The world’s forests could sequester more than 200 billion tons of carbon more than they currently capture. This corresponds to about twenty times global fossil carbon emissions in 2022. Restoring damaged forests has greater climate protection potential than planting new forests, according to a recent study involving hundreds of researchers around the world. . However, experts warn that this potential is unlikely to be fully realized.
The research team, which published its study Monday in the journal Nature, points out that forests cannot substitute for reducing greenhouse gas emissions. “However, our results support the idea that the conservation, restoration and sustainable management of various forests can make valuable contributions to achieving global climate and biodiversity goals,” the researchers write.
Criticism of previous works
It has long been known that forests have potential for climate and species protection. However, it is controversial how much carbon dioxide, a greenhouse gas, plants can extract from the atmosphere and thus fix the carbon it contains in the long term, for centuries or millennia. The main working group led by Thomas Crowther of ETH Zurich published an estimate in 2019 showing a reforestation potential of 205 gigatonnes. Other researchers criticized this value as too high.
Billions of tons of carbon could absorb less stressed forests from the atmosphere.
For the current study, the team has combined data that was collected in field surveys or through remote sensing from satellites. Terrestrial data are sometimes considered difficult to transfer to other regions and satellite data are subject to uncertainty. According to the current calculation, the results only differ by about one-eighth, the researchers write. According to the current study, forests that have not yet been converted to settlements or agricultural land currently store 226 gigatonnes (one billion tons) less carbon worldwide than would be naturally possible.
139 gigatonnes of this potential, almost two thirds, are found in current forest areas. The additional 87 gigatonnes could be stored in regions where the forest is only partially preserved but hardly used. “These areas are therefore particularly suitable, for example, to protect them and thus fully exploit their natural potential for storing carbon,” said Florian Zabel, a geographer at the Ludwig Maximilians University of Munich, who was not involved in the study. the German Scientific Media Center. Therefore, the potential for climate protection could be implemented with “minimal land use conflicts,” according to the study’s authors.
They have to put up with, for example, the criticism of Christian Körner. The emeritus professor of botany at the University of Basel assumes that they have a “static and mundane conception of forests.” Forests are dynamic systems. Centuries of construction alternate with sudden collapses caused by fire, wind or insects. “There are no forests that permanently have an ideal maximum storage capacity, as is assumed here,” says Körner. Furthermore, the fact that there is a conflict of objectives is overlooked: “If you fix a gigaton of carbon in forest biomass, it cannot be used at the same time to replace fossil raw materials.”
On the other hand, the authors avoid including areas that are currently used as grasslands, pastures or croplands or that are densely populated. In theory, these would have a potential of just over 100 gigatonnes, but reforestation there is not realistic. “Although there is potential here too, for example through agroforestry or carbon farming,” says Zabel.
In a press release from ETH Zurich, the authors themselves point out another limitation: if emissions are not reduced, droughts, fires and warming would threaten the ability of forests to absorb carbon. Emissions reduction and nature conservation must work together. “We need nature for the climate and we need climate protection for nature,” says Crowther.