Lidar derived models and NDVI trends indicate vegetation threshold response to hydroclimatic drivers across the Peace Athabasca Delta

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Aslami, Farnoosh
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Geography and Environment
In northeastern Alberta, Canada, the Peace Athabasca Delta (PAD) is a Ramsar and UNESCO World Heritage-designated wetland complex vital for biodiversity and well-being of the Indigenous communities residing there. In this study, remote sensing techniques were used to understand the changes that have occurred within the PAD over the past four decades. Initially, lidar data was used to quantify vegetation height changes and better understand NDVI (Normalised Difference Vegetation Index) trends across lidar survey sample areas. These findings were then utilized to interpret Landsat-derived vegetation and surface water trends across the entire PAD. Between 1984 and 2022, NDVI trend analysis indicated greening along ecotones surrounding perched basins (shrubification), accompanied by noticeable drying patterns in the surface water trends. Further, a significant drying event spanning 1999 to 2003, appears to have been initiated by the strong 1998 El Niño event. The overall average greening rates pre and post 1999-2003 were 2.1 m/yr. and 3.1 m/yr., respectively. The severe drying during that short interval appears to have altered the rate and patter of vegetation processes across the delta post-2003. The more recent period of 2018 to 2022 was also notable for the observed high levels of inundation. If the PAD’s open water and vegetation cover trends continue, surface moisture is generally expected to decrease, with commensurate increases in shrub cover. Meanwhile, certain areas like the southern region around Mamawi Lake, could become wetter due to localised changes in surface drainage. While flooding events are expected to continue to be a regular feature of this landscape, the extent to which the PAD can return to its historically large areas of persistent inundation remains uncertain.
remote sensing , lidar , Landsat , Peace Athabasca Delta , climate change , trend analysis