Global climate change is one of several important issues that will command the attention of policymakers and scientists in the 1990s. The evidence that concentrations of carbon dioxide (CO2), and other gases are increasing in the atmosphere is irrefutable. This evidence, and the knowledge that CO2 and trace gases may absorb thermal radiation sufficient to warm the atmosphere, has prompted much speculation that ensuing atmospheric warming may lead to changes in the distribution of precipitation, and of crop adaptation and productivity, that would alter the world supply of food and fiber. The implications of this speculation are compelling for agronomists, because agronomists are stewards of the world's food supply and of the natural resources that are used to produce food. Agronomists have a pivitol role in conducting the research needed to anticipate crop response to climate change, and in informing policymakers and the general public about the adequacy of our knowledge.
In this publication, leading scientists from the international community of agronomists assess the current status of scientific knowledge about the putative role of greenhouse gases in global climate change and report their findings. The information will be useful not only to scientists, but also to policymakers as background for deliberation on farm, environmental, and agricultural research legislation.
A.A. BALTENSPERGER, president
American Society of Agronomy
STEVE A. EBERHART, president
Crop Science Society of America
WILFORD R. GARDNER, president
Soil Science Society of America
GARY H. HEICHEL, editor-in-chief
The concentrations of CO2 and some other radiatively active trace gases are increasing in the global atmosphere, and these changes in composition have been predicted to significantly warm the Earth (the “greenhouse effect”) and possibly to alter precipitation patterns, as described by Taylor and MacCracken (Chapter 1). Agricultural productivity is greatly dependent on climate and weather, so these predictions or projections of climatic change should be of concern to agronomists and other agricultural scientists. Moreover, Burke and Lashof (Chapter 3) indicate agricultural practices and changing patterns of land use affect the emission rates of greenhouse gases. So to some extent, agriculture not only is vulnerable to the effects of climate change, but it is a possible cause as well. Not everyone agrees with the prediction of warming (Idso, Chapter 2), but nevertheless, it is prudent that we begin to consider the possibility of climate change and to make our planning for the future of agriculture as flexible as possible.
Even if climate does not change, the increased CO2 concentration will significantly affect the growth of plants and probably increase agricultural productivity (Acock, Chapter 4). If climate does change, however, significant interactions are likely to occur between the CO2 and the climate variables in their effects on plant growth (Idso, Chapter 5; Goudriaan & Unsworth, Chapter 8). These growth changes will not only affect our crop plants, but they will also affect the weeds with which they compete; and of course, competitive advantages among species growing in the wild may shift, so that the composition of plant communities may be altered (Patterson & Flint, Chapter 7). if the climate warms, soil organic matter content is likely to decrease while total N may increase in the temperate zone, but no major changes in fertilization practices are predicted (Buol et al., Chapter 6). Yet, even while global CO2 and climate changes may be affecting worldwide agricultural production, the availability of one important resource for coping with hotter and drier conditions, irrigation water, may be adversely affected (Goudriaan & Unsworth, Chapter 8). Thus, in this book we attempt to review what can reasonably be inferred from the scientific literature about the effects of elevated CO2 and changing climate on crop production and to describe their possible consequences for the future of agriculture.
This book is a direct result of a symposium held on 1 December 1988 at the American Society of Agronomy Annual Meeting in Anaheim, CA. Each chapter has been written by an invited expert speaker to that symposium, with the help of coauthors they have enlisted. Early in 1987, when first elected to be the 1988 program chair for Division A-3, severed colleagues urged me to organize a symposium on this timely topic. That it was timely proved to be an understatement when the Midwest drought of the summer of 1988 became headline news across the USA and raised the public consciousness level about the possibility that the greenhouse effect might be real and that the climate might already have changed. Only a few atmospheric scientists publicly attributed the USA drought of 1988 to the greenhouse effect.
Nevertheless, the interest in the topic and the symposium was high, and hopefully will also be high for this book.
In addition to the invited speakers (who, along with their coauthors, have produced the chapters in this book), the symposium also featured a session with 14 volunteered posters. Although the goal of the invited papers and this book was to review existing information and synthesize principles, the posters presented new research results, which also contributed to the interest in and success of the symposium. The abstracts of these poster presentations are in the 1988 Agronomy Abstracts (published by the American Society of Agronomy), but as an acknowledgement of their important contribution to the symposium and as an aid to the reader, a list of the poster presentations is included in Appendix A.
Several other acknowledgments are appropriate for contributions to the symposium and to this book. First, I thank the speakers and presenters who produced stimulating talks and posters that made the symposium a success. Similarly, I thank the authors and coauthors for writing their book chapters that provide an excellent compilation of current knowledge on this topic. Also toward this end, I appreciate the efforts of my colleagues on the editorial committee, Drs. Norman J. Rosenberg and Leon Hartwell Allen, Jr., who took their role seriously by rigorously and fairly reviewing and editing the manuscripts. Next, I wish to thank the 1988 program chairs of the several other divisions who cosponsored the symposium, particularly those who pledged financial support. The encouragement and the solicitations of financial support for the symposium by 1988 ASA program chair Dr. E.C.A. Runge are greatly appreciated. Similarly, the encouragement and suggestions of Dr. Roger C. Dahlman, Department of Energy, Carbon Dioxide Research Division, were helpful in shaping the symposium. Finally, the grant from the USDA-ARS, which provided travel expenses for the “non-society” speakers, is gratefully acknowledged.
BRUCE A. KIMBALL, editor
U.S. Water Conservation Laboratory, Phoenix, Arizona
Basil Acock, Research Leader, USDA-ARS, NRI, Systems Research Laboratory, Beltsville, MD 20705
Leon Hartwell Allen, Jr., Soil Scientist, USDA-ARS, University of Florida, Gainesville, FL 32611
S. W. Buol, Professor of Soil Science, Soil Science Department, North Carolina State University, Raleigh, NC 27695-7619
Lauretta M. Burke, Environmental Analyst, AMS, Arlington, VA 22009. Formerly Environmental Analyst, The Bruce Company, Washington, DC
Elizabeth P. Flint, Research Associate, Department of Botany, Duke University, Durham, NC 27708
J. Goudriaan, Crop Physiologist, Department of Theoretical Production Ecology, Agricultural University, Wageningen, the Netherlands
Sherwood B. Idso, Research Physicist, USDA-ARS, U.S. Water Conservation Laboratory, Phoenix, AZ 85040
Bruce A. Kimball, Soil Scientist, USDA-ARS, U.S. Water Conservation Laboratory, Phoenix, AZ 85040
J. M. Kimble, Research Soil Scientist, USDA-SCS, Lincoln, NE 68508-3866
Daniel A. Lashof, Senior Scientist, Natural Resources Defense Council, Washington, DC 20005. Formerly Environmental Scientist, USEPA, Washington, DC
Michael C. MacCracken, Division Leader, Atmospheric and Geophysical Sciences, Lawrence Livermore National Laboratory, Livermore, CA 94550
David T. Patterson, Plant Physiologist, USDA-ARS, Botany Department, Duke University, Durham, NC 27706
Norman J. Rosenberg, Senior Fellow and Director, Climate Resources Program, Resources for the Future, Washington, DC 20036
Pedro A. Sanchez, Professor of Soil Science, North Carolina State University, Raleigh, NC 27695-7619
Karl E. Taylor, Research Scientist, Lawrence Livermore National Laboratory, Livermore, CA 94550
M. H. Unsworth, Department of Physiology and Environmental Science, University of Nottingham, School of Agriculture, Sutton Bonington, LE12 5RD, England
S. B. Weed, Professor of Soil Science, Department of Soil Science, North Carolina State University, Raleigh, NC 27695-7619