ETH study shows how much extra CO2 can be stored by forests around the world

Forests play a key role in the fight against global warming because they absorb CO2 from the atmosphere as they grow. The more trees, the better for the climate.

However, studies have shown that some reforestation efforts are of little avail as the forests must be protected and cared for for decades. Timber industry cannot be exploited there. Most importantly, the potential for afforestation is limited by fierce competition for land. Where forests grow, there is no place for agriculture.

However, increasing CO2 storage does not necessarily require new forests. Targeted protection of existing forest areas also helps, because intact and natural forests store carbon dioxide very effectively.

An international research team led by ETH Zurich and the European Commission’s Joint Research Center (JRC) has now used artificial intelligence to calculate for the first time how much additional carbon could be stored in forests if humans stopped intervening in this ecosystem. ie no would harvest and use more wood. The results have just been published in the journal Science.

Their conclusion: the potential that has not yet been exhausted is quite small and less than half that assumed in previous work. According to this, only the amount of CO2 the world emits in just four years could be additionally stored.

“Forest carbon sequestration is often seen as the silver bullet for solving the climate crisis,” says first author and ETH PhD student Caspar Roebroek. However, this research shows that it is only a tool to offset the hard-to-avoid greenhouse gas emissions from agriculture, for example, in the long term. It is therefore not suitable for CO2 compensation of climate-damaging behaviour.

But still: without any forestry, 44 billion more tons of CO2 could be stored in the current forests, which corresponds to an increase of 15 percent. To achieve the same amount through afforestation, an area of ​​7.1 million square kilometers would have to be reforested, says Roebroek. This corresponds to an area larger than Germany, France and Spain combined.

Roebroek emphasizes that the determined values ​​are only theoretical figures. Because completely abandoning forestry is a utopia – and depending on the situation, even harmful to the climate. Because wood can replace greenhouse gas-intensive building materials such as concrete as a building material or fossil fuels such as coal, oil and gas as firewood.

The most effective strategy for forest-based climate protection therefore remains to halt global deforestation and slash-and-burn. However, this contrasts with the ongoing deforestation. According to Global Forest Watch, a total of 437 million hectares have been lost globally over the last 20 years, which equates to an 11 percent decline in tree populations.

But there is hope: at the 2021 World Climate Conference in Glasgow, 145 countries pledged to stop global forest destruction by 2030. (aargauerzeitung.ch)