Half a century ago, three decades before the word ‘biodiversity’ had been coined by Walter G. Rosen (in 1986) and long after the concept was recognized (for example Fisher et al. Reference Fisher, Corbet and Williams1943; Preston Reference Preston1948), Elton (Reference Elton1958) concluded his influential book on the Ecology of Invasions by expressing the fear that ‘wild beauty’ was under threat. These concerns proved justified, and we are witnessing a tide of extinctions that has exceeded Elton's (1958) gloomiest predictions. Disquiet about biodiversity loss is no longer restricted to a few visionaries; a large fraction of the ecological literature is devoted to quantifying the erosion of biodiversity and proposing methods for its conservation, world leaders debate the issue at summits and the morning newspaper delivers daily reminders that populations of charismatic species are becoming ever more precarious.
The question that Biodiversity Under Threat tackles is not new. However, the book's analysis of ‘biodiversity initiatives’ alongside its treatment of biodiversity loss gives it a fresh feel. Hester and Harrison's stated aim is ‘to provide a broad view of the many threats to global biodiversity and the policy responses required to combat them’. And indeed the book's breadth is impressive. Chapter 1 provides an informative overview of farmland biodiversity in the UK. Later contributions tackle a range of subjects including global insect biodiversity, biological invasions in Europe, biodiversity in the deep sea, marginal upland habitats, tropical forest diversity and the implementation of international biodiversity initiatives. The chapters vary in their emphases. Some focus on reporting patterns of biodiversity. We learn, for example, that there can be as many as 100 000 individuals of one type of insect, the springtail, in a single square metre of pastureland and that deep-sea fish are much more diverse than has hitherto been appreciated. Other chapters, such as the contribution by Furman and others, review the approaches used to stem biodiversity loss. As the ongoing debate on global warming shows, it is one thing to identify a problem, and quite another to persuade people to modify their lifestyles to help solve it. The challenges of conserving biodiversity are particularly stark in developing countries whose inhabitants struggle to feed themselves and their families. Nonetheless, even in the affluent world there can be marked resistance to change; initial attempts to conserve forest areas in south-west Finland disturbed some landowners so much that they embarked on hunger strikes.
It is inevitable that a book that covers so much territory must make some trade-offs against depth. One example is the discussion of biodiversity assessment. Here the book asserts (p. 220) that ‘simple species numbers and abundances are the most popular measures of diversity in practical use’ (a statement I agree with) but then comments that ‘this is surely resulting from the fact that species counts and abundance assessments are the very basic and intuitive way to address biodiversity-related questions’. Yet it is now clear that it can be extremely difficult to estimate species richness accurately, and comparisons or assessments made on species counts alone can give misleading results (see discussion in Gotelli & Colwell Reference Gotelli and Colwell2001). In fact there is a rich and growing ecological literature on biodiversity assessment (for example McGill et al. Reference McGill, Etienne, Gray, Alonso, Anderson, Benecha, Dornelas, Enquist, Green, He, Hurlbert, Magurran, Marquet, Maurer, Ostling, Soykan, Ugland and White2007) that is barely mentioned, and many of the pitfalls of using diversity statistics, such as the Shannon index, are glossed over in the text. Other sections skim over topics that deserve a fuller treatment. For instance, on p. 259 there is a claim that ‘biological invasion is the only biological driver of biodiversity’, but what about competition, predation and parasitism, not to mention speciation and extinction?
Overall the book is an interesting read and the editors have achieved their goal of producing a volume that will be accessible to a wide audience. The standard of presentation is generally good. Sometimes it is a little unclear why particular topics were included, or why the chapters appeared in the order they did. I think that introductory and concluding sections by the editors would have helped set the themes in context and produced a more seamless read. Nonetheless, the topic is timely, and much of the writing authoritative, so that despite its diverse content the book manages to be more than the sum of the parts.
