Temperature Elevation

The cold water of mountain streams is able to support trout and other coldwater fishes due to high elevation and forest shading.

Loss of forest cover near the stream lets sunlight shine on the water, resulting in increased stream temperatures. The duration of the temperature increase is shortlived (less than 5 years) if the vegetation is allowed to regrow, with temperatures returning to normal once the canopy closes over the stream again. However, if forest is cleared for other land uses such as agriculture or urban and suburban development, temperatures may be permanently elevated. Temperature increases may be particularly dramatic where forest cover is replaced by heat-storing pavement.

This warming may render stream habitat unsuitable for coldwater organisms adapted to the highlands and facilitate invasion by coolwater and warmwater species. When accompanied by other effects of forest loss, such as increased light from opening the forest canopy and increased nutrient levels in streamwater, greater photosynthetic activity and other ecosystem changes can result. The effects of land-use activities on thermal regime may be reduced by implementation of best management practices and protection of riparian zones.