Ecosystem theory and conservation

Abstract

Conservation of aquatic systems has broadened tremendously over the years. The original motives still stand: we conserve for a large number of utilitarian reasons – water supply for domestic, agricultural and industrial uses, fisheries and other natural resources, recreation, navigation, hydroelectricity and many more. The broadening has come about principally in terms of how the questions are viewed, and particularly how multiple issues need to be analysed and resolved. Thus the concept of ecosystem is invoked as a general framework in which the multiple factors interact. The framework is obviously important for this journal, which has ‘ecosystem’ in its title. We invoke ‘ecosystem health’ and a variety of ecosystem properties, like resilience, resistance and stability, in our rhetoric, and we imply that these concepts can be assessed and incorporated into conservation and management. Because our modern practice of conservation invokes ecosystem I consider it interesting and important to review its theoretical basis. In other words, how does ecosystem theory inform us about conservation practice? For my arguments we need to make a distinction between ‘community’ and ‘ecosystem’. There are good reasons for not doing this, as pointed out by many ecologists (e.g. Begon et al., 1986), but the artificial separation of the biological components (community) from their context within the environment (ecosystem) will illustrate some important phenomena. I will allocate all questions of energy and materials flow to ecosystem, and biodiversity, food webs and biotic interactions to community. Historically, ecology of communities and ecology of ecosystems have developed separately, and for