Response and risk in rural ecosystems: from models and plots to defined universes

This essay was prepared as an invited closure of a thematic session on “Scaling and Extrapolation” at the CGTE Conference on “Food and Forestry: Global Change and Global Challenges”. It is addressed to those who prognosticate at the global or other large levels about food and forestry systems, and who naturally confront several problems, and inevitably also some risk. The problems range from conceptual and practical to measuremental and statistical. For other than simplistic models, many constraints apply to procedures used to aggregate from small-scale to large-scale representations of agricultural systems, whether they be biophysical or socioeconomic, especially when uncertainty is explicitly recognized. Model-linking procedures work well in some cases but by no means all. The risks encountered in such work are similarly wide-ranging, depending on the intrinsic uncertainties, context, analyst and audience. These spectrums of problems and risks, along with some suggestions for what practically can be done about them (largely involving ad hoc simulation modeling), are examined from a response-analysis perspective across a range of biophysical and social phenomena pertinent to terrestrial ecosystems. Attention is given to policy applications of scaled-up models.