EXTREME CASES - A STRATEGY FOR ECOLOGICAL RISK ASSESSMENT IN ECOSYSTEM HEALTH

I contend that focusing on the ''absence of health,'' or what I will c all ''extreme cases,'' provides a basis for agreement about ecosystem health in ecosystem management. An extreme case is defined where there exists (1) scientific agreement about models, (2) scientific agreemen t about scale, (3) policy agreement that the risks will be great and u nnecessarily so. scientific agreement requires that a link be establis hed between biodiversity and ecosystem processes, goods, and services. I discuss recent work concerning ecosystem engineers that demonstrate s such a link. Agreement about scale requires consensus about the scal e of management decisions, both spatial and temporal,;md reconciliatio n Of management goals and objectives of the various stakeholders in an ecosystem. Finally, policy agreement requires that ecological risks b e great and unnecessarily so Where these extreme cases do not apply, I suggest that it will be useful to appeal to stakeholder negotiations to seek agreement concerning ecosystem health.