Assessing restoration potential for beaver (Castor canadensis) in the semiarid foothills of the Southern Rockies, USA

Abstract

AbstractWe used the Beaver Restoration Assessment Tool (BRAT) developed at Utah State University to develop spatially explicit estimates of maximum beaver‐carrying capacity in a 160 km2 watershed in the foothills of the Southern Rockies. The watershed does not currently have beaver but has extensive evidence of past beaver occupation. BRAT uses input data on stream flow, topography, and vegetation. We compared BRAT results using three different types of vegetation inputs: the default LANDFIRE data at 30‐m spatial resolution and pixel‐based and object‐based image analysis (OBIA) with 1‐m resolution National Agriculture Imagery Program imagery. OBIA produced the most accurate results relative to ground‐based vegetation mapping. Changes in vegetation input data resulted in substantial changes in BRAT estimates of beaver‐carrying capacity. Using historic LANDFIRE vegetation data and field evidence of past beaver activity, contemporary beaver‐carrying capacity is much lower than historical capacity throughout the watershed. These changes are especially pronounced in low‐order stream segments, suggesting that beaver reintroduction in this watershed could be facilitated by measures to restore riparian vegetation along low‐order streams. This case study demonstrates the value of using BRAT as a tool prior to beaver reintroduction and stream restoration.