A team of researchers has calculated that there is enough space on Earth to plant enough trees to absorb two-thirds of the carbon dioxide in the air.
This proposed solution to climate change, contained in a study published on Thursday in Science magazine, has however been described as exaggerated by other scientists.
In their study, professors of ETH Zurich University estimate that the Earth has enough space for 900 million more canopies, in addition to the 2.8 billion hectares of trees it currently has. They arrived at this figure by analysing the existing forests and taking climate and soil into consideration to see where trees could grow, excluding areas already under cultivation or occupied by cities.
These additional forests would have the capacity to absorb 205 gigatonnes of carbon, out of the 300 gigatonnes added to the atmosphere since the late 19th Century and the start of the industrial era. Half of the areas that could be reforested are in six countries: Russia, the United States, Canada, Australia, Brazil and China.
According to the study’s main author, Jean-François Bastin, governments need to take this into consideration in their national strategies against climate change.
The team argues that the reforestation goal, set last year by UN climate experts, of one billion hectares is “absolutely achievable in the current climate”.
It concludes that restoring the world’s ecosystems is “the most effective solution at our disposal” for countering climate change.
However, this conclusion has sparked criticism from specialists in Earth sciences, some of whom also feel that the methodology is simplistic or wrong.
Myles Allen, a geosystems professor at Oxford University said heroic reforestation could be useful, but people should stop saying there is a natural solution to using fossil fuels. “There isn’t any,” he said. “Sorry!”
In another commentary, published by Science Media Centre in the UK, University College London professor Simon Lewis wrote that new forests could play a role in absorbing excess carbon emissions, but the only way to stabilise the climate was to lower greenhouse gas emissions to zero.