Opportunistic wetland formation, characterization, and quantification on landforms reclaimed to upland ecosites in the Athabasca Oil Sands Region

Abstract

Surface mine operators in the Athabasca Oil Sands Region (AOSR) of northeastern Alberta are required by regulation to mitigate habitat impacts resulting from their operations, including impacts to wetlands. To date, most land reclamation efforts have focused on recreating upland forestlands that resemble the surrounding natural (dry) boreal forest. However, the surficial conditions on these reclaimed upland sites can also promote spontaneous wetland development. At Suncor’s Base Plant mine, opportunistic wetlands occurring on reclamation sites have not been formally included in the current inventory of reclaimed wetland areas and remain largely unquantified. We characterized and delineated an estimated 210 ha of opportunistic wetlands (consisting of shallow open water, marshes, and swamps) using aerial photo interpretation and remote sensing analysis in combination with follow-up field verifications. The remote-based (desktop) delineations consistently underestimated actual wetland extents, due mainly to underestimations in the extent of non-inundated vegetation zones (e.g., wet meadow) as well as shrubby swamp. After field corrections, opportunistic wetland habitat was estimated to constitute ~ 17% of the total study area (1209 ha), representing more than a fourfold increase in aerial wetland extent associated with reclaimed landforms over that delineated prior to this study. The interspersion of opportunistic wetlands with upland reclaimed landforms, although unintended, more closely reflects the pre-disturbance landscape, which was characterized by a matrix of forestlands, peatlands, and mineral wetlands (in contrast to the more peatland-dominated lowlands). At Suncor, wetland vegetation composition varied significantly across the study area and was influenced by topographic variation (e.g., in elevation and % slope) in combination with the reclamation substrates (soils) that were placed prior to seeding/planting. Thus, the inclusion of opportunistic wetland delineation in reclamation tracking and closure planning merits consideration as does the opportunity to manipulate current reclamation practices to promote the establishment and persistence of wetlands on reclaimed landforms.