Fine-Scale Vegetation Change and Its Implications for Methane Emissions in Arctic Aquatic Ecosystems

Abstract

While small water bodies (ponds) make up a small fraction of the surface area of Arctic permafrost landscapes, they have been observed to emit disproportionately high volumes of methane and carbon dioxide. To assess drivers of emissions, we mapped the spatial distribution of two aquatic graminoid species associated with high carbon fluxes in Utqiagvik, Alaska over a two-decade period. We combined in situ carbon flux observations with very high resolution panchromatic satellite imagery and drone photogrammetry to directly assess changes in 255 ponds across 5 drained thaw lake basins. Across the study, aquatic graminoid species significantly diminished in spatial coverage. We found that larger ponds (<330m2) drove the trends in vegetation cover loss, while smaller ponds remained stable. These changes also occurred mostly in the past decade (2012-2023). The rapid loss of aquatic emergent vegetation cover could stem from shifts to hotter and dryer climate, increases in pond temperature, and active layer depth. Given the role of methane transport by aquatic plants, our findings represent a significant change in methane emissions and a potential shift in the pathways of carbon in aquatic ecosystems in the Barrow Peninsula.