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Metapopulation growth rates in response to the early detection rapid response (EDRR) random, and the monitoring and source population management every year strategies, plotted against metapopulation growth rate without management for 20 yr with 15 initial populations, short distance dispersal, and 25 viable propagules produced annually by the source populations.
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Many land managers are faced with trying to optimize management of invasive plant species based on budget constraints and lack of knowledge of the true potential of the species. Generally, “early detection rapid response” (EDRR) is the assumed best management strategy and tends to drive management regardless of the invasion stage or possible variat...
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Context 1
... in the greatest number of populations in the management area, and in the highest l M . Management of populations was only able to slow the invasions (not cause decline) over the 20-yr simulation when starting from an early detection scenario (15 populations) or a later detection scenario (30 populations). When detection was allowed to occur earlier in the invasion ( # 10 populations), some management strategies could consistently drive the metapopulation to extinction or set it on a trend to extinction. The EDRR that restricted management to roadsides was the least effective management strategy for reducing the number of populations, regardless of the initial conditions or parameter value changes. This result was disconcerting considering the prevalence of management restricted to roadsides. Managing 10 populations per year of unknown type along the road had only a 0.54 probability of reducing the number of populations, more than no management after 6 yr, and 0.55 probability after 12 yr (Table 1). Managing 10 populations per year of unknown type (EDRR random), but not restricted to the roadside, was consistently the most effective strategy for reducing the number of populations in the management area over the first 10 yr (Figure 4). However, managing 5 source populations per year using monitoring to identify the source populations became the most effective strategy for reducing the number of populations in the management area after 10 yr (Figure 4). The monitoring to detect and manage source populations every year was the only strategy that reduced the metapopulation growth rate to near equilibrium ( l M 5 1.006) over the 20-yr simulation for the early invasion scenario (Table 1). It was assumed that half of the time dedicated to invasive plant management, crews were making measurements that would allow determination of which populations were sources of new populations, and using that knowledge to restrict management to the source populations. The simulations suggested a 0.98 probability that managing 5 source populations per year would reduce population numbers more than no management after 12 yr, and a 0.99 probability that it would reduce populations below the standard approach of managing 10 populations per year of unknown type along the road (Table 1). The simulations suggest that the strategy of using half of the management time for monitoring was not as effective for reducing the number of populations if management was only conducted on even years, and odd years were totally dedicated to monitoring. When initial number of populations was increased (Figure 5), or initial populations were restricted to occur along the road (Table 2), the monitoring and managing of 5 source populations continued to be the most effective strategy for slowing the invasion if the simulation was run for more than 10 yr. The results were consistent when dispersal distance was varied and metapopulation growth rates were held between 1.0 and 1.3 (data not shown). Simulation results starting with 15 populations distributed along the road indicated some improvement in the standard road management strategy (Table 2). The probability of management restricted to the road reducing the population below that of no management increased from 0.55 to 0.78 after 12 yr of simulated invasion. The initial roadside distribution of populations may simulate the earliest stages of invasion, where the road serves as a vector of introduction, but new populations disperse away from the roadside. The management strategies that included monitoring and managing source populations every year, or randomly choosing populations to manage without regard to their location (EDRR random), continued to be most effective for reducing the number of populations and decreasing the metapopulation growth rates over the 20-yr simulation (Table 2). If the habitat for the invasive species was restricted to the roadside, the road limited management strategy may perform much better relative to the other strategies (simulations not conducted). Results presented thus far indicate little difference between the EDRR random location management approach and the monitoring and managing source populations approach in the first 10 yr following initiation of management. Further simulations were conducted to determine under what unmanaged metapopulation growth rates and initial conditions one of these management approaches may be more likely than the other to reduce the metapopulation growth rate. Metapopulation growth rate was varied by increasing the number of viable propagules dispersed by source populations, and the metapopulation growth rates in response to EDRR random, and monitoring and managing source populations every year, were compared (Figure 6). The results suggested that the monitoring and managing source population strategy may be more effective than the EDRR random strategy for metapopulation growth rates between 1.05 and 1.15 over a 20-yr management period (Figure 6). It is not clear how significant the differences were between metapopulation growth rates in the range l M 5 1.0 to 1.2, but improved methods to monitor metapopulation growth rates may help identify which of these two strategies may be most effective for management of an invasion. The simulations suggested that if newly introduced populations can be identified early enough, and a high proportion of them ( . 67 % ) can be controlled (made to go extinct) then knowledge of which populations are sources (monitoring) will not be as valuable for managing the metapopulation. The simulations clearly demonstrated the reliance of the EDRR random management strategy on early and high population detection rates and high management efficacy (population removal), if budgets restrict the number of populations that can be eradicated. These aspects may not be easy to achieve, and thus further support the value of targeting management based on knowledge of the potential of population to be sources of further invasion (monitoring). Results of the simulations consistently indicated that monitoring to identify source populations, even with delay in the success of monitoring and only being able to manage half the populations, was an effective strategy when detection limitations allowed more than 10 populations to be present before initiation of management. When simulations were started with less than 10 populations, the EDRR random and the monitoring and management of source population approaches would frequently cause total extinction, supporting both strategies. However, detection would become limiting as more populations were able to become established, particularly away from the roads. Thus, the value in identifying source populations increased as the number of years of simulation was increased. Early detection is, by definition, plagued by the fact that the species occurs with low frequency and thus becomes increasingly costly to detect in the early phase of an invasion. Thus, invasions may rarely be detected early enough for EDRR to be the most effective strategy for reducing the invasion rate into a management area. Even with the penalty of not being able to manage as many populations because time is committed to monitoring, the value of knowing which populations are sources and would thus be the target of management becomes more valuable as an invasion progresses. The success of the monitoring based strategy is dependent upon the ability to efficiently and rapidly differentiate between source and nonsource populations. If source population occurrence could be correlated with environmental variables that are easy to map, and thus allow the ability to interpolate monitoring results across management areas and regions, then the number of populations managed could be increased over time on the fixed budget, and the strategy may be even more effective. These dependencies define a research agenda that includes development of field methods that will efficiently quantify the invasion or source potential of populations, and determine the ability to interpolate results. The model used for the above assessment of invasive plant monitoring and management strategies has several limitations that should be considered along with the conclusions that have been drawn. The model does not consider spatial heterogeneity or habitat preference in the management area and it does not directly combine the influence of existing populations on the probability of new populations. In addition, the model is limited by artificial classification of the population types, when in reality, populations represent a continuum of invasion potential (Mack et al. 2000). The model predicts exponential unregulated invasion, but includes the equally unrealistic, but offsetting assumption, of eradication of all managed populations. The transition rates between population types could be altered, but without empirical base we chose to assume equal transition rates between population types. The management approaches that include monitoring assume a cost associated with monitoring, but no cost was assumed for finding populations away from the road (EDRR random strategy). The model limitations tend to be offsetting, and thus are unlikely to change the generalized result, but they restrict use of the model to predict species-specific dynamics because the parameters do not lend themselves to empirical ...
Context 2
... population number in the management area had little influence on the unmanaged metapopulation growth rate ( l M was 1.127 starting with 15 populations, and 1.124 starting with 30 populations). The no-management control always resulted in the greatest number of populations in the management area, and in the highest l M . Management of populations was only able to slow the invasions (not cause decline) over the 20-yr simulation when starting from an early detection scenario (15 populations) or a later detection scenario (30 populations). When detection was allowed to occur earlier in the invasion ( # 10 populations), some management strategies could consistently drive the metapopulation to extinction or set it on a trend to extinction. The EDRR that restricted management to roadsides was the least effective management strategy for reducing the number of populations, regardless of the initial conditions or parameter value changes. This result was disconcerting considering the prevalence of management restricted to roadsides. Managing 10 populations per year of unknown type along the road had only a 0.54 probability of reducing the number of populations, more than no management after 6 yr, and 0.55 probability after 12 yr (Table 1). Managing 10 populations per year of unknown type (EDRR random), but not restricted to the roadside, was consistently the most effective strategy for reducing the number of populations in the management area over the first 10 yr (Figure 4). However, managing 5 source populations per year using monitoring to identify the source populations became the most effective strategy for reducing the number of populations in the management area after 10 yr (Figure 4). The monitoring to detect and manage source populations every year was the only strategy that reduced the metapopulation growth rate to near equilibrium ( l M 5 1.006) over the 20-yr simulation for the early invasion scenario (Table 1). It was assumed that half of the time dedicated to invasive plant management, crews were making measurements that would allow determination of which populations were sources of new populations, and using that knowledge to restrict management to the source populations. The simulations suggested a 0.98 probability that managing 5 source populations per year would reduce population numbers more than no management after 12 yr, and a 0.99 probability that it would reduce populations below the standard approach of managing 10 populations per year of unknown type along the road (Table 1). The simulations suggest that the strategy of using half of the management time for monitoring was not as effective for reducing the number of populations if management was only conducted on even years, and odd years were totally dedicated to monitoring. When initial number of populations was increased (Figure 5), or initial populations were restricted to occur along the road (Table 2), the monitoring and managing of 5 source populations continued to be the most effective strategy for slowing the invasion if the simulation was run for more than 10 yr. The results were consistent when dispersal distance was varied and metapopulation growth rates were held between 1.0 and 1.3 (data not shown). Simulation results starting with 15 populations distributed along the road indicated some improvement in the standard road management strategy (Table 2). The probability of management restricted to the road reducing the population below that of no management increased from 0.55 to 0.78 after 12 yr of simulated invasion. The initial roadside distribution of populations may simulate the earliest stages of invasion, where the road serves as a vector of introduction, but new populations disperse away from the roadside. The management strategies that included monitoring and managing source populations every year, or randomly choosing populations to manage without regard to their location (EDRR random), continued to be most effective for reducing the number of populations and decreasing the metapopulation growth rates over the 20-yr simulation (Table 2). If the habitat for the invasive species was restricted to the roadside, the road limited management strategy may perform much better relative to the other strategies (simulations not conducted). Results presented thus far indicate little difference between the EDRR random location management approach and the monitoring and managing source populations approach in the first 10 yr following initiation of management. Further simulations were conducted to determine under what unmanaged metapopulation growth rates and initial conditions one of these management approaches may be more likely than the other to reduce the metapopulation growth rate. Metapopulation growth rate was varied by increasing the number of viable propagules dispersed by source populations, and the metapopulation growth rates in response to EDRR random, and monitoring and managing source populations every year, were compared (Figure 6). The results suggested that the monitoring and managing source population strategy may be more effective than the EDRR random strategy for metapopulation growth rates between 1.05 and 1.15 over a 20-yr management period (Figure 6). It is not clear how significant the differences were between metapopulation growth rates in the range l M 5 1.0 to 1.2, but improved methods to monitor metapopulation growth rates may help identify which of these two strategies may be most effective for management of an invasion. The simulations suggested that if newly introduced populations can be identified early enough, and a high proportion of them ( . 67 % ) can be controlled (made to go extinct) then knowledge of which populations are sources (monitoring) will not be as valuable for managing the metapopulation. The simulations clearly demonstrated the reliance of the EDRR random management strategy on early and high population detection rates and high management efficacy (population removal), if budgets restrict the number of populations that can be eradicated. These aspects may not be easy to achieve, and thus further support the value of targeting management based on knowledge of the potential of population to be sources of further invasion (monitoring). Results of the simulations consistently indicated that monitoring to identify source populations, even with delay in the success of monitoring and only being able to manage half the populations, was an effective strategy when detection limitations allowed more than 10 populations to be present before initiation of management. When simulations were started with less than 10 populations, the EDRR random and the monitoring and management of source population approaches would frequently cause total extinction, supporting both strategies. However, detection would become limiting as more populations were able to become established, particularly away from the roads. Thus, the value in identifying source populations increased as the number of years of simulation was increased. Early detection is, by definition, plagued by the fact that the species occurs with low frequency and thus becomes increasingly costly to detect in the early phase of an invasion. Thus, invasions may rarely be detected early enough for EDRR to be the most effective strategy for reducing the invasion rate into a management area. Even with the penalty of not being able to manage as many populations because time is committed to monitoring, the value of knowing which populations are sources and would thus be the target of management becomes more valuable as an invasion progresses. The success of the monitoring based strategy is dependent upon the ability to efficiently and rapidly differentiate between source and nonsource populations. If source population occurrence could be correlated with environmental variables that are easy to map, and thus allow the ability to interpolate monitoring results across management areas and regions, then the number of populations managed could be increased over time on the fixed budget, and the strategy may be even more effective. These dependencies define a research agenda that includes development of field methods that will efficiently quantify the invasion or source potential of populations, and determine the ability to interpolate results. The model used for the above assessment of invasive plant monitoring and management strategies has several limitations that should be considered along with the conclusions that have been drawn. The model does not consider spatial heterogeneity or habitat preference in the management area and it does not directly combine the influence of existing populations on the probability of new populations. In addition, the model is limited by artificial classification of the population types, when in reality, populations represent a continuum of invasion potential (Mack et al. 2000). The model predicts exponential unregulated invasion, but includes the equally unrealistic, but offsetting assumption, of eradication of all managed populations. The transition rates between population types could be altered, but without empirical base we chose to assume equal transition rates between population types. The management approaches that include monitoring assume a cost associated with monitoring, but no cost was assumed for finding populations away from the road (EDRR random strategy). The model limitations tend to be offsetting, and thus are unlikely to change the generalized result, but they restrict use of the model to predict species-specific dynamics because the parameters do not lend themselves to empirical ...
Citations
... Simberloff [62] has stated that there are reasons to believe that many invasive plant populations could be eradicated, especially if eradication is coupled with a monitoring system that detects invasions at an early stage. In addition to early detection, monitoring of existing populations of invasive non-native species is also part of an effective invasion control strategy [63][64][65][66]. This early data can help to understand how these invasive plants are affected by land cover, disturbance regimes and local climatic conditions [67], which could be crucial to ensure a timely response and create efficient prevention plans. ...
Citation: Avramov, S.; Miljković, D.; Barišić Klisarić, N.; Živković, U.; Tarasjev, A. Multi-Year Monitoring of Asclepias syriaca L. Spread in the Deliblato Sands Protected Reserve in Serbia. Forests 2024, 15, 347. Abstract: The invasion of non-native plant species has a detrimental effect on native biodiversity. In a seven-year research project, we investigated the occurrence of the invasive species Asclepias syriaca L.in the Deliblato Sands protected area, located at a southeastern part of the Pannonian Plain, and identified the factors that contribute significantly to its colonisation. The distribution of this invasive species was monitored on more than 300 km of the accessory, bordering and selected internal roads. A. syriaca occurs within the protected area but is much more widespread on accessory and bordering roads. The number of locations of A. syriaca increased every year of the study, even within the protected area, indicating a further spread of this species. A. syriaca is much more abundant on the northeastern edge than in the southwest. The reason for this is most likely the much larger area of abandoned agricultural land in the northeast. Roads used for public transport are the main entry points for the further spread of A. syriaca. In contrast, recreational trail use does not enhance the spread in the Deliblato Sands natural reserve. This study can be used to further analyse the ecological dynamics of A. syriaca and to develop timely strategies by which to prevent or slow down its spread.
... Effective management strategies seek to identify high risk areas and invading populations early in their development [27]. A variety of such management strategies for pine trees have been proposed (see for example [23] or [20]). Some approaches attempt to reduce spread by eliminating 'source' populations of established trees, as these contribute more seed than peripheral populations [8]. ...
Invasive pine trees pose a threat to biodiversity in a variety of Southern Hemisphere countries, but understanding of the dynamics of invasions and the factors that retard or accelerate spread is limited. Here, we consider the past models of wilding pine spread and develop a new model of pine invasion. We show that many prior models feature parameter estimates which are not biologically supported and rely on a conjecture to obtain an asymptotic spread speed of invasive pine populations, the main output of these models. In contrast to prior approaches, we use partial differential equations to model an invasion. We show that invasions are almost static for a significant period of time before rapidly accelerating to spread at a constant rate, matching observed behaviour in at least some field sites. Our work suggests that prior methods for estimating invasion speeds may not accurately predict spread and are sensitive to assumptions about the distribution of parameters. However, we present alternative estimation methods and suggest directions for further research.
... To date, metapopulation concepts and models have been combined with data to inform various aspects of conservation and species management such as habitat protection, regulation of harvest, reserve design, and reintroduction (reviewed in Akçakaya et al., 2007). Similarly, they have been used to inform management of a diversity of invasive species including birds (Lenda et al., 2010), fish (Tamburello et al., 2019), mammals (Lurgi et al., 2016), gastropods (Facon & David, 2006), insects (Bogich & Shea, 2008), and plants (James et al., 2011;Maxwell et al., 2009). In addition, there have been a number of general theoretical treatments of invasive species management in spatially structured populations (e.g., Baker, 2017;Pepin et al., 2020;Perry et al., 2017). ...
Metapopulation models may be applied to inform natural resource management to guide actions targeted at location‐specific subpopulations. Model insights frequently help to understand which subpopulations to target and highlight the importance of connections among subpopulations. For example, managers often treat aquatic invasive species populations as discrete populations due to hydrological (e.g., lakes, pools formed by dams) or jurisdictional boundaries (e.g., river segments by country or jurisdictional units such as states or provinces). However, aquatic invasive species often have high rates of dispersion and migration among heterogenous locations, which complicates traditional metapopulation models and may not conform to management boundaries. Controlling invasive species requires consideration of spatial dynamics because local management activities (e.g., harvest, movement deterrents) may have important impacts on connected subpopulations. We expand upon previous work to create a spatial linear matrix model for an aquatic invasive species, Bighead Carp, in the Illinois River, USA, to examine the per capita contributions of specific subpopulations and impacts of different management scenarios on these subpopulations. Managers currently seek to prevent Bighead Carp from invading the Great Lakes via a connection between the Illinois Waterway and Lake Michigan by allocating management actions across a series of river pools. We applied the model to highlight how spatial variation in movement rates and recruitment can affect decisions about where management activities might occur. We found that where the model suggested management actions should occur depend crucially on the specific management goal (i.e., limiting the growth rate of the metapopulation vs. limiting the growth rate of the invasion front) and the per capita recruitment rate in downstream pools. Our findings illustrate the importance of linking metapopulation dynamics to management goals for invasive species control.
... Alternatively, Reaser et al. (2020) define EDRR as a "…a guiding principle for minimizing the impact of invasive plants in an expedited yet effective and cost efficient manner, where 'detection' is the process of observing and documenting an invasive plants, and 'response' is the process of reacting to the detection once the organism has been authoritatively identified and response options have been assessed." The use of EDRR, while proposed by many (e.g., Maxwell et al. 2009;Pyšek and Richardson 2010;Littell et al. 2012;Antunes and Schamp 2017), has not been shown to be entirely effective. Largely, the lack of suc-cess is knowing exactly how to implement "detection" and what the term "early" really means. ...
... salicaria), common reed (Phragmites australis), and garlic mustard (Alliaria petiolata), have been criticized for failing to provide sufficient supporting evidence (Blossey 1999). Such information may lead to inappropriate management strategies (Maxwell et al. 2009). Long-term monitoring of the invaded ecosystem, before, during, and after the invasion, is needed for a more comprehensive assessment of impacts (Blossey 1999). ...
... Alternatively, Reaser et al. (2020) define EDRR as a "…a guiding principle for minimizing the impact of invasive plants in an expedited yet effective and cost efficient manner, where 'detection' is the process of observing and documenting an invasive plants, and 'response' is the process of reacting to the detection once the organism has been authoritatively identified and response options have been assessed." The use of EDRR, while proposed by many (e.g., Maxwell et al. 2009;Pyšek and Richardson 2010;Littell et al. 2012;Antunes and Schamp 2017), has not been shown to be entirely effective. Largely, the lack of suc-cess is knowing exactly how to implement "detection" and what the term "early" really means. ...
... salicaria), common reed (Phragmites australis), and garlic mustard (Alliaria petiolata), have been criticized for failing to provide sufficient supporting evidence (Blossey 1999). Such information may lead to inappropriate management strategies (Maxwell et al. 2009). Long-term monitoring of the invaded ecosystem, before, during, and after the invasion, is needed for a more comprehensive assessment of impacts (Blossey 1999). ...
The invasion of alien species manipulates the structure, function, and composition of the recipient ecosystem causing ecological, economic, and social impacts. However, these impacts can be positive or negative, depending on the effect and context of the invasion. In some cases, invasions enhance primary productivity of the ecosystem and increase species richness. On the other hand, in the majority of cases, the invasive species displace native species, adversely impacting native ecosystem and jeopardizing natural resources. The outcome of the impacts is based on several factors, such as mode of introduction, type of invasive species, condition of the invaded habitat, and characteristics of native species. For instance, specialist native species are predicted to suffer adverse effects, while generalists may flourish even when invasive species are abundant. There has been considerable debate in recent times about whether claims of severe impacts of invasive species are exaggerated and whether efforts to manage them are unnecessary or even harmful, and some unintended consequences of invasive species management have been documented. Regardless of the lack of consensus on the impacts of invasive species, they are posing a measurable cost to society. Invasive species severely affect agriculture, fisheries, tourism, forestry, and property values. Countries that rely on agriculture with small landholders are the most vulnerable to the invasion of exotic species. The rate of spread of invasive species is currently surging due to increased travel, trade, and transport in combination with climate change. Accurate and comprehensive information on economic and environmental impacts of invasive species is seriously lacking, and more research is needed to develop management strategies based on the impacts of invasive species.KeywordsAgricultureBiodiversityEcosystem servicesFisheriesForestryLivelihoods
... Alternatively, Reaser et al. (2020) define EDRR as a "…a guiding principle for minimizing the impact of invasive plants in an expedited yet effective and cost efficient manner, where 'detection' is the process of observing and documenting an invasive plants, and 'response' is the process of reacting to the detection once the organism has been authoritatively identified and response options have been assessed." The use of EDRR, while proposed by many (e.g., Maxwell et al. 2009;Pyšek and Richardson 2010;Littell et al. 2012;Antunes and Schamp 2017), has not been shown to be entirely effective. Largely, the lack of suc-cess is knowing exactly how to implement "detection" and what the term "early" really means. ...
Due to numerous human activities, organisms have been transported and either accidentally or deliberately introduced all around the globe. Biological invasions are now considered to be one of the main drivers of global change because many invasive plants have severe ecological, economic, and health consequences. Thus, there is an ever-growing need to better understand invasions to determine how specific plant species are able to establish in communities and, in many cases, expand their range. Here, we describe the invasion process and how it contributes to the invasion of plant communities. We present an invasion-factor framework (IFF) model that uses three factors (climate dynamics, ecosystem resistance, and invader fitness) to explain how each plays a role in the introduction of plants and their ultimate failure or success (i.e., becoming invasive). The invasion of plant communities starts with the uptake of propagules from the native range, followed by their transport to and release into a new territory, where they become established and can spread or expand. Propagule pressure, prior adaptation, anthropogenically induced adaptation to invade, and post-introduction evolution are several theories that have been posed to explain the establishment of invasive plants. Further, traits of invasive plants, either before (existing) or after (developed) introduction, provide a mechanistic understanding with direct ties to the three factors of the IFF. The IFF is a general guide with which to study the invasion process based on specific factors for individual invaders and their target communities. The IFF combines (a) climatic dynamics, analogous to environmental filters; (b) ecosystem resistance, which prevents invasive plants from becoming established even if they are able to overcome the climate factor; and (c) invader fitness, relating to the genetic diversity of invasive plants, which allows them to become established after overcoming climate and ecosystem resistance factors. Case studies from the literature provide examples of research investigating each of the three factors of the IFF, but none exist that describe all the factors at once for any given invasive plant species. The application of the IFF for management is most appropriate once an invasive plant has become established, as preventative measures before this point rely only on accurate identification (detection) and removal (response). The IFF model should be considered as a tool to establish research priorities and identify components in the invasion process and inform restoration efforts. We advocate that the IFF should be integrated into management practices to help in the decision-making process that contributes to more effective practices that reduce the occurrence and impacts of invasive plants in a range of communities.
... Alternatively, Reaser et al. (2020) define EDRR as a "…a guiding principle for minimizing the impact of invasive plants in an expedited yet effective and cost efficient manner, where 'detection' is the process of observing and documenting an invasive plants, and 'response' is the process of reacting to the detection once the organism has been authoritatively identified and response options have been assessed." The use of EDRR, while proposed by many (e.g., Maxwell et al. 2009;Pyšek and Richardson 2010;Littell et al. 2012;Antunes and Schamp 2017), has not been shown to be entirely effective. Largely, the lack of suc-cess is knowing exactly how to implement "detection" and what the term "early" really means. ...
... salicaria), common reed (Phragmites australis), and garlic mustard (Alliaria petiolata), have been criticized for failing to provide sufficient supporting evidence (Blossey 1999). Such information may lead to inappropriate management strategies (Maxwell et al. 2009). Long-term monitoring of the invaded ecosystem, before, during, and after the invasion, is needed for a more comprehensive assessment of impacts (Blossey 1999). ...
The data available on the extent of global plant invasion shows a sharp increase in cases and associated costs over the last several decades. Indeed, most of the mixing of the planet’s flora due to human agency has occurred in the last 200 years. As in the case of rapidly emerging human pandemics that demand timely action, there have been urgent calls to stem the tide of plant invasions and prevent further spread and associated environmental and socioeconomic impacts. However, the response to most actual and potential plant invasions is far from simple. Naturalized plants have a broad range of impacts, such that a response specific to the particular plant species and habitat is often advisable, along with a meaningful dialog among stakeholders. Given the massive scale in changes of the flora in various regions, many naturalized species with minimal impacts are best left alone, whereas other naturalized species that have massive impacts warrant management to prevent further, often irreversible, effects on ecosystems. There exists a considerable array of invasive plants in this category, most of which are truly global, distributed on multiple continents. Of these high-impact invasive plant species, 37 are on the list of the International Union for Conservation of Nature (IUCN) 100 worst invasive alien species. Most of these high-impact species continue to spread in their non-native ranges, including sensitive island and mountain habitats. They also cause a range of socioeconomic impacts on agriculture, forestry, transportation, infrastructure, and cultural values. If current trends in plant invasions continue and are exacerbated by increasing global trade and climate change, many challenges lie ahead. We cannot turn back the clock to recover natural habitats free of invasive plants in most cases, but there are still ways of promoting ecosystem health through reducing populations of high-impact invasive plants and promoting holistic approaches to planet healing.KeywordsBiosurveillanceClimate changeGlobalizationInvasive plant costsIsland invasionsPlanet of weedsPlant invasion
... Alternatively, Reaser et al. (2020) define EDRR as a "…a guiding principle for minimizing the impact of invasive plants in an expedited yet effective and cost efficient manner, where 'detection' is the process of observing and documenting an invasive plants, and 'response' is the process of reacting to the detection once the organism has been authoritatively identified and response options have been assessed." The use of EDRR, while proposed by many (e.g., Maxwell et al. 2009;Pyšek and Richardson 2010;Littell et al. 2012;Antunes and Schamp 2017), has not been shown to be entirely effective. Largely, the lack of suc-cess is knowing exactly how to implement "detection" and what the term "early" really means. ...
... salicaria), common reed (Phragmites australis), and garlic mustard (Alliaria petiolata), have been criticized for failing to provide sufficient supporting evidence (Blossey 1999). Such information may lead to inappropriate management strategies (Maxwell et al. 2009). Long-term monitoring of the invaded ecosystem, before, during, and after the invasion, is needed for a more comprehensive assessment of impacts (Blossey 1999). ...
Humans have exchanged plant species beyond their native borders since millennia. The pathways of exchange and their relative importance have differed among regions, times and species. Here, we review the temporal developments of pathways of alien plant species introductions and how these relate to trends in alien plant species richness at a global scale. Although the rate of exchange of alien plants has grown steadily over time, significant advancements in human technological progress initiated new bursts of acceleration in global spread. Examples include the discovery of new seaways around 1500, the start of modern industrialisation in the early nineteenth century and the rise of global trade and human prosperity after World War II. Apart from a continuous intensification, the relative importance of pathways remained surprisingly stable. During the last 500 years, the introduction of plant species for cultivation represents the dominating pathway and was associated with more than half of all introductions. Although the relationship between horticulture and the occurrence of alien plants is often difficult to prove, the huge number of plants cultivated in the world makes it likely that, in the future, many introductions will continue to originate from private or public gardens. Indeed, horticulture remains the only introduction pathway which, up to now, has increased in relative importance among all pathways globally. Despite the rising awareness of the issues of introducing new alien species, the current socio-economic developments indicate that we have to expect many more alien plant species to come in the future.KeywordsBiological invasionsGlobalisationHistoricLong termNeophytesTime seriesWeeds
... 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 . On the other hand, studies focused on metapopulations often support prioritization of core populations that supply most of the new propagules 23,26,27 . Further, the optimal spatial arrangement of the control effort is considered to be highly context-dependent 5 . ...
... Therefore, if both source and destination functions influence dispersal success, our model suggests potential eradication success through simultaneous strategies that effectively weaken dispersals between core areas, where colonies tend to produce more propagules than other areas. Similar control strategies focusing on core populations have been suggested by metapopulation models 23,26,27 . These strategies have been applied in cases of invasive aquatic invertebrates and fish larvae transferred accidentally by ballast water 32,33 . ...
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.
... A number of management options are available for IAS, with their suitability depending on the invasive species traits, local social and environmental settings and their position on the introduction-naturalisation-invasion continuum (Blackburn et al. 2011;Wilson et al. 2011;Bach et al. 2019). Key parts of managing invasive species include monitoring the current state of invasion, monitoring management implementation effectiveness as well as anticipating further spread (Blossey 1999;Maxwell et al. 2009;Downey 2010;Shackleton et al. 2017). Effective monitoring is lacking for IAS management in many areas and for countless other environmental-related programmes, representing a major barrier to efficient environmental management Shackleton et al. 2016;Turner et al. 2016;van Wilgen et al. 2016). ...
Biological invasions are a major driver of human-induced global environmental change. This makes monitoring of potential spread, population changes and control measures necessary for guiding management. We illustrate the value of integrated methods (species distribution modelling (SDM), plant population monitoring and questionnaires) for monitoring and assessing invasions of Heracleum mantegazzianum (giant hogweed) over time in Switzerland. SDMs highlighted the potential spread of the species, uncovered ecological mechanisms underlying invasions and guided monitoring at a regional level. We used adaptive and repeat plant sampling to monitor invasive population status and changes, and assess the effectiveness of H. mantegazzianum management over three periods (2005, 2013 and 2018) within the pre-Alps, Vaud. We also conducted questionnaire surveys with managers and the public. Multiscale modelling, and integrating global and regional SDMs, provided the best predictions, showing that H. mantegazzianum can potentially invade large parts of Switzerland, especially below 2 000 m a.s.l. Over time, populations of invasive H. mantegazzianum in the Vaud pre-Alps have declined, which is most likely due to a sharp rise in management uptake post 2007 (7% of municipalities before 2007 to 86% in 2018). The level of known invasive populations has decreased by 54% over time. Some municipalities have even successfully eradicated H. mantegazzianum within their borders. However, a few areas, particularly in the rural, higher-altitude municipalities, where management was not implemented effectively, populations have expanded, which could hamper control efforts at lower altitudes. We provide encouraging evidence that control measures can be effective in reducing plant invasions with long-term commitment, as well as a good template for using integrated methodological approaches to better study and monitor invasive alien species.
