River Regulation Influences Land-Living Animals

Feb. 28, 2013 — Forest-living insects and spiders become less abundant and birds are adversely affected along regulated rivers. Three different studies by ecologists at Umeå University in Sweden show that river regulation has a negative effect also on land-living animals.

It is already well known that river regulation influences salmon migration, aquatic insects and streamside vegetation, but effects on land-living animals have been poorly studied.

When free-flowing rivers become regulated, there is a reduction in the number of aquatic insects that, during spring and summer, emerge and fly onto land where they become food for land-living animals.

"Our studies show that the number of flying insects is lower along regulated rivers than along free-flowing rivers. This results in fewer forest-living insects and spiders along regulated rivers, as the resource they feed upon -- emergent aquatic insects -- is reduced," says ecologist Micael Jonsson, the lead author on two of the articles.

Together with a group of researchers, he has compared the abundance of insect-feeding animals along similar river stretches at four regulated and four free-flowing large rivers in northern Sweden and the Finnish Kemi River. Along these rivers, flying and ground-dwelling insects were caught. The flying insects were caught with a net mounted on the top of a moving car, and the ground-dwelling insects and spiders were caught in pitfall traps.

Continued:  http://www.sciencedaily.com/releases/2013/02/130228080238.htm