Quantifying the impacts of land-cover changes on global evapotranspiration based on the continuous remote sensing observations during 1982–2016

Abstract

It is well documented that land use and land cover changes (LUCC) have profoundly affected global water cycles. However, the unclear relationship between hydrological effects and various LUCC characteristics and lack of observed continuous land cover data limit the accurate quantification of LUCC on global evapotranspiration (ET). Here, LUCC-induced ET changes were derived from continuously observed land cover maps during 1982–2016 using a Budyko type method (Zhang-curve), which suggests that woodland cover change is the key and most sensitive property of LUCC affecting water yield. A woodland reclassification scheme was proposed for applying the Zhang-curve. Separated global woodland coverage agreed well with observed data at the country level around the world. The Zhang-curve estimated global mean annual land ET as 540.8 mm·yr−1 (excluding Antarctica). We show that global LUCC increased ET 0.052 mm·yr−2 during the study period, contributing approximately 11.1% to the global ET increase estimated by Brutsaert (2017) about 0.47 mm·yr−2. The results suggest that human-induced increase in global woodland coverage during the past three decades has led to a notable positive increase in global land ET, which is contrary to previous findings based on potential land cover maps.