Root of the problem

Planting a trillion trees may not be a good idea

A new global initiative to ‘grow, restore and conserve’ one trillion trees around the world was launched last month by the World Economic Forum.

The ‘1t.org’ plan, backed at Davos by US President Donald Trump and primatologist Jane Goodall, aims to begin a “mass-scale nature restoration” to protect biodiversity and fight climate change.

“We are facing a planetary climate crisis and trees are one of the most effective ways to sequester carbon and stop the worst effects of climate change,” said Marc Benioff, chief executive of the software company Salesforce, which is funding the initiative, in a statement.

Critics, however, have been quick to point out caveats to the new initiative. They warn that tree planting as a major absorber of carbon has been

exaggerated and could distract from other important policies.

The initiative references a widely reported study by Swiss researchers published last year in the journal Science, that claimed planting a trillion trees could capture a third of all the carbon released by humans since the Industrial Revolution. However, a team of 46 scientists carried out a strong critique that was published in the Uame Ucientific LQWTnal shortly after.

They argued the study had vastly overestimated the amount of carbon which could be stored by growing trees, and failed to assess the impacts on people and ecosystems where these trees would be planted.

LOCATION, LOCATION, LOCATION

“A trillion trees is potentially a really bad idea, because of the ways that we must think about the implementation,” said Dr Joseph Veldman, assistant professor of ecology at the Texas A&M University and lead author of the critique. Choosing the right location is important. “Many of the places that are already deforested are not available to be turned back into forest,” he said, which means that trees may be planted in other types of less suitable landscapes.

“We know that maintaining current intact forests, savannahs and grasslands – existing ecosystems that don’t need to be restored – would be a better bet for carbon, rather than let them be destroyed and then have to plant some new trees,” he explained.

Last year’s report on land use by the International Panel on Climate Change (IPCC) also warned that widespread tree planting, also known as ‘afforestation’, could come with risks. For example, it could increase competition for land and threaten food security by raising food prices.

However, the IPCC concluded that at least some afforestation is likely to be needed in order to limit global warming to 1.5°C above pre-industrial levels.

“The study vastly overestimated the amount of carbon which could be stored by growing trees, and failed to assess the impacts on ecosystems”