Rivers in temperate ecoregions - overview
The pristine status
Rivers in temperature regions are usually characterized by permanent flow, but discharge may vary by orders of magnitude between seasons and watersheds. Ice cover is an exception and mean summer temperature is a main factor for community composition. Community structure depends to a large extent on size, altitude and catchment geology. Species number is considerably higher than in cold ecoregions, but far lower than in the hotter Mediterranean.
Human impactWhile some near natural small stream can still be found, almost all medium-sized and large rivers have been deteriorated by a multitude of impacts. For decades organic pollution was most significant, while nowadays hydromorphological degradation (straightening, dams, and removal of riparian vegetation) is most widespread.
Climate change impact
In the Atlantic zone of northwestern Europe, the more extreme climate events are likely to include heavy rainfall over short periods of time resulting in spates and dry periods, with high air temperatures and high evapotranspiration rates leading to drought. These environmental changes will affect streams and rivers. Higher precipitation will result in more surface runoff to streams and higher spates in rivers. Under predicted future climates, further stresses on streams and rivers will be introduced, including the combined effect of direct changes in precipitation and indirect climate-induced changes in land use patterns (Verdonschot and van den Hoorn, 2010).
- Edwards François K., Baker Roger, Dunbar Michael and Laizé Cedric (2012). REFRESH Deliverable 2.14: Review on processes and effects of droughts and summer floods in rivers and threats due to climate change on current adaptive management strategies link to article
- Verdonschot PFM, Van den Hoorn M (2010) Using discharge dynamics characteristics to predict the effects of climate change on macroinvertebrates in lowland streams. Journal of the North American Benthological Society, 29, 1491–1509. link to article