Land use and land cover change altered terrestrial water cycle and ecosystem dynamics in the conterminous United States over the past two decades

Land use and land cover change (LULCC), a major phenomenon resulted from human activities, has profound impacts on the land surface processes and regional-to-global climate through land-atmosphere interactions. The past LULCC in the conterminous United States (CONUS) in the current century typically happened at small spatial scales but across various vegetation types and climate zones. However, the subsequent impacts of these small-scale LULCC have not yet been examined. For examining the impacts of LULCC the first step is analyzing how the regional biophysical and biogeochemical processes, especially the water and carbon cycle, were influenced by these LULCC. In this study, we compiled multisource LULCC records, including the dynamics of natural and agricultural vegetation, C3/C4 vegetation distribution and irrigation activities, and generated a harmonized annual LULCC dataset for the Conterminous United States (CONUS) at 5-arcmin resolution since 2001.We then set up a land surface modeling experiment with the two-decadal-long LULCC dataset to examine the impacts of LULCC on the terrestrial ecosystem water-carbon cycle in the CONUS. Specifically, we ran transient simulations of the Community Land Model 5.0 with consistent land cover in 2000 (control run) and with transient land cover from the developed LULCC dataset (experimental run). We compared key variables associated with water cycle and ecosystem dynamics, such as evapotranspiration, runoff, phenology, and ecosystem productivity. Results provide evidence that LULCC has significantly altered spatiotemporal patterns of these key variables over the past two decades.