Decreasing relative importance of drawdown areas on waters in CO2 emissions in drylands

Abstract

Previous studies have mostly focused on the annual CO2 emissions from drawdown areas on a global scale. However, in drylands, which are more sensitive to global change, finely characterizing the relative importance of drawdown areas on waters (RIDW) in CO2 emissions at the spatio-temporal scale remains unclear. Here, we found that the total drawdown area of drylands could reach 22% of the waters area. From 2004 to 2020, the shrinking of the drawdown area of temperate lakes and reservoirs was the main factor leading to the decline of the total drawdown area. As a result, the mean total CO2 emissions from drawdown areas during 2013-2020 decreased by 18% compared with 2004-2012. The expansion of waters area led to a 29% increase in CO2 emissions from waters. The mean annual CO2 emissions from drawdown areas in drylands was as high as 132.3 ± 23.1 Tg C yr-1, which is equivalent to 61% of estimated CO2 emissions from waters, but its share of CO2 emissions of non-perennial waters shows a significant downward trend. Our study suggests that the spatio-temporal heterogeneity of CO2 emissions caused by the change of drylands waters area is an important part of the global carbon cycle.