Introduction

We study the management of a natural resource that serves a dual purpose. First, it supplies inputs for human production activities and is therefore being exploited for beneficial use, however defined. Second, it supports the existence of other species. Large-scale exploitation competes with the needs of the wildlife populations and, unless controlled, can severely degrade the ecological conditions and lead to species extinction and biodiversity loss. Examples for such conflicts abound, including: (i) water diversions for irrigation, industrial or domestic use reduce in-stream flows that support the existence of various fish populations; (ii) reclamation of swamps and wetlands that serve as habitat for local plant, bird and animal populations and as a ‘rest area’ for migrating birds; (iii) deforestation reduces the living territory of a large number of species; (iv) intensive pest control may lead to the extinction of the pests' natural predators and eventually to the invasion of an immune pest species which is harder to control; (v) overgrazing reduces soil fertility and entails the destruction of natural vegetation over vast semi-arid areas in central Asia and sub-Saharan Africa, contributing to the process of desertification; and (vi) airborne industrial pollution falls as acid rain on lakes and rivers and interferes with freshwater ecosystems.