Developing National Strategies to Combat Biological Invasions


Invasive Alien Species: a Toolkit of Best Prevention and Management Practices. Wittenberg, R., and M. J. W. Cock , editors . 2001 . CAB International Publishing , Wallingford, United Kingdom . 228 pp. $50.00 ( free of charge to developing nations ). ISBN 0-85199-569-1 .

The threat that alien plants and animals pose to native ecosystems is increasingly recognized as a global concern. The scientific field of invasion biology and published literature in this area are burgeoning. Practical guides for the control of invasive alien species and for the restoration of selected regions are becoming more widely available. Nevertheless, there are few resources on large-scale planning efforts for invasion management. Invasive Alien Species: a Toolkit of Best Prevention and Management Practices addresses this need, providing a general framework for developing a national strategy to combat invasions. Compiled by the Global Invasive Species Program, this book serves as a broad introduction to laypeople of the complex problems posed by biological invasions and the best approaches for addressing them at a national level.

The first chapter of the “toolkit” briefly introduces the structure of the book and alien species issues. The second focuses on the necessary organizational and political elements for building a national invasive-species strategy, including regulatory policy, social marketing, and community education. The third chapter concerns prevention of new invasions, providing a comprehensive overview of the pathways by which alien species are introduced and an introduction to risk assessment. The fourth chapter focuses on the value and methods of early detection programs. The fifth emphasizes management strategies, describing a variety of approaches that merit consideration. Finally, the sixth chapter briefly describes how to adapt the toolkit to local ecosystems. These chapters follow a logical sequence and are clearly organized, although they are obviously intended as a quick reference, not a compelling literary experience: the text is terse and punctuated by many bulleted lists.

About half of each chapter is dedicated to case studies, summarized in informational boxes. From these, one gains a global perspective on the diverse problems posed by invaders and the solutions that have been attempted to address them. Unfortunately, the boxes are superficial in their treatment and poorly edited. Moreover, the same species and programs recur in many different chapters and even in the same chapter to illustrate different points. The preface of the book mentions that the toolkit will soon be available as an on-line resource. Future hard-copy editions could be stream-lined by putting almost all this case-study material on web pages. A few particularly compelling examples—for instance, from the superb biological invasion programs in Australia and Hawaii—could then be woven into the text, where they would be much more effective.

This toolkit was compiled particularly for planners devising national strategies in developing countries, especially small island nations. The book is free of charge to developing countries and as such is definitely worth obtaining by the target audience. But is it also useful to a broader audience, such as those working on large continents at a smaller scale than the national level? We evaluated this question from our own perspective. We work on alien species research, management, and restoration issues at a small estuarine reserve in central California. Our reserve, like most coastal habitats and estuaries in the region, is dominated by alien species, with over 100 documented upland plant invaders and over 55 marine invertebrate invaders. We found the general concepts outlined in the book applicable to our broad planning efforts, including work with other organizations in our watershed to devise early detection, public-awareness, and control strategies. However, many of the political components relevant to national planning did not pertain to our more local work. We also found that a key difference between island and continental biogeography resulted in the book being less applicable to our issues. Most new continental invasions occur by diffusive spread from elsewhere on the continent as broad invasion fronts, whereas those faced by small, isolated islands occur by jump-dispersal, with rare, unpredictable arrivals by new species. Based on our own experience, we would therefore recommend the book as a valuable resource to those carrying out broad-scale, multiorganizational planning in developed and developing countries ( at the scale of a county to a nation ) but not to conservation practitioners or land managers engaged in purely local efforts.

Too often we tend to demonize invaders as the source of ecological crises. The toolkit avoids this mistake, correctly pointing out that human behaviors and economics lead to the introduction of alien species. The authors emphasize the need to consider the costs to society as a whole when new species are introduced because these may outweigh the benefits that accrue to a small number of individuals as a result of the importation. The social science and policy approach taken by the toolkit makes good sense in this context. Indeed, we believe the authors could have further discussed the need and the mechanisms for generating public support for a conservation strategy that values native diversity and recognizes the threats posed by alien species. Our own experience has taught us the difficulty of conveying to the public the ethical arguments in favor of regionally distinct species diversity versus “melting pots” of invaders from many regions. Certainly the challenge of articulating these values will be part of the work of creating a national strategy.

Another gap in this toolkit is the lack of economic analysis of alternative approaches to dealing with invasions. This shortcoming is no fault of the authors, but rather reflects the paucity of available information. Whether at the broadest level ( deciding between investment in prevention versus early detection versus control measures at a national level, for instance ) or at the most specific level ( such as determining whether to attempt biological or chemical control of a plant species ), it would be very helpful to have a sense of the relative costs and benefits of different alternatives. The approaches described in the toolbox for a national strategy and in case studies sound promising, but until a decade goes by and we have a sense of which ones succeed or fail, making decisions will be largely a matter of informed guesswork.

Because attempts to develop broad-scale strategies for dealing with invasions are new, this is a critical time for sharing information. For instance, the toolkit suggests that a comprehensive national survey of aliens must be conducted at the beginning of national planning. This is a daunting and expensive task and perhaps not an efficient use of resources. Neighboring regions are likely to share a common pool of existing invaders and to face similar threats of new invasions. Therefore, pooling resources to create a database of likely problem species to look for in early detection programs would be very effective. Development of such shared databases across bioregions merits more attention. Likewise, as different nations or regions implement strategies to prevent or manage invasions, it would be wise for them to document their efforts ( methods, costs, successes, and failures ) closely and to share the results.

The toolkit includes little in the way of scientific concepts, presumably because they were considered inappropriate for a lay audience. In terms of generalizing findings from one area to others, however, science is a powerful tool that should have been included in the kit. Replicated experiments rigorously testing different approaches to dealing with invasions would help identify the best management methods and would begin to shed light on the mechanisms contributing to their success or failure. Taking the time to thoughtfully design such experiments, and to broadly communicate the results, would rapidly advance the work of global invasion management.

The reader is reminded in every chapter that the focus of broad-scale strategic planning should be on the conservation and restoration of healthy ecosystems; dealing with alien species is simply one step in this process. This is sage advice and worth repeating; indeed, we might emphasize it even more. For instance, the authors strongly advocate biocontrol as the safest and most effective management method for alien species, a view that does not necessarily reflect a consensus among ecologists today. We suspect that this perspective comes largely from experience with relatively simple, human-managed systems, such as agricultural crops or forestry plantations—the source of most funding and thus most knowledge about invasion control. It is possible that traditional biocontrol will also prove the best approach in more natural systems, but it seems too early to come to that conclusion because other approaches may yet prove as effective. For instance, in complex natural systems, it may be possible to enhance populations of native predators, competitors, or parasites to control invaders, rather than drawing on those from the home range of the alien. Or, large-scale habitat management, such as decreasing nutrient inputs from pollution or reintroducing historical disturbance regimes, may prove most effective.

Furthermore, such restoration of native species, habitats, or ecosystem process should be considered not just for management of existing invasions but also for prevention of new ones. The toolkit outlines all the pathways by which invaders may be introduced. But the other part of the equation is the recipient environment: invasions will only succeed if the biological and physical environment is suitable. In some cases, especially in areas that have been strongly disturbed by human influences, it may be possible to prevent future invasions by returning the ecosystem to more natural, historical conditions. An exploration of such approaches to preventing and managing invasions seems very much in keeping with the philosophy of the toolbox, because they contribute directly not only to the proximate goal of controlling the invader, but also to the ultimate goal of ecosystem conservation.