Irreversibility, uncertainty, and learning: Portraits of adaptation to long-term climate change

The usefulness of adaptation strategies to changing climate depends on the characteristics of the system that must adapt. Divergent views on whether c limate change will seriously affect society and what society can do about i t can be traced, in part, to divergent views on these characteristics of sy stems. Issues of scale and how impacts are measured are also important. We identify a set of fundamental characteristics of natural systems and social systems that help to make underlying assumptions in climate change adaptat ion studies explicit. These are: Short-run autonomous flexibility; short-ru n non-autonomous flexibility; knowledge and capacity to undertake short-run actions; long-run autonomous flexibility; long-run non-autonomous flexibil ity; and knowledge and capacity to plan for and undertake adaptations that require changes in long-lived assets. Applications to crop agriculture and ecosystems illustrate how these portraits can be used. We find that if empi rical research is to resolve questions of adaptability, more careful specif ication of the exact measure of impact and far richer models of the process of adaptation, able to test implicit assumptions in much of the existing e mpirical research, are needed.