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Simulating the Spread and Management of Alien Riparian Weeds: Are they out of Control
Journal of Applied Ecology
Abstract
1. This paper examines the circumstances under which control programmes may reduce the range of two widespread invasive weeds of riparian habitats: Impatiens glandulifera (Himalayan balsam) and Heracleum mantegazzianum (giant hogweed).
2. The spread of both species was modelled using MIGRATE, a spatially explicit model that incorporates realistic demographic parameters and multiple dispersal mechanisms. Simulations of a range of control scenarios were run within a geographical information system (GIS) using authentic landscapes based on topographic, hydrological and land cover maps of County Durham, UK. Results were interpreted at both a catchment and a regional scale.
3. Six representative strategies were explored that prioritized control as follows: at random, in relation to human population density, or by the size, age (new and old) or spatial distribution of weed populations. These strategies were assessed at different intensities of management (area treated per year) and for varying efficiencies (proportion of plants destroyed) as well as the timeliness (how long since the species became established) of implementations.
4. Strategies that prioritized control based on weed population and spatial characteristics were most effective, with plant population size and spatial distribution being the key parameters. The reduction in geographical range within a catchment or region following control was always greater for H. mantegazzianum than I. glandulifera due to its slower rate of spread.
5. Successful control of both species at a regional scale is only possible for strategies based on species distribution data, undertaken at relatively high intensities and efficiencies. The importance of understanding the spatial structure of the population and potential habitat available, as well as being able to monitor the progress of the eradication programme, is highlighted. Tentative conclusions are offered as to the feasibility of eradicating these species at a regional scale.
... As such, waterways serve as major invasion corridors in the landscape (Pyšek and Prach, 1995). Due to the potential of long-distance dispersal, catchment colonization events have corresponded to major steps in the spread of I. glandulifera (Wadsworth et al., 2000). Waterways further serve as corridors for the invasion of adjacent non-riparian habitats, like grasslands and forest ecosystems (Čuda et al., 2020;Pyšek and Prach, 1993). ...
... Since I. glandulifera is an annual plant with limited seed dormancy, management actions should aim at preventing seed formation (Dawson and Holland, 1999;Wadsworth et al., 2000). Best timing for plant removal (uprooting or mowing; the latter when there is a high risk of soil erosion) is consequently before or at early flowering, the latest before first seed set, since successful seed set has been observed from plants cut late in the growing season (Clements et al., 2008). ...
... Best timing for plant removal (uprooting or mowing; the latter when there is a high risk of soil erosion) is consequently before or at early flowering, the latest before first seed set, since successful seed set has been observed from plants cut late in the growing season (Clements et al., 2008). Due to the species' ability to rapidly form large populations from a few individuals, efficiency of control must be very high (> 99 %) to achieve successful eradication (Wadsworth et al., 2000). Consequently, follow-up visits during the growing season are often necessary (Adriaens et al., 2019). ...
This paper presents all current knowledge on the biology of the invasive therophyte Impatiens glandulifera Royle (Himalayan Balsam), and covers aspects of taxonomy, morphology, distribution, habitat requirements, ecology, life cycle, genetics, history of invasive spread, ecological impact and management. Although a few review papers have been published on this species in previous decades, a great deal of insights have been gained in the last three decades, owing to the species’ notorious reputation as one of the most problematic invasive species in Europe. This study consequently focusses on this novel information, with a particular focus on information from Central Europe.
... Along with significant economic damage, invasions lead to a decrease in biological diversity and pose a threat to food security, which underscores the need for international cooperation in developing and implementing measures to regulate intruders (Paini et al., 2016;Pratt et al., 2017). The calculation of labor and material costs and the development of effective methods for managing invasions are limited by the lack of accurate data in the implementation of measures to reduce their numbers (Wadsworth et al., 2000;Hulme, 2006Hulme, , 2009Panetta and Lawes, 2007;Sim-berloff, 2008;Gren et al., 2009;Pyšek and Richardson, 2010;Pluess et al., 2012;Pergl et al., 2016;Rajmis et al., 2016). ...
... Management of invasions should include a mechanism for early detection and decision making on their elimination, sufficient quantity and efficient allocation of resources to perform the required types of work, and supervision. Elimination should be carried out at the earliest stage of the invasion, when the volume of invasion is relatively small (Wadsworth et al., 2000;Ebel et al., 2018). The condition for successful work is to estimate the frequency of occurrence of new invasions and determine their exact boundaries. ...
... Studying the biology of invasive plant species makes it possible to predict their distribution (Dalke et al., 2015;Chadin et al., 2017) and to improve the quality of management of invasions (Simberloff, 2008). The modeling of biological invasion management strategies shows that successful control of the population of giant hogweed on a regional scale is possible only on the basis of results of studies on spatial distribution of plants, population structure, ontogenesis, and ecological and physiological characteristics (Wadsworth et al., 2000;Dalke et al., 2015;Chadin et al., 2017). On the other hand, a meta-analysis of 136 campaigns on elimination of 75 invasive species showed the success of activities within a territory limited to the size of a settlement or a small region. ...
The analysis of competitive documentation, contract documents, and technical assignments from 477 government contracts on control of the Heracleum sosnowskyi Manden. invasion carried out in 18 Russian regions from 2011 to 2017 is presented. According to the data posted on the official website of the Unified Information System in the field of procurement, 95% of the contracts were signed to destroy H. sosnowskyi plants, and the rest were connected with the determination of invaded areas, the development of methods for their elimination, and the supervision of the works carried out. The stands of H. sosnowskyi were mapped on an area of 169 000 ha and were destroyed on an area of 18 000 ha. The total cost of the contracts amounted to 314 million rubles. The mowing cost of H. sosnowskyi was about 30 000 rubles/ha; the cost for treating thickets with herbicides was 14 500 rubles/ha (median values). The median cost of mapping the H. sosnowskyi stands was about 370 rubles/ha. The high variability of the cost of the work was revealed for the contracts with treatment of areas less than 5 ha. The largest scale works on H. sosnowskyi eradication were conducted in the Leningrad, Moscow, and Vologda oblasts, where the funds for invasion control were reserved in the regional budgets. In the context of limited funding, systemic work on H. sosnowskyi thicket control should be initiated with a pilot project on the territory of one or two settlements, and then this experience should be extended to a larger region. Data on 477 government contracts used in the paper are freely available on the server Zenodo.
... Наряду со зна- чительным экономическим ущербом инвазии приводят к снижению биологического разно- образия, представляют угрозу продовольствен- ной безопасности, что подчёркивает необхо- димость международного сотрудничества в разработке и реализации мер по регуляции вторжений [Paini et al., 2016;Pratt et al., 2017]. Расчёт трудовых и материальных затрат, раз- работка эффективных способов управления инвазиями ограничена недостатком точных данных при выполнении мероприятий по сни- жению их численности [ Wadsworth et al., 2000;Hulme, 2006;Panetta, Lawes, 2007;Simberloff, 2008;Gren et al., 2009;Pyšek, Richardson, 2010;Pluess et al., 2012;Pergl et al., 2016;Rajmis et al., 2016]. ...
... Управле- ние инвазиями должно включать в себя меха- низм раннего обнаружения и принятия реше- ний по их ликвидации, достаточное количе- ство и эффективное распределение ресурсов для выполнения необходимых видов работ, надзор. Искоренение следует проводить на самом раннем этапе вторжения, когда объём инвазии относительно небольшой [ Wadsworth et al., 2000;Эбель и др., 2018]. Условием ус- пешной работы является оценка частоты по- явления новых заражений и определение их точных границ. ...
... [Simberloff, 2008]. Моделирование стратегий управления биологическими втор- жениями показывает, что успешный контроль численности гигантских борщевиков в регио- нальном масштабе возможен только на осно- ве результатов исследований пространствен- ного распределения растений, структуры по- пуляции, онтогенеза, эколого-физиологичес- ких особенностей [Wadsworth et. al., 2000;Dalke et al., 2015;Chadin et al., 2017]. С другой стороны, мета-анализ 136 кампаний по иско- ренению 75 инвазионных видов показал, что успехом заканчиваются мероприятия, прово- димые на территории, ограниченной размера- ми населённого пункта или небольшого реги-вариабельность и размах показателей заклю- чённых контрактов, наличие значите ...
В работе представлены результаты анализа конкурсной документации, договорных документов и технических заданий 477 закупок по ликвидации инвазии борщевика Сосновского (Heracleum sosnowskyi Manden.), проведённых в 18 субъектах Российской Федерации с 2011 по 2017 г. Согласно данным, размещённым на официальном сайте Единой информационной системы в сфере закупок, 95% контрактов было заключено для выполнения работ по уничтожению нежелательных зарослей H. sosnowskyi, остальные контракты были связаны с определением площади зарослей растений, разра-боткой методов их уничтожения, надзором за выполненными работами. Растения H. sosnowskyi были ликвидированы на площади около 18 тыс. га, картографирование зарослей проведено на площади 169 тыс. га. Общие затраты на выполнение контрактов составили 314 млн руб. Стоимость работ по коше-нию H. sosnowskyi составила около 30 тыс. руб./га, затраты на обработку зарослей гербицидами 14.5 тыс. руб./га (медианные значения). Стоимость услуг по картографированию одного гектара зарослей H. sosnowskyi составила 370 руб. Выявлена высокая вариабельность стоимости работ для контрактов, техническое задание которых предполагало уничтожение растений на территориях площадью менее 5 га. Наиболее масштабные работы по уничтожению H. sosnowskyi были выполнены в Ленинградс-кой, Московской и Вологодской областях, где средства на борьбу с инвазией заложены в бюджете регионов. В условиях ограниченного финансирования системную работу против зарослей H. sosnowskyi необходимо начинать с реализации пилотного проекта на территории одного-двух населённых пунк-тов, а затем распространять этот опыт на регион. Сведения о 477 контрактах, заключённых для лик-видации зарослей H. sosnowskyi размещены в репозитории «Zenodo».
The analysis of 477 government contracts for the Heracleum sosnowskyi Manden. invasions eradication carried out in 18 Russia regions from 2011 to 2017 presented. According to the official data (http://zakupki.gov.ru) 95% of the contracts included works on the destruction of H. sosnowskyi plants, and the rest were connected with the determination of invaded areas, the development of methods for their elimination, and the supervision of the works carried out. Over seven years, H. sosnowskyi stands where mapped on an area of 169 000 hectares, and destroyed on an area of 18 000 hectares. The total cost of 477 government contracts amounted to 314 million rubles. About 90% of H. sosnowskyi stands was processed in the Leningrad, Moscow and Vologda regions, where funds for the fight against invasion where reserved in the regions budgets. The greatest variability of the work cost was between contracts with the areas subjected to processing less than 5 hectares. The median cost of mapping the H. sosnowskyi stands was about 370 rubles / ha. The mowing cost of H. sosnowskyi was about 30 thousand rubles / ha (median value), which was twice the cost of treating the stands with herbicides. Effective invasion management of H. sosnowskyi possible only with the knowledge of the key biological traits of the species. In the context of limited funding, systemic work on H. sosnowskyi populations control should start with a pilot project on the territory of one or two settlements, and then this experience should be spread to a larger region. Data on 477 government contracts used in the paper is freely available on the server Zenodo (https://zenodo.org/record/1257332#.WxFYEX8lGvF).
... Attempts to control I. glandulifera in the Todmorden Mills Wildflower Preserve in the Don Valley in Toronto, ON, have been partially successful (Stephen Smith, Urban Forest Associates, personal communication 2007). In Europe, I. glandulifera escaped from cultivation in the mid-19th century in the United Kingdom and is now a problematic invasive in many regions (Beerling and Perrins 1993; Wadsworth et al. 2000). Much of the research on the impact of this plant is from Europe, although it is clear that the same kind of impacts occur in North America (and to an increasing degree) (Toney et al. 1998; Urban Forest Associates 2002; Clements, unpublished observations). ...
... In its native range, I. glandulifera occurs throughout the northern Indian provinces from Kashmir to Garhwal and in Pakistan at altitudes generally between 2000 and 2500 m (Gupta 1989; Tanner 2007) but has been reported up to 4000 m (Polunin and Stainton 1984). Impatiens glandulifera is also widespread in riparian habitats in Europe (Wadsworth et al. 2000), particularly between the latitudes of 30 and 648N (Beerling and Perrins 1993). It has colonized the majority of mainland United Kingdom, much of Ireland, the Isles of Scilly, Shetland and Orkney (Beerling and Perrins 1993). ...
... In other Canadian regions, I. glandulifera is likewise associated with plants of riparian areas, but because of the tendency of I. glandulifera to form monotypic stands the diversity of plants within these stands is likely fairly low. Impatiens glandulifera is also associated with riparian communities in Europe (Wadsworth et al. 2000; Hejda and Pysěk 2006; Hulme and Bremner 2006). The species was considered widespread in four major communities, as identified according to the National Vegetation Classification System, along the Rivers Taff and Ely in Glamorgan (United Kingdom): (1) Inundation communities: river-gravel, river alluvium and river-shingle; (2) Fens: Phragmites australis (Cav.) ...
Impatiens glandulifera Royle (Himalayan balsam) is an invasive alien annual up to 3 m in height with showy flowers that are generally pink or purplish. Native to the Himalayan region, I. glandulifera was first recorded in Canada in 1901 in Ottawa, and is now found in eight Canadian provinces: British Columbia, Manitoba, Ontario, Quebec, Nova Scotia, New Brunswick, Prince Edward Island and Newfoundland. Impatiens glandulifera is typically found in riparian habitats and may spread rapidly because its seeds are readily transported via waterways. Up to 2500 seeds are produced per plant and dispersed explosively up to 5 m from the parent plant. This can result in dense monotypic stands which prevent establishment of native plants and make stream banks vulnerable to erosion when the shallow-rooted plants die back. Impatiens glandulifera is susceptible to glyphosate but because herbicide use in riparian areas is not advised, other control methods such as hand weeding, mowing or flaming have been used. Methods for eradication are most successful when upstream populations are controlled first, as the plants spread downstream. Removal of I. glandulifera should be managed synchronously with non-native control measures and ideally be accompanied by planting native species to ensure the restoration of native species composition. The prognosis for curbing its spread in Canada seems poor as it has quite rapidly become established along waterways in many regions, following a pattern seen over the past two centuries in Europe.
... However, with the need of applying spatial concepts for controlling invasive species being recently raised, various studies have sought to determine the efficiency of removal strategies based on the density of the species (e.g. removal of recently colonized and lowdensity areas (outliers of colonized areas) or relatively long-established and high-density areas (core of a colonized areas)) using various spatial models, including species distribution models and dispersal models (Moody and Mack 1988, Higgins et al 2000, Wadsworth et al 2000, Taylor and Hastings 2004, Chapman et al 2017, NYSDEC 2017. For example, the term 'Early Detection and Raid Responses (EDRR)' appeared in the field of policy (US General Accounting Office) and suggested a direction of control from localized populations (i.e. ...
... Species removal scenarios and overall modelling approach Two different removal strategies, outside-in and inside-out, were established. In, the former, removal starts from the low-density outliers populations and progresses to the high-density centre of the colonized area, while in the latter, the progress is in the opposite direction (Moody and Mack 1988, Higgins et al 2000, Wadsworth et al 2000, Taylor and Hastings 2004. ...
Invasive species have become a global problem owing to their wide-ranging adverse effects. With intensifying climate change and artificial impacts (human-mediated disturbances), which exacerbate the adverse effects of invasive species, there is an urgent need to implement strategies for the management of these species. Various removal policies have been implemented globally to manage the common ragweed (Ambrosia artemisiifolia var. elatior (L.,) Decs) owing to its high tendency to “spread”. Several studies on the control method, application of spatial perspective, and optimization have been conducted to establish and evaluate management strategies using different spatial models. Although each of these methods is essential for improving control efficiency, an integrated form of study is needed to determine the practicality of various policies. In this study, we developed an integrated spatial model using the species distribution model BIOMOD2, land change model LCM, dispersal model MigClim, and optimization model prioritizr, to construct an evaluation methodology. For modeling an optimal invasive species removal policy under climate change and human-mediated disturbances (2011–2079), we created two strategies from a spatial perspective, outside-in and inside-out, with the former entailing removal from the low-density outliers to the high-density center of the colonized area and the latter processing in the opposite direction. The optimal removal sites for each strategy were set for each removal rate. Subsequently, a novel index, “removal effect index”, was proposed for the evaluation, in time series. The results indicate that the removal effect of the outside-in strategy was more effective, and the newly dispersed sites were efficiently removed. Furthermore, it was verified that with the implementation of the outside-in strategy having a removal rate of 65% by the 2070s, the species would be completely eradicated. Thus, this study is expected to help improve the efficiency of policy implementation for invasive species.
... Within an infestation, one can distinguish primary patches that were typically established early in the invasion process and have developed to a large size, and nascent satellite patches that established later and are still small (Moody and Mack 1988). Whether management strategies should focus on removing primary patches or satellite patches in the invaded range is an ongoing debate (Moody and Mack 1988, Wadsworth et al. 2000, Whittle et al. 2007, Blackwood et al. 2010, Baker 2017, Hoffberg et al. 2018, Weston et al. 2019. Which removal actions comprise the most effective strategy may depend on the specific characteristics of the particular IAS, the phase of the invasion process, and the amount of available control effort considered (Liebhold and Bascompte 2003, Taylor and Hastings 2004, Epanchin-Niell and Hastings 2010. ...
... Moreover, although perimeter:area ratio was the strongest predictor of the spread potential of individual patches (Fig. 4), the position of patches within the landscape may comprise a more important constraint on patch spread potential (Fig. 5). These findings suggest that the ongoing debate regarding the removal of smaller or larger invasive species patches (Moody and Mack 1988, Wadsworth et al. 2000, Whittle et al. 2007. Results from a Principal Component Analysis (PCA) showing the correlation structure between patch geometrical properties, and the relative rate of spread of patches. ...
Effective management strategies are needed to control expansion of invasive alien plant species and attenuate economic and ecological impacts. While previous theoretical studies have assessed optimal control strategies that balance economic costs and ecological benefits, less attention has been paid to the ways in which the spatial characteristics of individual patches may mediate the effectiveness of management strategies. We developed a spatially explicit cellular automaton model for invasive species spread, and compared the effectiveness of seven control strategies. These control strategies used different criteria to prioritize the removal of invasive species patches from the landscape. The different criteria were related to patch size, patch geometry, and patch position within the landscape. Effectiveness of strategies was assessed for both seed dispersing and clonally expanding plant species. We found that, for seed‐dispersing species, removal of small patches and removal of patches that are isolated within the landscape comprised relatively effective control strategies. For clonally expanding species, removal of patches based on their degree of isolation and their geometrical properties comprised relatively effective control strategies. Subsequently, we parameterized the model to mimic the observed spatial distribution of the invasive species Antigonon leptopus on St. Eustatius (northern Caribbean). This species expands clonally and also disperses via seeds, and model simulations showed that removal strategies focusing on smaller patches that are more isolated in the landscape would be most effective and could increase the effectiveness of a 10‐yr control strategy by 30–90%, as compared to random removal of patches. Our study emphasizes the potential for invasive plant species management to utilize recent advances in remote sensing, which enable mapping of invasive species at the high spatial resolution needed to quantify patch geometries. The presented results highlight how this spatial information can be used in the design of more effective invasive species control strategies.
... Total eradication from an area may be impossible if neighbouring habitats harbour populations (Wadsworth et al., 1997;Wadsworth et al., 2000). ...
... Total eradication from an area may be impossible if neighbouring habitats harbour populations (Wadsworth et al., 1997;Wadsworth et al., 2000). Where the species occurs along a river system, a catchment-scale approach to control is the only realistic method to control this species, however, such a concerted approach is often difficult with traditional methods due to multiple land ownership along riparian systems and inaccessible habitats. ...
Himalayan balsam Impatiens glandulifera Royle (Balsaminaceae) is a highly invasive non-native annual species that has spread rapidly throughout Europe (Pyšek et al., 1995) and North America (Cockel and Tanner, 2011), since its introduction from the foothills of the Himalayas at the beginning of the 19th century. It is now the tallest annual plant species in Europe, attaining a height of up to 2.5 m (Beerling and Perrins, 1993, Tanner et al., 2014). Himalayan balsam is predominantly a weed of riparian habitats, though it will flourish in damp woodlands and waste grounds (Environment Agency, 2010, Tanner et al., 2013).
Himalayan balsam has been shown to displace native vegetation when the cover is high (Hulme and Bremner, 2006) and displace associated invertebrate populations (Tanner et al., 2013). In turn, a reduced cover of native vegetation can negatively impact on above ground invertebrate communities, which are reliant on native plant species (Tanner et al., 2013). Below-ground invertebrate populations are largely unaffected and in some cases increase (e.g. Collembola) beneath infested stands, due probably to increased root biomass (Tanner et al., 2013).
Prevention: The most appropriate measures for preventing Himalayan balsam from entering a Member State are (1) the ban on keeping, importing, selling, breeding and growing as required under Article 7 of the IAS Regulation and (2) Phytosanitary measures, i.e. phytosanitary inspections. Seeds are the most likely life stage to ban from sale as the species is not traded in live plant form (Personal Observation, Tanner 2017).
The only feasible method for early detection of Himalayan balsam is visual inspection. The species is relatively easy to identify in the field, as it is now the tallest European annual plant species with bright purple/pink flowers. Citizen science networks could help to expand the local and regional network for identifying Himalayan balsam in the field.
Rapid eradication, following identification in the field, may be conducted using manual, mechanical and chemical options. All of the aforementioned control options are effective at controlling populations of Himalayan balsam – from small to large extents. Management should be conducted on a catchment scale, working downstream. It is however, the habitat where the species occurs which limits the effectiveness of the control options. For example, where Himalayan balsam occurs in a riparian system downstream management efforts may be limited. Chemical application to a population close to a riparian habitat is unlikely to be permitted, and if so only to a limited extent and any application will need to adhere to guidance and restrictions. Chemical control may be viewed negatively by stakeholders due to the non-target damage. In addition, there will be many areas where chemical application is not allowed. In relation to chemical control, EU/national/local legislation on the use of plant protection products and biocides needs to be respected.
Management of existing populations is feasible with manual, mechanical and chemical options taking into consideration the limitations to management on rivers as detailed above. In addition to these methods, biological control has been researched and applied against this species in GB. Using a host specific rust fungus (Puccinia komarovii var. glanduliferae) the biocontrol of the species looks promising. The rust was released in GB in 2015 and has since survived over winter. It should be borne in mind that the release of macro-organisms as biological control agents is currently not regulated at EU level. Nevertheless national/regional laws are to be respected. Before any release of an alien species as a biological control agent an appropriate risk assessment should be made.
... Reflecting a common challenge for resource managers, this framework considers how a manager can minimize the costs of invasive species, including both damages and management costs, while facing both an annual budget and a complex, multi-location ecosystem (Wadsworth et al. 2000;Hulme 2006;Epanchin-Niell and Hastings 2010). To address the potential for interactions between spatial, dynamic, and stochastic aspects of the invasive species management problem, and other such optimization problems, this paper incorporates several key aspects of stochastic spatial-dynamic species. ...
... Formally, using a Markov decision process, the manager's objective is to minimize the present discounted value of the costs of the invasive species-including damages and management costs-subject to an annual binding budget. The choice of objective function and assumption of a budget constraint reflect conversations with managers and the policy literature, and implies that the IS marginal damages always outweigh marginal costs of treating the IS (Wadsworth et al. 2000;Hulme 2006;Epanchin-Niell and Hastings 2010). Rather than emphasizing an eventual steady state, this analysis focuses on the optimal spatial-dynamic management during the process of invasion and spread. ...
Recent analyses demonstrate that the spatial–temporal behavior of invasive species requires optimal management decisions over space and time. From a spatial perspective, this bioeconomic optimization model broadens away from invasive species spread at a frontier or to neighbors by examining short and long-distance dispersal, directionality in spread, and network geometry. In terms of uncertainty and dynamics, this framework incorporates several sources of stochasticity, decisions with multi-year implications, and temporal ecological processes. This paper employs a unique Markov decision process planning algorithm and a Monte Carlo simulation of the stochastic system to explore the spatial-dynamic optimal policy for a river network facing a bioinvasion, with Tamarisk as an example. In addition to exploring the spatial, stochastic, and dynamic aspects of management of invasions, the results demonstrate how the interaction of spatial and multi-period processes contributes to finding the optimal policy. Those interactions prove critical in determining the right management tool, in the right location, at the right time, which informs the management implications drawn from simpler frameworks. In particular, as compared to other modeling framework’s policy prescriptions, the framework here finds more use of the management tool restoration and more management in highly connected locations, which leads to a less invaded system over time.
... Epanchin-Niell and Hastings [1] provide a detailed review of the studies on the economically optimal control of some established invasive species. Moody and Mack [5] and Martin et al. [6] perform a comparative study of the efficiency of different treatment variants on invasive species, while Wadsworth et al. [7] compare alternative strategies based on proximity for human settlements, weed population size, age and spatial distribution. Jetter et al. [8] study and provide a review for the benefits and costs of biological control programs. ...
... Thus, the interest group that cares about dispersed resources will have to compensate those groups wanting to protect more spatially concentrated resources. The actual treatment strategies are obtained from the optimization problem (7). The three damage trajectories when all the parties are in coalition are shown in Figure 2. The damage values are obtained by solving the optimization problem (1), (2), (4) and (5) with objective (10) when considering all parties are in coalition. ...
We formulate and solve a long-term multi-objective dynamic model for controlling invasive species using conflict resolution. This optimization framework is then applied to the case of buffelgrass control in the Arizona desert. Three players each value protection of three different threatened resources: riparian vegetation, buildings and saguaro cactus. The model optimally allocates labor and a monetary budget to protect these resources by controlling the buffelgrass population in a multi-period planning horizon, based on the theory of cooperative games.
... As Otte and Franke (1998) documented, seed dispersal in the absence of water, wind, or soil movement is poor. However, once the population has expanded into riparian areas, regional population increase can occur rapidly through waterborne dispersal (Pysek, 1994;Wadsworth et al., 2000;Pysek et al., 2007). ...
... Population growth in the British Isles has followed a similar pattern (Tiley et al., 1996;Collingham et al., 2000). Wadsworth et al. (2000) modelled the rate of spread of H. mantegazzianum in a single watershed and found there was a lag phase of 10 to 25 yr before exponential growth in occupancy of suitable habitats occurred. ...
Introduced from Europe for its unique appearance, Heracleum mantegazzianum Sommier & Levier (giant hogweed) is becoming increasingly prevalent across North America especially in the Northwestern and Northeastern States of the United States and Canada. Currently it is found along riverbanks, roadsides, waste places, and abundant lands. It is a member of the carrot family, Umbelliferae (Apiaceae). It is a biennial or a monocarpic short-lived perennial. It generally flowers in its third year of growth. It
resembles different plant species during different stages of its life cycle and is often mistakenly planted as an ornamental due to the attractive flower heads it produces. Heracleum mantegazzianum is closely related to Heracleum lanatum Michx. (cow parsnip). It poses a threat to natural ecosystems and is also a weed in agricultural and urban areas. This species represents an increasing public health hazard. The plant exudes a clear watery sap which contains furanocoumarins. Contact with H. mantegazzianum can cause phytophotodermatitis, a serious skin inflammation caused by UV photo-activation, resulting in severe burns to the affected areas and severe blistering. Control measures must be taken in order to prevent its further
infestations. The perennial nature of H. mantegazzianum and toxicity of the plant sap limits mechanical control options. Chemical control options include postemergence application of growth regulator herbicides, glyphosate or triclopyr, although limited information on its control is available. Ability to identify this weed and understand its biology will aid successful management efforts. Public education to dissuade gardeners from planting this attractive but noxious plant in their gardens is also necessary. This species should be watched carefully for its future infestation and subsequent spread as an invasive weed in agricultural and urban areas.
... According to Moravcová et al. [111], seeds can float in water for at least 8 h, resulting in long-distance dispersal when seeds are dispersed by fast-flowing streams. Wadsworth et al. [114] suggest that dispersal by water can lead to seed dispersal over a distance of 10 km. Anthropogenic activities are also an important means of colonizing new areas. ...
Improving ecological connectivity (EC) within landscapes by establishing corridors and ecological networks has been proposed to counteract the negative effects of habitat fragmentation and climate change on biodiversity. To be functional, ecological networks should be kept free of opportunistic invasive species that can disrupt EC between protected areas and cause biodiversity loss. The present study focused on perennial herbaceous species whose occurrence in the Adriatic-Ionian region has increased in the last two decades, namely common milkweed (Asclepias syriaca), Jerusalem artichoke (Helianthus tuberosus), Japanese knotweed (Reynoutria japonica), Bohemian knotweed (Reynoutria × bohemica), giant hogweed (Heracleum mantegazzianum), giant goldenrod (Solidago gigantea), Canadian goldenrod (Solidago canadensis), and Bermuda buttercup (Oxalis pes-caprae). All species have a high potential to spread in grasslands, abandoned agricultural fields, forest edges, and riparian areas and pose a significant threat to native plant communities and biodiversity. Restoring heavily infested sites is a major challenge because these perennial invaders are very persistent and tend to alter the soil environment in invaded habitats and prevent the recolonization of native plant communities. Therefore, early action should be taken to prevent the spread of these environmental weeds in ecological networks and protected areas with high conservation value.
... One can then optimize the much simpler surrogate models, and a Monte Carlo approach can be used to quantify uncertainty and obtain output statistics (Rumpfkeil, 2013). As with ADP, surrogatebased optimization techniques have been used mostly in (2000), Wadsworth et al. (2000), Grevstad (2005), Pepin, Smyser, et al. (2020) Note: The spatial column indicates the ability of the method to handle large spatial extents (++, can handle large spatial areas or numbers of patches; +, can handle small numbers of spatially distinct patches; À, does not represent space explicitly or handle large numbers of spatial patches). Note that here we contrast optimization methods that are commonly applied to spatial optimization problems. ...
Dispersal drives invasion dynamics of nonnative species and pathogens. Applying knowledge of dispersal to optimize the management of invasions can mean the difference between a failed and a successful control program and dramatically improve the return on investment of control efforts. A common approach to identifying optimal management solutions for invasions is to optimize dynamic spatial models that incorporate dispersal. Optimizing these spatial models can be very challenging because the interaction of time, space, and uncertainty rapidly amplifies the number of dimensions being considered. Addressing such problems requires advances in and the integration of techniques from multiple fields, including ecology, decision analysis, bioeconomics, natural resource management, and optimization. By synthesizing recent advances from these diverse fields, we provide a workflow for applying ecological theory to advance optimal management science and highlight priorities for optimizing the control of invasions. One of the striking gaps we identify is the extremely limited consideration of dispersal uncertainty in optimal management frameworks, even though dispersal estimates are highly uncertain and greatly influence invasion outcomes. In addition, optimization frameworks rarely consider multiple types of uncertainty (we describe five major types) and their interrelationships. Thus, feedbacks from management or other sources that could magnify uncertainty in dispersal are rarely considered. Incorporating uncertainty is crucial for improving transparency in decision risks and identifying optimal management strategies. We discuss gaps and solutions to the challenges of optimization using dynamic spatial models to increase the practical application of these important tools and improve the consistency and robustness of management recommendations for invasions.
... Early attempts to derive these formulations such as dynamic programming, optimal control theory, and genetic algorithms to solve the ISM problem considering economic impacts (Rago and Van Dyne 1978;Epanchin-Niell and Hastings 2010;Taylor and Hastings 2004;Marbuah et al. 2014) are reviewed in Olson (2006). When given a budget constraint, some studies have sought to minimize the time to achieve a given level of control or to maximize the amount of control achieved (Hof 1998;Wadsworth et al. 2000;Grevstad 2005;Hof and Bevers 2000). In 2018, Büyüktahtakın and Haight (2018) reviewed mathematical optimization models in ISM, discussing the state of the art, challenges, and future research directions. ...
Invasive species have long been difficult and expensive to eradicate, raising the need to develop more efficient and optimal management strategies. This paper presents a bi-objective mathematical model for controlling invasive species, combined with geospatial visualizations to aid with actionable strategy. The optimization model employs a multi-objective approach that incorporates functional connectivity of the infested sites to achieve an optimal specified minimum control level for a given invasive plant species. Subsequently, the model serves as a decision tool to identify optimal Invasive Species Management (ISM) strategies when mapped with GIS. This paper applies the framework to the case of Chinese privet (Ligustrum sinense) control on 317 acres of conservation land in Chattanooga, Tennessee, at Reflection Riding Arboretum and Nature Center. The proposed model simultaneously optimizes two objectives and provides an optimal configuration for species control by maintaining functional connectivity. Results display how changes in model parameters (namely, the decision maker’s preference of objective functions and desired minimum control level) create variation in optimal solutions based on these inputs, while reflecting on desired options. The research indicates multi-objective optimization contributes to complex decision-making in ISM, and placing these mathematical models in a geographic context provides insight into potential improvement in ISM practices.
... However, the presenting review emphasized the paradoxically small number of articles on the impact of Caucasian hogweeds on biodiversity. Their distribution on a global scale, including North America [4,5], the significant role of human density in their spread [6], the unpredictability of the invasion dispersal since its beginning [7], and rich chemical composition indicated that this is a big mistake. As plants that cause burns of mammals, including humans, alien hogweeds are especially recommended for removal, and the consequences are unknown. ...
Caucasian hogweeds are plants introduced to Europe from the Caucasus area. This review concerns the two most common ones—the giant hogweed Heracleum mantegazzianum and the Sosnowsky’s hogweed Heracleum sosnowskyi. The first of them was imported as garden decorations from the 19th century, mainly to Western Europe, while the second one was introduced from the mid–20th century to agricultural areas in Eastern Europe. Nowadays, these two species create one of the most problematic invasions in the world. This review aimed to synthesize research on those invaders based on 277 articles selected from the “Scopus” database. Most of the articles concerned their extensive distribution, at least on a continental scale and the rapid dispersal. The reviewed research showed that the complex physicochemical properties of hogweeds tissues and secretions significantly affected insects, aphids, ants, nematodes, fungi, soil microorganisms, plant communities, birds, and many other components of the ecosystems. This knowledge turned out to be disproportionately small to the scale of the problem. The review also showed what ecological traits of hogweeds were responsible for their wide and various role in the environment. Thus far, no effective method to eradicate Caucasian hogweeds has been found. This could be a growing mistake, given that they are probably during the rapid evolutionary changes within the range of their invasion.
... In the literature, few possible methods for control or elimination of populations of I. glandulifera are known: manual and mechanical control (Hartmann et al., 1995;Tanner, 2011), chemical control (Wadsworth et al., 2000) and biological control (Wood et al., 2020). The manual and mechanical control refers to a technique, which involves the cutting of plants below the first node to avoid regrowth and plant removal (Rapid, 2018). ...
Based on data from available scientific publications, a review of the insects, trophically related to Impatiens glandulifera in its European invasion zone has been made. As a result, nine insect species ( Pristerognatha fuligana, Deilephila elpenor, Xanthorhoe biriviata, Chrysolina herbacea, Siobla sturmi, Impatientinum asiaticum, Aphis fabae, Aphis nasturtii, Phytoliriomyza melampyga ) were found on the invasive plant. Of the identified insects, seven species ( D. elpenor, X. biriviata, A. fabae, A. nasturtii, C. herbacea, P. fuligana, P. melampyga ) are widespread in the country, of which only two – C. herbacea and P. fuligana are associated with I. glandulifera . The remaining two ( I. asiaticum and S. sturmi ) are not pre-sented in the Bulgarian entomofauna. Тhe potential role of these insects as agents of biological control of populations of I. glandulifera in Bulgaria has been assessed.
... Particularly, when the resource limits population growth, the priority of controlling effort allocation should be given to the areas with higher concentrations of resource. This result provided a new aspect because earlier work mainly focused on determining the optimal strategy of control based on species density/ abundance distribution (Menz et al., 1980;Wadsworth et al., 2000), without considering the difficulty of detecting and estimating population density/abundance in the field (Bonneau et al., 2019;MacKenzie et al., 2003). Therefore, when it is impossible to explore as many areas as needed to detect early population establishment, projecting population abundance based on the local resource level is a more accessible solution. ...
Invasive species, disease vectors, and pathogens are significant threats to biodiversity, ecosystem function and services, and human health. Understanding the optimal management strategy, which maximizes the effectiveness is crucial. Despite an abundance of theoretical work has conducted on projecting the optimal allocation strategy, almost no empirical work has been performed to validate the theory. We first used a consumer-resource model to simulate a series of allocation fractions of controlling treatment to determine the optimal controlling strategy. Further, we conducted rigorous laboratory experiments using spatially diffusing laboratory populations of yeast to verify our mathematical results. We found consistent results that: (1) When population growth is limited by the local resource, the controlling priority should be given to the areas with higher concentration of resource; (2) When population growth is not limited by the resource concentration, the best strategy is to allocate equal amount of controlling efforts among the regions; (3) With restricted budget, it is more efficient to prioritize the controlling effects to the areas with high population abundance, otherwise, it is better to control equally among the regions. The new theory, which was tested by laboratory experiments, will reveal new opportunities for future field interventions, thereby informing subsequent biological decision-making.
... Despite the large number of alien species, only few of them cause a trouble due to their invasive ability (e.g., Buddleja davidii or Reynoutria japonica in Europe). For this reason, they were widely investigated by the scientific community (Vitousek et al. 1997;Wadsworth et al. 2000;Hobbs et al. 2009;Alexander et al. 2016); however, developing a model assessing the success of the establishment of a biological component is probably impossible (Gilpin 1990). The mechanism underlying this influence can be related to many factors, such as nutrient cycling, water availability, species competition and a suitable habitat for the population dynamic (Levine et al. 2003;Alexander et al. 2011;Sitzia et al. 2018). ...
This research aims at finding the potential plant successions in riparian vegetation along gravel-bed streams of Lombardy (Northern Italy), investigating the influence of exotic species and proposing a more sustainable and efficient management planning for habitats conservation. To characterise the riparian vegetation, 65 phytosociological relevés were carried out along four rivers in Lombardy (Pioverna, Staffora, Ogliolo and Grigna). We evaluated a series of ecological indexes to assess the ecology of plant communities. A clustering analysis detected five different plant communities characterised by specific ecological traits. On the basis of such results, we discuss about a model of plant succession describing: (i) the typical native species succession representing the riverine forests of the study areas; (ii) a succession with moderate presence of exotic species; and (iii) a succession dominated by alien species with an unclear development. To preserve the natural heritage and landscape with a small rate of alien species, it is important to plan vegetation management actions, which limit the presence of new empty space. For containing the exotic species, mechanical and chemical measures could lead to good results, but they can be expensive and cause adverse effects. Otherwise, biological control, combined with other actions, has the potential to bring results with low environmental and economic impact. Ecological restoration measures using fast-growing and spreading native species could restrict alien plant colonisation. In this regard, a better comprehension of the invasive alien plants behaviour is necessary, especially in terms of their competition mechanisms. Nevertheless, the application of long-term vegetation management of river ecosystems is crucial for a continuous monitoring and for addressing the goals of the 2030 global agenda concerning biodiversity conservation.
... Management of invasive species requires a targeted approach for maximum effect. A number of studies using spatially explicit models have demonstrated that where the effort is initially targeted can have a profound effect on outcome 5,[22][23][24][25] . Controls based on population biology have generally supported prioritization of the edges of a population as primary targets of initial control efforts 5,23,24,26 . ...
Rapid range expansions of invasive species are a major threat to ecosystems. Understanding how invasive species increase their habitat ranges and how environmental factors, including intensity of human activities, influence dispersal processes is an important issue in invasion biology, especially for invasive species management. We have investigated how spatially heterogeneous factors influence range expansion of an invasive species by focusing on long-distance dispersal, which is frequently assisted by human activities. We have developed models varying two underlying processes of a dispersal event. These events are described by source and destination functions that determine spatial variations in dispersal frequency and the probability of being a dispersal destination. Using these models, we investigated how spatially heterogeneous long-distance dispersal influences range expansion. We found that: (1) spatial variations in the destination function slow down late population dynamics, (2) spatial variations in the source function increase the stochasticity of early population dynamics, and (3) the speed of early population dynamics changes when both the source and the destination functions are spatially heterogeneous and positively correlated. These results suggest an importance of spatial heterogeneity factors in controlling long-distance dispersal when predicting the future spread of invasive species.
... High-quality UGAs can support source/core populations, whereas low-quality UGAs can serve as stepping stones and vanguards for invasion. For species with limited dispersal capacity, control efforts should target vanguard populations to hamper rapid range expansion (Wadsworth et al. 2000). This simple rule of thumb has been especially well supported for slowing the spread of invasive trees (e.g. Watson 1985; Moody and Mack 1988;Doren and Jones 1997;Higgins et al. 2000). ...
... invertebrates , native flora (Bradford et al., 2007;Truscott et al., 2008;) or ecosystem functioning (Hulme and Bremner, 2006;Hladyz et al., 2011). The propagation and distribution of non-native species is also a recurring theme within this subcategory (Wadsworth et al., 2000;Tickner et al., 2001;Maskell et al., 2006;Walker et al., 2009). Manchester and Bullock (2000) detailed the principal non-native species introduced in the UK and their possible impact on UK native biota. ...
... High-quality UGAs can support source/core populations, whereas low-quality UGAs can serve as stepping stones and vanguards for invasion. For species with limited dispersal capacity, control efforts should target vanguard populations to hamper rapid range expansion (Wadsworth et al. 2000). This simple rule of thumb has been especially well supported for slowing the spread of invasive trees (e.g. Watson 1985;Moody and Mack 1988;Doren and Jones 1997;Higgins et al. 2000). ...
Urban landscapes are highly fragmented (leading to the extinction of native species) as well as transformed and disturbed (creating novel environments). Such conditions provide non-native species with opportunities to establish and spread through “urban green areas” (UGAs). UGAs can serve as stepping stones for many alien species to recruit and may become sources of propagules to launch invasions in adjoining natural ecosystems. There is great diversity in the spatial structures of UGAs worldwide; these are determined by the city’s level of development, human density, urban planning policy, and history. We explore the invasion risks of, and the potential of invasive spread in, UGAs in the world’s 100 most populous cities (in 40 countries). Based on maps of enhanced vegetation index at 250 m resolution over the extent of 25 by 25 km for each city centre, we simulate the invasion and spread of a reference species (a virtual ruderal invasive species) from the city centre into surrounding urban or rural areas. Doing so allowed us to provide an objective baseline for comparing urban susceptibility to such invasions across diverse cultures, histories and societies. We derive the global ranking of invasive spread potential for each city based on the rate of spread of the reference species, and the ranking of 40 countries, based on the average rate of spread in their cities. We explore correlates of spread rates after 100 time steps (years) by examining the roles of climate (mean annual temperature and rainfall), human demography (city population size and growth rate), and socio-economic indicators [human footprint, human development index and gross domestic product (GDP) per capita]. Small city population size and high GDP per capita are the only significant predictors of high potential for invasive spread. Among the G20 countries, Canada, South Korea, South Africa, France, USA and Brazil all feature in the top-10 countries, and Atlanta, Washington, D.C. and Dallas in the USA, Chittagong in Bangladesh, Toronto in Canada and Brasilia in Brazil are listed among the top 10 cities overall. Our results can serve as a global baseline assessment of invasive spread risks through UGAs, and call for improved protocols for monitoring, planning and management of UGAs.
... Besides the six species described above, there are some other alien species showing a tendency of spreading in riparian habitats. In central Europe, Reynoutria sp., Heracleum mantegazzianum, Impatiens glandulifera, Echinocystis lobata, Aster sp. and Solidago gigantea are the most frequent aliens on the banks of rivers, often forming large monodominant stands (BeeRliNg & peRRiNs, 1993;BRaNDes & oppeRmaN, 1994;BRaNDes & saNDeR, 1995;WaDsWoRTh et al., 2000;uherčíková, 2001). Acer negundo and Robinia pseudoacacia are common invaders in riparian floodplain forests, often in a combination with Impatiens glandulifera, Solidago gigantea and Aster sp. in the herbaceous layer in gaps with higher light availability. ...
Riparian zones provide suitable habitats for spreading of non-native plant species, simultaneously serving as migration pathways. At the same time, non-native invasions indicate the increasing anthropogenic pressure and make up a significant part of today’s changing biota. This paper presents a study of distribution of six alien species (Aster salignus, Petasites hybridus, Helianthus tuberosus, Impatiens glandulifera, Echinocystis lobata and Heracleum sosnowskyi) in Latvia. All species are known as non-native invaders of riparian habitats, such as riparian shrubs, floodplain meadows, tall herb nitrophilous communities on the riversides and wet slopes of valleys. Distribution data are based on the recent data gathered in field surveys and herbarium records as well as literature references. Maps of the current distribution, habitat preferences of all studied species and their spreading dynamics over the last century are presented.
... It differs from the SES trap literature by largely ignoring or simplifying the complexity of social feedbacks to managers and resource users (often excluding people as actors in ecological models) and in its focus on how to manage variance in the supply of ecosystem services (Carpenter & Brock 2006). Its primary modus operandi has been to use a scenario-based or pseudoexperimental modeling approach to inform management decisions (e.g., Wadsworth et al. 2000), without questioning manager goals and motivations. For example, the parameters of an ecological limit to growth model of an expanding herbivore population in a small protected area may be manipulated to explore alternative management strategies (Starfield & Bleloch 1991). ...
Successful conservation depends as much on people working together as it does on sound science and good governance. Research on cooperation in businesses, economics, psychology, and natural resource management has identified shared social and social-ecological dynamics, reviewed and categorized in this article, that can create unwanted surprises and problems for conservation efforts. Cooperation may fail when (a) individual and group benefits are in conflict (social dilemmas) or (b) social-ecological systems become caught in problem-causing and problem-enhancing feedbacks (SES traps). Knowing about and recognizing these dynamics can help decision-makers to understand and change key elements of problems and learn from the experiences of others. Social dilemmas have winners and losers, and involve give-some or take-some choices; SES traps are lose-lose situations. Solutions to problems of cooperation in conservation contexts involve identifying the conservation objective and context, diagnosing systemic social dilemmas and SES traps, and developing practical solutions that work with group processes and individuals towards shared and positively reinforcing goals, goal structures, and expectations. Research on cooperation in conservation has largely ignored problems of scale, scaling, and group heterogeneity. The field would benefit from a shift from a probabilistic, empirical approach to a stronger theory-driven, mechanistic, and more diagnostic approach. This article is protected by copyright. All rights reserved
... North America and Oceania were first mentioned in 1998 (e.g. Edwards et al., 1998;Lampo and De Leo, 1998), and Europe in 2000 (Wadsworth et al., 2000). The first study covering more than one continent was published in 2004 (Morrison et al., 2004), and since then more continents were simultaneously targeted by modelling studies (Fig. 3b). ...
Invasive species are increasing in number, extent and impact worldwide. Effective invasion management has thus become a core socio-ecological challenge. To tackle this challenge, integrating spatial-temporal dynamics of invasion processes with modelling approaches is a promising approach. The inclusion of dynamic processes in such modelling frameworks (i.e. dynamic or hybrid models, here defined as models that integrate both dynamic and static approaches) adds an explicit temporal dimension to the study and management of invasions, enabling the prediction of invasions and optimisation of multi-scale management and governance. However, the extent to which dynamic approaches have been used for that purpose is under-investigated. Based on a literature review, we examined the extent to which dynamic modelling has been used to address invasions worldwide. We then evaluated how the use of dynamic modelling has evolved through time in the scope of invasive species management. The results suggest that modelling, in particular dynamic modelling, has been increasingly applied to biological invasions, especially to support management decisions at local scales. Also, the combination of dynamic and static modelling approaches (hybrid models with a spatially explicit output) can be especially effective, not only to support management at early invasion stages (from prevention to early detection), but also to improve the monitoring of invasion processes and impact assessment. Further development and testing of such hybrid models may well be regarded as a priority for future research aiming to improve the management of invasions across scales.
... Acting in many nodes at once requires many more eradication actions in total than acting at a single node (Fig. 2) (Menz, Coote & Auld 1980;Wadsworth et al. 2000). Although the cost of simultaneous eradications at Edgbaston may be low, widespread use of controversial actions such as piscicides for eradication may be undesirable and a compromise policy may be useful. ...
Spatial management of invasive species is more likely to be successful when multiple locations are treated simultaneously. However, selecting the best locations to act is difficult due to the many options available at any time.
We design a near‐optimal policy for applying multiple actions simultaneously for faster invasive species control within a network. Our method uses a recent optimisation tool, the graph‐based Markov decision process (GMDP). Since the policy can be difficult to interpret, we extracted a simpler policy using classification trees. We applied our approach to the eradication of invasive mosquitofish Gambusia holbrooki from the habitat of the red‐finned blue‐eye Scaturiginichthys vermeilipinnis , a critically endangered fish with a global population that is restricted to seven artesian springs in Queensland, Australia.
The policy returned by the GMDP was to manage springs occupied by mosquitofish and their connected neighbours, unless the neighbours were occupied by red‐finned blue‐eyes.
Simultaneous management resulted in rapid declines in simulated mosquitofish occupancy even if eradication effectiveness was low; however, the cost of simultaneous eradication was high and sustained eradication effort was necessary to maintain low mosquitofish occupancy.
Synthesis and applications . Our paper finds a near‐optimal, multi‐action control policy to remove an invasive species from a multi‐species spatial network. We introduce the graph‐based Markov decision process and apply it to a real case study – eradication of invasive mosquitofish from the habitat of the red‐finned blue‐eye. We find that the graph‐based Markov decision process can generate policies for networks with extremely large state spaces; however, it works best when nodes have fewer than five neighbours. We conclude that simultaneous eradications are effective for rapid control of invasive species; however, managers should consider the cost and time required for an effective eradication program.
... (2) models based on both host and pest population sizes (e.g., Sims et al. [2010], Kovacs et al. [2014]); and (3) models based on pest occupancy (e.g., Wadsworth et al. [2000], Marco et al. [2002], Carrasco et al. [2010], Epanchin-Niell and Wilen [2012], Konoshima et al. [2013], Epanchin-Niell et al. [2014], Meier et al. [2014]). The choice of a modeling approach is dependent on the approach that best captures the characteristics of the ecological system the scientist is trying to model, and it can generally be said that, there is no one single approach that is superior or ecological more realistic than the other. ...
We propose a new optimization model that captures the spatial dynamics of invaders by a cellular automaton model and finds the optimal solution to control its spread within a 0–1 integer programming framework. The model seeks a solution by minimizing the total costs to implement treatments for preventing the spread and damage caused by invaders’ colonization. By incorporating a cellular automaton model governed by state- and distance-dependent probability rule of colonization, the model is transformed into a linear model, so that a 0–1 integer programming formulation is used to evaluate and compare an optimal allocation of treatments on colonized and uncolonized areas. The study uses a hypothetical map to show that treatments on colonized cells are more effective when implemented at the front line of the invaders, while treatments on uncolonized areas are effective when conducted with some distance or buffer zone away from the front line. These buffer zones are likely to be colonized regardless of treatment. Under annual budget limits, treatments on colonized cells are implemented first. With heterogeneity in the invaders’ dynamics, the proposed optimization model provides an optimal allocation of treatments much different from the solution with homogeneous environment. However, treatment at the front line of the invading species is always recommended.
... In central and western Europe, H. mantegazzianum has long been recognized as a prominent example of an invasive alien (Pysek, 1991;Tiley et al., 1996;Collingham et al., 2000;Wadsworth et al., 2000); however, its genetic relationship to the other large Heracleum taxa that are also invasive in parts of Europe (H. sosnowskyi and H. persicum) has been studied only recently (Nielsen et al., 2005;Jahodová et al., 2007). ...
... Pour les autres espèces, la mise en place de mesures d'atténuation semblerait le plus réaliste. Pour empêcher au mieux la propagation de l'espèce à travers les paysages, il est judicieux de cibler les plans d'eau/populations à risque ( Wadsworth et al., 2000), c'est-à-dire les plans d'eau envahis étant à la source de nouvelles populations-satellites (e.g. plan d'eau en amont de bassin versant ; plan d'eau abritant des espèces animales pouvant disperser des fragments de plantes ; plan d'eau faisant l'objet de curage ; etc.). Des priorités de gestion doivent donc être dégagées dans ce sens. ...
Among rapidly spreading invasive species in Europe, amphibious plants are particularly problematic. These plants are capable of developing a photosynthetic activity both below and above the water surface, and they typically form dense floating populations. Controlling amphibious plants, whether for the purposes of total eradication or for the regulation of their spread, represents an important challenge for managers. A literature review of existing control methods for Crassula helmsii, Hydrocotyle ranunculoides, Ludwigia grandiflora, Ludwigia peploides and Myriophyllum aquaticum was carried out, taking into account efficiency and costs. Of the 87 studies analyzed, a great variation was evident in the research efforts undertaken (number and spatial scale of studies) between species and between control methods. However, overall, the different control methods described showed a similar level of efficiency between species. Reports of total eradication of amphibious plants were rare. Such cases resulted from the application of mechanical or chemical methods, most often coupled with complementary methods such as manual finishing. The use of chemical control methods (less laborious and costly than others) was found to be frequently documented in the literature. However, except in the case of some active substances, such chemical methods were found to provide low control efficiency. Similarly, to date, biological control has not been found to provide convincing results. In addition, it should be noted that several biological control agents are considered as invasive species in Europe. On the other hand, although little related research has been carried out, methods such as manual or mechanical removal with manual finishing have often been found to result in satisfactory control levels. Aware of the difficulty of controlling amphibious plants, as well as the potential collateral damage caused by control methods to aquatic ecosystems, we argue that consensus still needs to be found between scientists, decision-makers and managers before decisions at regional or national scale can be made.
... Several case studies demonstrate that invasive vascular plant species can change native ecosystems in different ways: Competitive tall herbs (e.g. Fallopia japonica, Helianthus tuberosus) in nutrient-rich, well-watered sites form dense stands, outcompete native taxa (Walser 1995;Kowarik 1999), change succession patterns, and form new vegetation types (Sukopp & Sukopp 1994;Hartmann & Konold 1995;Walser 1995, Wadsworth et al. 2000Bimova et al. 2004). Most of these species show vegetative growth and are able to store nutrients in tubers or rhizomes in winter, allowing fast growth in the subsequent vegetation period. ...
... In fact, all four countries have actually implemented management plans for a number of the Black List species. As way of example, a range of mechanical, chemical, and in rare cases also biological, methods have been employed to control Australian swamp stonecrop (Dawson 1996), Himalayan balsam and giant hogweed (Wadsworth et al. 2000), floating pennywort, water primrose Japanese knotweed and Parrot's feather (see control sheets in Q-bank: Comprehensive Databases on Quarantine Plant Pests and Diseases, http://www.qbank.eu/). Trapping, hunting and shooting are the preferred management options for animals such as the ruddy duck (Robertson et al. 2014), American bullfrog , grey squirrel and American mink (Bonesi and Palazon 2007). ...
Horizon scanning for high-risk invasive
non-native species (INNS) is crucial in preparing and
implementing measures to prevent introductions, as
well as to focus efforts in the control of species already
present. We initiated a trans-national horizon-scanning
exercise focused on four countries in western
Europe: Great Britain, France, Belgium and The
Netherlands, which share similar environmental and
socio-economic characteristics. We followed a structured
four-step approach combining existingknowledge about INNS, with a collaborative identifi-
cation of priorities for research and management: (1)
systematic review of potential INNS of concern, (2)
discrimination of INNS into an Alert and Black List
depending on their absence or presence in the study
area respectively, (3) risk analysis of the Alert List,
and (4) expert ranking of species in the Black List.
Amongst species not yet present in the four countries
(i.e. Alert List), assessors reliably pointed to the
Emerald ash-borer (Agrilus planipennis) and Sosnowski’s
hogweed (Heracleum sosnowskyi) as those
INNS with the highest risk of invasion and impact. The
Japanese knotweed (Fallopia japonica), Himalayan
balsam (Impatiens glandulifera), zebra mussel(Dreissena polymorpha) and killer shrimp
(Dikerogammarus villosus) were consistently highlighted
as some of the most problematic INNS already
present in the study area (i.e. Black List). The
advantages of our combined approach include that it
is inclusive of all-taxa, prioritizes both established and
emerging biological threats across trans-national
scales, and considers not only the ecological impact,
but also potential direct economic consequences as
well as the manageability of invasive species.
... A major invasive alien plant in Europe (, Dawson & Holland 1999, Weber 2000, Peltre et al. 2002), but also in North America (Toney et al. 1998 ), is the east- Asian Impatiens glandulifera (Balsaminaceae; 2n = 18, 20). This tall annual plant was selected for study because it is currently expanding its European range (Beerling 1993) and causes problems for ecosystem management (Wadsworth et al. 2000). However, little knowledge exists about possible herbivores (but see Schmitz 1995), and virtually nothing is known about fungal or viral diseases as stated in the reviews by Beerling & Perrins (1993), Shaw (2003) and Sheppard et al. (2006). ...
There are few observations of fungal or viral diseases in invasive non-native plant species, and no account of such infections exists for Impatiens glandulifera, which is a problematic weed in moist and half-open habitats of central Europe. We now observed for the first time viral infections in plants from nine European regions in a common garden experiment. The infection was systemic and could be transferred to two species of Chenopodium and several species of Nicotiana leading to local necrotic spots within a week. In Chenopodium quinoa, C. amaranticolor and Nicotiana debneyi the infection remained local; in N. tabacum, N. rustica, N. clevelandii and N. benthamiana the infection became systemic. The symptoms resembled Tobacco Rattle Virus, but an ELISA-test turned out negative. In I. glandulifera the virus led to reduced aboveground biomass which can be taken as a measure for fecundity. Relative stem biomass and basal diameter were also lower in the infected plants, whereas no significant differences occurred in plant height and number of main branches. Also no effect of virus infection was found for six reproductive traits, i.e. time till flowering, pollen viability, fruit abortion, seed–ovule ratio, seed number per fruit and individual seed mass. The virus was not transmitted through seeds from infected plants. The potential effects of such viral infections for population dynamics and biological control are discussed.
Despite research into the dynamics of seed transport in fluvial systems, few consider how far seeds will travel, and how far from local or upstream seed sources passive regeneration can occur. We experimentally test the seed floating time of 60 plant species (50 native and 10 exotic) commonly found in riparian corridors of southeastern Australia. Around 50% of species had seeds that floated for 2 days or less, and for most species' (90%) all seeds had sunk within one week. Seeds of native species tended to sink more quickly than exotic, with 64% of native species' seeds floating for less than 2 days. In contrast, most exotic species (80%) floated for longer than 2 days, and 40% had seeds still floating after one week. This suggests that exotic species are good floaters and likely to travel long distances, making them excellent hydrochores. Finally, we applied the findings to a real case study, Wollombi Brook, NSW, Australia. We combined the findings from the seed floating experiment with low flow hydrology calculations to map the potential travel distance of seeds from known extant vegetation sources. We show that maximum seed travel distance per day could be up to 21 km. Thus, species that float for a week could potentially travel almost 150 km downstream before sinking or being deposited. We discuss how local versus upstream seed sources, and hydrochory, could be utilised in passive revegetation and weed management of riparian corridors.
Some of the main rivers of the Central European Highlands and Plains flow into the Baltic and North Seas, including the rivers Weser, Elbe, and Oder, drain the ecoregion of the central European highlands and plains. In addition to these rivers, this chapter describes some smaller but peculiar rivers such as the Em (Sweden), Skjern (Denmark), Spree (Germany), and Drawa (Poland). Much of the landscape is dominated by glacial and periglacial geomorphic elements such as moraines, outwash plains adjacent to terminal moraines, different types of lakes (ice-scour lakes, moraine-dammed ribbon lakes, kettle lakes, and glacial drift-plain lakes formed under the ice sheet), large glacial valleys, and large lowland plains consisting of glaciofluvial deposits. The different retreat stages of the glacial sheet produced a sequence of glacial valleys forcing meltwaters toward the North Sea. These valleys are used partially by some rivers today, including the Elbe, Spree, Warta, and Skjern. As river sediments mainly consist of sand, sediment transport occurs nearly continuously, creating ripples or subaqueous sand dunes often reaching a crest height of up to 1.5 m. Regional ecological characteristics of flowing waters in the ecoregion were summarized. This chapter summarizes the hydrology, biochemistry, geomorphology, flora and fauna, and economic importance of each of these rivers. Human intervention to conserve and manage these rivers is also discussed.
The British Isles, comprising the United Kingdom (Scotland, England, Wales, and Northern Ireland) and the Republic of Ireland, lies at the northwest Atlantic seaboard of Europe. The latitude and longitude ranges from around 50°N to 61°N and 2°E to 11°W. As the landmasses of mainland Britain and the island of Ireland are small, the sea is always close, and the rivers are small in comparison with continental Europe. Despite this, the area has marked differences in climate, geology, and population densities that result in a diverse range of rivers with distinctive physical, chemical, and ecological characteristics and varying degrees of human impact.
Owing to their potentially wide-ranging adverse effects, invasive species are a growing global problem. The common ragweed (Ambrosia artemisiifolia var. elatior (L.) Desc) is one of the most important invasive plants, necessitating management because of its tendency to “spread.” Various studies and management strategies are being conducted based on the concept of “density” because of the increasing importance of the spatial perspective in this application. Although eradicating from the outliers (low-density regions) has a high efficiency, there is a lack of validation methodology for deriving both spatial and statistical results. We formed a general validation methodology by assessing various removal scenarios based on two removal strategies, namely Outside-in and Inside-out. These approaches exhibited several removal rates, and take into account the spatial perspective by considering species density. The Outside-in strategy entails the removal of species, which commences from the low-density regions, whereas the Inside-out removal initiates from the high-density regions. To classify the spatial regions for priority removal using each strategy, we defined the density level and then processed the removal of the occurrence points for each strategy to derive generalized results. We used the species distribution model MaxEnt to determine the predicted distribution of the target species for each removal strategy applied; subsequently, the final randomly generalized occurrence point results were used as model input data. Assessment analyses were conducted based on the final probability distribution and appearance level for each scenario, which included a newly proposed index was termed the “removal effect index.” Results indicated that the efficacy of the Outside-in removal strategy exceeded that of the Inside-out strategy for all assessment analyses, with the removal effect index showing a difference of about 2–5 times between strategies in each removal rate. In addition, through numerical analysis of the changed area of each scenario, the Outside-in strategy showed a successful removal effect in the “removal management priority spatial range,” whereas the Inside-out strategy showed limitations. We confirmed the efficacy of the Outside-in strategy as an optimal removal approach that takes into account spatial information of the priority spatial range for eradication in terms of the removal effect.
To increase the ecological realism in an economic analysis of invasive species management in a river network, this paper identifies optimal spatial-dynamic management while accounting for specific invasive species strategies, including long-distance dispersal, exogenous arrivals, propagule pressure, and seed fitness. Although a stylized framework, the inclusion of native species permits analysis of trade-offs between the management actions of invasive species control and of habitat restoration for a range of settings and species characteristics. In general, more aggressive invasive species and more invasion-susceptible ecosystems require greater investment in habitat restoration despite its relative expense. Explicitly modeling invasion strategies reveals that the specific ecological mechanism of invasion defines the location of management activities in the river network, and the choice between invasive species control and habitat restoration. The analysis of this bioeconomic model develops insights that help managers to harness the power of native-invasive species establishment interactions in stemming bio-invasions across time and space.
Background and purpose: The objectives of our study were to identify invasive alien plant species (IAS) in the main Natura 2000 forest habitat types (FHT) along the Mura River in Slovenia, and to estimate their abundance and cover. The aim of our study was to find out a) Which IAS appear in the research forests? b) What is their frequency and cover percentage? c) Whether individual IAS prosper better in some FHT than others? d) What is the correlation between the cover of IAS and the tree layer cover? Materials and methods: We analysed the fidelity of invasive plant species to individual FHT. The studied FHTs along the Mura River were the following: 91E0* (Alluvial forests with Alnus glutinosa and Fraxinus excelsior), 91F0 (Riparian mixed forests of Quercus robur, Ulmus laevis and Ulmus minor, Fraxinus excelsior or Fraxinus angustifolia, along the great rivers) and 91L0 (Illyrian oak-hornbeam forests). Two forest areas of about 600 ha were studied in total. With the intention to calculate number and cover of IAS some statistical analysis was made. In addition, correlations between the abundances of the most present IAS and cover of upper tree layer were carried out. Results: In total, 15 IAS were recorded in studied FHTs. Some species, like Robinia pseudoacacia, Impatiens glandulifera, I. parviflora, Fallopia japonica (incl. F. x bohemica), Erigeron annuus, Ambrosia artemisiifolia, Amorpha fruticosa, Conyza canadensis and Juncus tenuis occur only in one or two FHTs, while some species can be found in all studied FHTs (e.g. Solidago sp.). We found out that the most threatened forests are those with prevailing Salix alba, Alnus glutinosa, Fraxinus angustifolia and Ulmus laevis tree species. Those are the forests of FHT 91E0 which have less dense tree canopies, grow closest to the river and on the wettest sites. We found a statistically significant higher number and cover of IAS in the FHT 91E0 and the lowest number and cover in FHT 91L0. Conclusions: Alluvial forests with Alnus glutinosa and Fraxinus excelsior (FHT 91E0) along the Mura River are most prone to invasion of IAS. The increasing presence of IAS in the study areas seriously affects natural regeneration, stability, and continuity of floodplain forests in all other FHTs in the study area. At the same time the amount of IAS in these forests also depends on management measures and their intensities which accelerate light availability. Some measures and guidelines for managing of these forests with the purpose of reducing IAS impacts are suggested in this study. © 2017, Croatian Society of Natural Sciences. All rights reserved.
Plant invasions are considered as an enormously complex process, nonetheless, they can be understand using simplified models. In Polish scientific literature articles linking theoretical background of ecology of plant invasion with the practical approach are relatively scarce. It results in a lack of Polish nomenclature concerning ecology of invasion. We present essential concepts of invasion ecology as: invasion level, range infilling, invasibility, propagule pressure. Mechanism driving distribution of invasive plant species, including landscape level, and environmental variables used for modelling of plant invasions were described. Foundations of biological invasion management and post-invasion ecosystem restoration were also reviewed.
This review was prepared for the New Zealand Department of Conservation as the first step towards the development of landscape-scale population models for invasive pests. Such models have been identified as important tools for future management of the conservation estate.
We summarise previous studies of weed invasions in New Zealand and discuss techniques for modelling invasive populations in space and time. We then review existing projects of particular relevance and draw some conclusions about fruitful approaches to modelling pest spread across real landscapes.
Long-term permanent plot data have been used to reconstruct weed invasions in some New Zealand conservation areas. Such data will be invaluable for parameterising and testing the predictions of landscape-scale population models.
GIS-based statistical techniques are able to predict habitat suitability for particular species and therefore their potential distributions.
Existing models for invasive species tend to concentrate on rates of spread, and so highlight the importance of long-distance dispersal. However, local demography and short-distance dispersal is also important for practical
management of such species.
While spatial population modelling is well advanced, realistic modelling of populations in real (i.e. GIS-based) landscapes is in its infancy. The most advanced GIS-based models are for the spread of wildfire, which has Obvious similarities to pest invasions but tends to operate on smaller spatial scales.
Few existing weed population models have explicitly evaluated alternative management scenarios.
One study used loosely-coupled GIS and population models to evaluate weed control strategies at a regional level in the UK. This approach might be enhanced to form a useful tool for evaluating pest control strategies in the New Zealand conservation estate.
We experimentally tested the feasibility of a control campaign of purple jewelweed ( Impatiens glandulifera ), an exotic invasive species in Europe and North America. We evaluated the amount of time and money required to control the plant along riverbanks, with particular attention paid to the recovery of riparian vegetation following hand pulling and bagging. Work time was directly and significantly related to stem density and fresh biomass of the invader, but the relationship was stronger for density. Density and biomass were strongly reduced by the first hand-pulling operation from a mean of 45 to 2 stems m ⁻² and from a mean of 0.95 kg m ⁻² to nearly zero, a good performance but not enough to negate the need for a second hand pulling later in the summer. A single hand pulling significantly reduced the cover of purple jewelweed from to 30% to 7%. Riparian vegetation disturbed by the first hand pulling largely recovered during the following 30 d. Expressed over an area of 1 ha, the total amount of time required to control purple jewelweed is 1,400 work hours over 2 yr, or a minimum investment of Can$21,000 (US$17,000). Although controlling a well-established purple jewelweed population is expensive, to properly evaluate the benefits, we must also consider the costs of soil erosion caused by this species.
Książka przedstawia sposoby eliminacji 15 pospolitych w Polsce inwazyjnych gatunków roślin. Dla każdego gatunku przedstawiono jego oddziaływanie na środowisko oraz szczegółowy przegląd stosowanych w Polsce i na świecie metod zwalczania: mechanicznego, chemicznego, biologicznego i kombinowanego. Uzupełnieniem przeglądu metod jest zestawienie aktualnych regulacji prawnych dotyczących zwalczania gatunków obcych w Polsce. Każdemu rozdziałowi towarzyszy obszerna bibliografia. Książka może być cenną pomocą dla służb ochrony przyrody, samorządowców i leśników. Jak zaznaczają autorzy we wstępie, publikacja nie przedstawia antidotum na inwazje gatunków obcych, ale niesie wiedzę, mogącą ułatwić podejmowanie trafnych decyzji wszystkim, którzy zmagają się tym problemem.
Książka przedstawia sposoby eliminacji 15 pospolitych w Polsce inwazyjnych gatunków roślin. Dla każdego gatunku przedstawiono jego oddziaływanie na środowisko oraz szczegółowy przegląd stosowanych w Polsce i na świecie metod zwalczania: mechanicznego, chemicznego, biologicznego i kombinowanego. Uzupełnieniem przeglądu metod jest zestawienie aktualnych regulacji prawnych dotyczących zwalczania gatunków obcych w Polsce. Każdemu rozdziałowi towarzyszy obszerna bibliografia. Książka może być cenną pomocą dla służb ochrony przyrody, samorządowców i leśników. Jak zaznaczają autorzy we wstępie, publikacja nie przedstawia antidotum na inwazje gatunków obcych, ale niesie wiedzę, mogącą ułatwić podejmowanie trafnych decyzji wszystkim, którzy zmagają się tym problemem.
Global changes in climate, land-use and the economy rapidly alter large-scale distributions of animal and plant species. Under these varying climatic and land-use conditions, species may shift their distributions or, if they are too migration limited to do so, they can adapt to the new conditions or they may go extinct. Additionally, because of the increase in international trade, species are being introduced to new areas more frequently and, due to their ability to spread rapidly, are becoming one of the main reasons for species decline. The aim of this thesis was to investigate the factors that drive such long-term dynamics at different spatial scales by using species distribution models. The results showed that competition between species was a key factor influencing species distributions, especially under favourable climate conditions. It was further shown that migration limitation was an additional key factor shaping species distributions and was mainly caused by competition, adverse climatic conditions and habitat fragmentation. As a result, tree species that occur mainly in competitive environments may not be able to keep pace with climate and land-use change, while ruderal species may have only minor delays in the readjustment of their distributions. Another important finding was that knowledge on the variation in migration rates due to habitat heterogeneity can be used successfully for developing strategies to control invasive plants more economically. Overall, the findings of this thesis will be helpful for investigating and better predicting large-scale species distributions under global change scenarios and for developing mitigation strategies to reduce the effects of global change on species distributions.
Biological diversity, or biodiversity, is broadly defined as the variety of life on Earth and the natural patterns it forms. Almost two million species have now been identified and the actual number of species in the world is estimated to be between 10 and 30 million (IUCN 2006). This enormous biodiversity is an essential provider of ecosystem goods and services. However, despite the important role biodiversity plays in our lives, all species that together comprise biodiversity face risk.
The investigation results of the transformer species participation (Echinocystis lobata (Michx.) Torr. & A. Gray, Heracleum sosnowskyi Manden., Impatiens glandulifera Royle, I. parviflora DC., Reynoutria japonica Houtt., Robinia pseudoacacia L.) in different plant communities of the Ukrainian Polissya (Forest zone of Ukraine) are presented. All the abovementioned species are strong edificators in the region that can significantly change important species composition parameters of communities and character of landscape.
A review in Swedish of threats, policy strategies etc concerning a number of invasive plant species occurring in roadside habitats and other infrastructure biotopes. The review is based on literature and interviews with oficials at national, regional, and local authorities, responsible for biodiversity conservation and infrastructure planning.
2015. Inventory and review of quantitative models for spread of plant pests for use in pest risk assessment for the EU territory. EFSA supporting publication 2015:EN-795, 190 pp. Available online: www.efsa.europa.eu/publications ABSTRACT This report considers the prospects for increasing the use of quantitative models for plant pest spread and dispersal in EFSA Plant Health risk assessments. The agreed major aims were to provide an overview of current modelling approaches and their strengths and weaknesses for risk assessment, and to develop and test a system for risk assessors to select appropriate models for application. First, we conducted an extensive literature review, based on protocols developed for systematic reviews. The review located 468 models for plant pest spread and dispersal and these were entered into a searchable and secure Electronic Model Inventory database. A cluster analysis on how these models were formulated allowed us to identify eight distinct major modelling strategies that were differentiated by the types of pests they were used for and the ways in which they were parameterised and analysed. These strategies varied in their strengths and weaknesses, meaning that no single approach was the most useful for all elements of risk assessment. Therefore we developed a Decision Support Scheme (DSS) to guide model selection. The DSS identifies the most appropriate strategies by weighing up the goals of risk assessment and constraints imposed by lack of data or expertise. Searching and filtering the Electronic Model Inventory then allows the assessor to locate specific models within those strategies that can be applied. This DSS was tested in seven case studies covering a range of risk assessment scenarios, pest types and dispersal mechanisms. These demonstrate the effectiveness of the DSS for selecting models that can be applied to contribute to EFSA Plant Health risk assessments. Therefore, quantitative spread and dispersal modelling has potential to improve current risk assessment protocols and contribute to reducing the serious impacts of plant pests in Europe.
Publisher Summary
This chapter examines some representative rivers of the British Isles that encompass much of the geographical diversity. These include the northern rivers of the Spey, Tay and Tweed that drain mountainous parts of Scotland. In England and Wales, the focus shifts initially to rural rivers that have upland headwaters but also more marked lowland influences, including the Severn and Wye. The chapter assesses those rivers that drain catchments with more dominant urban influences. The small Frome–Piddle River in southern England shifts attention back to lowland catchments, albeit of a much more rural character. The river Shannon is the largest river system considered and lies within the Republic of Ireland. It has a distinct history and quite different character to the rivers on the British mainland. The chapter describes these rivers within a wider systematic consideration of the environmental characteristics of the British Isles. It describes the general geographical setting of the region and outlines the main topographic, climatic, and land use characteristics of this area. It also examines the way in which these factors produce a wide spectrum of geomorphic, hydrological, and biogeochemical characteristics and considers the manner in which this physico-chemical template affects the biodiversity of riverine and freshwater habitats. The chapter further reviews how a long legacy of increasingly intense human-environment interactions have affected these rivers and how future environmental changes are likely to be mediated by the increasingly sophisticated institutional arrangements that have evolved for their sustainable management.
1. The invasion of fynbos shrublands by woody weed species can reduce the water yield from catchment areas dramatically. We modelled the consequences of uncontrolled invasion on water yield using a geographical information system (Arc/Info). 2. Five important processes were recognized: the occurrence of fire; the spread and establishment of alien plants after fire; rainfall-to-run-off ratios; growth and changes in biomass between fires; and effects of these changes on streamflow. 3. The simulations of water yield were modelled with the Arc/Info GRID module using a 200 x 200-m grid. It was assumed that the interval between fires was 15 years and that proliferation and dispersal of alien plants took place only after fires. 4. Between fires, the model simulated the growth of the vegetation and its effects on streamflow, using relationships between rainfall and run-off, and run-off and above-ground biomass. 5. Results for the Kogelberg area in the Western Cape Province showed that alien plants invaded about 40% of the grid cells within 50 years. Cover of alien plants increased from an initial estimate of 2.4% to 62.4% after 100 years. 6. Invasion of catchment areas would result in an average decrease of 347 m3 of water per hectare per year over 100 years, resulting in average losses of more than 30% of the water supply to the city of Cape Town. In individual years, where large areas would be covered by mature trees, losses would be much greater. 7. In addition, invasion of fynbos by alien plants will cause the extinction of many plant species, increase the intensity of fires, destabilize catchment areas with resultant erosion and diminished water quality, and decrease the aesthetic appeal of mountain areas. 8. Control of alien weed species is necessary to avert the above impacts, and the costs of control operations could be justified by the savings achieved in maintaining adequate water run-off from stable catchments in the long term.
Describes the distribution, history, habitat, communities, autecology, reproduction and associated organisms of Indian balsam. Impatiens glandulifera is an alien, but completely naturalized in Britain on the banks of many types of waterways, waste ground, thin woodlands and occasionally mires. -from Authors
Impatiens glandulifera was estimated as having a rate of spread of up to 38 km yr-1, compared to a rate of up to 24 km yr-1 for I. parviflora. Impatiens capensis was also studied. The use of vice-county data as opposed to 10 km squares is discussed. To identify characters which enabled I. glandulifera to be so successful, frost tolerance and seed output seem to be important factors. Occasional long distance dispersal events, probably aided by humans, are considered to be responsible for the rapid spread of I. glandulifera. Impatiens glandulifera is a pest plant because it forms dense monospecific stands in damp woodland, swamping all other plants. It is able to do so because of early germination and rapid growth to a height higher than any other British annual. Local spread is limited to 2 m yr-1 from its own ballistic dispersal and to a small multiple of that from animal spread. -from Authors
. Palaeoecologists have shown that trees migrated at rates of 100–1000 m/yr in response to post-glacial warming. In order to predict the impact of forecast anthropogenic climate changes upon forest ecosystems we need to simulate how trees may migrate in response to the changes predicted for the next 1–2 centuries. These predictions must take account of the impacts upon migration of human land-use and habitat fragmentation. We have developed a spatially-explicit mechanistic model (MIGRATE) able to simulate the migration of a single species across a realistically heterogeneous landscape. MIGRATE uses biological parameters that readily may be estimated from data in the literature or from field studies, and represents the landscape as a grid of cells, each with an associated carrying capacity. A one-dimensional version of MIGRATE has been compared both with Skellam's (1951) diffusion model and with the more recent analytical models of van den Bosch et al. (1990, 1992); despite its fundamentally different approach, MIGRATE provides comparable estimates of migration rates, given equivalent input parameters. An example is described that demonstrates the ability of the two-dimensional version of MIGRATE to simulate the likely pattern of spread of a species across a heterogeneous landscape. It is argued that MIGRATE, or models like it, will play a central role in a spatially-hierarchic modelling strategy that must be developed if we are to achieve the goal of simulating the likely response of trees, and other organisms, to both global climate change and the increasing pressures of human land-use.
SUMMARY (I) We evaluated through simulation the spatial growth of an invading terrestrial plant population and various strategies for its control. The initial population comprised a single large expanding focus but had the potential for the continual establishment of new foci. (2) We compared the area occupied through the establishment and expansion of these "satellite" foci to the area occupied by the initially large or main focus under varying regimens of repeated control, in which either the area of the main focus was reduced or some satellites were destroyed, or both. (3) Whether varying growth rates for the foci, rates of satellite establishment, the level of reduction of the main focus or the intensity of satellite detection and destruction, the overall effectiveness of control measures was greatly improved by destroying even 30% of the satellites. (4) These predictions contrast with much current practice in the control of alien plants, where large or otherwise conspicuous infestations are often treated at the expense of eradicating isolated populations while they still remain small. As supported by empirical precedents, consistent implementation of the general strategy suggested by our model should improve the control of alien plants.
1. The prediction of water quality is increasingly required in river catchment management, but methods are still developmental. We therefore derived empirical models to predict the concentrations of base cations, H+ and alkalinity at any point in a complex Scottish river system, and under diverse discharge conditions. Input data were readily available from geological and topographic maps, whole rock composition data and catchment land use inventories in geographical information systems (GIS).
2. A key and novel feature of the model was prediction using geological data for the riparian zone within 50 m of the river. The discharge contributions that passed through soil derived from each parent rock were estimated and used as weightings in predicting final run-off quality.
3. Typical equations for upland catchments for mean, maximum or minimum river water Ca concentration, [Ca], were of the form [Ca] = a + b √{Carz}, where {Carz} denotes flow routing-weighted rock CaO concentration of the riparian zone rock types present. These equations were significant at P < 0·0001. Similar approaches were applicable to alkalinity and to other base cations.
4. Predictions of [Ca] in catchments with mixed land use were improved by including model terms for catchment riparian zone cover of agriculturally improved (intensified) grassland and arable land. These results indicated anthropogenic effects on base cation flux that would not be represented by geological data alone.
5. Similarly, concentrations of Na, Mg and K were correlated with Cl concentration in the river water, primarily as a consequence of marine-derived Cl. Including distance from the east coast as a predictive variable in place of [Cl] obviated the need for direct [Cl] measurement in model operation.
6. We advocate further work to assess whether similar models can be developed and applied in other geographical locations, where features such as land use, geology and sea salt inputs will all vary.
1. The Mediterranean monk seal is an endangered marine mammal with only a few populations thought to be viable. The largest aggregation of this species is found at the Peninsula of Cap Blanc, on the western Sahara, where a colonial structure is maintained. The size of this colony is estimated by annual capture–recapture surveys, but it is unclear if the attained level of precision is enough to detect changes in numbers in the short term.
2. In this study, simulated capture–recapture experiments were used to investigate the relationship between population estimates and abundance. The statistical power necessary to detect a population decline with ongoing surveys was estimated, and the requirements for an improvement in precision were evaluated. Additionally, changes in abundance over consecutive surveys were examined for comparison with an alternative method of Bayesian inference.
3. Results indicated that the power to detect trends from the actual surveys was lower than should be required for the conservation of a small population, such as the colony at Cap Blanc. A 5% annual rate of decline in abundance would only be detected with high power after 12 years, with a population of 317 seals being reduced to 172. If the annual rate of decline was 10%, 8 years would be required to detect a reduction of 317 to 136 seals.
4. Capture–recapture surveys can produce reliable data but do not identify moderate or low population declines. The increase in precision of surveys is costly and time consuming, and other monitoring methods are needed to detect early signs of a decline. Bayesian methods cannot provide a better result because they are not robust to small sample size and heterogeneity in capture probabilities. Despite the need for alternative methods for earlier detection, capture–recapture surveys are still required to estimate the size of the colony, and precision in population estimates can be evaluated in relation to cost effectiveness.
1. There is still some uncertainty about large-scale influences on nutrient budgets in rivers. In particular, reduced forms of nitrogen (N) in organic forms might represent a significant fraction of the soluble N present in headwater streams, but this is not well quantified. Nitrate increases in relative importance downstream within agriculturally dominated areas. Here we appraise variations in N dynamics for a representative temperate but upland river, the Dee.
2. In the Dee catchment, the source of organic N appears to vary seasonally. During summer under low flow conditions it originates primarily from in-stream biological production, while during the winter–spring period leaching from the plant–soil system would be the major contributor.
3. On any individual sampling day, a wide range of N : P ratios can occur in the catchment area. Generally the narrowest N : P ratios occur during the summer and early autumn, particularly for upland catchments dominated by semi-natural vegetation. It is possible that some of the tributaries and upper region of the main river may be limited by N during the summer. The interpretation of the N : P ratios depends greatly upon the potential biological availability of the organic N, which remains unknown.
4. Together, these data further illustrate that simple ideas about the relative limiting effects of N and P in temperate freshwaters may be misleading.
1) The invasion of the fynbos by woody weed species can reduce water yield from catchment areas dramatically. We modelled the conseuences of uncontrolled invasion on water yield using a geogrpahical information system(Arc/Info).
2) Five important processes were recognised: the occurrence of fire; the spread and establishment of alien plants after fire; rainfall to run-off ratios; growth and changes in biomass between fires; and effects of these changes on streamflow.
3) The simulations of water yield were modelled with Arc/Info GRID module using a 200 x 200m grid. It was assumed that the interval between fires was 15 years and that proliferation and dispersal of alien plants took place only after these fires.
4) Between fires, the model simulated the growth of vegetation and its effects on streamflow, using relationships between rainfall and run-off, and run-off and aboveground biomass.
5) Results for the Kogelberg area in the Western Cape Province showed that alien plants invaded 40% of teh grid cells within 50 years. Cover of alien plants increased from an initial estimate of 2.4% to 62.4% after 100 years.
6) Invasion of catchments would result in a average decrease of 347m3 of water per hectare per year over 100years, resulting in average losses of more than 30% of the water supply to the City of Cape Town. In individual years, where large areas would be covered by mature trees, losses would be greater.
7) In addition, invasion of fynbos by alien plants will cause the extinction of many plant species, increase the intensity of fires, destabilise catchment areas with resultant erosion and diminished water quality, and decrease the aesthetic appeal of mountain areas.
8) Control of alien weed species is necessary to avert the above impacts, and the costs of control operations could be justified by the savings achieved in maintaining adequate water run-off from stable catchments in the long-term.
The use of a spatially explicit model to simulate the spread of riparian weeds. Species Dispersal and Land Use Processes
- Y C Collingham
- B Huntley
- P E Hulme
- Y C Collingham
- B Huntley
- P E Hulme
Seasonal dynamics ofImpatiens glanduliferain two riparian localities in central England
- K Prach
Habitat suitability and the distribution of alien weeds of riparian ecosystems. Species Dispersal and Land Use Processes
- S G Willis
- P E Hulme
- B Huntley
- S G Willis
- P E Hulme
- B Huntley
Control and management of Heracleum mante-gazzianum (giant hogweed) Ecology and Management of Invasive Riverside Plants
- F S Dodd
- L C Waal
- P M Wade
- G E D Tiley
Dodd, F.S., de Waal, L.C., Wade, P.M. & Tiley, G.E.D. (1994) Control and management of Heracleum mante-gazzianum (giant hogweed). Ecology and Management of Invasive Riverside Plants (eds L.C. de Waal, L.E. Child, P.M. Wade & J.H. Brock), pp. 111±126. John Wiley & Sons, Chichester, UK.
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