Air pollution weakens global spring greening

Abstract Climate change is causing widespread land surface greening in spring1–4, but the impacts of anthropogenic air pollution on these changes remain poorly understood. Using global ground and satellite observations of fine particulate matter ≤ 2.5 μm (PM2.5) from 2000 to 2020, here we show that PM2.5 concentration offsets global spring greening as indicated by significant decreases in the normalized difference vegetation index (NDVI), leaf area index (LAI), and solar-induced fluorescence (SIF). Our experiments and meta-analyses involving up to 104 worldwide species reveal that pollution-induced greenness declines are primarily due to physical blockage and damage to leaf stomata. However, factors such as increased diffuse radiation and nitrogen deposition may occasionally enhance greening. Moreover, we observed significant variations among state-of-art terrestrial ecosystem models in replicating these greenness declines, with incorrect representation of PM2.5 effects on vegetation greening for roughly one third of global land coverage, further underscoring the importance of empirical data for benchmarking these models. This study reveals the negative feedback between anthropogenic air pollution and terrestrial carbon uptake, emphasizing the critical need for major polluting countries to mitigate air pollution and CO2 emissions.