INTEGRATING RESEARCH ON ECOHYDROLOGY AND LAND-USE CHANGE WITH LAND-USE MANAGEMENT

One objective of the International Geosphere-Biosphere Programme is to provide a scientific basis for sustainable development policies. Land use change and ecohydrology are important components of this scientif ic basis, but predicting change is difficult because of the scale and complexity of the interactions between non-linear ecohydrological and socio-economic processes at different spatial and temporal scales. A s ystems framework, the Ecosystem Approach, has been developed to concep tualize these interactions for the purpose of providing information fo r sustainable development policy. The Ecosystem Approach combines the dynamics of the Holling figure-eight model - a conceptual model of dyn amics that stresses discontinuous change and destruction as an interna l property of the system - and the properties of self-organizing syste ms with the socio political aspects of decision making. The Ecosystem Approach highlights the problems of managing change in complex systems when that change may involve unpredictable shifts to a different attr actor. Although there are methods available to detect the occurrence o f such shifts, both detection and modelling are complicated by the pre sence of semi-stable attractors. When a model or an ecosystem is on a semi-stable attractor, it may appear to remain stable for an extended period prior to changing as a consequence of inherent instabilities. W hen the shift to a new attractor occurs, it is quite sudden and unpred ictable. A technical discussion on prediction under conditions of semi stability and chaos is included because it enhances our understanding of the role of surprise in ecosystems, as well as the utility of simul ation models. The principles of the Ecosystem Approach are derived fro m the theoretical discussion and an example of a land use policy in th e Huron Natural Area in south-western Ontario. These principles provid e a clear role for scientific research, and particularly simulation mo delling, within the larger context of policy and land use management. (C) 1998 John Wiley & Sons, Ltd.