KNOWLEDGE BASE

This text charts the history of the North American beaver from before European colonisation to the present. It explains how overhunting led to a severe reduction in beaver numbers, beaver ponds, and the amount of sediment that those ponds had been stopping from flowing downstream. Beaver populations have partially recovered to around one-tenth of their prior levels. Today, beaver dams still trap significant sediment. Beaver dam collapses are more common than many people think, and the collapses can cause floods and infrastructure damage.

In efforts to restore habitats for Pacific salmon, wood structures are often placed in streams to encourage beaver activity. This is because beaver dams create pools for young salmon. This study discovered that beavers used only three types of structure in the Bear River, USA, to build dams. The researchers developed a model to predict which structure beavers were likely to use, based on the features of the structures and their environment. This helps design better wood placement projects for salmon habitat restoration.

Pollution from human and animal waste can spread diseases to wild animals. This article looks at how two parasites affect various land and sea mammals, wild and captive. The analysis is based on different animals' fecal samples, including beavers. The disease caused by one of the parasites is sometimes called 'beaver fever' in North America because beavers are often implicated in its spread.

In this article, researchers report on how the wolf's return to a Canadian National Park affected local ecology. Wolves avoided areas with high human activity, creating two areas that could be compared. In the low-wolf area, elk numbers were higher, leading to greater browsing of willow and aspen. This reduced beaver numbers, measured by a lower density of beave rlodges. This study highlights how wolves' presence can affect the entire ecosystem, and how human activity has a large role in shaping that effect.

This article explores the role of small streams, often found in hilly or mountainous areas. These streams usually don't carry much dirt or debris. Heavy rains can lead to more sediment flow. Tree-felling can, too, as well as leading to more landslides. When temporary ponds form, beavers sometimes occupy them, leading to longer-term changes to the sediment flow of these systems.