Potential Effects of Mongolian Beaver Activity on Riparian Ecosystems in the Upper Ulungur River

Abstract

The Mongolian beaver (Castor fiber birulai) is rare in China and occurs only in a small part of Xinjiang. Local studies describe where it lives and what habitat it selects, but few studies have asked what its activities do to the surrounding riverbank environment. This paper reviews 17 sources published from 1994 to 2024, including five local studies or official reports, seven studies or reviews from other regions, and five environmental or technical sources. The evidence supports a clear but scale-dependent conclusion. Although Mongolian beavers may not significantly alter the entire upper Ulungur River, their activities—such as dam building, burrowing, lodge construction, and feeding—can change nearby water flow, vegetation, and riverbank conditions. The strongest evidence suggests that beaver dams slow water flow, trap sediment, and change the shape of nearby riverbanks. Feeding on willows may also affect willow regeneration and distribution. The upper Ulungur River is arid, with limited wet riverbanks and willow stands. Therefore, even small wet patches created or maintained by beaver activity may be important to the local ecosystem. This paper argues that the Mongolian beaver is a localized ecosystem engineer. It may not significantly alter the entire watershed, but its effects around frequently used sites are real and deserve attention. Protecting the Mongolian beaver therefore requires more than monitoring population size. It also requires protecting the river sections where beavers are active, keeping riverbank habitats connected, and preserving enough willow resources.