Reforestation Benefit Calculator

The climate benefit of a planting project comes from net biomass accumulation, not from the number of seedlings put in the ground. Dry woody biomass is roughly 47 to 50 percent carbon, and every kilogram of carbon fixed corresponds to 3.667 kg of CO2 removed from the atmosphere, since 3.667 is the ratio of the molar mass of CO2 (44) to that of carbon (12). An annual increment of 22 kg of carbon per stem therefore represents about 80.7 kg of CO2 per tree per year. Planting density of 1,100 stems per hectare corresponds to roughly 3 by 3 metre spacing; timber plantations run 800 to 1,600 stems per hectare, mixed-species restoration 400 to 1,100, and agroforestry as low as 100 to 400. The main limitation of a constant annual increment is that real stands follow a sigmoid growth curve. Uptake is close to zero during the establishment phase of years one to three, rises steeply toward canopy closure, then flattens as mortality and respiration offset growth, so a flat rate overstates early credits and understates mid-rotation ones. Survival is the other dominant term: field survival ranges from about 40 percent on harsh sites to 95 percent under intensive aftercare, with most losses occurring in the first three growing seasons from drought, browsing and weed competition. Registries also withhold 10 to 20 percent of issued credits into a buffer pool against fire, pest and reversal risk, and leakage plus monitoring costs further reduce the net revenue implied by a simple price multiplication.

Organized replanting long predates carbon accounting. State forestry services in Germany and France systematized artificial regeneration during the nineteenth century, and the United States Civilian Conservation Corps planted on the order of three billion trees between 1933 and 1942, mainly for erosion control on Dust Bowl and cut-over land. The explicit climate framing arrived with the Kyoto Protocol in 1997. The Marrakesh Accords of 2001 then made afforestation and reforestation the only land-use activities eligible under the Clean Development Mechanism, and defined reforestation narrowly as replanting land that carried no forest on 31 December 1989 - a cut-off designed to prevent credit for stands that would have regrown anyway. Because the CDM forestry rules proved cumbersome, most planting credits migrated to voluntary registries: the Gold Standard was founded in 2003 with WWF backing, and the Verified Carbon Standard emerged from 2005 to 2007 through the Climate Group, the International Emissions Trading Association and the World Economic Forum. Verra later consolidated its planting methodologies into VM0047 for afforestation, reforestation and revegetation. Landscape-scale restoration targets came from the Bonn Challenge, launched in 2011 by the German environment ministry and IUCN with a goal of 150 million hectares under restoration by 2020, extended to 350 million hectares by 2030 under the 2014 New York Declaration on Forests. A 2019 Science paper by Bastin and colleagues on global tree restoration potential sharpened the debate, drawing criticism for overstating achievable storage and for treating native grasslands and savannas as plantable land.