Landscape-level quantification of potential impact of water holding borrow pits on beaver populations in the southern oil sands area of the Lower Athabasca Region

In a recent study, it was suggested that water-holding borrow pits provide suitable habitat for beavers, increasing the beaver population and promoting the growth of predator populations (wolves), which could negatively impact caribou populations. This may present a challenge for the inclusion of water-holding borrow pits as a closure feature on the reclaimed landscape, and could also lead to the expectation for removing pads at reclamation to return fill material to borrow locations, despite potential for such features to contribute habitat diversity. The purpose of this Phase 1 study is to screen the risk of increased beaver populations as a result of increasing suitable habitat provided by reclaimed water-holding borrow pits within the southern Athabasca oil sands region, focusing on risk quantification to determine whether further study is required and what this would entail. Beavers use multiple criteria to select habitat, including vegetation type and availability, and water availability. A beaver habitat suitability index (HSI) model was used to identify beaver habitat and assess habitat change over time.

The model estimated ~ 13.3 to 26.6 K beavers lived in reference areas and ~8.6 to 16.7 K beavers lived in developed areas historically. Increases in habitat supply in both areas were predicted. In the reference case, it likely occurred due to wildfires burning ~50% of the area; only a modest amount of habitat increases in developed sites could be attributed to wildfires. Overall, beaver abundance grew by ~10 to 11% in reference areas and ~28 to 30% in developed areas. Water-holding borrow pits have small footprints; estimated impact was a 0.5 to 2.0% population increase. However, they increased habitat supply in previous unsuitable areas, representing a change in distribution of beaver habitat and abundance that requires further investigation. Suggested next steps: (1) include data from Peace River; (2) fieldwork to: (a) collect data on shrub/woody plants and proportion of biomass used by beavers on perimeters of borrow pits and area, depth and ice thickness of these water bodies, (b) collect data on beaver occupancy/abundance at borrow pits, and (c) ground-truth AVI and land cover classifications; (3) examine how distribution of borrow pits relates to habitat supply and occupancy frequency in primarily upland areas (i.e.. away from natural water sources); and (4) use aerial imagery to ground-truth historical land classifications.