13.2.1 LAKES

Freshwater resources will be generally reduced by climate change. They will become increasingly contaminated by organic compounds, toxic metals and nutrients as the result of land-use changes and long-range transport in the atmosphere. Freshwaters are already in short supply in many areas of the world. Research on the effects of global change on freshwaters must therefore be considered to be of the highest priority.

   As abiotic conditions (e.g. mean and maximum temperatures) change with climate shifts, major biogeographic changes will occur. Differences in dispersal capacity, increased variability in local populations, local extirpations, and invasion by exotics will occur. Species of primary interest as resources (e.g. fishes) will respond in ways that create important challenges to management.

   In an ecosystem context the most important changes to consider are temperature effects, hydrologic inputs (flushing rate and nutrient load) and contaminant load. New whole-lake manipulations are needed in two major areas.