Ecosystem

Primary distinguishing features of freshwater ecoregion onservation

Connectivity 1 is essential to maintaining freshwater biodiversity. This includes connectivity between and within aquatic habitats, connectivity with the riparian zone and floodplains, and connectivity with subterranean systems. Loss of connectivity will fundamentally alter ecosystem processes and negatively affect species.

Because aquatic habitats are linked to each other, focusing solely on the protection of discrete sites will be an incomplete solution to developing a biodiversity vision, except perhaps in systems characterized by isolated, hydrologically unconnected habitats.

The recovery of disturbed habitats normally is dependent on the presence of adjacent or connected undisturbed habitats —called spatial refugia —that can serve as sources of recolonization. Among the most effective spatial refugia may be ecologically intact catchments, if they remain.

Within a catchment, the effects of land-based activities are propagated downhill and downstream, so an assessment must look beyond target freshwater habitats and consider land uses within the larger catchment. Although we know that land use affects aquatic habitats, we generally do not know the degree or extent of effects for different land uses, which complicates the analysis and design of a vision.

Downstream impacts can also propagate upstream, especially in systems characterized by migratory species. For coastal areas, a vision may need to extend to the marine environment.

Physical processes may be the most important ecosystem components to protect, particularly for large river systems with active floodplains. One of the primary challenges for freshwater ecoregion conservation is developing approaches to protect hydrologic processes operating over large spatial scales. In altered systems this may include restoration of the natural hydrograph.

For most freshwater species, we are currently unable to identify minimum...