Decline in net primary productivity caused by severe droughts: evidence from the Pearl River basin in China

Understanding the spatiotemporal characteristics of drought events and their impacts on terrestrial net primary productivity (NPP) is crucial for drought mitigation and environmental protection. This study, by taking the Pearl River basin as the case region, investigated drought duration, severity, intensity, affected area, and centroids during 1960-2015 based on the Standardized Evapotranspiration Deficit Index and three-dimensional clustering algorithm and then revealed how these drought characteristics have affected NPP. Results showed that there were altogether 32 severe drought events lasting at least 3 months in the basin, with half lasting longer than 6 months. The total NPP loss significantly correlated with drought severity and intensity. Most drought events caused reduce in NPP across more than half of the drought-affected area; specifically, the February-December drought in 2011 has cut NPP by 31.85 Tg C, accounting for 11.7% of the regional annual mean NPP, while the September 2009-September 2010 drought caused a decrease of 20.26 Tg C in NPP. Our research improves the insight into the relationship between NPP and drought, which helps decision-makers manage droughts and provides guidance for drought-related studies across other regions. HIGHLIGHTS Most drought events identified in the Pearl River basin from 1960 to 2015 lasted for more than 3 months. The total NPP loss significantly correlated with drought severity and intensity. The February-December 2011 drought in the PRB reduced NPP by 31.85 Tg C.