The ecology of large rivers: a symposium in perspective (Krems, Austria, 1995)
Large river ecosystems are, above all, manipulated systems. According to Dynesius & Nilsson, fragmentation of river channels by dams and water regulation affects 77% of the total discharge of the 139 largest river systems in the northern third of the world. A similar picture seems likely to occur when considering the remaining two-thirds of the world. Such a situation could result in catastrophic ecological and economic consequences at regional and national levels. Clearly, an important issue for future decades will be to conserve, restore or rehabilitate large river systems.