Ecosystem change and public health: a global perspective

Edited by JL Aron, & JA Patz Johns Hopkins University Press, Baltimore, MD, USA, 2001. Hb ISBN 0-8018-6581-6, price US$ 82 Pb, ISBN 08018-6582-4, price US$ 38.00

A decade ago one would not have expected to find a title like this on bookshop shelves. But much in the biophysical world around us has changed in the last 10 years, and much of that change is attributable to human interventions and pressures. The symptoms of planetary overload are becoming familiar to many readers of the Bulletin. They include global climate change, stratospheric ozone depletion, freshwater depletion, declines in agroecosystem productivity, losses of biodiversity, and the pervasive geo-atmospheric spread of persistent organic pollutants.

Public health scientists who recognized the potential importance of these large-scale environment changes early on had to improvise new types of research and data analysis, often muddling through with coarse-grained statistical correlations and imperfect models for forecasting future impacts. Such research induced uneasiness: many of the underlying causal processes were complex, non-linear, and riddled with uncertainties. But the clock could not be turned back: society at large was seeking answers to questions about the current and future health consequences of environmental change and ecosystem disruption.

As has happened many times before in the history of science, this branch of research has found its feet and is now maturing. The approaches to it that have proved useful are being mainstreamed. The methods of modelling it uses are becoming more robust. Ways of characterizing and communicating uncertainties have evolved. Research funding is beginning to flow. There is, also, a growing literacy about ecosystems among environmental epidemiologists. Interestingly, this trend has been accompanied by the rise of "social epidemiology", with its emphasis on community-level influences on health and disease. Stocks of social capital (such as civic institutions, shared levels of trust, and equity of income distribution) are major factors here, as well as social, cultural and economic relations. Taken together, these shifts in emphasis bespeak a greater understanding of the ecological perspective, and recognition that much of the causation of states of health in populations derives from what happens in complex, multi-level systems.

The material presented here, mostly by US authors, is a product of these maturing ideas and methods. Pleasingly, it is much more than a compilation of disconnected chapters. The two editors have had experience in teaching graduate students about these issues, and have sought to maximize the book's usefulness for master's-level courses as well as for self-instruction by those interested. Most of the chapters are about approaches, environmental changes, and case studies, but there is also thoughtful advice on how to use this book; a review of the evolving role of textbooks in an Internet age (and of models of learning and remembering); and an inventory of web-based data resources, classified by institutional type, geographical relevance, and environmental system. A glossary, a list of abbreviations and a good detailed index are included too.

The section on approaches comprises chapters that explore the dimensions of global change, define and illustrate epidemiological research, and review spatial analysis (geographical information systems (GIS)), the science/policy interface, and integrated assessment models (IAM). All are expertly written, although the IAM chapter lacks an adequate discussion of the potential use of models to forecast health impacts that are decades distant in time. There are, after all, several well-known early examples (by non-US scientists) of modelling the impacts of stratospheric ozone depletion on skin cancer rates, and of global climate change on the potential transmission of malaria. Much has been learnt from such studies, and simple illustrative critiques would have enhanced the chapter.

In the epidemiological research chapter, the conventional use of the "ecological study design" jars a little in a book about ecosystem change. That term was coopted from the social sciences half a century ago, and has long been misleadingly used by epidemiologists to describe any study that compares "exposures" and "disease rates" at the supra-individual level. The time has come to confine the use of the word "ecological" to references to ecological systems and processes.

Several of the most important domains of global environmental change are covered in the second section. They include human impacts on the biosphere at large, atmospheric and climatic changes, disruption of the Earth's great natural cycles (carbon and other elements, energy, and the hydrological cycle), water resource management, and disturbances in infectious disease systems and patterns. These chapters are written by experts, and contain many clear and useful diagrams and examples.

Then we come to the case studies, of which there are just four, though the editors are well aware that this topic area is rich with large and complex examples. The four are: changes in the occurrence of cholera in relation to a range of ecosystem processes and changes; malaria in the same context of change; the interplay between climate change and air pollution; and how water supplies influence population health. These are well-presented and well-referenced chapters, with interesting historical dimensions, and they help to consolidate in the reader's mind the concepts and methods emphasized in earlier chapters.

This book has been well produced, particularly for the purpose of expanding and enlightening the teaching curricula in environmental health. Each of the main chapters ends with an unobtrusive but useful section of study projects for students, briefly outlined. The editors suggest how the book's contents can be used for differently structured courses. Strategies for enhancing communication among course participants are proposed. In short, it is an innovative and timely textbook which will influence the evolution of teaching and research in this topic area, whose international importance continues to grow rapidly.

Pedagogical considerations aside, it is a book that non-students can very comfortably and usefully go through — or even read in bed. I know; I did.