Response of vegetation water use efficiency to climate change and human activity in the Guangdong-Hong Kong-Macau Greater Bay Area, China

Abstract

Vegetation water use efficiency (WUE) describes the interaction between carbon assimilation (photosynthesis) and water vapor (transpiration) and is one of the most important vegetation indicators of ecosystems. However, there are fewer previous studies specifically focusing on WUE in subtropical regions. The Guangdong, Hong Kong and Macao Greater Bay Area (GBA), a representative of subtropical regions strongly affected by climate and human activities, was selected as the research object. Based on MODIS GPP, ET, and climate data from 2000-2018, this study analyzed the spatial and temporal characteristics of WUE and its response to climate change and human activities by using Theil-Sen median trend analysis, partial correlation analysis, and multiple regression residual analysis. The study showed that the vegetation WUE in the GBA was low near the Pearl River estuary and high in the periphery, and 65.85% of the area WUE showed an increasing trend; however, only 10.25% of the area maintained a consistent increase in the future. The mean value was 1.30 g C m⁻² mm⁻¹, increasing at a rate of 0.001 g C m⁻² mm⁻¹ per year. WUE was negatively, positively, and positively correlated with precipitation, temperature, and solar radiation, respectively. The highest correlation coefficient was 0.31 with solar radiation. Human activities also had a profound effect on the region, causing an increase in WUE in 40.60% of the area.