Change in natural and managed ecosystems: detection, measurement and assessment

Abstract

Change is an intrinsic property of ecosystems. For effective conservation acceptable rates and directions of change need to be determined. A preliminary step is the development of methods for detecting, measuring and assessing the significance of ecological change. Prolonged surveillance of ‘natural’ and artificially modified systems is necessary to distinguish those elements of change which are short-term fluctuations (cyclical or stochastic) and those which are part of long-term, perhaps irreversible, trends. Criteria for selecting appropriate parameters (for example, biocoenoses, community diversity, populations of indicator species or production estimates) are required, together with appropriate techniques for monitoring them. Although few ecosystems are totally isolated from anthropogenic influence, those which remain largely unaffected serve as reference systems against which changes in intensively exploited or unmanaged (i. e. unprotected) ecosystems may be compared.