Figuring out flora and fauna

Biodiversity - bandwagon, buzz-word, growth industry, global resourceI what exactly is it? and how should scientists define it? Despite burgeoning interest in biodiversity the concepts and methods associated with its measurement have received rather little attention. By focusing on this in detail, and at an advanced level, Biodiversity: A Biology of Numbers and Difference successfully addresses the issue of how to assign meaningful numerical values to the term biodiversity.

Following a short introductory chapter defining biodiversity, the text is divided into three sections: "Measuring biodiversity", "Patterns in biodiversity" and "Conservation and management". The first provides comprehensive coverage of the theory and methodology of measuring biodiversity at the genetic, species and community level. A valuable inclusion here is a chapter on the more recent approach of using functional aspects, such as ecological processes, as parameters of biodiversity. The assessment and value of character differences between organisms is particularly well explained (by Neo D. Martinez), and deals with types of characters (genetic, phenotypic, functional), models of their evolution (genealogical trees and molecular clocks) and the use of surrogate measures. The "Patterns in biodiversity" section describes temporal and spatial patterns of genetic, taxonomic and functional diversity. Coverage is again comprehensive, for example taxonomic diversity in space is considered in terms of global gradients (latitudinal, altitudinal etc), extremes ("hot and cold spots" of endemism) and levels of coincidence between hotspots of species richness in different taxa. Three crucial questions are addressed in the final section: does biodiversity matter? how do we manage it? and how can priorities for its conservation be identified?

These issues are covered in more detail in many other current texts but their value here is in highlighting the importance of biodiversity measurement in practical conservation and in drawing the preceding chapters together. The text is illustrated throughout with figures, examples and case studies and each chapter is accompanied by an extensive and up-to-date reference list.

Edited collections are frequently criticised for containing chapters of variable standard or for lacking continuity - this one suffers in neither respect. The quality of the chapters is uniformly high thanks to an impressive list of contributors, Paul Harvey, Chris Humphries, Richard Vane-Wright, Paul Williams, to name but a few and the opening and closing chapters put the rest into context giving a "focused whole" rather than just a collection of papers.

One note of caution to "potential purchasers" - quite an advanced level of knowledge is assumed of the reader. For example equations of Hardy-Weinberg equilibrium and Wright's neighbourhood population size appear in the first few pages of a chapter on "The genetics of biological diversity" (by James Mallet). This is not a criticism but merely an illustration of the fact that this is a book for the well informed - subsections entitled "identifying anomalous clades" and "covariance in diversity" are not intended for first-year undergraduates. The value of this publication lies in the advanced level at which it addresses a complex topic. It will be an asset to staff involved in teaching or research and to final-year degree students.

While the previous publication has a clearly identified audience and subject area it is difficult to decide who would read Biodiversity assessment: A Guide to Good Practice, or why. This edited text, which draws largely on contributors from The Natural History Museum, Royal Geographical Society, and Royal Botanic Garden, Edinburgh, comprises three separate documents: a review and two field manuals. Its stated purpose is to "help those who have the responsibility to survey and assess the biodiversity of their own countries I and field workers who want to put their own work into perspective". A purpose unlikely to be met by a text that is heavily biased towards the United Kingdom given that the majority of the earth's biodiversity is found in poorer countries of the world and it is here that expertise and technology is most needed.

The contents of the review are a curious mix ranging from quite a good general introduction to biodiversity to the legal and ethical aspects of its assessment (intellectual property rights, collecting permits etc). Two chapters are devoted to the role of UK research institutes, universities and learned societies in biodiversity assessment and contain a great deal of information that is likely to become redundant rather quickly. For example details of the budget and funding structure of the Natural Environment Research Council change rapidly and lists of postgraduate training courses at universities drawn from the Directory of Environmental Courses 1992-1993 are already out of date. Two subsequent chapters describe specimen, bibliographic and archival data banks held in the UK and only one of the seven chapters addresses international approaches to inventories and monitoring.

The so-called field manuals are really guides to collecting and preserving plants, fungi and microorganisms (manual 1) and animals (manual 2) - quite good guides, but there is more to "biodiversity assessment". There are few details on in situ approaches, the methodology or design of field surveys or analysis of results. A second criticism is that the huge breadth of methods covered, from the use of pitfall traps, foggers and epibenthic sleds to sample invertebrates, for example, means that there is insufficient detail about any to be really useful practically. They are however well referenced and so it is possible to follow up the information given.

A field biologist would probably do better to invest in a book such as the recently published Ecological Census Techniques edited by Bill Sutherland and a specific identification key for the taxonomic group of interest. In general this rather glossy publication smacks more of a publicity exercise than of a serious attempt at providing help to field workers either in the UK or abroad.

Juliet Vickery is lecturerin animal ecology, University of Edinburgh.