Ecosystem Engineering by invasive exotic beavers reduces in-stream diversity and enhances ecosystem function in Cape Horn, Chile.

Anderson, C.B. and Amy D. Rosemond, 2007. Ecosystem Engineering by invasive exotic beavers reduces in-stream diversity and enhances ecosystem function in Cape Horn, Chile. Ecosystem Ecology, 154: 141-153.

Beavers were introduced to the Cape Horn region of South America during the early 20th century in order to start a fur industry. The industry didn't work out, but the beavers were well adapted to the region and soon expanded their territory throughout the islands. This study was done to find the effects beavers were having on stream ecosystems, including their effects on aquatic insects. In general, greater species diversity tends to equal greater productivity in ecosystems. In the beaver affected areas, however, the opposite was happening. The areas downstream of the beaver dams had fewer species of aquatic insects, but the overall numbers of insects were larger. The beavers changed the substrate of their streams by covering up the natural rock beds with organic debris. This destroyed the habitats for many insects, but allowed the insects that could live in the area to thrive due to the increase in nutrients. So while the beavers seemed to harm some species, they allowed the streams to have higher productivity due to increases in other areas. This further shows that exotic species can be complex issues.

The area the samples I'm studying came from is slightly affected by beavers. They have dams throughout the watershed, but the stream I care about is not directly downstream of them. If possible, I may be able to compare insects found at the source of the watershed, above any beaver sites, to the insects found at other sites.