The term “natural climate solutions” was coined by Griscom et al. in a scientific publication in The Proceedings of the National Academies of Science (PNAS) in 2017 (see link to publication at the bottom of this page). They defined natural climate solutions as “20 conservation, restoration, and/or improved land management actions that increase carbon storage and/or avoid greenhouse gas emissions across global forests, wetlands, grasslands, and agricultural lands.”
The figure below from the Griscom et al. paper ranks the mitigation potential of the 20 different practices.
At the top you’ll see that reforestation of deforested land has the greatest carbon mitigation potential (top bar), but avoided deforestation is more cost effective (the second bar from the top). Within agriculture, biochar has the greatest carbon mitigation potential, but nutrient management is the most cost effective method of mitigation.
Source: Griscom, B. W. et al. 2017. Natural climate solutions. Proceedings of the National Academies of Science. www.pnas.org/cg/doi/10.1073/pnas. 1710465114 (see link to paper at bottom of this page)