RIVERINE LANDSCAPES - BIODIVERSITY PATTERNS, DISTURBANCE REGIMES, ANDAQUATIC CONSERVATION

The term riverine landscape implies a holistic geomorphic perspective of the extensive interconnected series of biotopes and environmental g radients that, with their biotic communities, constitute fluvial syste ms. Natural disturbance regimes maintain multiple interactive pathways (connectivity) across the riverine landscape. Disturbance and environ mental gradients, acting in concert, result in a positive feedback bet ween connectivity and spatio-temporal heterogeneity that leads to the broad-scale patterns and processes responsible for high levels of biod iversity. Anthropogenic impacts such as flow regulation, channelizatio n, and bank stabilization, by (1) disrupting natural disturbance regim es, (2) truncating environmental gradients, and (3) severing interacti ve pathways, eliminate upstream-downstream linkages and isolate river channels from riparian/floodplain systems and contiguous groundwater a quifers. These alterations interfere with successional trajectories, h abitat diversification, migratory pathways and other processes, thereb y reducing biodiversity. Ecosystem management is necessary to maintain or restore biodiversity at a landscape scale. To be effective, conser vation efforts should be based on a solid conceptual foundation and a holistic understanding of natural river ecosystems. Such background kn owledge is necessary to re-establish environmental gradients, to recon nect interactive pathways, and to reconstitute some semblance of the n atural dynamics responsible for high levels of biodiversity. The chall enge for the future lies in protecting the ecological integrity and bi odiversity of aquatic systems in the face of increasing pressures on o ur freshwater resources. This will require integrating sound scientifi c principles with management perspectives that recognize floodplains a nd groundwaters as integral components of rivers and that ave based on sustaining, rather than suppressing, environmental heterogeneity. (C) 1998 Published by Elsevier Science Ltd.