From reach to landscape: assessing beaver habitat suitability to guide wetland restoration in Rocky Mountain National Park

Abstract

Beavers play a critical role in shaping riparian and wetland ecosystems, enhancing water retention, increasing habitat complexity, and supporting biodiversity. This study investigated the vegetative and geomorphic factors influencing beaver occupancy and habitat suitability across the east side of Rocky Mountain National Park, with the goal of informing broader wetland restoration efforts. Data were collected at two spatial scales: a landscape-level assessment of beaver occupancy and habitat condition, as well as a fine-scale analysis of nine focal riparian areas representing a gradient of beaver activity (active, recent, and historic). The broad-scale survey revealed that current beaver activity is considerably reduced compared to historical levels. The habitat condition assessment showed substantial variability across the landscape, with a strong negative correlation between ungulate browsing pressure and willow height. At the fine-scale, multivariate analyses showed that active beaver occupancy is most closely linked to geomorphic characteristics—specifically, wider and deeper stream channels, broad valley bottoms, and expansive riparian zones. In contrast, vegetation metrics such as willow height and forage biomass were uniformly suitable across sites. The fine-scale analysis offered a more nuanced perspective, revealing that vegetation is not currently a limiting factor and that many suitable sites remain unoccupied. These findings suggest that while ungulate browsing contributed to historical habitat degradation and beaver decline, it is unlikely to be the primary factor limiting beaver re-establishment today. Whereas past declines may have been driven by vegetation loss, current occupancy patterns appear to be more strongly influenced by geomorphic suitability and limited beaver dispersal. This study highlights the importance of integrating multi-scale assessments of habitat suitability into wetland restoration planning. By identifying the key drivers and constraints of beaver occupancy, this research offers a more holistic understanding of beaver habitat dynamics and provides practical guidance for restoration site selection.