River fragmentation

The fragmentation of natural landscapes has become a pervasive conservation issue in the 21st century. On land, the need to better connect natural habitats has led to some large-scale conservation planning which seeks to create connected and protected area networks (CPANs). Rather than simply protected areas, CPANs explicitly consider landscape connectivity and ensure species can disperse between protected areas. Ultimately this creates more robust conservation planning especially in the face of climate change which is causing species to migrate their range to match shifts in global climate patterns. 

In freshwaters and rivers specifically ecological connectivity is considered to be particularly sensitive to fragmentation. Whereas on land a barrier to dispersal can often be circumvented with redundant paths between two places, species occupying rivers have very constrained dispersal pathways determined by the watercourse. This increased sensitivity is due to the unique structure of watersheds where the path between two places is unique and longer than a straight line between them. In fact, the placement of the first few barriers on a watershed have the largest impact on connectivity with subsequent barriers having less and less of an impact. This underscores the importance of understanding how aquatic barriers are fragmenting watersheds and where the most significant barriers are found.