Carbon sink potential and the cost of afforestation in northwest China when accounting for ecosystem service value

The cost effectiveness of mitigating climate change through afforestation needs to be evaluated for regions with a fragile environment and vulnerable ecosystems. This study develops an integrated geographic-economic-ecological framework to evaluate the cost-effectiveness of afforestation for carbon sequestration in Northwest China. It employs a spatial model of natural factors and a bioeconomic optimization model to identify marginal lands suitable for afforestation. Results indicate that nearly five million hectares of land are ecologically suitable and available for afforestation, but only some 215,000 to 583,000 ha are economically feasible for afforestation, accounting for about one-eight of ecologically available land. The lands suitable for afforestation are primarily grasslands and other marginal lands distributed in Qinghai and Gansu provinces. Afforestation has the potential to remove 1.05–1.21 million tons of CO₂ per year from the atmosphere in Northwest China. By 2060, this potential will cumulatively sequester 31.12–35.76 Mt CO₂ but contribute only 1%∼2% (depending on the level of incentives) of the region's CO₂ uptake required to attain carbon neutrality. Further, compared with industrial emissions reduction and forestry activities in other jurisdictions, afforestation in Northwest China is not a cost-effective means for mitigating climate change. This conclusion likely relates to negligence in many studies regarding the inclusion of non-climate related ecological opportunity costs of potential candidate marginal lands for afforestation.