Spatiotemporal patterns of evapotranspiration along the North American east coast as influenced by multiple environmental changes

The North American east coast has experienced significant land-use and climate changes since the beginning of the 20th century. In this study, using the Dynamic Land Ecosystem Model 2.0 driven by time-series input data of land use, climate and atmospheric CO₂, we examined how these driving forces have affected the spatiotemporal trends and variability of evapotranspiration (ET) in this region during 1901-2008. Annual ET in the North American east coast during this period was 648.3±38.6mm/year and demonstrated an increasing trend. Factorial model simulations indicated that climate variability explained 76% of the inter-annual ET variability. Although land-use change only explained 16% of the ET temporal variability, afforestation induced the upward trend of ET and increased annual ET by 12.8mm/year. Elevated atmospheric CO₂ reduced annual ET by 0.84mm, and its potential impacts under future atmospheric CO₂ levels could be much larger than estimates for the historical 1901-2008 period. Climate change determined the spatial pattern of ET changes across the entire study area, whereas land-use changes dramatically affected ET in watersheds with significant land conversions. In spite of the multiple benefits from afforestation, its impacts on water resources should be considered in future land-use policy making. Elevated ET may also affect fresh water availability for the increasing social and economic water demands.