TROPICAL ECOSYSTEMS: USE THEM OR LOSE THEM?

Authors


Kellman, M. & Tackaberry, R. (1997). Tropical environments. the functioning and management of tropical ecosystems. Routledge, London. xix + 380 pp, figs, tables, photos, glossary, index. Paperback: Price £18.99. ISBN 0 415 11609 0. Hardback: Price £60.00. ISBN 0 415 11608 2.

This is an excellent book, containing a formidable array of source material on tropical ecosystems. Throughout the book, the authors stress the importance of a synthetic rather than fragmented approach to understanding tropical ecosystems. The book provides a good example of the synthetic approach, in particular by demonstrating how an understanding of tropical ecology can be integrated with management strategies.

In an introductory chapter, the authors stress the point that the tropics do not have the infinite agricultural potential that has sometimes been ascribed to them, largely because water and soil nutrients are often limiting. Arising from this, Kellman and Tackaberry argue that in many regions of the tropics the carrying capacity for human populations is quite low. Unsustainable exploitation of some tropical environments may result in their long-term degradation. Site-specific solutions are nevertheless possible for the sustainable development of many tropical environments, There is, however, an inevitable tension between efforts to exploit and to preserve tropical ecosystems. Nevertheless, tropical environments are generally more robust than has been previously supposed.

The next three chapters deal with abiotic factors in tropical environments. A chapter on the history of tropical environments gives a fascinating background to the debate on the origins of biotic diversity. Kellman and Tackaberry use this opportunity to present current thinking on contentious issues involved with biodiversity. Chapters on climate and hydrology, and on soils and nutrient limitation are both comprehensive and comprehensible; for this reader at least, even the illusive topic of variable-charge chemistry of tropical soils was accessible.

There follows a chapter on tropical biotas, which provides a solid treatment of some important ideas in tropical biology. These ideas include the related themes of coexistence of numerous species, competitive exclusion, the regulation of populations, and predator intensity. The authors review evidence supporting or refuting the Janzen-Connell hypothesis. The last part of the chapter addresses the issues of the conservation of biodiversity in the tropics and tropical pests and diseases.

Remaining chapters in the book cover particular types of tropical ecosystems and their management. There are wide-ranging and detailed chapters on tropical forests and forestry, traditional agricultural systems, and animal production and utilization. A chapter on intensified agriculture somewhat curiously also includes detailed discussion of human populations in the tropics. This is, justifiably, a recurrent and important theme throughout the book, but it is not clear why the authors have chosen this particular chapter to develop their case for the need for stablization of human populations in the tropics. The chapter on savannas is particularly strong, and includes an authors’ hypothesis to account for the ‘savanna anomaly’, i.e. the stable coexistence of graminoid and tree species, which are two potentially incompatible plant groups.

The concluding chapter, Land use planning, rehabilitation and research includes a timely argument for applied, site-specific research. This is in contrast to the historical dominance of pure research (often based at field centres situated in pristine ecosystems) from which much of our understanding of tropical ecosystems has been extrapolated. The authors make a strong case for participatory methods involving local land users, rather than the ‘top-down’ approach which is often used. It is, after all, local inhabitants who have potentially the most to gain or lose from their own environment.

The book does not have many obvious weaknesses. Among the relatively minor shortcomings is the index, which is incomplete and even some major terms that are listed in the glossary are strangely not included (though they are well covered in the text). A small detail, which for some potential readers may be an annoyance, is that the book’s title and introduction do not make it clear that coverage of tropical aquatic ecosystems is minimal, while a focus on only terrestrial environments is entirely reasonable, the scope of the book could have been defined more carefully at the outset.

Topics in the book are generally treated very thoroughly and competently, though there are some omissions. For example, a chapter on tropical forests and forestry does not refer to low impact or reduced impact logging techniques, though other methods for sustained timber production are described. Agroforestry is not extensively covered, although this is possibly because the authors feel that, as a ‘panacea’ for problems in farming in the tropics, the benefits ascribed to agroforestry are generally unconvincing.

The authors refer to a ‘virtual explosion of empirical data on the tropics’. In some respects, the book is an extended review of our current understanding of tropical environments. The authors concede that they have made a ‘highly selective use’ of literature, based on availability and familiarity of source material. This selectivity has not resulted in any serious bias, although readers may find themselves wondering whether studies in the neotropics are over-represented.

This book is likely to be a much-used resource for researchers and students with an interest in the tropics. The approach is largely descriptive rather than prescriptive or predictive, but this does not detract from the value of this compact and worthwhile volume.

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