By John Reilly

The agriculture sector assessment is nearing completion, with a draft report in review, and publication expected by late spring.  The sector report will be a stand-alone document consistent with reports of other parts of the assessment.  It serves as a major input into the Agriculture section of the National Assessment Synthesis Team Foundation Document.  Plans are also underway to submit technical articles for publication in a variety of journal outlets.

As reviewed in the agriculture sector report, there have been a number of assessments of the impacts of climate change on U.S. agriculture dating to the late 1970's.   The approaches taken in these assessments have ranged from literature reviews, comprehensive quantitative assessments, and development of integrated models to elicitation of expert judgement and analysis of the implications of potential effects for adaptation and policy. 

The agriculture sector assessment combined many of these approaches.  Using methods developed in past assessments, we conducted new quantitative studies of impacts on production agriculture using the new climate scenarios made available to the assessment.  Past assessments relied on doubled CO2 climate scenarios ("equilibrium runs") and generally did not include the cooling effects of aerosols.  In contrast, we used transient runs that included aerosol effects.  We also explicitly considered changes in pesticide expenditures, effects on livestock, and changes in water resource supply and irrigation demand.  Thus, we were able to consider more completely the effects on production agriculture and the implications for resource use.

The sector team also forged into new areas.  These included the complex interactions of environment, agriculture and resources.  We conducted case studies of the impacts of climate change on nitrogen loading in the Chesapeake Bay and the interrelationships of groundwater use, agriculture, preservation of endangered species habitat, and urban water use in the San Antonio, Texas area that relies on the Edwards' aquifer for water supplies.  We investigated the implications for agriculture of potential changes in El Niño/Southern Oscillation (ENSO) intensity and frequency, considering the potential economic losses and the value of improved ENSO forecasts if intensity and frequency increase.  We also studied the migration of crop production over the past century to provide an historical perspective on changes in agriculture.

The results of our analysis confirm some of the broader results of past assessments while adding a deepened understanding of how climate change will affect agriculture.  The sector has attempted to link these climate change impacts that could occur over the next several decades and the next century to some of the other fundamental forces that are likely to reshape US agriculture.  As co-chair of the Assessment, I find the new results fascinating and, I believe, once finalized, readers will find the report to be useful and interesting -- essential reading for those who are thinking about the future of agriculture over the next century. For an early glimpse of some the results, those readers who are interested should access the agricultural sector technical working papers available on the national assessment web site.

For more information, contact:
John Reilly, Joint Program on the Science & Policy of Global Change; MIT E40-263, 1 Amherst St., Cambridge, MA 02139; phone: (617) 253-8040; email: jreilly@mit.edu.