KNOWLEDGE BASE

This study reports on the water quality impact of removing a 2-metre-high man-made dam in the USA. They found that the chemistry of the water - with the exception of one component - did not change significantly after dam removal. The authors compare this to the literature on small natural dams such as those made by beavers. Please note, this resource is not open-access.

Researchers studied how birds used 29 different wetlands in the USA. Shallow beaver wetlands supported more duck broods than deep, glacial wetlands. The beaver wetlands had high phosphorus levels and diverse plant life, providing nutrients and physical cover for insects to thrive. This benefitted insect-eating birds. Please note, this resource is not open-access.

Six years after their reintroduction, scientists analysed the impact of beavers on young oak forests in Croatia. They found that 75% of plants were undamaged but six species did receive damage. They found that damage typically occurred 30-40 cm above ground on trees around 2-4 cm in diameter. In the article, the scientists also report on the type of damage and how far away from the bank the damaged trees were found.

Over four years, researchers in the USA studied the movements, survival, and habitat of beavers in suburban and rural areas. Adult and juvenile beavers had high survival rates, but juveniles faced more risks. Deaths in rural areas were more often due to human activities and in suburban areas due to non-human factors like disease. Beavers' new areas were often smaller wetlands with less in the way of woody vegetation for beavers to eat on.

Beaver dams, by shaping freshwater ecosystems, can affect the growth of Atlantic salmon. In a Canadian stream, researchers studied the impact of a beaver pond on the growth and maturity of salmon. Fish in the pond grew faster and stayed in better condition compared to those above or below it.