ADAPTATION IN AGRICULTURE

In some parts of the world, climatic limits to agriculture are estimated to shift by 200-300 km perdeg.C of warming (or 100 km per decade under the IPCC Business-As-Usual scenario). The warming-induce upward shift in thermal zones along mountain slopes would be in the order of 150-200 m perdeg.C of warming.

Agriculture has an ability to adjust, within given economic and technological constraints, to a limited rate of climatic change. This capability probably varies greatly between regions and sectors, but no thorough analysis of adaptive capacity has yet been conducted for the agricultural sector.

In some currently highly variable climates farmers may be more adaptable than those in regions of more equable climate. But in less developed economies, and particularly in some marginal types of agriculture, this intrinsic adaptive capability may be much less. It is important to establish in more detail the nature of this adaptability, and thus help determine critical rates of climatic change that would exceed those that could be accommodated by within-system adjustments.

FUTURE TASKS

This book has emphasized the inadequacy of our present knowledge. It is clear that more information on potential impacts would help us identify the full range of potentially useful responses and assist in determining which of these may be most valuable. Some priorities for future research may be summarized as follows.

* Improved knowledge is needed of effects of changes in climate on crop yields and livestock productivity in different regions and under varying types of management.

* Improved understanding is needed of the effects of changes in climate on other physical processes, for example on rates of soil erosion and salinization; on soil nutrient depletion; on pests, diseases and soil microbes, and their vectors; on hydrological conditions as they effect irrigation water availability.

* An improved ability is required to "scale up" our understanding of effects on crops and livestock to effects on farm production, on village production, and on national and global food supply. This is particularly important because policies must be designed to respond to impacts at national and global levels.

* Further information is needed on the effects of changes in climate on social and economic conditions in rural areas (e.g., employment and income, equity considerations, farm infrastructure and support services).

* Further information is needed on the range of potentially effective technical adjustments at the farm and village level (e.g., irrigation, crop selection, fertilizing, etc.) and on the economic, environmental and political constraints on such adjustments. In particular, national and international centres of agricultural research should consider the potential value of new research programmes aimed at identifying or developing cultivars and management practices appropriate for altered climates.

* Finally, information is needed on the range of potentially effective policy responses at regional, national and international levels (e.g., reallocations of land use, plant breeding, improved agricultural extension schemes, large-scale water transfers, etc.).

To date, less than a dozen detailed regional studies have been completed that serve to assess the potential impact of climatic changes on agriculture. It should be a cause for concern that we do not, at present, know whether changes of climate are likely to increase the overall productive potential for global agriculture, or to decrease it. There is therefore currently no adequate basis for predicting likely effects on food production at the regional or world scale. All that is possible at present is informed speculation. The risks that stem from such levels of ignorance are great. A comprehensive, international research effort is required, now, to redeem the situation.