Climate change and agriculture: Analysis of potential international impacts

Climate change and agriculture: Analysis of potential international impacts

138 Book reviews author feels the need to present an overview of the nature and extent of the soil degradation problem and the urgency of solving it...

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138

Book reviews

author feels the need to present an overview of the nature and extent of the soil degradation problem and the urgency of solving it. When reviewing the conclusions of the different papers there are at times apparent contradictions between them. It was notable that some conclude that the use of chemical fertilizers is essential for optimizing and sustaining the high levels of crop production required to feed the world’s growing population. Others see the key to sustainable soil productivity as the promotion of practices that would raise and maintain soil organic matter levels. Such differing views would appear to reflect the different disciplinary backgrounds and research interests of the authors in question. Many of the papers make passing reference to the need for the farming community to participate in the research, development, and testing of improved sustainable land use management technologies. Regrettably there are no papers in this proceedings that describe how this can or should be done. Instead, what the papers show is that research on soil resilience is still largely the preserve of the research worker in a university or research station environment. There is one token economics paper in the proceedings, by A.-M. N. Izac (Ecological-Economic Assessment of Soil Management Practices for Sustainable Land Use in Tropical Countries). Although a valuable macrolevel paper, it does not address what should be of concern to all those seeking to promote soil resilience for sustainable land use; the critical need for research-derived sustainable land management practices to be subjected to appropriate financial analysis at the micro or farm household level. Too many past research recommendations in the soil conservation field have failed to be adopted because farmers saw them as resulting in short-term costs for at best long-term benefits. A criticism that has to be levelled against the book is its cost. The price of &60 means that this is a book which will be restricted to the reference shelves of University libraries rather than finding itself on the shelves of those who may wish to apply the findings to the field situation. It is to be hoped that the publishers will release a cheaper paperback edition so that this worthwhile book can be more widely purchased, read, and used. Malcolm Douglas

Climate Change and Agriculture: Analysis of Potential International Impacts. Edited by C. Rosenzweig, L. H. Allen Jr, L. A. Harper, S. E. Hollinger and J. W. Jones. ASA Special Publication Number 59, American Society of Agronomy, Inc., Madison, WI, 1995. 382 pp. Price: US$ 37.40 (paperback, including foreign postage). ISBN 0 89118 126 1.

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This book comprises the proceedings of a symposium held in Minneapolis in November 1992, sponsored by the American Society of Agronomy. The symposium consisted of invited and contributed papers on the potential impacts of climate change and on related topics. The results, published in this volume, cover various countries representing every continent. The book is divided into four chapters. The first contains two papers dealing with experimental results regarding climate change impacts. One assesses the response of cotton and the other, the response of rice, to elevated CO2 levels and increased temperatures using controlled environment chambers. The next chapter deals with simulation models suitable for analysing crop response to climate change. Various methodological issues are presented, such as creating climate change scenarios, coupling these scenarios to crop models, analysing the models’ sensitivity to changing environmental variables, and the results of these sensitivity analyses. The models discussed are the IBSNAT crop models - CERES and CROPGRO with alterations to simulate the direct effects of atmospheric CO* concentrations on crop photosynthesis and transpiration. The third chapter presents regional climate change simulation studies. These 10 papers cover a wide range of areas and crops: wheat in Canada; soybean and rice in the USA; wheat in California; winter wheat and winter barley in Uruguay and Argentina; maize in Zimbabwe; wheat and maize in France; maize in Spain; wheat in the Commonwealth of Independent States; rice, maize and wheat in Japan; rice in Southern China; and sorghum in India. Most papers apply the same methodology: using the output of three general circulation models (global climate simulation models that are used to estimate future climate change) and long-term historical daily weather data, researchers create long-term daily time series for the future in which a doubling of atmospheric CO2 and other trace gases occurs (this is thought to be reached at a level of 555 ppm COz). The crop models, modified to describe the direct effects of CO* level on crop transpiration and photosynthesis, are then run with the original historical weather scenarios and the newly-created climate change scenarios. The results of the simulations are compared to estimate the effects of the changed climate and the elevated CO* level on crop yield, phonology, crop duration, and water balance. Most of the studies attempt to assess several adaptation strategies, such as changing sowing date, choice of another variety, or modified irrigation and fertilization regimes. There are also attempts to aggregate the site-specific results of the models to estimate regional or country level effects, and some of the studies examine the impacts of a transient climate change (gradual warming and increase of atmospheric COz concentrations during the next 50 years).

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The results, as expected, differ widely according to geographical location, crop type, and production technology; they also differ according to the global climate model chosen. One of the studies uses the mixedlayer global climate model of Oregon State University for climate change predictions, whereas the others compare the results of three global climate models, those of the Goddard Institute for Space Studies (GISS), the Geophysical and Fluid Dynamics Laboratory (GFDL), and the United Kingdom Meteorological Office (UKMO). Of these, the latter generally produces the largest yield decreases, whereas the GISS and GFDL models often suggest a minor decrease or even a favourable change, at least with some viable management adjustments. The fourth chapter of the book contains one extensive study that attempts to estimate the impacts of climate change on world food supply, demand and trade. This work is based on the basic linked system, a model of world food trade, using the GISS, GFLD and UKMO climate change scenarios and yield changes predicted by crop simulation models. The results, reassuringly, indicate that no major change is expected in global food supply. At the same time, however, low latitudes seem to be badly afflicted, whereas higher latitudes may benefit from the projected changes; this can only heighten the contrast between rich and poor and increase yet further the disparity between developed and developing countries. The studies published in this volume are the results of international cooperation, using the same approach and methodology, which makes it possible to compare the findings for the countries and crops studied. The authors and the editors point out the somewhat preliminary nature of the results, as at present there are still many uncertainties regarding the expected change in world climate, future change in crop production technology, and other factors. This underlines the importance of continued and intensified international cooperation. The present volume is an excellent example of joint efforts contributing greatly to the vital task of understanding the potential and actual impacts of climate change on agriculture around the world. The book is a paperback, with practically no typing or printing errors, although some of the charts, especially the maps (which were probably coloured originally), are not very clear in black and white. Extensive references help the reader to follow up on earlier achievements in the field. For researchers and students interested in analysing the impacts of climate change, this excellent collection is very good value. Zsuzsanna Bacsi