As mentioned above, changing climate scenarios all include a warming trend in those regions of the northern hemisphere that contain the majority of the world's lakes. We can logically expect that the thermal limits of current biogeography will change. Studies of ponds and lakes heated by effluents from power plants have provided some information about the effects of temperature change on aquatic ecosystems. However, no study has included adequate premanipulation data or good reference ecosystem studies. A thorough study of thermal effects on lakes and streams is required, and might be relatively inexpensive if combined with construction of new power plants.

   Some of the major changes anticipated in aquatic systems do not require whole-lake experiments; many major effects on freshwater lakes are predictable from current knowledge. For example, reduced water flows will cause increased concentrations of all chemicals including both nutrients and contaminants. These are predictable from models developed for eutrophication. Salinization will be a growing problem for shallow lakes in increasingly arid areas, but whole-lake manipulations are not needed for this issue. Preservation or replacement of fisheries will present major challenges to managers. For example even moderate warming may eliminate some major coldwater fisheries, requiring that they be replaced by warmwater assemblages. Fisheries and aquatic community changes will require much research, as well as development of new management capacities, but not necessarily whole-lake manipulations.