Ploughing on for centuries

Agricultural practices affect ecosystems by exploiting natural ecosystems for food, by replacing the natural biota with new species and by introducing new biota to regions which were unproductive. These processes have occurred at different times and in different places in the development of agriculture.

Agriculture and Environmental Change: Temporal and Spatial Dimensions covers the historical development of agriculture in two chapters. The inter relationships of the social and technological forces of this process are reviewed. In the subsequent transfer of agriculture from the centres of development two drivers are important: environmentalism and materialism. Environmentalism suggests changes in environmental factors forced the development of agriculture in new regions. It may have been climatic change, which meant that hunter-gathering techniques were not providing enough. Materialism suggests that factors such as greed, population pressure or the desire for a more sedentary lifestyle drove the adoption of agriculture.

In reality, these drivers may have acted in tandem. The origin and development of the major domesticated species of crops and animals are described, highlighting, but not discussing another incidental environmental impact: the redistribution of species.

A wide range of examples is used to describe the major types of agriculture found globally. These are grouped as transitory (nomadic pastoralism and shifting cultivation) and settled (arable, pasture and mixed farming). The author provides a wealth of information about agricultural exploitation of the environment and its consequences. From these discussions the all-important environmental issues spring: habitat loss in the tropics, resulting in the release of carbon dioxide; cultural eutrophication, and the release of chemicals into the environment; land degradation, desertification and salinisation. The temporal dimension is again important. For example, the developed world has fragmented its natural habitat, the impact of which can only be guessed at, while the present understanding of the impact of the destruction of natural habitat in the developing world has made this a major environmental issue.

The competing forces of materialism and environmentalism make it necessary for the developing world to increase its production while the developed world attempts to decrease production. Given the global cost of deforestation in terms of greenhouse gas emissions, the cost of supplying food to developing countries should surely demand revised global trading which takes environmental costs into account. Technology and population pressure are reviewed.

Agriculture is closely related to the environment, but is also modified by historical, social, economic and technological factors. This book emphasises all of these factors without attempting to disassociate one from another, a difficult task to achieve. If anything, the environmental aspect of agriculture is underplayed in favour of the social and historical context. This text will be useful to undergraduates studying geography. It reviews a wide range of literature in a well-presented and readable form.

Paul Brignall is a research scientist, Environmental Change Unit, University of Oxford.