What are four ways in which human activities are disrupting and degrading freshwater systems?
As with coastal systems, human activities are also degrading lakes, streams, and freshwater wetlands. Dams and canals fragment freshwater systems, destroying habitats, eliminating migratory fishes like salmon, and turning flowing systems into lakes. Flood control levees and dikes disconnect rivers and streams from their floodplains, which affects not only the stream, but also the floodplain habitat, whether it is terrestrial or aquatic. Pollution from farms, cities, and industries can affect primary productivity (both up and down) and kill or reduce the abundances of numerous aquatic species. Wetland destruction from farming and municipal development eliminates all of the ecosystem services that these ecosystems provide.