conflicts of interest.
... The density of alien plant cover (% cover) is also estimated for each MU. IAP cover was delineated using 1) density data from ISU site assessments and 2) the total area of trees and tall trees (> 3 m) outside of the urban edge (as per our land classification) -fynbos is typically depauperate of trees ( Rundel et al. 2014) and plant species taller than 3 m are likely to be alien ( Richardson et al. 1996). The area covered by these delineations within each grid cell was calculated and weighted based on the sum of corresponding ES and EDS detailed in Table 2. ...
Background
Natural resources within and around urban landscapes are under increasing pressure from ongoing urbanisation, and management efforts aimed at ensuring the sustainable provision of ecosystem services (ES) are an important response. Given the limited resources available for assessing urban ES in many cities, practical approaches for integrating ES in decision-making process are needed.
Methods
We apply remote sensing techniques (integrating LiDAR data with high-resolution multispectral imagery) and combined these with supplementary spatial data to develop a replicable approach for assessing the role of urban vegetation (including invasive alien plants) in providing ES and ecosystem disservices (EDS). We identify areas denoting potential management trade-offs based on the spatial distribution of ES and EDS using a local-scale case study in the city of Cape Town, South Africa. Situated within a global biodiversity hotspot, Cape Town must contend with widespread invasions of alien plants (especially trees and shrubs) along with complex socio-political challenges. This represents a useful system to examine the challenges in managing ES and EDS in the context of urban plant invasions.
Results
Areas of high ES provision (for example carbon sequestration, shade and visual amenity) are characterized by the presence of large trees. However, many of these areas also result in numerous EDS due to invasions of alien trees and shrubs – particularly along rivers, in wetlands and along the urban edge where tall alien trees have established and spread into the natural vegetation (for example increased water consumption, increased fire risk and reduced soil quality). This suggests significant trade-offs regarding the management of species and the ES and EDS they provide.
Conclusions
The approach applied here can be used to provide recommendations and to guide city planners and managers to fine-tune management interventions at local scales to maximise the provision of ES.
... Pine plantations specifically make up 660 000 ha of this coverage in South Africa, and invasive pine stands cover an additional 2.9 million ha (van Wilgen, 2015). Alien pine plantations and invasions have been shown to modify local ecosystem properties and functioning, negatively impact local biodiversity and, in South Africa, consume large amounts of water and increase wildfire intensities (Richardson & Higgins, 1998;Richardson et al., 1996;Stephans & Wagner, 2007;Stock & Allsopp, 1992;van Wilgen, 2009van Wilgen, , 2015. Pine plantations and invasions are particularly problematic in the fynbos-dominated mountains of the Cape Floristic Region (CFR), in the south-west of South Africa (van Wilgen, 2015). ...
Commercial plantations and alien tree invasions often have substantial negative impacts on local biodiversity. The effect of plantations on faunal communities in the fire‐adapted fynbos vegetation of the Cape Floristic Region biodiversity hotspot is not yet well quantified. We studied small mammal community structure in alien Pinus radiata plantations and adjacent fynbos regenerating after clear‐felling of plantations on the Cape Peninsula, South Africa. Small mammal sampling over 1,800 trap‐nights resulted in 480 captures of 345 individuals (excluding recaptures) representing six species. Significantly more species, individuals (12 X) and biomasses (29 X) of small mammals occurred on recovering fynbos sites compared to plantations. This was commensurate with a higher diversity of plant growth forms, vegetation densities and live vegetation biomass. Only one small mammal species, the pygmy mouse ( Mus minutoides ), was consistently trapped within plantations. Fynbos sites were dominated by three small mammal species that are ecological generalists and early successional pioneer species, rendering the recovering fynbos slightly depauperate in terms of species richness and evenness relative to other studies done in pristine fynbos. We make three recommendations for forestry that would facilitate the restoration of more diverse natural plant communities and progressively more diverse and dynamic small mammal assemblages in a key biodiversity hotspot.
... The Common Starling has been described as having the potential to disrupt natural processes such as seed dispersal (Richardson et al. 1996); however, not much work has been published on these impacts in the Cape region. The Starling is also thought to be able to displace cavity-nesting birds in southern Africa through nesting competition, as it does with the Olive Woodpecker Mesopicos griseocephalus (van der Merwe 1984). ...
The Common Starling Sturnus vulgaris has progressively expanded its range in South Africa since its introduction into Cape Town in the late 19th century. In the past few decades it has extended this range into Gauteng province. Using data from the Southern African Bird Atlas Project 2, this paper examines the spread and relative abundance changes for the species across South Africa over the past 10 years, with a detailed look at the recently-colonised Gauteng. Across South Africa, the Common Starling's distribution has shifted, and grown. As it spreads north along the coastline and northwards inland, some of the former range has been lost. In Gauteng, the species has shown a range and abundance expansion over the same period. If the observed trends are to continue, this species is likely to eventually become a prominent species across the entire country, and further north into the sub-region. However, the potential impact that this species has on indigenous avifauna is unknown and, in the face of rapid anthropogenic change, remains to be investigated.
... The major woody invasive plants in the (semi)natural vegetation within the boundaries of Cape Town are species of Acacia (wattles), Eucalyptus (gums), Hakea (hakeas) and Pinus (pines) (Richardson et al. 1996;Gaertner et al. 2016). Distribution of main woody invasive species is shown in Fig. 2. Gums were given the highest relative weighting in terms of impacting ecosystems and reducing natural vegetation recovery (65%), although these species cover a small area (c. ...
Resources for biodiversity conservation and invasive plant management are limited, and restoring invaded vegetation is labour-intensive and expensive. Managers must prioritize their actions to achieve their goals efficiently and effectively. They must distinguish between areas that require only the removal of invasive alien plants (“passive restoration”) from those that require additional restoration measures (“active restoration”). This study used a multi-criterion approach (Analytical Hierarchical Process) to develop a framework for identifying areas that require active restoration, and then to prioritize these areas for active restoration. The South African city of Cape Town is used as a test case to illustrate the utility of the framework. Framework criteria selected in determining the need for active restoration included: dominant alien species invading the area, density of invasion, duration of invasion, indigenous vegetation cover, adjacent land use, level of disturbance, size of the area, aspect, soil texture, soil depth and erodibility, slope and vegetation type. In deciding which areas to prioritize for active restoration, factors such as vegetation conservation status, selection in a regional conservation plan and connectivity function were assessed. Importance in ecosystem functioning (by providing a diversity of habitats and soil conservation) and the delivery of ecosystem service benefits were also considered. The resulting framework provides an objective tool for prioritizing sites for active restoration.
... ES provided by natural, functioning ecosystems and their biodiversity underpin the City's Integrated Development Plan. However, urban expansion, agriculture and IAPs (Richardson et al., 1996) are major threats to the loss of habitat and native biodiversity and have considerable impacts on the provisioning of ES such as surface water run-off (van Wilgen et al., 2008). ...
The original version of the article unfortunately contained an error with the figure captions. The appropriate captions for Fig. 3-6 are published accordingly. The original article has been corrected.
... The discovery of naturalising populations of C. ladanifer prompted an assessment of its invasive ecology, the potential invasive risk posed by the species and options for its management. Of major concern is the threat posed by C. ladanifer to valuable fragments of native heathland vegetation or "Fynbos" in urban areas where the use of fire as a tool to manage fire-adapted alien invasive plants is not always possible (Richardson et al., 1996;Prestemon et al., 2002;Van Wilgen et al., 2010) and where disturbance favours the spread of invasive alien species (Alston and Richardson, 2006). Since C. ladanifer is a newly discovered species (with a residence time of a few decades) with apparent invasive tendencies and is currently not listed according to South African legislation (i.e. ...
This research provides the first detailed assessment of Cistus ladanifer, a woody, perennial shrub native to the Mediterranean, as an invasive species in South Africa. Three small naturalising populations (all less than 0.1 ha) of this species were discovered in 2012 in native heathland vegetation (“Fynbos”) of the Western Cape Province of South Africa. Prior to this discovery, C. ladanifer had not previously been recorded or recognised as an invasive species in South Africa. It poses a significant threat to the local endemic vegetation, largely due to its pre-adaptation to similar environmental conditions, and, if left unmanaged, it has the potential to invade further. However, given the small size of currently known populations and its ease of management, we propose that eradication of C. ladanifer is feasible in South Africa. Here we provide insights into options for the management of C. ladanifer, in particular its eradication from South Africa. Based on the weed risk assessment presented here, we recommend that C. ladanifer be listed as an invasive species under national legislation, thus requiring compulsory management. The results of this study provide detailed information on the extent of the invasion by C. ladanifer and the aspects of its biology pertinent to management (e.g. its reproductive ability, soil-stored seed banks). We show that complete removal of C. ladanifer populations is feasible and results in a steady decline in population size over time. Local extirpation of populations of C. ladanifer can be enhanced through fire-stimulation of the seed bank, but this may not be feasible in an urban setting. Our study emphasises the importance of scientific research in the development and evaluation of species-based management plans for invasive species.
... ES provided by natural, functioning ecosystems and their biodiversity underpin the City's Integrated Development Plan. However, urban expansion, agriculture and IAPs (Richardson et al., 1996) are major threats to the loss of habitat and native biodiversity and have considerable impacts on the provisioning of ES such as surface water run-off (van Wilgen et al., 2008). ...
Many alien plant species are introduced to urban areas to create, augment or restore ecosystem services (ES). However, many of these species spread beyond original plantings, sometimes causing negative effects on existing ES or creating novel ecosystem disservices (EDS). An understanding of the perceptions of urban residents regarding invasive alien plants (IAPs) and the ES and EDS they provide is needed for the effective prioritisation of IAP management efforts in cities. Using the city of Cape Town, South Africa as a case study, we conducted questionnaire-based surveys (online and face-to-face) to determine the perceptions of urban residents regarding IAPs and their capacity to provide ES and EDS. Most urban residents perceive IAPs negatively (i.e. agreeing that they create EDS), but many recognise their importance in providing ES. Although most residents are not opposed to the management of IAPs, such actions are not perceived as a high priority relative to other environmental problems. Socio-demographic variables such as age, education, environmental awareness, and ethnicity shape urban residents' perceptions of IAPs. Older, more educated respondents were more likely to perceive IAPs negatively, while respondents with greater environmental awareness were aware of the benefits provided by IAPs. This study highlights the need to integrate public perceptions into the planning and management of IAPs and emphasises the importance of including ES assessments into the decision-making process, particularly in urban areas.
... Much before its official recognition as a national park, a 300-km 2 area of Cape Peninsula Protected Natural Environment (CPPNE) had already been set aside (SANParks 2004, Wilgen et al. 2012. Table Mountain National Park is split into a number of smaller reserves, completely surrounded by urban development, agricultural land and ocean (Richardson et al. 1996). Hence, ecosystem processes and functioning may be heavily influenced by human activities and by the changing land management practices within the park. ...
... As a result, IAPs have invaded an estimated 10 million uncondensed hectares in South Africa (Le Maitre et al. 2000Maitre et al. , 2011. The control of IAPs has therefore become an important area of focus, despite the challenges that exist, because of their ability to propagate in different climates while overcoming both biotic and abiotic factors Richardson et al. 1996). In an effort to control IAPs, the South African government, through the Department of Environmental Affairs, launched the Natural Resource Management programme (DEA:NRM). ...
This study assesses the efficiency of contractors hired by the Natural Resource Management programme of the Department of Environmental Affairs (DEA:NRM) in clearing invasive alien plants. We analyse the efficiencies of 49 contractors in two catchments for three time periods, namely 2003 to 2006, 2007 to 2010 and 2011 to 2014. It was found that the size of the contract areas allocated for clearing decreased slightly from 2003 to 2014, while the unit costs (in real terms) have increased considerably. A reason for the increase in the costs can be attributed, among others, to the increase in the infestation densities of stands, because the more densely the infestation is, the more time is required to clear a hectare (Pd/ha) and hence the higher the costs of clearing (R/ha). This is an important observation, as it suggests that focusing on early restoration will further accelerate the clearing of invasive alien plants (IAPs) towards achieving the desired targets.
... Until about 1910, most species introduced into South Africa entered through the country's oldest port, Cape Town (Wells et al. 1986), which is situated within the Cape Floristic Region, an area of exceptional biodiversity and endemism (Myers et al. 2000). This region's biodiversity is principally threatened by invasive species (Latimer et al. 2004;Richardson et al. 1996;Rouget et al. 2003) and landuse change around Cape Town, the fastest-growing metropolis in South Africa . Centranthus ruber has recently been recognized as an invasive species in the Cape Metropolis (Forsyth 2013), with anecdotal evidence of invasion into near-pristine areas. ...
Plant species that receive significant human introduction effort and assistance generally are the most problematic invaders. Despite this, invasive ornamental species in urban settings have received relatively little attention if not invading natural areas. Here we consider Centranthus ruber in an urban setting in South Africa as a case study and explore when emerging invaders are able to cross the urban–wildland interface and what hinders early eradication in urban environments. Centranthus ruber was introduced into Cape Town, South Africa, more than a century ago as a garden ornamental, but until recently was not considered invasive. We determine the current and potential future distribution in South Africa, evaluate current management activities, and provide recommendations for control and legislation. By August 2013, we had found 64 populations, of which 31 were casual, 27 naturalized, and 6 invasive. This increased to more than 530 identified populations by the end of 2015, due to both spread and increased awareness. Centranthus ruber can invade near-pristine areas, with one population found in natural vegetation in the Table Mountain National Park. However, with only one slowly spreading population, the threat might be limited. We found no difference in plant mortality between chemical and mechanical clearing, but with mechanical clearing stimulating the soil seedbank, we recommend chemical methods. Using a species distribution model, we found large parts of South Africa, including the southwestern Cape where we conducted our surveys, to be climatically suitable for this species. Consequently, the category 1b regional listing in NEM:BA in the Western Cape is justified, but a listing in other parts of the country also might be appropriate. Based on our findings, we suggest that the extirpation of C. ruber in South Africa is possible, but without buy-in from residents in urban environments, reinvasion will render this impossible. This study stresses the importance of managing and legislating emerging invaders at the urban–wildland interface and the monitoring of common ornamental species with invasive traits.
... For example, Monterey pine (Pinus radiata) is used in commercial plantations in Table Mountain National Park (South Africa), where it is popular among hikers, cyclists and tree enthusiasts (Richardson and Brown 1986). However, P. radiata escaped from the plantations and became invasive, negatively impacting the biodiversity of this national park (Richardson et al. 1996). Although management actions aiming to reduce the negative impacts of P. radiata have been developed, managers have encountered strong public resistance to the removal of these trees from the current plantations (van Wilgen 2012). ...
Management of invasive species often raises substantial conflicts of interest. Since such conflicts can hamper proposed management actions, managers, decision makers and researchers increasingly recognize the need to consider the social dimensions of invasive species management. In this exploratory study, we aimed (1) to explore whether species’ taxonomic position (i.e. animals vs. plants) and type of invaded landscape (i.e. urban vs. non-urban) might influence public perception about the management of invasive species, and (2) to assess the potential of public awareness to increase public support for invasive species management. We reviewed the scientific literature on the conflicts of interest around the management of alien species and administered two-phased questionnaires (before and after providing information on the target species and its management) to members of the public in South Africa and the UK (n = 240). Our review suggests that lack of public support for the management of invasive animals in both urban and non-urban areas derives mainly from moralistic value disagreements, while the management of invasive plants in non-urban areas mostly causes conflicts based on utilitarian value disagreements. Despite these general trends, conflicts are context dependent and can originate from a wide variety of different views. Notably, informing the public about the invasive status and negative impacts of the species targeted for management appeared to increase public support for the management actions. Therefore, our results align with the view that increased public awareness might increase the public support for the management of invasive species, independent of taxonomic position and type of landscape.
... In the Cape Floral Kingdom, South Africa, invasive alien trees and shrubs from other Mediterranean climate regions threaten the conservation of fynbos shrubland ecosystems (Rebelo 1992). These invasive fire-tolerant woody species are preadapted to local conditions and are able to spread and form dense stands following fires (Richardson et al. 1990(Richardson et al. , 1996. Dense alien stands suppress native species and alter ecosystem processes such as nutrient and water cycling and the fire regime (Stock & Allsopp 1992;Le Maitre et al. 1996;van Wilgen et al. 1998). ...
... Siegfried 1992, Richardson et al. 1996, Bomhard et al. 2005, Loarie et al. 2009, Bellard et al. 2013. ...
Invasive species are considered a major threat to ecosystem functioning and native biodiversity. Their negative impacts on ecosystems and the provisioning of ecosystem services have been widely documented. South Africa faces one of the most significant challenges from invasive species globally, and the South African government spent an estimated US $100 million to mitigate impacts of non-native species between 1995 and 2000 alone. Here, we modeled the current climatic niche of 162 non-native trees and shrubs within South Africa and explored potential shifts in their distribution with projected climate change. Our results indicate that over half of these species will experience a decrease in their suitable climate over the next decades, although not uniformly so and ranges are predicted to expand into some regions. We also compared recent vs. historical introductions and showed similar patterns, indicating that possible violation of equilibrium assumptions in our distribution models likely does not strongly influence our findings. We suggest that climate change may therefore provide a window of opportunity for more effective invasive species control within South Africa, but that large range shifts are likely for many non-natives in the future, and new invasive threats might emerge.
... South Africa represents many African countries with extremely rich biodiversity that are at risk, boasting at least three global biodiversity hotspots (Myers et al., 2000). These are as are under threat from many global direct and indirect drivers (Richardson et al., 1999;Wynberg, 2002). Additionally, South Africa is a developing nation, and many communities are still heavily reliant on ecosystem services for their livelihoods which is also common elsewhere in the world (Le Maitre et al., 2000;Shackleton et al., 2007). ...
... Island animal populations are particularly vulnerable to extinctions because of their small ranges and isolation (Gillespie & Roderick, 2002). Extinction probability is greatly amplified by anthropogenic influences such as urbanization, forestry plantations, alien introductions and pollution (Richardson et al., 1996). Of great concern is that island endemics are often lost due to reduction in natural habitat and the subsequent disturbance of any remaining natural areas (Whittaker, 1998). ...
Island species are susceptible to extinction through disturbances
such as habitat transformation. Due to the small
size and isolation of islands, species have limited options for
refuges and recolonization, making their rehabilitation a
conservation priority. Robben Island is a continental
island, isolated from the mainland ca. 15 000 years ago,
and has been degraded by humans and alien species for
nearly 400 years. Mainland areas with similar vegetation
should be good reference sites for the biological restoration
of the island due to historical connectedness. However,
very little information exists as to which species were lost.
Here we aim to identify the best mainland sites to use as
reference sites for Robben Island based on remaining
arthropod diversity on the island. Sites found to be most
similar in terms of arthropod diversity to Robben Island
were sites north of Robben Island (Elandsbaai and
Dwarskersbos) rather than the geographically closest
locations. These sites therefore represent ideal reference
sites for biological restoration of the island. We do not
suggest the reintroduction of species from these localities,
but rather Robben Island should be restored to match their
vegetation height and cover.
... Monterey pine (P. radiata), on the other hand, occurs in commercial plantations that are popular for the same reasons as karri plantations (high perceived benefit), but they are highly invasive (Richardson & Brown, 1986) and pose a substantial threat to the biodiversity of Table Mountain National Park (Richardson et al., 1996) (high impact). Monterey pines thus require active engagement, and there are plans to systematically remove them from plantations and protected areas. ...
... La invasión de especies arbóreas ha sido documentada en algunos ecosistemas (Richardson et al. 1989, Etienne 2001, donde generan problemas de conservación, tales como cambios en la composición de las comunidades vegetales, una reducción en la tasa de regeneración de especies arbóreas nativas y alteraciones de la fi sionomía del paisaje (Di Castri et al. 1981, Groves & Di Castri 1991, Richardson et al. 1996, Richardson 1998, Etienne 2001, Becerra 2006). Un ejemplo de esta situación se observa con Acer platanoides L., cuyos impactos afectan negativamente la diversidad nativa y desempeño ecológico de especies de bosques secundarios en New Jersey, USA, y Ligustrum lucidum W.T.Aiton que está cambiando la estructura del paisaje en la zona central de Argentina (Aragón & Groom 2003, Galbraith-Kent & Handel 2008. ...
Tree invasions can lead to changes in the plant community composition and reductions in the number of native species. Acacia dealbata Link (silver wattle) was introduced to Chile as an ornamental. This species originated in Australia and Tasmania has been documented as invader in several ecosystems in the world. In Chile, this species is strongly associated to roads, rivers and human disturbances, performing as an invader in natural and semi-natural ecosystems. However, A. dealbata impacts at community levels have been scarcely studied. In order to determinate the relationship between A. dealbata invasion and the species richness and composition of plants in natural communities of south-central of Chile, we recorded the plant composition in three study conditions: under Acacia canopy, inside an adjacent native forest and in the edges between both conditions. We selected five study sites near to Concepcion, Chile (37 degrees S) and in each condition we surveyed three transects of 20x2 m(2) with a total of 15 transects at the three conditions. Results showed that the total species richness is significantly lower under Acacia canopy compared with the stand edge and native forest. Native species richness is higher within native forest and alien species richness is significantly higher in the stand edge. Plant composition also changes in the presence of A. dealbata. This study demonstrates the positive relationship between the presence of A. dealbata stands and the reduction of plant diversity in the south-central area of Chile.
... This paper presents a novel method for producing an essential prerequisite for such an analysis, a prediction of species distributions and species richness in the absence of transformation. Unlike standard approaches to quantifying past and potential effects of alien plant invasions, 4 the method presented here, using the output from Bayesian hierarchical regression models 5 together with maps of transformation derived primarily from satellite imagery, facilitates a description of the effects of different kinds of transformation on individual species distributions and species richness. One aim of this study was to assist in objective priority formulation for management programmes aimed at clearing invasive alien plants in natural and seminatural vegetation. ...
Nearly a third of the area of South Africa's Cape Fioristic Region has been transformed by human land use and invasive alien plants. The vulnerability of remaining natural areas to transformation has been assessed, but less attention has been given to characterizing how different types of habitat transformation have affected features of natural communities. A comparison of the effects of invasive alien species with other forms of transformation, including agriculture, forestry and urbanization, can distinguish unique features of invasive alien species and inform responses to their effects. Using Bayesian hierarchical regression models, we predicted what the potential distributions of a set of species of Proteaceae would have been before transformation. We used these predictions to describe and compare the impacts of different forms of habitat transformation. Results show that: 1) agriculture is by far the most important agent of transformation, in area and in severity of species loss; 2) forestry and urbanization cause relatively high species loss where they occur; 3) invasive alien plants are widespread, but have the least severe effects on diversity where present; and 4) agriculture affects common species disproportionately, whereas forestry and invasive alien plants influence species in direct proportion to their prevalence. Invasive alien plants have thus had by many measures a smaller effect on diversity than other forms of habitat transformation. However, they may pose the greatest continuing threat to diversity and rare species if they are allowed to persist and spread to their full potential.
... They can cause drastic ecological shifts in the natural or semi-natural vegetation they colonize and deeply alter the nature and functioning of invaded ecosystems (Richardson and Higgins, 1998). Trees can deeply modify vegetation richness and cause local extinction of resident species (Richardson et al., 1996). However, in the Massif Central secondary woodlands provide favourablehabitats for wildlife and represent a key step in forest succession towards the ecologically valuable climatic forests, as late-successional species, such as beech (Fagus sylvatka L), naturally establish in these woodlands (Curt et ni.;. ...
The Chaîne des Puys, a mid-elevation volcanic massif of the French Massif Central, has been subject to large-scale field abandonment in the past five decades, leading to tree colonization, especially by Scots pine and silver birch. Monospecific woodlands have thus established naturally on past croplands, pastures and heathlands. They often exhibit narrow and unimodal distributions of age, and their origin could be explained by a low resistance of the initial ground vegetation after grazing cessation. Woodlands differ in their dendrometric characteristics, floristic composition and soil properties according to past land use. Stands on past croplands are less dense but with a more developed shrub layer, and show a greater abundance of nutrient-demanding species. In these situations the soils have a lower C/N ratio, higher nitrate content and higher nitrate production. Knowledge of former agricultural use appears, therefore, to be a key component in understanding stand development, present vegetation composition and soil fertility of naturally established woodlands.
... Assessments of the economic value of biodiversity (Turpie et al. 2003) as well as analyses of the threats to biodiversity (Richardson et al. 1996) have been used to encourage support for conservation policy and practice. One of these threats was the self-seeding and spread of pine trees from plantations (Richardson 1998;Hoffmann et al. 2011;van Wilgen and Richardson 2012). ...
Given increased pressure on natural resources to deliver benefits, complex trade-offs and the regulation of behaviours in relation to benefits is of key concern. Behaviours that signify resistance to the rules according to which benefits are allocated prompt us to consider causal links and feedbacks between benefits, perceptions of benefits, meanings attached to the benefits, and the regulatory instruments that mediate the distribution of benefits. An understanding of how meanings influence the perception of benefits exposes the complexity inherent in how people perceive and allocate value to natural resource benefits. Meanings are personal, sometimes overlapping, context dependent and variable across space and time. A challenge in directing resource user behaviour in common pool resources is that the relationship between the resource and resource use is typically not interpreted to include the manner in which users associate resource benefits with meanings. We propose that collective ordering of meanings and associated rules help to direct behaviours and in doing so they contribute to the purposeful maintenance of desirable elements of a social-ecological system (i.e. robustness). Using an example, we illustrate how tensions around benefit sharing are rooted in the emergence and changing prioritisation of contexts and meanings over time. The importance of eliciting, ordering and sanctioning of meanings is emphasised. We conclude by discussing the implications for robustness and benefit sharing in social-ecological systems and we comment on the usefulness and limitations of the framework.
... In South Africa, the Western Cape has been favoured by human settlement for the past 350 years, leading to substantial land transformation through agricultural and urban development, and alien plant encroachment (Deacon 1992;Rebelo 1992a;Richardson et al. 1996). Subsequently, much of the remainder of southern Africa has also undergone extensive land transformation over the past 100 years (Macdonald 1991;Van Rensburg et al. 2004). ...
Human demographic and socio-economic measures (anthropogenic variables) reflect the detrimental impact of humans on plant diversity globally. The Pretoria (PRE) Computerised Information System (PRECIS) of the South African National Biodiversity Institute (SANBI), provided three sets of South African plant richness data, overall (OPR), endemic (EPR), and threatened (TPR), to investigate the relationships between richness and six anthropogenic variables. Spearman's Rank order correlations, Kruskal Wallis Analysis of Variance (ANOVA) and Generalized Linear Models (GLZ) were used. Although all three plant richness measures were correlated with anthropogenic variables, individual anthropogenic variables contributed a small fraction to the explained variation in richness. Differences in spatial and temporal scaling of the datasets, or the response to another causal mechanism, may have contributed to this low explained variation. Because more variation was accounted for in OPR than EPR or TPR, OPR is a more suitable surrogate measure of plant biodiversity when investigating the anthropogenic variables used here. Average human density (HD), infrastructure (degree of urbanization and road cover) (LRU) and percentage land area transformed and degraded (LTD) were identified as useful surrogates of human impacts on OPR. LTD may be a more inclusive human impact measure when conducting analyses of human impacts using OPR. LTD includes the effects of urban expansion, road networks and other land transformation impacts, such as agriculture.
... Owing to its high concentration of endemic taxa, especially of plants (Goldblatt 1978, Cowling and McDonald 1999, Goldblatt and Manning 2000 and invertebrates (e.g. Picker and Samways 1996), and its vulnerability to processes that threaten this unique biodiversity (Rebelo 1992, Richardson et al. 1996, the CFR is recognised globally as a biodiversity hotspot (Myers 1990, Mittermeier et al. 1998. Globally, the region is also listed as a Centre of Plant Diversity (WWF and IUCN 1994), an Endemic Bird Area (Bibby et al. 1992) and a Global 200 Ecoregion (Olson and Dinerstein 1998). ...
Despite many decades of vegetation-related research, the globally significant Cape Floristic Region (CFR) lacks a system of land classes that can be used as surrogates for biodiversity in conservation planning at the region-wide scale. Here we present a system of Broad Habitat Units (BHUs), suitable for planning at the 1:250 000 scale or larger. The BHUs were derived by intersecting coverages of Homogeneous Climate Zones, geology and topography in a geographic information system. A vegetation type coverage (Low and Rebelo 1996) was used to guide the classification under certain circumstances. A total of 15 primary and 88 secondary BHUs were identified in the CFR (87 892 km2). Of the latter, 69 were included in the Fynbos biome, which covered 81.5% of the CFR. At the primary BHU level, the system is very similar to existing vegetation treatments. The system is a good surrogate for biodiversity pattern and process, and therefore has good potential to provide meaningful entities for systematic and strategic conservation planning in the region.
... Examples include the following. • Alien pine species ( Pinus halepensis , P. pinaster and P. radiata ) invade and transform the species-rich fire-prone fynbos shrublands in South Africa's Cape Floristic Region (Cowling, 1992;Richardson & Cowling, 1992;Richardson et al ., 1996). The pines, which have serotinous cones, colonize fynbos after fires. ...
This chapter examines how the novel ecosystem concept is applied with reference to sites affected by alien plant invasions in different parts of the world. It summarizes what is known about the mechanisms and processes whereby plant invasions are known to generate impacts in invaded ecosystems. The chapter also explains how such drivers and impacts link with key facets of current discussions and debates around novel ecosystems. Finally, it discusses the usefulness of the novel ecosystems concept for understanding and managing plant invasions in the face of rapid global change. The concept of ecosystem resilience and associated thresholds has been suggested as a helpful framework for identifying the degree of ecosystem degradation.
... This section of the park covers 7 750ha (Figure 1). The natural vegetation and flora (Taylor 1969, 1983, 1984a, 1984b, Fraser and McMahon 1994, Privett 1998, Privett et al. 2001) and the invasive alien flora (, Macdonald et al. 1987, Fraser and McMahon 1994, Richardson et al. 1996) have been well documented. The reserve was therefore considered ideal for this study, as it is one of the very few areas in the Cape Floristic Region for which reasonable data (some dating back to 1941) was available on the history of invasive alien plant management. ...
Integrated control aimed at reducing impacts of alien woody plant invasions on biodiversity is underway in many parts of the Cape Floristic Region. However, the kinds of control measures applied may themselves affect the recovery of the natural vegetation. In view of this, we investigated the effects of past management practices, viz: 'bulldozing and aerial-spraying', 'aerial-spraying', 'boom-spraying' and 'foliar-spraying' aimed at clearing invasive alien woody plants on subsequent fynbos recovery in the Table Mountain National Park. Changes in soil (pH and depth) and vegetation (species cover, richness, diversity, evenness) properties, the total cover of species representing different dispersal guild, regenerative mode, and life form categories were compared between the differently treated and control plots at three different sites in the reserve. Only partial recovery of fynbos was observed in the 'boom-sprayed' and one of the 'foliar-sprayed' plots where measured species richness was significantly lower than that in control plots. However, marked changes in community structure were observed following 'boom-spraying' and 'foliar-spraying' at one site where a significant reduction in long-lived obligate reseeding species and an increase in the graminoid component was measured, though high fuel loads with possible post-fire erosion may also have aggravated the effects of foliar-spraying. Growth form structure changed the least following 'aerial-spraying' and 'foliar-spraying'. Multivariate analysis of plant functional types indicated a greater similarity between the control plots than the differently treated plots, implying a treatment effect on subsequent fynbos recovery. However, past land use and residual effects of the alien woody invaders may also have contributed to the differential recovery in the treated plots. It is concluded that re-introduction of species in the under-represented guilds may speed up fynbos recovery. The recommendation is a comprehensive seed mix containing the major guilds, and an initial seed mix of fast-growing indigenous species to stabilise the soil.
... While troop sizes varied considerably, they fell within the species' range from multiple sites [Swedell, 2011] and did not exceed the maximum ecologically tolerable size based on the mean annual rainfall and mean annual temperature of the study area [Dunbar, 1992]. Our study site also offered an ideal setting for assessing how human-modified habitat influences ranging patterns as 37% of the Cape Peninsula landscape was transformed by human habitat modification [Richardson et al., 1996]. Along with natural habitat (fynbos vegetation), local troops had various levels of access to three types of human-modified habitats-agricultural habitat, urban habitat, and invasive alien vegetation-all of which are known to affect baboon ranging patterns locally [Hoffman & O'Riain, 2010] and elsewhere across their distribution [Hill, 2005;Strum, 2010]. ...
Conflict with humans poses one of the greatest threats to the persistence and survival of all wildlife. In the Cape Peninsula, South Africa, human-baboon conflict levels remain high despite substantial investment by conservation authorities in a variety of mitigation measures. Here we explore how spatial ecology can inform wildlife managers on the extent and severity of both current and projected human-baboon conflict. We apply conservative and generous densities--2.3 and 5.9 baboons/km2--to hypothetical landscape management scenarios to estimate whether the chacma baboon (Papio ursinus) population in the Cape Peninsula is currently overabundant. We correlate conflict indices with spatial variables to explain intertroop differences in conflict levels. We investigate how an understanding of key elements of baboon ecology, including sleeping-site characteristics and intertroop territoriality, can direct management efforts and mitigate conflict. Our findings suggest that the current population of 475 baboons is below even the most conservative density estimate and that the area could potentially sustain up to 799 baboons. Conflict levels correlated positively with the loss of access to low-lying land through habitat transformation (Pearson r = 0.77, p = 0.015, n = 9 troops), and negatively with the distance of sleeping sites from the urban edge (Pearson r = 0.81, p = 0.001, n = 9 troops). Despite the availability of suitable sleeping sites elsewhere, more than half of all troops slept
The southern African subcontinent and its surrounding oceans accommodate globally unique ecoregions, characterized by exceptional biodiversity and endemism. This diversity is shaped by extended and steep physical gradients or environmental discontinuities found in both ocean and terrestrial biomes. The region’s biodiversity has historically been the basis of life for indigenous cultures and continues to support countless economic activities, many of them unsustainable, ranging from natural resource exploitation, an extensive fisheries industry and various forms of land use to nature-based tourism.
Being at the continent’s southern tip, terrestrial species have limited opportunities for adaptive range shifts under climate change, while warming is occurring at an unprecedented rate. Marine climate change effects are complex, as warming may strengthen thermal stratification, while shifts in regional wind regimes influence ocean currents and the intensity of nutrient-enriching upwelling.
The flora and fauna of marine and terrestrial southern African biomes are of vital importance for global biodiversity conservation and carbon sequestration. They thus deserve special attention in further research on the impacts of anthropogenic pressures including climate change. Excellent preconditions exist in the form of long-term data sets of high quality to support scientific advice for future sustainable management of these vulnerable biomes.
This chapter reviews the increasing importance of Mediterranean pines as invasive non-native species outside the natural range of the genus, especially in temperate parts of the Southern Hemisphere where several species are important weeds. It first discusses human-mediated changes to the ranges of Mediterranean pines and their colonization and persistence ability within and immediately adjoining their natural ranges. Next, it reviews the history of plantings and emergence of invasions of these pines in the Southern Hemisphere. Aspects of the ecology of the most widespread invaders (P. halepensis and P. pinaster) are discussed by considering the factors that influence invasive success. The impacts of the invasive pines are discussed, and management approaches and challenges are reviewed.
This contribution provides an overview of the ecology and distribution of the various habitat types which are dominated by small and intermediate-sized woody plants.
Dense vegetation, especially thickets of trees or shrubs, has been associated with actual and perceived crime risk in several parts of the world. In some contexts, invasive alien trees and shrubs can create a habitat structure that is very different from that provided by native vegetation. The role of alien and native plant species at different stages of invasion/densification in mediating criminal activity within a managed landscape remains poorly documented and elaborated. Using the South African city of Cape Town (a rapidly growing metropolitan centre within a global biodiversity hotspot) as a case study, we discuss the role of alien, invasive and native vegetation in mediating criminal activity in urban areas, particularly in a developing-country context. We argue that the incidence of crime may not always be determined by the biogeographical status of dominant plants (i.e., whether vegetation is dominated by native, alien, or invasive alien species), but rather on the structure/habitat they provide. A stronger link between crime and vegetation is likely in areas where tree invasions have drastically altered vegetation structure. This paper draws attention to a novel interaction between humans and vegetation and highlights the need for context-specific approaches when managing plant invasions, particularly in urban areas.
In 1945, the Royal Society of South Africa published a wide-ranging report, prepared by a committee led by Dr C.L. Wicht, dealing with the preservation of the globally unique and highly diverse vegetation of the south-western Cape. The publication of the Wicht Committee’s report signalled the initiation of a research programme aimed at understanding, and ultimately protecting, the unique and diverse ecosystems of the Cape Floristic Region. This programme has continued for over 70 years, and it constitutes the longest history of concerted scientific endeavour aimed at the conservation of an entire region and its constituent biota. This monograph has been prepared to mark the 70th anniversary of the Wicht Committee report. It provides a detailed overview of the circumstances that led up to the Wicht Committee’s report, and the historical context within which it was written. It traces the development of new and substantial scientific understanding over the past 70 years, particularly with regard to catchment hydrology, fire ecology, invasive alien plant ecology, the harvesting of plant material and conservation planning. The Wicht Committee’s report also made recommendations about ecosystem management, particularly with regard to the use of fire and the control of invasive alien plants, as well as for the establishment of protected areas. Subsequently, a combination of changing conservation philosophies and scientific conservation planning led to the creation and expansion of a network of protected areas that now covers nearly 19% of the Cape Floristic Region. We also review aspects of climate change, most of which could not have been foreseen by the Wicht Committee. We conclude that those responsible for the conservation of these ecosystems will face many challenges in the 21st century. These will include finding ways for effectively managing invasive alien plants and fires, as foreseen by the Wicht Committee. While the protected area network has expanded beyond the modest targets proposed by the Wicht Committee, funding has not kept pace with this expansion, with consequences for the ability to effectively manage protected areas. The research environment has also shifted away from long-term research conducted by scientists embedded in management agencies, to short-term studies conducted largely by academic institutions. This has removed a significant benefit that was gained from the long-term partnership between research and management that characterised the modis operandus of the Department of Forestry. Growing levels of illegal resource use and a changing global climate also pose new challenges that were not foreseen by the Wicht Committee.
Present studies were carried out to investigate ethnobotanical profile of Utror and Gabral. The twin valleys are located in the remote northwestern part of District Swat. The area is gifted with diverse and unique flora as it is adjacent to the confluence point of Himalayas, Hindu Kush and Karakorum. The people are mostly poor, illiterate and depend upon plant resources for their domestic needs. The inhabitants of Utror and Gabral utilize 176 plant species for more than 42 domestic needs. Based on their type of usage, the major usage types include 133 medicinal plants, 29 fuel wood species, 33 fodder species, 24 vegetables and pot herbs, 18 veterinary medicinal plants, 19 fruit yielding plants, 16 spices and condiments, 8 for construction and timber requirements, 10 ornamental plant species and 8 used as mouth wash (Maswak). Other miscellaneous uses of plants include aesthetics sense (1 species), anti lice (2 sp.), agricultural tools (8 sp.), thatching and roofing (5 sp.), baskets making (2 sp.), brooms (2 sp.), bridges (3 sp.), cosmetics (3 sp.), dye (2 sp.), dish cleaner (2 sp.), home decoration (2 sp.), feed (1 sp.), fencing (10 sp.), fish poison (2 sp.), furniture (8 sp.), honey bee attractant (8 sp), match industry (2 sp.), mythological use (6 sp.), naming (9 sp.), narcotic (3 sp.), oil (3 sp.), packing material (2 sp.), poisonous plants (6 sp.), ropes (2 sp.), anti snake and scorpion bite (5 sp.), soil binder (1 sp.), sticks/handles (3 sp.), snuff ash (1 sp.), shade tree (3 sp.), sport tools (1 sp.), tea (1 sp.) and utensil making (3 sp.). Most of the plants are used for multiple purposes. Some plants are also sold in the local markets, thus providing an additional source of income.
The Cape Floristic Region (CFR) which covers about 90 000 km2 at the southwestern tip of Africa is especially well known for its exceptional species richness and high levels of endemism in vascular plant taxa. The region has been flagged as one of the world’s foremost “hotspots” of plant diversity and endemism (Myers 1990). Although levels of diversity in most other taxonomic groups are generally less impressive than for plants, the CFR also boasts high levels of endemism for some invertebrate groups, amphibia and fish (references in Macdonald and Richardson 1986; Rebelo 1992).
Relative to their area, the five mediterranean-climate regions of the world harbour a disproportionate number of plant species, including exceptionally high numbers of rare and locally endemic species (Greuter 1994; Cowling et al. 1996a). Foremost amongst these is the Cape Floristic Region (CFR) where 8550 plant species, of which 68% are endemic, are crammed into 90 000 km2 (Bond and Goldblatt 1984). Landscape degradation, especially in the Cape lowlands, has transformed vast areas of natural habitat, resulting in the highest concentration of threatened plant species and subspecific taxa (1435) in the world (Rebelo 1992a; Cowling and Hilton-Taylor 1994). Indeed, in Myers’ (1990) parlance, the CFR is the “hottest” of the world’s hot-spots of plant biodiversity and endemism.
Classical weed biological control is widely used in natural areas. It is based on introduction of specialised natural enemies (herbivorous insects and fungal pathogens) from the weed’s native range. It can be used safely if specialised natural enemies are selected and can be highly effective in suppressing weeds over large areas. Agents used in modern projects typically have genus or species level specificity and are safe when proper risk analysis and procedures are followed. Agents spread over large areas and can move into hard-to-reach areas. If correctly selected, agents are safe for use in areas too ecologically sensitive for chemical or mechanical control. Costs are independent of area to be treated because agents are self-reproducing, and results are self-sustaining. Biological control is most appropriate for use against widespread weeds, difficult to control with other methods that occur in critical habitats and damage biodiversity or ecosystem function. Finding suitable agents is easier against weeds distantly related to local native plants. Such targets reduce risk to native flora, facilitate agent screening, lower cost, and increase likelihood of success. Projects should be partnerships between biological control scientists and conservation biologists, and biological control activities should be done within a comprehensive restoration plan for the ecosystem. In some cases, suppression of the invasive weed may be sufficient, but sometimes additional actions, such as replanting native species or modifying ecosystem processes such as fire or flooding regimes may be essential.
The frequency and abundance of invasive alien plants were recorded along roadsides and at watercourse crossings in 82.9% (145/175) of the quarter degree squares in the study area (31-35°S, 17-25°E and covering ± 90 000 km2). The survey yielded 102 species of which the most prominent (in order of prominence) in roadside and veld (natural and modified) habitats were: Acacia cyclops, A. saligna and A. mearnsii. The most prominent species (in order of prominence) in streambank habitats were: A. mearnsii, A. saligna and Populus x canescens. The greatest intensity of invasion was recorded in forest and fynbos vegetation types in the relatively narrow belt stretching from the coastline to the tops of the coastal mountain ranges. In the coastal lowlands Acacia cyclops and A. saligna form the most extensive and continuous stands of alien vegetation recorded anywhere in South Africa. In the arid interior invasion was largely confined to watercourses.
Ecological theory suggests that intermediate connectivity between protected areas will increase their resilience by facilitating dispersal, recolonisation, and genetic mixing. Conversely, over-connectivity may make areas less resilient to contagious perturbations such as pathogen outbreaks. In a similar manner, socioeconomic connectivity should enhance the spread of effective management strategies and the sharing of scarce resources, but over-connectivity carries the risks associated with one-size-fits-all strategies. We used network analysis to examine the topology of management collaborations and related exchanges of information and equipment in two protected area networks in South Africa using the Eastern and Western Cape Provinces as study sites. National protected areas displayed the highest degree of centrality in the Western Cape, while provincial protected areas occupied the central role in the Eastern Cape. Managers in the Western Cape were more concerned about establishing ecological connectivity between protected areas whereas tourism emerged as an important driver in the Eastern Cape protected area network. Our results support the argument that both location and network membership are important for the socioeconomic resilience of protected areas. As with ecological corridors, deliberate fostering of particular socioeconomic corridors may make the protected areas more resilient to perturbations.
In the 150 years since their introduction to the state, species in the genus Eucalyptus have become the most common non-native trees in California. A clearer understanding of the ability of different species to reproduce in the state is important for how we monitor the ecological impact of these abundant non-native trees and for predicting possible future invasions. Here we present current data on the diversity of Eucalyptus in California, which species are spontaneously reproducing, or have the potential to do so, where they can be found, how they can be identified, and our analysis, based on herbarium and field observations, of the potential ecological impacts of various species in the locations where they have been introduced. We also present a new dichotomous identification key, and botanical drawings of all naturalized species. We discuss the degree to which factors such as life history traits, commonness of planting, and native range influence reproductive behaviors of different species.
In 2009, the Chinese government approved the use of Hengqin Island for a large-scale development that will have serious consequences for plant biodiversity and plant communities in the island ecosystem as a whole. To construct an integrated and healthy vegetation ecosystem on Hengqin Island, we investigated the current vegetation and soil and developed a plan for vegetation conservation and rehabilitation. Satellite images captured over the last 30 years show that the island's coastline has changed greatly and that the forest land, water area, farmland, and urban land has greatly increased because of reclamation. The island currently supports 896 species of vascular plants, which are distributed in nine types of community. The plantation is the dominant community, although there are several patches of secondary forest. The typical soil types are lateritic red soil, salt swamp soil, littoral sandy soil, and fill soil. The poor physical and chemical properties of the soil are considered the limiting factors for vegetation restoration and rehabilitation. We propose to protect the secondary forests and mangroves and to improve the terrestrial plantations. We also recommend that, during the process of island urbanization, vegetation in the protected areas and in the newly constructed urban areas should be spatially connected, i.e. the sea should be connected to the mountain, the remnant forests should be connected to new urban green spaces, and the aquatic plant communities should be connected to the terrestrial plant communities. Hengqin government has adopted these plans and implementation has already begun.
Hakea sericea, an alien invader in fynbos, can be controlled successfully by cutting and then burning after seedlings emerge. The increase in fire intensity ascribed to burning the dry slashed material was measured. The effect of the increased fire intensity on soils, soil erosion, vegetation and termites were measured. Results show that the present management technique for the control of H. sericea (especially where it occurs in dense stands) has a negative effect on the ecosystem. It is also incompatible with overall management objectives of maintaining both diversity and ecological processes. Alternative techniques for controlling dense infestations should be evaluated.
The Cape Peninsula is an area of outstanding natural beauty and exceptional biodiversity, worthy of proclamation as a World Heritage Site. The area is dominated by fynbos vegetation, usually managed by means of prescribed burning, together with various programmes aimed at the control of invasive alien plant species. Effective management of the Peninsula is bedevilled by the fact that the area is controlled by no less than 14 different public bodies, resulting in fragmentation of effort and the lack of a standardized approach to management. Historically, many official and unofficial investigations have called for this problem to be resolved, without success. The lack of coherent, focused, and well funded fire and alien weed control management plans for the entire Peninsula is a serious deficiency. Despite this, considerable progress has been made towards the establishment of a database for the Peninsula, and the development of decision support systems that can utilize this database for rational management. Adoption of such a system would provide a powerful uniting tramework that would standardize and influence the management approaches adopted by the various controlling authorities.
With 2285 species of higher plants crammed into 471 km2, the flora of South Africa's Cape Peninsula is exceptionally rich. Similar sized areas in other Mediterranean-climate region biodiversity hot-spots support between 4.7 and 2.7 times fewer species. The high plant species richness of the Cape Peninsula is due to the exceptionally high turnover between moderately species-rich sites in different habitats (beta diversity) and between sites in similar habitats along geographical gradients (gamma diversity). Highest beta diversity, encompassing almost complete turnover, was recorded along soil fertility gradients. Although similar patterns for these independent components explain the richness of other regions in the Cape Floristic Region, it is the very long and steep habitat gradients of the Cape Peninsula that makes this region exceptionally rich. Furthermore, the flora is characterized by a high degree of rarity, a phenomenon that undoubtedly influences the turnover. Future research should focus on developing a biological and ecological understanding of the different forms of rarity and integrating this into management plans for the maintenance of biodiversity.
The Cape Peninsula, a 470 km2 area of rugged scenery and varied climate, is located at the southwestern tip of the Cape Floristic Region, South Africa. The Peninsula is home to 2285 plant species and is a globally important hot-spot of biodiversity for higher plants and invertebrates. This paper provides a broad overview of the physiography, biological attributes and history of human occupation of the Peninsula. The Peninsula is characterized physiographically by extremely high topographical heterogeneity, very long and steep gradients in annual rainfall, and a great diversity of nutrient-poor soils. Thus, the Peninsula supports a high number of habitats and ecological communities. The predominant vegetation is fynbos, a fire-prone shrubland, and 12 broadly characterized fynbos types have been described on the Peninsula. Animal community structure, especially with regard to invertebrates, is poorly known. Vertebrate community structure is probably strongly influenced by nutrient poverty and recurrent fire. Generally, most vertebrates are small and typically occur in low numbers. Some invertebrates play keystone roles in facilitating ecological processes. Human occupation of the Peninsula was limited, until relatively recently, by nutrient poverty. After Dutch colonization in 1652, direct and indirect impacts on the natural ecosystems of the Peninsula escalated dramatically, and by 1994, some 65% of original natural habitat was either transformed by urbanization and agriculture, or invaded by alien plants. Nonetheless, there is still excellent potential to conserve the Cape Peninsula's remaining biodiversity.
Includes Knysna forest, strandveld, mountain renosterveld, coastal renosterveld, coastal macchia, macchia and false macchia in the fynbos biome. Some 34% of the natural vegetation has been removed by farming and other human activities. -P.J.Jarvis
The Mediterranean Basin has played a prominent role in humanity’s biological and cultural evolution. From archaeological sites scattered throughout the region, and from the rich written records of historical times, we can trace our development from hunters and gatherers to a species able to reap the benefits of pastoralism, agriculture, and finally sophisticated technology — from harvesters of the wild to managers of our environment. People of the Mediterranean Region have, through the ages, been pioneers in the search for a balance between exploitation and conservation of natural resources. Their efforts have resulted in the domestication of livestock, the development of high-yield cereal grains, and the establishment of important cultivation techniques. The relatively benign winter-rainfall climate of post-Pleistocene times, and the rich diversity of terrestrial and marine biota, were both important factors in human social evolution.
The intercontinental analysis of mediterranean-climate ecosystems started in the 1960s with dual comparisons of the soil fauna of Chile and Italy (di Castri 1963), and above all the vegetation: that of California and Israel (Naveh 1967), France, California and Australia (Specht 1969a,b) and California and Chile (Mooney and Dunn 1970a,b).
This review covers the use of fire in the management of vegetation in selected areas of southern Africa. Major existing reviews of the ecological effects of fire in Africa have appeared in the recent past (Booysen and Tainton 1984; Komarek 1972; Phillips 1974; Trollope 1980b). It is not our intention to repeat what has been covered by earlier reviews, but rather to concentrate on the use of fire in the management of southern African ecosystems. Information on the objectives of management in areas of natural vegetation and the means by which they are achieved through the use of fire is widely scattered. The research results on which such policies are based are also scattered, and a synthesis would seem timely. The areas we have selected as examples cover the major vegetation types as well as the major forms of land use (agricultural, conservation, and catchment areas).
An annotated species list of the alien vascular plant flora of the Cape of Good Hope Nature Reserve is presented. The flora comprises five gymnosperm and 68 angiosperm species that are definitely alien to the reserve and four angiosperm species that are possibly alien. The life-form distribution of the alien flora is shown to be significantly different from that of the indigenous flora; trees, shrubs and annual herbs are more important in the alien flora, and dwarf shrubs and perennial herbs are much less important. Biotic factors are suggested as being important in determining the success of alien invasions, in particular grazing by ungulates. The invasion rate is currently about one new species per year. By ceasing to introduce tree species and by restricting human disturbance, the rate of invasion of new species could be reduced.
Pinus radiata, an important plantation species in South Africa, also invades mountain fynbos in the S and SW Cape Province and is a threat to the conservation of this vegetation type. Invasion began almost immediately after the first release of seeds from an adjacent plantation. Initial colonizers established at distances of up to 3 km from the seed source. Populations increased rapidly after a fire and resultant stands were dominated by cohorts that established during the immediate post-fire phase. Where fire had been excluded, population growth was slower and less dense, uneven-aged stands resulted. -from Authors
From the time of the first European settlement of the Cape in 1652, the pattern and degree of land-usage of the Table Mountain massif has been drastically altered. Today the future conservation status of the unique fauna, flora and natural beauty of the mountain is seriously threatened, unless co-ordinated management and consolidation of ownership is effected. This essentially heterogeneous mountain has been, is, and will always be used by main in many different ways, and the need for adequate planning and control has never been more acute. Perhaps the most vital planning goal is the education of the multitude of users to respect this natural asset which lies in the heart of a major metropolitan area.
Dense stands of the alien shrub Hakea sericea were felled and later burned accidentally under severe weather conditions. The recovery of the natural vegetation was monitored for 19 months on 12 permanent plots. Cover increased slowly to 13% and 42 species were recorded. Data were collected at a similar but uninvaded site burnt in the same fire. Mean cover on 12 plots at this site 19 months after the fire was 34% and the total number of species was 95. Sprouters were adversely affected at the invaded site, where species regenerating from seed stored in the soil predominated. Sprouters were dominant at the uninvaded site. Fire behaviour was simulated using Rothermel's fire model. Simulated fire intensity at the invaded site was particularly high (79 700 kW/m). Managers should attempt to burn felled hakea under conditions that will lead to less intense fires to reduce the adverse effects caused by high fuel loads. Fire behaviour prediction models should prove useful in this regard. Alternative control strategies for dense stands should also be investigated.
The reduction of species richness of indigenous plants is one of the major problems associated with the presence of dense stands of invasive alien trees and shrubs in the Fynbos Biome of the Cape Province, South Africa. A synthesis was made of published and unpublished data on plant species richness in fynbos with different levels of invasion and different histories of control. Linear regressions of species richness on the log of quadrat size were significant for both uninvaded fynbos and fynbos under dense stands of alien trees and shrubs. The slopes of the regression equations did not differ significantly between invaded and uninvaded sites, but elevations were significantly different, indicating a marked reduction in richness of indigenous plant species in invaded areas. The linear regression of species richness on quadrat size for cleared areas was not significant, but quadrats at most cleared sites showed species richness values intermediate to those of uninvaded fynbos and dense stands of aliens. Reductions in species richness at the scale of the sample quadrats used in this study (4–256 m) occur once the canopy cover of aliens exceeds about 50% and there is evidence of reduced species richness with increased time of suppression. For this reason, stands should be cleared before canopy closure is achieved.
The Cape Peninsula, a landscape of profound scenic beauty, is also botanically exceptionally species-rich and has high concentrations of both endemic and threatened plant species. Alien invasive trees, urban expansion and growing tourism are impacting increasingly on the landscape and biota. Three reserve scenarios were modelled, the primary objective being to maximize the conservation of biodiversity in a manner which takes both cost and efficiency into account. A comprehensive plant species database, an endemic animali species database, a vegetation type database, land-tenure and land-use data were used in this process. The resolution of all databases was by 1 km cells. The first scenario investigated the effectiveness of the existing reserve system in conserving the Peninsula's biodiversity. The second assessed the benefit of adding all publicly owned and to the existing reserves. In scenario three, a reserve-selection algorithm was applied to conserve those plant species outside existing reserves at least once. Where endemic animal species, and areas with high concentrations of threatened and endemic plant species were not adequately conserved, extra cells were added for their inclusion. Finally, one cell was added to cater for one inadequately conserved vegetation type. Fifty-one cells were needed to satisfy the requirements stipulated for scenario three. Analyses showed that 22% of plant species have all their records within existing reserves. Adding all public land improves the status to 43% with 97% having >50% of their records included in reserves. In scenario three, these figures are 32 and 87% respectively. In terms of animal species, four species are unconserved in scenario one, two in scenario two, and all species are conserved in scenario three. We conclude that scenarios two (including all public areas) and three (iterative selection to conserve each species once) provide practicable options for conserving the Peninsula's remaining biodiversity.
The Cape Peninsula (area: 471 km2), situated at the south-western extremity of the Cape Floristic Region, has exceptionally high plant species richness (2285 species and infraspecific taxa) and numbers of endemic (90; 88 species and two infraspecific) and threatened (141; 138 species and three infraspecific) taxa (termed species from here on). This biodiversity is threatened by urban development and the spread of invasive alien plants. Peninsula endemics are concentrated in a few, predominantly species-rich families and these correspond well with endemic-rich families in other areas of the Cape Floristic Region. A high level of similarity exists between families with threatened and families with endemic species. A frequency analysis of the biological traits of both endemic and threatened species shows that low growing, ant-dispersed shrubs are over-represented in both groups. Endemics are most likely to be non-sprouters, but threatened plants do not have a specific post-fire regeneration strategy. Threatened species have higher frequencies of geophytes, sprouters and wind-dispersed species compared to endemic species. Numbers of endemic and threatened species are not randomly distributed with regard to occurrence in vegetation types and patterns are similar for both groups. The habitat and biological profiles of both endemic and threatened species suggest that they are highly vulnerable to extinction as a result of increasing rates of alien plant infestation, urbanization and inappropriate fire regimes.
A wildfire in February 1986 destroyed most of an afforested research catchment in the southwestern Cape region of South Africa. The hydrological consequences of the fire were quantified using monitored pre-fire and post-fire stream flow and sediment data from the burned catchment and a nearby control catchment. Soil loss and soil wettability were also measured.In the first year after the fire, weekly stream flow totals increased by 12%, quick flow volumes increased by 201%, peak flow rates increased by 290% and catchment response ratio increased by 242%. Soil loss on overland flow plots ranged from 10 to 26 t ha−1, and suspended sediment and bedload yields each increased roughly four-fold following the fire.Wettability of the soils was greatly reduced by the passage of fire. Surface soil layers (0–10 mm) were burned clean of any inherent water repellency by the passage of a hot fire, but more severe repellency, in broader bands, was induced in deeper soil levels by the heating of the soil. It is postulated that the widespread development of water repellency in the soil led to overland flow during larger rainstorms, which in turn caused the markedly altered hydrological behaviour of the catchment and the high soil losses relative to the unburned condition.
Distribution trends are reviewed among 1808 plant species known to be in the IUCN Red Data Book categories and which occur in the fynbos and karoo biomes of the Cape Province, South Africa. The field-search and taxanomic limitations of the data are noted. Aspects of extinction biology are considered in relation to natural and human-caused factors which increase rarity. The genetic biogeography of the isolation of the plant populations in the region is discussed as a guide to future research. The priority ranking of species for conservation treatments is critically examined and a method for its evaluation is proposed.
Schemes are set out for the location of noda of nature reserves aimed at protecting the floral diversity of Fynbos vegetation in the Cape Floral Region, in South Africa, using distributional data on the Proteaceae. Species richness is significantly correlated between the Proteaceae and other major families and genera of plants representative of Fynbos, for which data are available. In our ideal scheme, 95% of all vascular plant species could be accommodated in 16% of the area occupied by Fynbos vegetation. However, several of our ideal-world noda are not viable options for Fynbos protection. Hence, we identify additional nodal areas that could be proclaimed as nuclei for nature reserves and incorporated into a real-world option for maximizing the protection of Fynbos floral diversity.
In this report a list is given of 1 808 rare, threatened and recently extinct plants in the fynbos and karoo biomes in the Cape Province of South Africa. The area covers the south-western and southern Cape, Namaqualand and the Karoo. Following the IUCN categories the area has 29 plants Extinct, 118 Endangered, 183 Vulnerable, 495 Critically Rare. 281 Indeterminate and 702 Uncertain. Local lists are given for the main biogeographic zones in the area. The extent and causes of the threatened plant problem are discussed and lines along which research and conservation action might follow are proposed. Data are provided on the populations and conservation priorities of about 250 species
Using computer technology in fire management: an example from the mountain catchment areas of the Cape Province, South Africa
- D M Richardson
- B W Wilgen
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- D C Maitre
- K B Higgins
- G G Forsyth
Flora and vegetation. In The Ecology of Fynbos: Nutrients, Fire and Diversity
- R M Cowling
- P M Holmes
Cowling, R.M. and Holmes, P.M. (1992) Flora and vegetation. In The Ecology of Fynbos: Nutrients, Fire and Diversity (R.M. Cowling, ed.) pp. 23-61. Cape Town: Oxford University Press.
Threatened plants of the Cape Peninsula
- A V Hall
- E R Ashton
Hall, A.V. and Ashton, E.R. (1983) Threatened plants of the Cape Peninsula. University of Cape Town: Threatened plants Research Group.
South Africa's Leading Edge? A Guide to the Western Cape economy
- D H M Bridgman
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- D.H.M. Bridgman
Bridgman, D.H.M., Palmer, I. and Thomas, W.H. (1992) South Africa's Leading Edge? A Guide to the Western Cape economy. Cape Town: WESGRO.
Field Manual for Mapping Populations of Invasive Plants for use with the Catchment Management System. Version 1.1. Division of Forest Science and Technology CSIR
- D C Le Maitre
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Le Maitre, D.C. and Versfeld, D.B. (1994) Field Manual for Mapping Populations of Invasive Plants for use with the Catchment Management System. Version 1.1. Division of Forest Science and Technology CSIR, Jonkershoek Forestry Research Centre, Stellenbosch.
Diversity, rarity, and conservation in mediterranean-climate regions
- M L Cody
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