When nature attacks

Species invasion - the expansion of species beyond their native ranges - is one of the most vexing conservation issues of the day.

Integrating into (and sometimes destroying) native species assemblages, non-indigenous species can cause extinctions, species displacements, infectious diseases, modifications to ecosystem cycles and reconfiguration of habitats. In recent years, conservation science and policy has placed a new priority on research and management of species invasions.

To fill the need for conservationists and natural resource managers trained to deal with invasive species, ecology and environmental science departments have introduced a range of courses and training programs. Until recently, textbooks have been scarce, doubtless because of the schizophrenic nature of the problem. Is it an ecological problem, pertaining to the kinds of species that become invasive? Or is it a cultural, social and economic one, because species are typically introduced either as a direct result of trade in biological materials or as a byproduct of commerce? Partly, this scarcity of material is due to the fact that there are no comprehensive theories of species invasion or universal solutions. Thin on generalities, invasion ecology is thick with case studies, speculative ideas and divergent environmental policies ranging from local co-operative agreements to international conventions. This makes for messy science and messier textbooks. It is on this mess that Invasion Ecology aims to impose some structure.

Conceptually, this task is thanklessly difficult and the result is a mixed success. The book aims to be a text for the upper-level undergraduate special topics course and is less advanced than the two main alternatives, Conceptual Ecology and Invasion Biology by Marc William Cadotte et al, and Species Invasions by Dov F. Sax et al. While the present volume gets this audience right more often than not, there are occasional slips. Further, while the authors have represented the breadth of invasion ecology as conceived by ecologists, relatively little attention is paid to the interconnected disciplinary web in which the science is situated - weed science, biological control, fisheries, entomology and others.

When it comes to the systematic presentation of invasion ecology, the authors are more successful. Topics are treated roughly in proportion to their representation in the scientific literature. Individual chapters cover introduction pathways, patterns in data, disturbance, biotic interactions, models of range expansion, effects of introduced species, evolution and practical aspects of management such as forecasting, risk assessment and control.

Excising fads, authorial prerogative is exercised to balance traditional explanations and platitudes with critique and data. This is a useful overview of the main ideas and well suited to the survey course. However, the authors are not without opinion. To the extent that there are schools of thought in invasion ecology, there are two. One holds that the most important determinants of species invasions are species-species interactions and species-environment interactions. The other holds that invasion has little to do with these factors because rates of invasion are driven by human activities resulting in species introduction, and that it is the rate of introduction that best explains observed patterns of invasion. These authors hold to the latter perspective, albeit not strictly, and make a good case for it in a welcome antidote to prevailing views.

Invasion ecology is an evolving field for both research and application. It is not a temporary environmental fad and will not disappear as a science for no other reason than that it is entwined with globalisation, trade and politics. Invasion Ecology is a welcome introduction and overview of a field plagued by the particularities of unique situations and recalcitrant to systematisation.