Modes of Agricultural Adaptation to Climate Change.

The terms resilience and adaptation are often used interchangeably to describe the process by which agricultural production systems can be expected to cope with climate change.  In systems ecology, resilience is a measure of the ability of an ecosystem to absorb external forcing without major damage or change in form or governing process.  Once the forcing abates, the ecosystem drifts back to its initial metastable state.  Adaptation is a measure of the ability of an ecosystem to disintegrate in response to external forcing and then successfully reassemble into a different form with different governing processes.  The ecosystem emerges in a more efficient state with respect to external forcing.  Using those systems ecology definitions, the resiliency and adaptation potential of U.S. agricultural production systems are examined.  Examples from the literature of simple adjustments to climate variability and change are presented to illustrate resiliency.  Adaptive reorganization is demonstrated in the historical experience of production systems co-evolving with environmental stresses that are analogous to climate change, such as slow decline of irrigation groundwater.  Neither resiliency nor adaptation are cost-free, but the historical evidence suggests that agricultural production systems in the U. S. are well-positioned to cope with climate change--up to a point.  Success is crucial because current understanding suggests that the U. S. and other major mid-latitude grain producers will assume even greater responsibility as supplier of last resort to the developing nations of the Tropics.