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This chapter argues that solutions to the management of invasive species need to be reworked to take into account the fact that invasive species can impact human livelihoods both negatively and positively. Besides the existing strategies for the management of invasive species, there is a need for alternative strategies in terms of the net benefit they yield, taking of course all benefits and costs into account. A specific case of control of invasive species in largely tropical landscapes is considered, with the attendant problems of human dependence on natural resources as well as lack of investment portfolios to control invasive species. Management strategies are proposed that promote use of the invasive as a way of minimizing the net costs of the invasive species.

Invasive species control is a public good. Once provided, the benefits it offers in terms of enhanced protection of human, animal, and plant health, and the productivity of agriculture, forestry, aquaculture, and fisheries, are available to everyone. Like all public goods it will be undersupplied if left to the market. This makes it a collective responsibility — a legitimate role of government at many different scales. This role involves two different functions. One is the development of broad strategies and supporting institutions, statutes, regulations, or agreements for addressing the problem. A second function involves the implementation of that policy, and specifically the use of public resources to undertake all of the actions described in this volume: inspection and interception at the port of entry; sanitary and phytosanitary measures both along pathways; and in situ detection, eradication, and control of harmful species that have been introduced, established, and spread. This chapter considers both broad issues of policy and specific challenges to management.

This chapter begins with a discussion of the impact of invasive species throughout human history, and the role of trade, transport, and travel in species introductions. It then considers the ecological and economic dimensions of the problem of invasive species, and policy and management options. The need to recognize the global dimension of the problem is discussed.

This chapter describes and critically evaluates the ‘state-of-the-art’ for national policy and management efforts designed to prevent the arrival of invasive species. Preventing the introduction of invasive species will almost always be less costly than managing and adapting to species once they arrive. Although this is widely recognized by biologists and economists, only a handful of countries have embraced this approach in their policies for environmental invaders. As nations work to meet their obligations under the Convention on Biological Diversity (CBD), it is likely that the number of countries with programs for preventing invasive species will grow.

This chapter reviews what is known about those invasive alien species that impact on the terrestrial, freshwater, and marine ecosystems of South Africa. It briefly reviews the pathways by which these species have arrived, how these pathways have changed over time, and how many have become invasive. It then considers the current levels of understanding with respect to impacts, both ecological and economic. This is followed by an account of the prognosis for the growth in these impacts should current trends continue.

This chapter reviews the literature to understand the significance of making decisions about the prevention and/or control of invasive alien species (IAS) that ignore impacts on ecosystem services. It reports damage costs associated with IAS in monetary terms. The costs presented for various provisioning, regulating, and cultural services may be roughly comparable since most of the literature mostly clusters around the early 2000s. Whether damage costs of any magnitude will change the way IAS is managed will naturally depend on the benefits of the activities that lead to the introduction and spread of each species. Identifying potential damage costs and estimating their magnitude is a positive first step towards properly accounting for the full impact of IAS.

This chapter constructs a model to analyze optimal policy and management to reduce damage from invasive species that includes strategies for information collection and control, to prevent introduction and to control already introduced species. The chapter is organized as follows. Section 8.2 presents the model of prevention, detection, and control. The model is analyzed, and results of the analysis are presented in Section 8.3. Section 8.4 contains a brief set of concluding remarks and a discussion of challenges needing further research.

Daniel Simberloff presents an overview of invasive species, their impacts and management in this chapter. Invasive species cause myriad sorts of conservation problems, many of which are complicated, some of which are subtle, and some of which are not manifested until long after a species is introduced. The best way to avoid such problems is to prevent introductions in the first place or, failing that, to find them quickly and eradicate them. However, many established introduced species can be managed by a variety of technologies so that their populations remain restricted and their impacts are minimized.

The risk posed by an introduced species depends on a number of factors, some of which are within the control of regulatory authorities and some of which are not. It is a product of the probability that imports will introduce new species and the expected damage done by those species. Among the risk factors taken as exogenous by the regulatory authorities are the invasiveness of the species itself (whether it is a generalist or a specialist, its plasticity, and so on), the bioclimatic similarity between the trading partners, the volume and composition of trade, and the vulnerability of the host (economic and ecological) system. The sanitary and phytosanitary (SPS) measures taken by the exporter may or may not be taken as exogenous. These together determine both the likelihood that a unit of trade will introduce species of different types and the expected damage if a particular species (or class of species) is introduced. This chapter focuses on the nature of the SPS response to the invasive species risks of international trade, and the effect this has on the dispersion of species. More particularly, it asks what determines current country-level decisions to mitigate the risks of species introductions or to adapt to the consequences of establishment and spread, and how these are reflected in the dispersion data.

This chapter explores the issue of whether policies toward invasive species should look like those adopted in response to other forms of ‘pollution’. It argues that this will depend on whether damages are low enough that preventing invasions should be seen as a ‘lost cause’ and abandoned, or if damages are high enough that prevention is a wise investment and significant resources should be put into preventing invasions. A simple model is developed that lays out these considerations. It is also shown that fixing parameters describing the demand for imports, their cost, and the cost of treating imports to reduce the likelihood of invasion allows the definition of the optimal strategy by reference to the anticipated damages resulting from invasion.

This chapter focuses on the spatial characteristics of invasive species management. Specifically, it looks at control of the spread of a species introduced to an area. It begins with a review of the emerging literature on the spatial economics of invasive species. The studies are reviewed in terms of their use of space: the inclusion of local heterogeneity and the analysis of a network of areas (i.e., two-patches versus multiple-patches). It is shown that most of the studies either focus on heterogeneity in simple landscapes with two patches, or on complex landscapes with multiple areas but ignoring spatial heterogeneity. The chapter develops a simple model to explore the role of spatial heterogeneity in invasive species management in a landscape with multiple areas. A final section recapitulates the main points and offers conclusions.

The concern over the introduction of invasive species into the Arctic environment has been relatively new. In the context of climate change, among many other consequences, the possible introduction of invasive species is one. Gradual access to the Arctic marine area, resulting from the opening up of the two new sea routes, facilitates the introduction of aquatic invasive species in its waters. The study suggests that, in Arctic waters, invasive species may primarily be introduced via four sources: ballast water exchange and treatment, hull fouling, cargo operations, as well as casualties or shipwrecks. The introduction of invasive species in Arctic waters will have multifaceted consequences, including the unexpected disturbance of its unique ecosystem, which will eventually pose diverse economic, health, and environmental problems, as well as an overall loss of native biodiversity. This chapter intends to achieve the following three objectives. Firstly, it will examine the overall concerns related to the introduction of invasive species into the Arctic. Secondly, it investigates which available international legislative mechanisms may be applicable to this context and how. Lastly, how invasive species are presently addressed in the Arctic governance regime.

This chapter presents analyses that suggest increasing levels of invasion will be observed with increasing climate change, and that invasions of species from far away will increase disproportionately. It suggests that climate change will require us to reconsider our attitudes to the distinction between native and non-native species, because many species are only expected to survive climate change by establishing in new regions, outside their historical ranges.

Range expansions, biological invasions, and disease spread are all inherently spatial processes that involve the successful introduction or colonization, establishment, and dispersal of organisms (or their propagules) into new areas. Population spatial spread thus involves the interaction of both dispersal and demography with landscape structure. This chapter begins by exploring landscape effects on species’ range shifts and the extent to which species can shift their distributions in response to future land-use and climate-change scenarios. Next, the chapter evaluates the effect that landscape structure might have on invasive spread, including an overview of spatial models that are used to predict whether, when, and how fast an invasive species is likely to spread. The chapter concludes with a discussion of disease spread in a landscape context (landscape epidemiology), which involves the study of how pathogens, vectors, and hosts interact with environmental heterogeneity to influence the incidence and persistence of disease in an area.

An exotic or native species from one continent may spread quickly and dominate wetlands in another continent. Such species are known as invasive species and may displace other native species in wetlands. In the United States, more than 50,000 species of plants, animals, and microorganisms are believed to have been introduced to wetlands. This chapter examines what makes some species invasive, the effects of invasive species on wetlands, and what should be done to control invasive species. It looks at two hypotheses that have been proposed to explain why some plant species become invasive: the landscape sink or disturbance hypothesis, and the superior competitor hypothesis. According to the landscape sink/disturbance hypothesis, a wetland becomes more susceptible to invasion due to changes in hydrology, water chemistry, or physical disturbances. The superior competitor hypothesis emphasises the ability of invasive species to outcompete and displace the native species. This hypothesis has many variants, including enemy release, hybrid vigor, allelopathy, broader tolerance, efficient use, and empty niche.

This chapter discusses the use of ecological niche modeling to study species invasions, and more specifically to identify and understand genuine exceptions to ecological niche equivalency between native and introduced ranges of species. In addition, it examines the degree to which the geographic course of species’ invasions can be anticipated based on scenopoetic variables and biotic interactions. The chapter also reviews practical considerations that must be taken into account when exploring the utility of ecological niche models in understanding species’ invasions, such as using niche conservatism to predict likely changes in the distributional potential of invasive species under scenarios of changing environmental conditions. Finally, it describes caveats and limitations of the approach and outlines future research directions and challenges involved in the application of niche modeling ideas in species invasions.

The Endangered Species Act (ESA) was enacted to promote the conservation of threatened and endangered plants and animals and to preserve their critical habitats. Invasive species continue to compromise the effectiveness of the ESA. Today, more than 40 percent of all species listed on the endangered species list have been or continue to be significantly impacted by invasive species within their range. For marine protected species, the impacts are significant. Invasive species established in U.S. waters have altered critical habitats and trophic dynamics, decreased juvenile recruitment through increased predation on native species, increased parasitism, altered genetic diversity, decreased species resilience, impaired nutrient cycling and altered water quality, and have reduced marine biodiversity. This chapter addresses the application of the ESA to a rapidly changing marine environment, with emphasis on how current responses to marine invasive species and climate change may affect implementation of the ESA to marine species.

The chapter describes the geology, oceanography, and patterns of biogeography of the California kelp forests. The structure and biodiversity of the kelp forest food web for all trophic guilds is described as well as findings from experimental manipulations and long time series studies. The chapter finishes with a discussion of the role of fishing, habitat loss, and climate change on these kelp forests.

The rapid and often shocking consequences of the spread of invasive species has led to calls for the application of rules of thumb in their management. This contrasts significantly with arguments that in these types of situations, effort-intensive characterizations of optimal rules of management are likely to be worthwhile. To provide some insight into this debate facing policy makers, this chapter weighs the trade-offs, and characterizes critical parameters of applying simple decision rules in contrast to dynamically optimal decision rules for a simple example of the management of invasive species. It poses the question of whether or not managers can use second-best policies that do not vary over time, nor as conditions change, and not significantly waste resources in comparison to first-best programs of dynamically optimal management which might vary tremendously over time or as conditions change. Over an infinite time horizon, second-best policies always waste some resources compared to first-best policies, but the magnitude of the waste tends to be small. In situations with fast-spreading invasions, low rates of growth in marginal damages, and high rates of growth in marginal costs, second-best policies will waste less compared to dynamically optimal policies. In the opposite circumstances, with slowly spreading invasions, high rates of growth in marginal damages, and low rates of growth in marginal costs, second-best policies will waste more in total compared to dynamically optimal policies.