In its second Assessment Report (December 1995) the Intergovernmental Panel on Climate Change (IPCC), established by the World Meteorological Organization and the United Nations Environment Programme, concluded that 'the balance of evidence suggests a discernible human influence on global climate'. A change in climatic conditions will affect agricultural production systems the world over. Until now, the projections of the Food and Agriculture Organization of the United Nations (FAO) on the state of agriculture in the forthcoming decades, such as Agriculture: Towards 2010 (FAO and John Wiley, 1995) have not included the potential effects of any anthropogenic climate change at global and regional levels. Instead, they concentrated on the expected increase in human populations, their basic needs and aspirations for increased well-being, and the associated demands on natural resources, especially land and water resources, to provide them with the necessary food, fibre, animal feed, forest products and living space.
Although there can be no doubt that the increase in human populations and their capacity to influence land cover and land use will remain of predominant influence, projections beyond 2010 will have to reckon with changes in agroclimatic conditions as a result of the enhanced greenhouse effect (including temperature rise, CO2 increase, and nitrogen deposition) envisaged to be larger than any natural climatic variation in the last few thousand years.
With the financial support of the United Nations Environment Programme (UNEP), an Expert Consultation at FAO headquarters in Rome was held to discuss direct and indirect effects on agriculture at the regional level. Agriculture was defined in the broad sense to include crop growing, animal husbandry, forestry and fisheries - all within the mandate of FAO. However, for a number of reasons the Consultation and the resulting texts concentrated on changing climatic conditions for annual and perennial crop growing, with emphasis on the effects of changing hydrological, pedological and plant physiological processes. In doing so, it attempted to strike a balance between the negative effects of the anticipated climate change on natural and managed ecosystems - so often emphasized in the debate on the enhanced greenhouse effect - and the potential positive effects on plant production of higher temperatures, an increased CO2 fertilization and higher water-use efficiency - which might constitute a blessing in disguise for the future of humanity.
It should be mentioned that the projections on the pace and severity of climate change, as the basis for models on land productivity discussed in several chapters, are still those of the IPCC First Assessment of 1990 and its Supplement of 1992 (global temperature rise till 2100 between 2 and 5°C, and a sea-level rise between 30 and 100 cm); in some cases, such as the projections for Africa, the models have even taken the maximum rather than the middle values of these changes as a starting point.
The new 1995 estimates of IPCC are lower (between 1 and 3.5°C temperature rise and between 15 and 50 cm sea-level rise). Modelling on the basis of the latter values still has to start. A reassessment of the effects on agricultural production will therefore be necessary in a few years' time. This is also in view of the ever-increasing amount of free-air measurements and experimental data on the effects of increasing atmospheric CO2 concentrations on plant growth and soil conditions.
The editors gratefully acknowledge the contributions to the conclusions and recommendations 1 by the participants of the 1993 Expert Consultation, including all members of FAO's standing Working Group on Climate Change. We appreciate the willingness of the authors of the various chapters to update their texts with information that became available only after the meeting.
1 See: Highlights from an Expert Consultation on Global Climate Change and Agricultural Production, FAO. Rome, 1994. Available from Dr. R. Gommes, Agrometeorology Group, FAO, Viale delle Terme di Caracalla, 00100 Rome.
Special thanks are due to Ms. Linda See for the preparations for the meeting, Ms. Margaret Farrell for the conscientious handling of the large amount of correspondence involved, Dr. David Norse for his initial editing work, and Ms. Chrissi Smith-Redfern for the careful screening of the final texts.
Fakhri Bazzaz and Wim Sombroek Rome, January 1996