A new study by hundreds of scientists around the world, including Stellenbosch University (SU), found that forests globally have the potential to store approximately 226 gigatonnes of carbon (226 Gt C). That is enough carbon to fill an area the size of South Africa and Switzerland combined. Achieving this potential will, however, require the conservation, restoration and sustainable management of the vast natural and degraded forests worldwide, to help us meet international climate and biodiversity targets.
The study, titled “Integrated global assessment of the natural forest carbon potential", was published recently in the journal Nature. It forms part of a collective effort of the Global Forest Biodiversity Initiative in counting and mapping the world's forest ecosystem.
The international team of researchers, led by the Crowther Lab at ETH Zürich (Swiss Federal Institute of Technology), built an integrated assessment using a comprehensive range of approaches, including vast ground-sourced data and satellite datasets. They wanted to investigate the impact of human land-use change on forest carbon stocks globally.
“We found that total forest carbon storage is, at present, 328 Gt C below its full potential. Of this potential, 102 Gt C exist in urban areas, cropland and permanent pasture sites, in which substantial restoration is highly unlikely. Yet, a potential of 226 Gt C is in existing forests," says one of the co-authors Prof Cang Hui, holder of the South African Research Chair in Mathematical and Theoretical Physical Biosciences at SU.
“About 60% of this potential can be achieved by protecting existing degraded forests" adds Hui.
According to the scientists, this highlights that the prevention of deforestation does not only contribute to the reduction of carbon emissions but also has a large carbon drawdown potential if ecosystems can be allowed to return to maturity.
They point out that, so far, humans have removed almost half of Earth's natural forests, and we continue to lose a further 0,9–2,3 Gt C each year through deforestation, about 15% of annual human carbon emissions.
The scientists say that understanding the potential for carbon storage in natural forests is crucial for comprehending their role in combating climate change.
“A key step in reducing deforestation and revitalizing ecosystems is gaining a comprehensive understanding of the global distribution of existing forest carbon stocks, as well as the potential for carbon recapture if degraded ecosystems are allowed to recover."
They add that it is, however, important to keep in mind that forests cannot be a substitute for cutting fossil fuel emissions.
According to the scientists, the vulnerability of forests underscores the urgency of conserving existing ecosystems to maintain their carbon sink potential and highlights the urgent need to uphold no-deforestation pledges at the 26th United Nations Climate Change Conference of the Parties (COP26), including public and private-sector commitments to end forest loss as soon as 2025.
“If fossil fuel emissions continue to rise, the capacity of ecosystems to capture and store carbon will be threatened by climate-change-induced factors such as increasing temperature, drought and fire risks with CO2 fertilization likely to further change this system."
The scientists admit that the protection and restoration of natural forest ecosystems are complex social, political and economic challenges that require the development of land-management policies and practices that prioritise the rights and well-being of local communities and indigenous people, and also promote biodiversity in managed systems.
“Only when healthy biodiversity is the preferred choice for local people can ecosystem-restoration initiatives be sustainable in the long term. When built in a socially and ecologically responsible way, the promotion of diverse forests can contribute substantially to achieving our combined climate and biodiversity goals."