Decoupling of rainfall and vegetation greening in the arid Asian
endorheic basins due to the irrigation intensification
Abstract
A large portion of Central-Western Asia is made up of contiguous closed
basins, collectively termed as the Asian Endorheic Basins (AEB). As
these retention basins are only being replenished by the intermittent
precipitation, increasing droughts in the region and a growing demand
for water have been presumed to jointly contributed to the land
degradation. To understand the impact of climate change and human
activities on dryland vegetation over the AEB, we conducted trend and
partial correlation analysis of vegetation and hydroclimatic change from
2001 to 2021 using multi-satellite observations, including vegetation
greenness, total water storage anomalies (TWSA) and meteorological data.
Here we show that much of the AEB (65.53%) exhibited a greening trend
over the past two decades. Partial correlation analyses indicated that
climatic factors had varying effects on vegetation productivity as a
function of vegetation types and aridity. In arid AEB, precipitation
dominated the vegetation productivity trend. Such a rainfall dominance
gave way to TWSA dominance in the hyper-arid AEB. We further showed that
the decoupling of rainfall and hyper-arid vegetation greening was
largely due to a significant expansion (17.3%) in irrigated cropland
across the hyper-arid AEB. Given the extremely harsh environment in the
hyper-arid AEB, our results therefore raised the concerns on the
ecological and societal sustainability in this region, where a mild
increase in precipitation might not be able to catch up the rising
evaporative demand and water consumption resulted from global warming
and irrigation intensification.