Incorporating systems dynamics and spatial heterogeneity in integrated assessment of agricultural production systems

Agricultural systems are complex and dynamic, being made up of interacting bio-physical and human sub-systems. Moreover, agricultural systems are remarkably diverse, both within geographic regions and across regions. Accordingly, this
paper focuses on dynamics and heterogeneity in coupled, multi-disciplinary simulation
models of agricultural systems. We begin with a discussion of the principal features
of agricultural production systems. We then present an example of a ‘loosely coupled’
model, the type of model most researchers have used to represent agricultural systems.
We discuss the loosely coupled model’s features and limitations, and show how it can
be modified to incorporate feedbacks among sub-models. Finally, we use a case study of
a hillside production system in Ecuador to illustrate the importance of model coupling,
dynamics and heterogeneity in the analysis of production systems. This example shows
that feedbacks and threshold effects are most important at sites most vulnerable to tillage
erosion.