Rivers in warm ecoregions - indicators for climate change
The raising temperatures and changes in precipitation patterns due to climate change will result in complex cause–effect chains, linked by many interacting environmental parameters. The degree of ecosystem response will depend on the ecoregion (cold, temperate or warm) and ecosystem type (lakes, rivers or wetlands), and on species-specific adaptations of different organisms.
The purpose of this section is to suggest indicators for the effects of climate change on lake, river and wetland ecosystems that reflect the direction of their pathways, relative importance, and magnitude of change.The term ‘indicator’ is used here simply to describe a detectable signal of a complex process that can be used as an early warning of ecosystem change. Indicators may be chemical, hydrological, morphological, biological or functional parameters, which reflect key processes influenced by climate change and are relatively simple to monitor.
The purpose of this section is to suggest indicators for the effects of climate change on lake, river and wetland ecosystems that reflect the direction of their pathways, relative importance, and magnitude of change. It addresses the three ecosystem types and the three climatic regions always with four categories of indicators: (a) abiotic variables; (b) primary producers; (c) macroinvertebrates; and (d) fish.
Temperature is a key variable in determining physical properties of the water (such as oxygen solubility), duration of water stratification in lakes and biotic properties such as life history traits, reproduction success and metabolic rates. River temperatures in Europe have increased over the last 20?30 years. For example, in upland Wales, Scotland, southern English chalk streams, the upper Rhone, the Swiss Alps and Austria, by up to 1oC per decade.
How to measure:
Using in-situ fixed gauging stations, routine fieldwork or remote-sensing techniques (where possible) can provide data on changes in water temperature regime.
Tolerant/sensitive macroinvertebrate groups
Prolonged droughts in warm rivers will cause a shift from perennial to intermittent streams. lotic species, such as Ephemeroptera, Plecoptera and Trichoptera (EPT) will be replaced by more tolerant invertebrate groups, such as Odonata, Coleoptera and Heteroptera (OCH)
How to measure:
The ration between EPT and OCH
Lawrence, J.E., Lunde, K.B., Mazor, R.D., Bęche, L.A., McElravy, E.P. & Resh, V.H. (2010) Long-term macroinvertebrate responses to climate change: implications for biological assessment in mediterranean-climate streams. Journal of the North American Benthological Society, 29: 1424-1440.