Date Published: June 4, 2019
Publisher: Public Library of Science
Author(s): Virgil C. Hawkes, Travis G. Gerwing, Julian Aherne.
While there is no denying that oil sands development in the Athabasca Oil Sands Region (AOSR) has large impacts upon the habitat it disturbs, developers are legally required to return this land to “an equivalent land capability.” While still early in the process of reclamation, land undergoing reclamation offers an opportunity to study factors influencing reclamation success, as well as how reclaimed ecosystems function. As such, an Early Successional Wildlife Dynamics (ESWD) program was created to study how wildlife return to and use reclaimed upland boreal habitat in the AOSR. Wildlife data comprising 182 taxa of mammals, birds, and amphibians, collected between 2011 and 2017 and from five oil sands leases, were compared from multiple habitat types (burned [BRN], cleared [CLR], compensation lakes [COMP], logged [LOG], mature forest [MF], and reclaimed sites [REC]). Overall, similarity of wildlife communities in REC and MF plots varied greatly, even at 33 years since reclamation (31–62% with an average of 52%). However, an average community similarity of 52% so early in the successional process suggests that current reclamation efforts are progressing towards increased similarity compared to mature forest plots. Conversely, our data suggest that REC plots are recovering differently than plots impacted by natural (BRN) or other anthropogenic disturbances (LOG), which is likely due to differences associated with soil reconstruction and development on reclaimed plots. Regardless of the developmental trajectory of reclaimed habitats, progression towards increased wildlife community similarity at REC and MF plots is apparent in our data. While there is no expectation that reclaimed upland habitats will resemble or function identically to naturally occurring boreal forest, the degree of similarity observed in our study suggests that comparable ecological functionality is possible, increasing the probability that oil sands operators will be able to fulfill their regulatory requirements and duty to reclaim regarding wildlife and wildlife habitat.
Located in the northeastern portion of the Canadian province of Alberta, the Athabasca Oil Sands Region (AOSR) has received national and international attention regarding the environmental costs of large-scale resource extraction [1, 2]. Of the ~142,200 km2 of land in the boreal forest that comprise the Alberta oil sands deposits, 93,000 km2 occur in the AOSR, where ~4,800 km2 are part of the surface mineable area available for oil and gas development . As of December 2017, ~895 km2 of the 4,800 km2 has been cleared or disturbed , all of which must be reclaimed . Like most intensive resource extraction initiatives, the development of the Athabasca Oil Sands results in large-scale anthropogenic disturbances [1, 2] and poses substantive challenges for conservation, land management, and habitat reclamation . Given the duration of operations associated with most oil sands mines in the AOSR (many exceed 50 years at current planned production rates), long-term disturbance to wildlife and their habitat is unavoidable. The primary agent of disturbance is habitat loss and isolation , leading to area and edge effects that can impact biodiversity  and alter the abundance and composition of flora and fauna near disturbed sites [8–11]. These impacts will have variable effects on wildlife species: some will adapt to a more fragmented environment while others will not and may become at risk of extirpation within the project area. However, oil sands developers are legally required to return disturbed land to “an equivalent land capability [1, 4],” defined as the ability of the land to support similar, but not necessarily identical land uses that existed prior to disturbance [3, 12].
Permits for this work were provided by the Alberta Environment and Parks, Policy and Planning Division, Fish and Wildlife Policy Branch.
A total of 182 taxa of wildlife (S1 and S2 Tables) were documented from all sampled oil sands leases. Overall more taxa were detected on REC habitats (n = 133) and those habitats were also associated with the largest number of unique taxa (n = 25). COMP habitats were associated with 127 taxa, of which 20 were unique. On BRN sites 72 taxa were observed and only 2 were unique. LOG and CLR habitats were the least with 54 and 55 taxa, respectively, and neither treatment was associated with any unique taxa of wildlife. Finally, 95 taxa of wildlife were observed in MF reference sites, 15 of which were unique. Each of the taxa associated with a given treatment was expected based on known patterns of wildlife habitat use, occurrence and distribution. This includes those taxa unique to a given habitat type (S1 and S2 Tables).
To assess reclamation progress with regards to wildlife usage in habitats disturbed by mining activities in the AOSR, as well as to assess the early applicability of the ESWD program, wildlife communities were studied at various treatments (REC, BRN, LOG, COMP, and CLR), and at several times since reclamation (age; 1–33 years). Current developmental progress was assessed by comparing wildlife communities of REC to MF plots. Overall, wildlife communities (presence/absence) at REC plots increased in similarity to reference plots over time, supporting preliminary observations of bird community succession in the oil sands [5, 57]. Similarity of wildlife communities in REC and MF plots varied greatly, even at 33 years since reclamation (31–62% with an average of 52%). This suggests that even though reclaimed plots are over time starting to resemble mature boreal forest wildlife communities, variation still exists. Rowland, Prescott  observed a similar relationship regarding plant communities, with REC plots resembling vegetative conditions at MF sites more over time, but differences remained. Overall, 33 years post-disturbance the average similarity between wildlife communities in REC and MF plots was 52%. Such a high community similarity value is promising from a reclamation success perspective, as upland stands 33 years of age are still immature relative to mature boreal forest, and vegetative communities appear to stabilize 25 years following reclamation . More generally, plant communities in the boreal forest start to resemble mature plots at ~50 years of age, with resemblance increasing at 60–100 years; however, succession can continue on these plots 250–300 years following disturbance, with few stands transitioning into old growth forest before natural disturbances such as fire resets succession [59–62]. That REC plots on average exhibit wildlife communities ~52% similar to MF reference plots only 33 years into the recovery process suggests that current upland reclamation efforts in the AOSR is progressing towards increased similarity when compared to mature forest plots. However, further assessments of habitat productivity and function are needed before reclamation success can be more fully assessed.