Peatland-dominated boreal ecoregions at risk of drying in a warmer climate

The response of evapotranspiration (ET) to future climate warming is of critical importance to the global water cycle, land surface energy balance, and ecosystem carbon cycling. While a warming climate is expected to lead to increasing atmospheric demand for water (through higher vapour pressure deficit [VPD]), its impact on ET and water availability remains poorly understood for many ecosystems including those of the boreal biome. The vast boreal biome is a mosaic of forest, peatland, and lake ecosystems with more accumulated carbon than currently stored in the atmosphere. Utilizing a pan-boreal ET dataset obtained from 90 eddy covariance flux tower sites, we show that boreal peatland ET increases more than forest ET in response to increasing VPD. We also show that by the end of the 21st century, increases in growing season ET are expected to exceed changes in projected growing season precipitation …