Natural climate solutions

Better stewardship of land is needed to achieve the Paris Climate Agreement goal of holding warming to below 2 degrees C; however, confusion persists about the specific set of land stewardship options available and their mitigation potential. To address this, we identify and quantify "natural climate solutions" (NCS): 20 conservation, restoration, and improved land management actions that increase carbon storage and/or avoid greenhouse gas emissions across global forests, wetlands, grasslands, and agricultural lands. We find that the maximum potential of NCS-when constrained by food security, fiber security, and biodiversity conservation-is 23.8 petagrams of CO2 equivalent (PgCO(2)e) y(-1) (95% Cl 20.3-37.4). This is >= 30% higher than prior estimates, which did not include the full range of options and safeguards considered here. About half of this maximum (11.3 PgCO(2)e(-1)) represents cost-effective climate mitigation, assuming the social cost of CO2 pollution is >= 100 USD MgCO(2)e(-1) by 2030. Natural climate solutions can provide 37% of cost-effective CO2 mitigation needed through 2030 for a >66% chance of holding warming to below 2 degrees C. One-third of this cost-effective NCS mitigation can be delivered at or below 10 USD MgCO2-1. Most NCS actions-if effectively implemented-also offer water filtration, flood buffering, soil health, biodiversity habitat, and enhanced climate resilience. Work remains to better constrain uncertainty of NCS mitigation estimates. Nevertheless, existing knowledge reported here provides a robust basis for immediate global action to improve ecosystem stewardship as a major solution to climate change.