KNOWLEDGE BASE

This article reviewed the research on the engineering of beaver dams for both living species of beaver. It found that beaver dams reach lengths of 850 m and heights of up to 5.3 m. Beavers sometimes use rocks up to 30 cm in diameter as well as wood. The dams have a big impact on water flow, sediment processing, and flooding. The author suggested that beaver construction methods could inspire nature-based solutions for river restoration and flood control.

Eurasian beavers were reintroduced to Romania around the turn of the millenium, with almost 200 individuals released over a 5-year period. Since then, beavers have successfully expanded their population to an estimated 2000 individuals in 2016. This study compared beaver-modified and beaver-free wetland areas near the Barsa River, Romania. The results showed how beavers - through flooding and deforestation - had transformed the types of habitat and vegetation in the area, initiating a new phase of ecological succession from forested wetland to shrub wetland.

This article reports on studies of Swedish beaver ponds, and the influence they had on the processing of dissolved organic material: that is, material which contains carbon. The age of the beaver pond was very important, with differences in processing between ponds and un-dammed streams disappearing as the pond ages. Therefore, beaver ponds temporarily increase organic matter in the water, diversifying the ways that carbon gets processed in the ecosystem.

In the context of widespread re-introduction efforts, this study tried to understand why North American beavers did not settle in certain areas of the USA. They found that typical cattle grazing disrupts the relationship between beavers and willow trees. By grazing, cattle make stretches of rivers unsuitable for beaver. Livestock management will have to change for successful beaver restoration in these areas. Please note, this resource is not open-access.

Published in 2016, at the time of writing the two wild populations of beavers in Scotland were present on a trial basis with the case of their full reintroduction is being considered by Scottish ministers. This review investigated the mechanisms by which beavers act as ecosystem engineers and discussed the possible impacts of beavers on the biodiversity of Scotland. The review states that a widespread positive influence on biodiversity would be expected, though detrimental impacts on certain woodland habitats and species of conservation importance is to be considered.