Long-term climate-influenced land cover change in discontinuous permafrost peatland complexes

The discontinuous permafrost zone is undergoing rapid transformation as a result of unprecedented permafrost thaw brought on by circumpolar climate warming. Rapid warming over recent decades has significantly decreased the area underlain by permafrost in peatland complexes. It has catalysed extensive landscape transitions in the Taiga Plains of northwestern Canada, transforming forest-dominated landscapes to those that are wetland dominated. However, the advanced stages of this landscape transition, and the hydrological and thermal mechanisms and feedbacks governing these environments, are unclear. This study explores the current trajectory of land cover change across a 300 000 km2 region of northwestern Canada's discontinuous permafrost zone by presenting a north–south space-for-time substitution that capitalizes on the region's 600 km latitudinal span. We combine extensive geomatics data across the Taiga Plains with ground-based hydrometeorological measurements collected in the Scotty Creek basin, Northwest Territories, Canada, which is located in the medial latitudes of the Taiga Plains and is undergoing rapid landscape change. These data are used to inform a new conceptual framework of landscape evolution that accounts for the observed patterns of permafrost thaw-induced land cover change and provides a basis for predicting future changes. Permafrost thaw-induced changes in hydrology promote partial drainage and drying of collapse scar wetlands, leading to areas of afforestation forming treed wetlands without underlying permafrost. Across the north–south latitudinal gradient spanning the Taiga Plains, relatively undisturbed forested plateau–wetland complexes dominate the region's higher latitudes, forest–wetland patchwork are most prevalent at the medial latitudes, and forested peatlands are increasingly present across lower latitudes. This trend reflects the progression of wetland transition occurring locally in the plateau–wetland complexes of the Scotty Creek basin and informs our understanding of the anticipated trajectory of change in the discontinuous permafrost zone.

The trajectory of landcover change in peatland complexes with discontinuous permafrost, northwestern Canada

The discontinuous permafrost zone is undergoing rapid transformation as a result of unprecedented permafrost thaw brought on by circumpolar climate warming. Rapid climate warming over recent decades has significantly decreased the area underlain by permafrost in peatland complexes. It has catalyzed extensive landscape transitions in the Taiga Plains of northwestern Canada, transforming forest-dominated landscapes to those that are wetland-dominated. The high rate and large spatial extent of this thaw-induced landcover transformation indicates that this region is particularly sensitive to warming temperatures and will continue to respond to climatic changes and landscape disturbances. This study explores the current trajectory of landcover change across a 300 000 km2 region of northwestern Canada's discontinuous permafrost zone by presenting a space-for-time substitution that capitalizes on the region's 600 km latitudinal span. To illustrate this trajectory of change we present the distribution of peatland-rich environments that govern permafrost coverage in this region of the discontinuous permafrost zone. We also establish that relatively undisturbed forested plateau-wetland complexes dominate the region's higher latitudes, forest-wetland patchworks are most prevalent at the medial latitudes, and forested peatlands are increasingly present across lower latitudes, indicating not only a climatic gradient but also a landscape in transition as local mean temperatures increase. This study combines extensive geomatics data with ground-based meteorological and hydrological measurements to inform a new conceptual model of landscape evolution that accounts for the observed patterns of permafrost thaw-induced landcover change, and provides a basis for predicting future changes.