Recovery of ecosystem productivity in China due to the Clean Air Action plan

Severe air pollution reduces ecosystem carbon assimilation through the vegetation damaging effects of ozone and by altering the climate through aerosol effects, exacerbating global warming. In response, China implemented the Clean Air Action plan in 2013 to reduce anthropogenic emissions. Here we assess the impact of air pollution reductions due to the Clean Air Action plan on net primary productivity (NPP) in China during the period 2014–2020 using multiple measurements, process-based models and machine learning algorithms. The Clean Air Action plan led to a national NPP increase of 26.3 ± 27.9 TgC yr⁻¹, of which 20.1 ± 10.9 TgC yr⁻¹ is attributed to aerosol reductions, driven by both the enhanced light availability as a result of decreased black carbon concentrations and the increased precipitation caused by weakened aerosol climatic effects. The impact of ozone amelioration became more important over time, surpassing the effects of aerosol reduction by 2020, and is expected to drive future NPP recovery. Two machine learning models simulated similar NPP recoveries of 42.8 ± 26.8 TgC yr⁻¹ and 43.4 ± 30.1 TgC yr⁻¹. Our study highlights substantial carbon gains from controlling aerosols and surface ozone, underscoring the co-benefits of regulating air pollution for public health and carbon neutrality in China.