Total ecosystem carbon stocks of tropical peat forests and greenhouse gas emissions from their disturbance

Because of their unique biodiversity and inordinately large carbon stocks, tropical peat forests are considered key wetland ecosystems for conservation and restoration. Despite this recognition continued deforestation and land cover change result in these ecosystems becoming significant sources of greenhouse gases. There is a strong need for accurate quantification of carbon stocks and emissions at scales relevant for participation in carbon markets and nationally determined contributions. Based upon analyses of 125 forests in 4 continents (Asia, Oceania, the Americas) there was a broad range in peat depths (19–1414 cm) with total ecosystem carbon stocks (TECS) ranging from 172 to 9379 Mg C ha −1 (mean of 2137 Mg C ha −1 ). Among the 47 sampled sites known to be tidally-influenced (i.e., blue carbon ecosystems), TECS ranged from 206 to 5591 Mg C ha −1 with a mean of 1979 Mg C ha −1 . Those sites with deep peats (> 7 m depth) have a mean TECS of 4620 ± 395 Mg C ha −1 and we know of no ecosystems with an equivalent ecosystem carbon stock. Peat soils composed a mean of 86 % of TECS, and peat depths were strongly correlated with soil carbon stocks at continental and global scales (R 2 > 0.80) suggesting inventories that include measurement of peat depth can accurately estimate carbon stocks. Degradation of peat landscapes comes with high ecological and social costs including the largest greenhouse gas emissions from any forest land use globally. The social carbon costs to future generations associated with the conversion of tropical peat forests to oil palm plantations is conservatively estimated to be nine times the value of the palm oil generated from the conversion. Such costs and values of the tropical peat forests underscore the importance of the conservation and restoration of these wetlands for future generations – an important element of sustainability. • Tropical forests with deep peats are the largest carbon stocks on earth. • Tidally influenced peat forests have the largest C stocks of blue carbon ecosystems. • Mean carbon stocks are 2137 Mg C ha −1 (range of 172–9379 Mg C ha −1 ). • Peat forest loss likely results in the greatest greenhouse gas emissions from any land use. • Social carbon costs of peat forest loss exceed values coming from deforestation.