Erosion control under different political and economic conditions

It is generally accepted that changes in agricultural management during the last decades have had negative effects in the forms of increased erosion and nutrient losses, Even in a country like Norway, which has a low intensity in agricultural production, there has been an increase in erosion. Farmers are assumed to maximize expected profits using their farm as an economic entity. Economic incentives or direct regulations of agronomic practices may be used to change the farmers' management into a direction that will reduce the losses of nutrients and erosion. In an interdisciplinary research project with economists and ecologists, the effect of different policy measures on erosion and nutrient losses has been analysed. Policy measures analysed were, among others, catch crop requirements and subsidies for spring ploughing instead of autumn ploughing. First, an economic decision making model was ran for farms for a period of 20 years. The model decides the agronomic practice for each year on the different fields for a set of model farms. With the newly developed erosion model, the European soil erosion model (EUROSEM), the effect of the different agricultural practices were analysed not only at the level of single model farms, but also at the landscape level by use of a terrain model. The paper discusses the gains obtained by integrating economics and ecology with emphasis on erosion analysis. Results of the model analysis are presented showing the challenges associated with controlling erosion within agricultural activity mainly controlled by economic relations. The important insight from this modelling experience is that integration between economic and ecological models in one project gave more reliable results than separate analyses by economists or ecologists. (C) 1998 Elsevier Science B.V. All rights reserved.