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Managing fynbos for biodiversity: constraints and options in a fire-prone environment
Abstract and Figures
Fynbos is unique among Mediterranean-type ecosystems, both in terms of its biodiversity, and in the degree of management it receives. The management of fynbos ecosystems consists mainly of applying fire, and of controlling alien invasive weeds. Both have important impacts on overall diversity, and both are constrained by a lack of funds. Managers base their fire prescriptions on the well-documented responses of Proteaceae to fire, in the belief that what is good for those species is good for all others. Fixed fire regimes may lead to an impoverishment of diversity, however, and variable fore regimes may be more appropriate. We describe four options for management, which vary in intensity from fixed prescribed burning, to natural fire zones where fires burn freely within defined areas. The options allow for optimisation of scarce managerial resources on the one hand, and for highly variable fire regimes on the other. The effects of management on biodiversity are difficult to monitor, and we suggest that application of the four management options should be aimed at specifically achieving a diversity of fire regimes, rather than of biodiversity. Progress towards such an aim would be far easier to monitor. We describe how a catchment management system, currently being implemented in fynbos areas, can be used to store, retrieve and assess information on the fire history of the areas. The system allows for informed decision-making based on the goals of achieving varied fire patterns, thus eliminating the disadvantages of fixed fire regimes, and improving the goals of maintaining biodiversity
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... On sait que la fréquence et la gravité des incendies sont influencées par les conditions atmosphériques, la charge en combustible et les inflammations. Wilgen et al., 1994). From a South African perspective, it is therefore important to understand the environmental conditions that favour the occurrence of fires, in order to effectively determine where fire management efforts should be directed. ...
... To date, many studies have discussed the importance of fire for biodiversity (Bond & Keeley, 2005;Van Wilgen et al., 1994Van Wilgen & Richardson, 1985), and most of them concur that fire is necessary to promote the richness of species and to eradicate alien invasive species. Unmanaged fires can, however, have an adverse effect on the environment, economy and human lives (Dube, 2013). ...
... The study also showed that only a small area was burned under prescribed burns and that most fires occurred as wildfires, which suggests that prescribed burning in these environments will not reduce the risk of wildfires. Van Wilgen et al. (1994) suggested that, instead of having prescribed burning, a better option would be to allow wildfires to burn freely in delineated areas, based on an as- ...
Our research provides a detailed overview of the progress in remotely sensed fire monitoring techniques, which have been developed and employed for fire occurrence and detection. Our overview is provided from a literature search of English-peer reviewed articles, conference proceedings and scientific book sections published between the periods of 1980 and 2019. Literature reveals that historically, fire detection through remotely sensed techniques has mainly occurred through ground-based, airborne and satellite systems. Mathematical models, such as decision tree models, Species Distribution Models, Dynamic Global Vegetation Models and Global Climate Models, have also been employed alongside satellite systems to facilitate a greater understanding of fire dynamics and its susceptibility to changes in ecological and climatic variables. Fire frequency and severity are known to be influenced by atmospheric conditions, fuel load and ignitions. However, the literature suggests that targeting inappropriate wildfires with these techniques may still result in wild-fires outside of the natural fire regime. Most studies regarding fire occurrence and/ or monitoring focus on satellite-based techniques as they provide the greatest coverage of wildfires at varying spatial and temporal resolutions depending on the sensor used. Satellite systems are advantageous for fire monitoring as they provide extensive coverage inexpensively. Finally, fire occurrence is explicitly influenced by moisture-limited climatic conditions and/or fuel load in the form of leaf-litter or water-stressed plants. Résumé Notre recherche fournit un aperçu détaillé des progrès réalisés dans les techniques
... Because fires have continued to occur (including a few deliberate ignitions by park managers in the past), and because they presumably do not pose a threat to an ecosystem that has evolved under such a regime, we propose that fire management should opt for a laissez-faire approach. Using this approach, any natural (i.e., lightning-ignited) fire would be allowed to burn freely, while fires of anthropogenic origin would be contained if necessary (Seydack 1992; van Wilgen et al. 1994). ...
Background
Fire regimes in South African fynbos shrublands have been quantified in the western (winter rainfall) and central (aseasonal rainfall) parts. They have not been quantified at their eastern extremity (summer rainfall), where fynbos transitions to grassland and is embedded in other fire-resistant vegetation types. We assessed fire regimes at the eastern extremity of the fynbos biome and discussed the ecological and management implications of our findings.
Results
Using remote sensing, we assessed fires over 21 years in a 350,000-ha study area at the eastern edge of the fynbos biome. Only 9% of the study area burned, almost exclusively in mixed grassland-fynbos vegetation. The largest proportion (44% of the total area burnt) burnt in late winter and early spring, but fires occurred throughout the year. Fires only occurred in 39% of the mixed grassland-fynbos vegetation. Of the mixed grassland-fynbos vegetation that did burn, 44%, 11%, 26%, and 19% experienced one, two, three, and four fires, respectively. Areas with multiple fires had return intervals ranging from 3 to 15 years, with 76% of the area with multiple fires burning every 4 to 6 years. Most large fires were preceded by two relatively dry months, when fuels were drier and more flammable.
Conclusions
The mixed grassland-fynbos vegetation at the eastern extremity of the fynbos biome is surrounded by fire-resistant vegetation and exhibits a varied fire regime, with different parts experiencing frequent, infrequent, or no fire over 21 years. Fires were largely aseasonal, occurring throughout the year, although data over more years may reveal that a greater proportion of fires will occur in winter, when grasses are cured and rainfall is low, as well as after relatively long (> 2 months) periods of below-average rainfall. As most fires would burn out safely against fire-resistant vegetation, we conclude that lightning-ignited fires should be allowed to spread unhindered to approximate a natural and heterogeneous fire regime, provided that no neighboring properties or infrastructure are threatened. The response of the biota to fires is not well understood for this transition area, and further research is needed.
... Historically, conservation managers viewed fire as a process that disrupted natural systems and often applied management efforts to achieve complete fire exclusion (often resulting in catastrophic wildfire events). Contemporary managers and ecologists have progressed beyond these views and consider fire to be beneficial for driving ecosystem dynamics (van Wilgen et al. 1994;Granström 2001;Bergeron et al. 2002;Parr & Andersen 2006;Penman et al. 2011). In many areas around the world, fire suppression and fixed monotonic fire intervals are no longer advocated and are thought to be too rigid (van Wilgen et al. 2003;Parr & Andersen 2006). ...
As an ecological process fire plays a global role in structuring ecosystems and their constituent fauna and flora. Fire is also regularly applied as a landscape management tool and altered fire regimes affect global biodiversity. Fire can have a marked influence on vegetation composition and structure with resultant flow on impacts on faunal communities. However, faunal responses to fire are often quite varied and management recommendations of appropriate fire regimes therefore generally include utilising a fire mosaic approach to fire management. This thesis investigates the relationship between variable fire regimes, vegetation composition, condition and structure, and ground-dwelling vertebrate faunal communities.
The literature review (Chapter 1) revealed several gaps in current knowledge. This included a lack of detailed knowledge on the effects of variable fire regimes, including repeated management burns and fire mosaics, representative of multiple fire parameters (time since fire, number of fires, fire interval and fire type), on ecosystem biota. This was particularly evident for subtropical ecosystems. To analyse the effects of repeated burns, fire exclusion and wildfire, this study targeted one of the longest running fire experiments in Australia, at Bauple State Forest, where fire treatments have been applied annually since 1952 and triennially since 1973. Additional dry eucalypt forest sites at St Mary and Tiaro State Forests were included that represented variable fire management practices. Detailed fauna trapping surveys and vegetation assessments were completed on 35 plots across eight fire treatments at all three sites. Additionally, a broader scale GIS analysis of fire history was done across the three forests with surveys undertaken at an additional 74 sites allowing a comparison of reptile communities, forest condition and structure among variable fire regimes at multiple scales.
To quantify the structural and compositional influences that fire has on vegetation communities in subtropical systems, Chapter 3 involved a detailed analysis of the communities within the three dry eucalypt forests. Fire treatments significantly altered vegetation community diversity, structure and composition. Annual burning resulted in reduced floral diversity among all strata and reduced structural heterogeneity in the ground and shrub layers. Long unburned areas were more diverse but had lower canopy heterogeneity. Wildfires did not significantly impact the vegetation community.Consistent with previous research, this chapter found that frequent, repeated burning can reduce the diversity and structural complexity of forests.
The effects of disturbance (fire and logging) on forest condition and forest variables across the landscape were investigated in Chapter 4 using a biodiversity condition assessment toolkit among 63 plots. Forest variables and overall condition were correlated with historical disturbance patterns, derived from GIS, among Regional Ecosystems (RE), including time since fire, number of fires, fire interval, fire type and years since logging. The majority of forest variables were negatively affected by more frequent (61.5% of variables), or recent fire disturbances (76.9% of variables). The most pronounced negative impacts occurred for tree species richness, and two key habitat attributes for fauna including coarse woody debris and litter cover, which were maximised in long unburned areas highlighting the importance of maintaining long unburned refuges in the landscape.
Chapter 5 investigated the response of reptile and anuran communities, surveyed at 35 trapping plots, to different fire regimes and habitat characteristics quantified in Chapter 3. Reptiles were more vulnerable to fire impacts than anurans, particularly frequent fires (annual burning) which reduced the abundance of several species; however, species were generally not affected by wildfire. Species such as Lampropholis delicata and Eulamprus martini favoured long unburned areas, however, other species, i.e. Carlia p. pectoralis, preferred frequently and recently burned sites. Anurans, on the other hand appeared to be resilient to fires, corroborating previous studies on this taxon as they are able to retreat into moist microhabitats to survive. The ‘risk’ and ‘impact’ of fires to individual species was interpreted using a conceptual model that was able to categorise species as either tolerant or resilient to fire. These species-specific responses are important considerations when planning fire management guidelines that advocate frequent burning, as some species may be negatively affected.
In a parallel analysis, Chapter 6 assessed small mammal communities across the three sites and their response to variable fire regimes and habitat parameters. Mammals generally were not strongly influenced by fire but had highly variable responses which made it difficult to determine the factors influencing either species richness or abundance. It therefore appears likely that small mammal communities are not being negatively affected by repeated burning practices or infrequent wildfire. However, species were often correlated with habitat heterogeneity characteristics, highlighting the importance of maintaining a structurally diverse habitat that supports a variety of mammal species. As such, the indirect effects of fires may lead to a reduction in ideal habitat for certain mammals.
In Chapter 7, reptile communities were assessed across the landscape and correlated with various fire parameters and forest variables from Chapter 4. Number of fires, time since fire and fire type were key predictors for overall reptile abundance, as well as the abundance of four of the seven common study species. Overall abundance was negatively affected by number of fires and it also altered the overall reptile assemblage, while at a species level Carlia spp. were negatively associated with time since fire. Fire was generally a stronger predictor of reptile responses than habitat parameters with only shrub cover found to be negatively associated with Carlia spp. A reduction in total number of fires of some areas and increase in variability of burn intervals may support a greater diversity and abundance of reptiles in parts of the landscape where the total number of fires is high.
Fire heterogeneity was quantified within fire regimes across multiple scales in Chapter 8, using the variation in time since fire, number of fires, fire interval and unique (combination) fire mosaic regimes derived from GIS. Heterogeneity at the patch, local and site scales calculated from the Shannon-Wiener diversity index was weakly correlated with reptile communities and the heterogeneity measures appeared to be a poor surrogate of ‘fire diversity’. While this heterogeneity measure could not explain patterns in reptile communities, it is important to note that it captures only one element of landscape ‘pyrodiversity’. As other fire parameters including fire type revealed significant responses amongst reptiles, the specific nature of any biodiversity response to pyrodiversity appears linked to both scale and specific parameters used.
This thesis has demonstrated that aspects of the vegetation community as well as faunal species, favoured different fire regimes, where some species and structural characteristics preferred frequently burned areas while others (although more often than not) preferred infrequently burned or long unburned areas. Support is provided for the suggestion that a mix of frequently burned, infrequently burned and long unburned areas across the landscape will maximise floral and faunal communities, and help meet management goals of maintaining biodiversity. However, the scale of these unburned refuges is an important question that requires more research.
... Notably, only one study (Frost 1996) has been carried out in the fire-prone, dystrophic miombo and associated broadleaved savanna vegetation type, despite its widespread occurrence spanning 2.7 million km 2 across seven countries (Kutsch et al. 2011). Conversely, despite its limited extent, somewhat longer fire return periods (van Wilgen et al. 1994) and low biomass of large mammals (Boshoff and Kerley 2001), Cape Mediterranean shrublands (fynbos) were included in a relatively large number of studies. ...
An improved understanding of how fire affects African mammals is important for the management of both fire regimes and mammal populations. The response of mammals (>5 kg) to fire was reviewed to identify habitat preferences, and to inform fire management. Sixty-four studies reported on 51 species at 34 locations. Body size was strongly correlated with fire response, with smaller grazing species more likely to respond positively to fire (i.e. to occupy recently-burnt areas) than larger browsing species. Frequently-studied species (≥4 studies) were classified as either ambivalent in their responses to fire (four large browsers) or as responding positively to fire (fourteen grazers). An additional 30 less frequently studied species (<4 studies), including carnivores, were preliminarily assigned to fire response categories. Almost all studies were conducted in savanna and grassland vegetation, with the fire-prone dystrophic miombo, and more arid sites under-represented. Much of the research was aimed at establishing the preferences of a rare or declining species of concern, and fire management recommendations often called for increasing fire frequency to benefit such species. However, it is clear that co-occurring species have different requirements. We conclude therefore that managers should aim to promote spatial heterogeneity through fire application.
... Regression coefficients are log odds, standard errors in brackets composition (Hoffmann & Solbrig, 2003;Kraaij et al., 2013b;Roques, O'Connor & Watkinson, 2001;Van Wilgen, Richardson & Seydack, 1994), through keeping woody plants small and therefore vulnerable to fire (Bond & Midgley, 2001). In savannas, very short (1-6 year) fire return intervals (Govender, Trollope & Van Wilgen, 2006) reduce the tree-grass ratio by supressing post-fire recovery of some woody species despite the ability to resprout (Bond & Midgley, 2001;Hoffmann & Solbrig, 2003;Roques, O'Connor & Watkinson, 2001;Smit et al., 2010). ...
It has been hypothesised that high-intensity fires prevent fire-dependent fynbos from being replaced by fire-avoiding subtropical thicket on dune landscapes of the Cape Floristic Region (CFR). Recent extensive fires provided an opportunity to test this hypothesis. We posit that (1) fire-related thicket shrub mortality would be size dependent, with smaller individuals suffering higher mortality than larger ones; and (2) that survival and resprouting vigour of thicket shrubs would be negatively correlated with fire severity. We assessed survival and resprouting vigour post-fire in relation to fire severity and pre-fire shrub size at two dune landscapes in the CFR. Fire severity was scored at the base of the shrub and categorised into four levels. Pre-fire size was quantified as an index of lignotuber diameter and stem count of each shrub. Resprouting vigour consisted of two variables; resprouting shoot count and resprouting canopy volume. A total of 29 species were surveyed. Post-fire survival of thicket was high (83–85%). We found that smaller shrubs did have a lower probability of post-fire survival than larger individuals but could detect no consistent relationship between shrub mortality and fire severity. Fire severity had a positive effect on resprouting shoot count but a variable effect on resprouting volume. Pre-fire size was positively related to survival and both measures of resprouting vigour. We conclude that thicket is resilient to high-severity fires but may be vulnerable to frequent fires. Prescribed high-intensity fires in dune landscapes are unlikely to reduce the extent of thicket and promote fynbos expansion.
... Where an alien species is adapted to fire in the invaded ecosystem, management interventions need to be carefully integrated to promote ecosystem recovery and avoid exacerbating the invasion through fire-stimulated germination and spread of the alien species. In the case of serotinous invaders such as Hakea and Pinus species, fire may be used after felling adult populations to kill their released seed, seedlings and saplings (van Wilgen et al. 1994;Table 23.1, Langeberg case study). The case study of Cape Flats Sand Fynbos restoration at Blaauwberg Nature Reserve highlights the legacy effects to be overcome following Acacia invasion for a critically endangered ecosystem in which restoring and conserving biodiversity is the ultimate goal ( In riparian ecosystems, invasions of alien Acacia species and River Red Gum, Eucalyptus camaldulensis, also induce legacy effects. ...
Invasive alien plant species can be a major cause of ecosystem degradation in South Africa, and ecosystem recovery may require restoration interventions beyond controlling the target alien species. Active restoration interventions are usually required if legacy effects result from the invasion. Legacy effects may induce regime shifts when thresholds to autogenic recovery are breached. In such cases, active restoration interventions will be required to manipulate the ecosystem along a trajectory to recovery. In some cases, alien control measures may be sufficient to restore a structurally and functionally representative ecosystem, provided that implementation occurs early in the invasion process and that the control methods do not hamper spontaneous regeneration. It is important that key stakeholders discuss and set realistic restoration goals at the project planning stage. Studies on the costs and benefits of ecological restoration indicate that when important services are improved, benefits outweigh the costs of alien clearing (assuming spontaneous regeneration of the native ecosystem). The costs of moderate, active restoration interventions are economically viable, whereas the costs of fully restoring ecosystem structure, functioning and composition in highly degraded ecosystems are rarely deemed economically justifiable. Valuations of specific biodiversity components, such as threatened ecosystems and species, remain problematic to assess, and these components could be under-valued in such studies. South African researchers have made significant contributions to the theory and practice of restoration ecology globally and have produced local guidelines for ecological restoration. However, there has been limited uptake in implementing active restoration projects at larger scales. This apparent knowing-doing gap may have three causes: firstly, insufficient co-production by all stakeholders in planning restoration projects, including prioritisation and goal setting; secondly, shifting beyond clearing invasive alien species to restoring ecosystems; and thirdly, insufficient resources to implement active restoration projects at the necessary scale. To achieve Convention on Biological Diversity and the UN Sustainable Development Goals, interventions must shift from controlling invasive alien species alone to restoring native ecosystem structure and functioning.
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.
Mountains supply essential resources, making them attractive areas for human settlement. Variation in elevation in mountainous areas determines local and regional climates, leading to complex biodiversity patterns. Mountains in the Cape Floristic Region have high species richness and beta diversity, and very high levels of local endemism. Table Mountain is an iconic mountain in the region, and unusual, as it is in the centre of the city of Cape Town. It is exceedingly rich in biodiversity, including many localized endemic species. However, increasing urbanization in the area is adversely affecting the local biodiversity, especially in the lowlands. Climate change effects to date are minimal, but projected to interact with the impacts of urbanization. Here we review the biodiversity patterns of green and blue spaces in and around Cape Town, including Table Mountain, focusing on aquatic arthropods. We also review the major threats that lead to biotic impoverishment, and provide information on current conservation efforts aimed at protecting the rich biodiversity of Table Mountain and its surrounds. Finally, we focus on the shortcomings of existing conservation actions, and then provide conservation strategies to limit aquatic arthropod biodiversity losses, based on actions that have already worked well. To ensure protection of all arthropods, freshwater habitats across all elevations require further conservation action. Education and creating awareness must continue to close the gaps between scientists, conservation practitioners and civil society as a crucial part of the conservation plan.
Despite advances in our understanding of the geographic and temporal scope of the Paleolithic record, we know remarkably little about the evolutionary and ecological consequences of changes in human behavior. Recent inquiries suggest that human evolution reflects a long history of interconnections between the behavior of humans and their surrounding ecosystems (e.g., niche construction). Developing expectations to identify such phenomena is remarkably difficult because it requires understanding the multi-generational impacts of changes in behavior. These long-term dynamics require insights into the emergent phenomena that alter selective pressures over longer time periods which are not possible to observe, and are also not intuitive based on observations derived from ethnographic time scales. Generative models show promise for probing these potentially unexpected consequences of human-environment interaction. Changes in the uses of landscapes may have long term implications for the environments that hominins occupied. We explore other potential proxies of behavior and examine how modeling may provide expectations for a variety of phenomena.
The research programme in Swartboskloof evolved with the aim of providing further understanding of the functioning of mountain fynbos ecosystems, through comparison with other fynbos ecosystems, and with mediterranean-type ecosystems on other continents (see Preface). This chapter provides a description of the salient features of the climate of the Swartboskloof study site to facilitate these comparisons. We begin by examining the climate of Swartboskloof in a mediterranean-climate context. We describe features of the climate that influence the biota and hydrology, namely rainfall, temperature, vapour pressure deficit, radiation, evaporation, wind and droughts. We also describe the fire climate of the study site.
The effects of fire intensity on shrub regeneration have been little studied in fynbos. Using the extent of canopy damage as a measure of fire intensity, we sampled seedling regeneration of two myrmecochorous species of Proteaceae, Leucospermum conocarpodendron and Mimetes fimbriifolius, over low and high fire intensities in a burnt area on the Cape Peninsula. The results show that seedling recruitment is strongly and positively related to local fire intensity.
The National Programme for Ecosystem Research was established in 1972 to address a wide diversity of complex environmental problems which required a multiorganizational, interdisciplinary research approach. The central goal of the programme is to develop a predictive understanding of the structure, functioning and dynamics of South African terrestrial and inland water ecosystems. - from Author