Dam removal is now a common river management and restoration practice with substantial ecological consequences, and recent removals of large dams with potentially far-reaching effects have elevated the importance of understanding these consequences. We ask the question from the peer reviewed literature - what have been the general ecosystem responses to dam removal? Our primary method to answer this question was to evalute the peer reviewed literature and identify process-response regimes in the upstream, reservoir, and downstream environments.
We found that documented responses of ecosystem processes to dam removal include restored longitudinal connectivity for organism movement, shifts from lentic to lotic states in former reservoirs, transitions in community structure, and habitat modification through sediment transport and deposition. In all cases, however, short-term effects are typically followed by longer-term responses that bring ecosystems to a new condition that may or may not approach those existing prior to impoundment. We conclude with a presentation of conceptual models that link physical and biological response to dam removal.