Greenness in the Namib Desert across 2000-2018—an analysis of trends and drivers based on satellite observations

Abstract:

Monitoring vegetation trends and examining the drivers of the observed trends in drylands, which represent the largest terrestrial biome on the planet, is of great importance to understand the response of dryland vegetation to future climate changes and achieve environmental sustainability. Recent findings based on satellite data indicate greenness has increased in several regions worldwide, such as China, India, and the Sahel. These regional-scale greening patterns are sufficiently driven by human activities (e.g., land-use management) and combined human activities and climate factors (e.g., climate change, CO₂ fertilization). However, the analyses of greenness trend for regions without direct human activities in drylands are still lacking. To this end, this study investigates the secular vegetation trend across the sand dune portion of the Namib Desert over 2000-2018 and examines several potential causative factors including precipitation, temperature and CO₂ fertilization. A significant greening trend in the study region was found between 2000 to 2012 based on the linear least squares regression trend analysis on monthly NDVI. Structural equation modeling results showed CO₂ fertilization was the dominant driver of greening. These findings suggested that increased levels of atmospheric CO₂ played an important role in the observed greening of the Namib biome without the direct influences of human activities.