Generic structures of decision support systems for evaluation of policy measures to reduce catchment-scale nitrogen fluxes

Abstract

Decision support systems (DSSs) for evaluation of different policy measures have two important functions: to assess how considered policy measures may influence the behavior of actors, and to predict the effects of a given set of actions generated from the anticipated behavior. So far, almost all attempts to construct DSSs for environmental management have focused on assessing the impact of a set of actions on the environment. Here, we describe the generic structure of a DSS that enables more complete evaluation of regional or national policies to reduce nitrogen inputs to water. In particular, we expound the principles for linking models of farm economic behavior to catchment-scale models of the transport and transformation of nitrogen in soil and water. First, we define system boundaries for nitrogen fluxes through the agricultural sector and the ambient environment to create a basis for model integration. Thereafter, we show how different modules operating on different temporal and spatial scales can be interlinked. Finally, we demonstrate how statistical emulators or meta-models can be derived to reduce the computational burden and increase the transparency of the DSS. In particular, we show when and how the temporal or spatial resolution of model inputs can be reduced without significantly influencing the estimates of annual nitrogen fluxes on a catchment scale.