Mapping the Irrecoverable Carbon in Earth's Ecosystems

Avoiding catastrophic climate change requires rapid decarbonization and improved ecosystem stewardship at a planetary scale. The carbon released through the burning of fossil fuels would take millennia to regenerate on Earth. Though the timeframe of carbon recovery for ecosystems such as peatlands, mangroves and old-growth forests is shorter (centuries), this timeframe still exceeds the time we have remaining to avoid the worst impacts of global warming. There are some natural places that we cannot afford to lose due to their irreplaceable carbon reserves. Here we map 'irrecoverable carbon' globally to identify ecosystem carbon that remains within human purview to manage and, if lost, could not be recovered by mid-century, by when we need to reach net-zero emissions to avoid the worst climate impacts. Since 2010, agriculture, logging and wildfire have caused emissions of at least 4.0 Gt of irrecoverable carbon. The world's remaining 139.1 ± 443.6 Gt of irrecoverable carbon faces risks from land-use conversion and climate change. These risks can be reduced through proactive protection and adaptive management. Currently, 23.0% of irrecoverable carbon is within protected areas and 33.6% is managed by Indigenous peoples and local communities. Half of Earth's irrecoverable carbon is concentrated on just 3.3% of its land, highlighting opportunities for targeted efforts to increase global climate security. The concept of irrecoverable carbon is intended to discriminate among the billions of tonnes of carbon stored in the biosphere on the basis of three criteria relevant for conservation efforts. We assess ecosystem carbon stocks according to: (1) how they can be influenced by direct and local human action ('manageability'), (2) the magnitude of carbon lost upon disturbance ('vulnerability') and (3) the recoverability of carbon stocks following loss ('recoverability'). Applying the three criteria across all terrestrial, coastal and freshwater ecosystems reveals that some places contain irrecoverable carbon, or manageable carbon stocks that, if lost, represent a permanent debit from the remaining carbon budget. Effective strategies to reduce the risk of catastrophic climate change will need to locate large irrecoverable carbon reserves that are at risk due to anthropogenic action and prioritize their protection and sustainable management, alongside efforts to phase out fossil fuel emissions and restore degraded ecosystems. The concept of irrecoverable carbon in ecosystems was introduced in a 2020 study. Here, we map irrecoverable carbon globally and at high resolution (300 m), using remotely sensed or modelled products that were created or substantially improved within the last year. We identify areas with recent losses of irrecoverable carbon and areas facing near- or medium-term risks from land-use conversion or climate change, and assess how much irrecoverable carbon lies within state-designated protected areas or Indigenous peoples and local communities' lands.