Species without frontiers

Life out of Bounds: Bioinvasion in a Borderless World

W. W. Norton/Earthscan: 1998. 287pp $13/£12.95 (pbk)

The threat of biological warfare has resulted in extraordinary measures by nations to detect and defend themselves against potential weapons of destruction. But inadvertent biological invasions have actually been occurring for centuries, decimating human populations and the crops and livestock upon which they depend. The fundamental driver of this has been the transport of people and their goods, along with biological stowaways, some of which have been benign, others extraordinarily destructive.

For some reason, insufficient attention has been paid to the scale of this interchange, its increasing tempo, and its enormous economic and ecological impact. International commerce has broken down the ancient biogeographic barriers that allowed the evolution of the rich biological diversity on which we based our civilizations. The breakdown of these barriers has resulted in a biological scramble of species competing for newly opened resources. This is now happening on a global scale, with serious consequences for the future course of evolution and the number of species that will populate the Earth.

This is pretty dramatic stuff — and yet the forces to counter this tidal wave have not yet been assembled. The first part of the job of resistance is to raise awareness of the problem and of the potential courses of action available to deal with it. Chris Bright has done an admirable job of marshalling the facts and writing about them in a clear and compelling manner.

This book developed from an excellent article he wrote in 1995 for World Watch, on the spread of exotic species. Since then, a landmark conference on alien species held in Norway in 1996 has provided new information as well as the beginnings of an international plan to address this complex and urgent issue. Much of this information appears in this well-documented book.

The book is in three sections. First, Bright surveys the geography of invasions and shows that none of the major biotic realms — fields, forests, waters and the special case of islands — is now free of the impact of invaders from other continents. He then describes how the change described by some as the new geological epoch of biological homogeneity, the Homogocene, came about. Both intentionally and by accident, human activity has mixed up the biota of the Earth, incurring large economic and environmental costs in the process. Finally, a course of action to deal with this crisis is presented.

Plant-locked: the spread of the water hyacinth in Lake Victoria has closed small ports and harbours. Credit: HARTMUT SCHWARZBACH/STILL PICTURES

In the section on the geography of invasions, Bright provides case after well-documented case of invading species that have had a profound impact on human societies. He describes, for example, the dramatic story of Lake Victoria, which may now be in a state of ‘chronic emergency’ as a result of successive waves of invasive species. The first of these was the Nile perch, introduced in 1962, which drove a couple of hundred native fish species to extinction and indirectly altered the surrounding forested ecosystems as local firewood was used by fishermen to dry the very large Nile perch. These major alterations apparently led to the successful establishment of water hyacinth in 1990. This invader is in turn making the shoreline anoxic, clogging pumping stations and severely affecting fishing activity. It is also apparently increasing the incidence of snail- and mosquito-borne diseases. This chain of events has affected millions of people.

The ‘villain’ species in such cases are either purposeful or accidental introductions. Cases of accidental introductions are growing because of increased shipping and the use of ballast water. Ballast water, acquired in one port and dumped in another, brings large numbers of live animals to new habitats. Around 1982, a small comb jellyfish was brought in this way from the east coast of the Americas to the Black Sea. This organism became well established and devastated the fisheries, affecting two million people. In a poor exchange, the zebra mussel was apparently taken in ballast water from the Caspian Sea to the Great Lakes of North America around 1986. This mussel is doing so well in its new habitat and its numbers are now so high that it controls the ecological dynamics of many areas, and adversely affects waterworks such that remediation is costing billions of dollars.

Doing something about invasive species will not be easy, as Bright points out, because we generally do not know which organisms will become successful invaders, where and when invasions will occur, or what effects they will have. If ever there was a rationale for the precautionary principle on the release of any biotic material into a new ecosystem, this is it. The policy response to the threat of invasions has been weak and uncoordinated, and only the most devastating invaders get serious attention. Bright thinks we need to strengthen the treaties relevant to invasive species, develop codes of conduct for industries involved in the trade of biotic material, create an information clearing-house, improve our capabilities of biological control, and increase ecological literacy. All of these are important and achievable goals.

There is some hope of providing an international focus on the problem, and for the development of tools and determination to deal with this issue. The Scientific Committee on Problems of the Environment, and its partners the World Conservation Union (IUCN), the United Nations Environment Programme and the Commonwealth Agricultural Bureau International, have launched a Global Invasive Species Programme to provide the means for recognizing and dealing with this pervasive problem. Of particular concern is the threat it poses to species diversity and ecosystem services and to human welfare in general.

Bright's book is a clarion call to action. It is exceptionally good value in every sense. Every biologist should be well versed on this issue, and reading this book would be an excellent starting point.

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Mooney, H. Species without frontiers. Nature 397, 665–666 (1999). https://doi.org/10.1038/17740

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