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of our society, and because each process within it is in turn relatively small, savings are unimportant . Surely the answer to the world energy problems will not be a few large savings but the accumulation of many small ones. As several papers suggest, we need a 'finer tuning' of our operations. We need irrigation which uses water very efficiently, which does not outf low salinized water, and which moistens only the roo t zone of the crop thus avoiding leaching of nutrients. We need fertilizer systems which are precise. We need herbicide applications which are timely and only used when absolutely neces- sary. We need to use rail instead of t ruck for non-perishable bulk items. And, dominating all considerations, we need to minimize the use of nitrogenous fertilizers, by the use of 'wastes' and above all fixation of nitrogen by bacteria with or wi thout association with legumes.

This book is excellent value as a reference on any shelves. It would be par- ticularly useful to students and teachers, with its copious illustrations of the energy problems of U.S. and third world agriculture. It would be useful to see a similar volume for some countries with rather different agricultural systems. For instance, the Australian scene would be markedly different because of the widespread use of legumes in rotat ion with crops, the very efficient range livestock industries in much of the country, the lower population and the great distances.

DAVID F. SMITH (Launceston, Tasmania, Australia)

CLIMATIC CHANGE AND FOOD PRODUCTION

Climates of Hunger. Reid A. Bryson and Thomas J. Murray. University of Wisconsin Press, Madison, Wisconsin, 171 pp., £ 6.70, ISBN 0-299-07370-X.

The book is divided into four parts. The first part, Two Tales of Famine, discusses the fall of two earlier civilizations -- those of Mycenae in Greece and the prairie peninsula in the United States. The Mycenaen civilization declined around 1200 B.C., and the authors, by at tempting to reconstruct the climatic patterns of that time, conclude that "a drought could have caused the decline of Mycenae. We have proof that the proposed Mycenaen drought pattern can exist. We also have evidence that the pattern did domi- nate about 1200 B.C." (p.16). Similarly, they contend that the changed climate brought the downfall of the plains farmers of the United States and this change lasted some 200 years.

The second part deals with climates since 900 A.D. The authors quote extensively the work of Bergthorsson, who has a t tempted to reconstruct the climate of Iceland for the last 1000 years. It shows that the climate of Iceland was warm and variable between 900 and 1200 A.D., and it was then quite cold for the subsequent 200 years. They suggest that " f rom the late sixteenth

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through the nineteenth century, the best years in Iceland were only as good as the worse years the Vikings had seen. Then in our century a great warming set in" (p.55). Similarly, Bryson and Murray have attempted to reconstruct the climates of the past 1000 years for Europe, the North Atlantic and the United States, from information obtained from tree ring and pollen analyses, as well as from other sources.

The third part is on the failure of the monsoons in the Sahelian region of Africa and the Indian subcontinent. Discussing the Indus civilization of Harappa and Mohenjodaro, the authors claim that it is "another tale of mon- soon failure", which was essentially created by people by accident, since "they helped make a dustbowl out of a breadbasket, and hence kept it that way" (p.I09). "A worldwide climatic change may have helped make the desert and started the Harappan's decline" (p.ll0).

The last section is a perspective on climatic change. It briefly sketches the climatic Changes of the last million years, and points out that the 'normal' climate -- the 30-year period that weather agencies define as normal -- is quite abnormal in the perspective of the last 1000 years. Past records of climate may give some interesting clues to the future, but the pattern of past climate has not been regular enough to reveal what is coming next. The Northern Hemi- sphere has cooled by almost 0.6°C since the nineteen-forties, and "a continua- tion of the cooling trend, or even a stabilization of today's temperatures, means problems for temperature zone agriculture as well, in the form of slight- ly shorter growing seasons, less summer warmth on the average, and unreliable rainfall. For crops that have been highly developed to match the climates of recent decades -- 'normal' climates -- any change in conditions brings a lower yield" (p.i55).

'Climates of Hunger' is an unusual book. It is written by a well-known climatologist, Reid A. Bryson, and a science writer, Thomas J. Murray, and is aimed not at specialists but at the general audience. It contains much food for thought. We know for a fact that the world climate is not fixed over time: it has changed many times in the past and there is no doubt it will continue to do so in the future. Thus, the real question is not whether the climate will change in the future, for it will undoubtedly do so, but rather when will the next climatic change take place, and what will be the magnitude and duration of that change. Naturally, there are some climatologists who may not agree with some of the hypotheses on climatic change put forward by Bryson and Murray. It is, however, a chilling thought that when Copernicus put forward his theory, very few scientists of his time believed him. We must remember that if science had to progress by consensus, we would still be in the Dark Ages.

ASIT K. BISWAS (Ottawa, Ont., Canada and Laxenburg, Austria)