The world’s forests could sequester more than 200 billion tons more carbon than they currently do. This corresponds to around twenty times global fossil carbon emissions in 2022. According to a recent study involving hundreds of researchers around the world, restoring damaged forests has greater climate protection potential than planting new ones. forests. However, experts warn that this potential is unlikely to be fully exploited.
The research team, which published its study on Monday in the journal Nature, stresses that forests cannot replace reduced greenhouse gas emissions. “However, our results support the idea that the conservation, restoration and sustainable management of diverse forests can make valuable contributions to achieving global climate and biodiversity goals,” the researchers write.
Criticisms of previous work
It has long been known that forests have the potential to protect climate and species. However, it is controversial how much of the greenhouse gas carbon dioxide plants can extract from the atmosphere and thus bind the carbon it contains in the long term, over centuries to millennia. The main working group led by Thomas Crowther of ETH Zurich published an estimate in 2019 that showed a potential through reforestation of 205 gigatons. This has been criticized by other researchers as being significantly high.
Billions of tons of carbon could absorb less stressed forests from the atmosphere.
For the current study, the team has now combined data collected from ground-based studies or through satellite remote sensing. Terrestrial data is sometimes considered difficult to transfer to other regions and satellite data is 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 into settlements or agricultural land currently store 226 gigatons (billion tons) less carbon worldwide than would be naturally possible.
139 gigatons of this potential, almost two-thirds, are found in current forest areas. The additional 87 gigatons could be stored in regions where the forest is only partially preserved but is little used. “These areas are therefore particularly suitable, for example, to be protected and thus fully exploit their natural potential to store carbon,” said Florian Zabel, a geographer at Ludwig Maximilians University in Munich who was not involved in the study. the Science Media Center Germany. The climate protection potential could therefore be implemented with “minimal land use conflicts,” according to the study authors.
They have to endure criticism from Christian Körner, for example. The professor emeritus of botany at the University of Basel assumes that they have a “static and supernatural concept of forests”. Forests are dynamic systems. Centuries of construction alternate with sudden collapses caused by fire, wind or insects. “Forests that permanently have an optimal maximum storage capacity, as assumed here, do not exist,” says Körner. Furthermore, the fact that there is a conflict of objectives is overlooked: “If a gigaton of carbon is fixed 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 meadows, pastures or arable land or that are densely populated. Theoretically, these would have a potential of just over 100 gigatons, but reforestation is not realistic. “Although there is potential here too, for example, through agroforestry or carbon agriculture,” 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. Reducing emissions and conserving nature must work together. “We need nature for the climate and we need climate protection for nature,” says Crowther.