Status: 09/22/2022 8:00 p.m
Afforestation makes sense regionally, but cannot replace traditional climate protection. This is the conclusion reached by an Israeli research team.
Afforestation brings less than assumed in the fight against the climate crisis. This is the conclusion reached by an Israeli research team in a study published in the journal Science. The researchers disagree with the thesis that one only has to reforest enough to offset the emission of greenhouse gases. There are enough grasslands and savannahs available.
Forests also warm atmosphere
The new study concludes that while new forests sequester CO2, they also reheat the atmosphere. This is due to the albedo effect: forests are darker than grasslands and therefore absorb more solar energy. Globally, this negates two thirds of the climate protection effect of new trees. Large areas of Central Asia would warm up even more through afforestation.
Three years ago, a group led by Jean-Francois Bastin from ETH Zurich made headlines with the news that 900 million hectares of land worldwide could be reforested without having to lose land for food production. Grasslands and savannahs played an important role. This measure could save more than 200 billion tons of carbon – and thus offset the entire greenhouse gas emissions of the past 20 years.
Afforestation as the ultimate solution
The widespread dissemination of this assessment led to a public debate as to whether afforestation was the ultimate solution to the climate problem. Although the authors may not have intended it that way.
The debate in scientific circles, on the other hand, was controversial from the start. For example, dry steppes or moors also have important ecological functions and therefore cannot be converted into forests without side effects.
However, the discussion also shows in an exemplary manner how research is evolving. From the start, experts pointed out that forests are darker than grasslands. And that this effect was not considered in Bastin’s study.
Less binding of CO2 than assumed
Now scientists working with Shani Rohatyn from the Technion-Israel Institute of Technology have analyzed this in more detail. Namely for dry areas, which make up 40 percent of the world’s land area and, with around 450 million hectares, would represent a good part of the potential afforestation areas. If you did that, the researchers calculate, you could bind 32 billion tons of carbon over the next 80 years. This is a significantly lower amount than in Bastin’s analysis, who was accused of overly optimistic assumptions anyway.
And then the albedo effect comes into play. The Israeli group performed a high-resolution spatial analysis of global drylands and simulated the climatic impact of afforestation in these regions. The result varies greatly from region to region available in interactive maps.
Global low cooling effect
Globally, however, the authors show that the cooling effect of the afforestation of these huge areas is only very small. Depending on the scenario for the future development of greenhouse gas emissions, this only accounts for one percent of these emissions.
Afforestation would only be proportionally more effective in a model that is already characterized by strong climate protection. Then almost three percent of the remaining emissions could be bound. The authors come to the conclusion that afforestation makes sense regionally, but that it cannot even begin to replace classic climate protection.
This study could also have an impact on compensation offers that are offered by flight and tour operators, for example, but also used by companies that then describe themselves as climate-neutral. Nina Buchmann, environmental scientist at ETH Zurich, points this out. Because these programs mostly ignore the albedo effect.