The scientific community is divided over the effectiveness of massive tree planting as an antidote to climate change.
In a commentary in the Science Magazine, about 40 researchers, including one from the University of Liège (ULiège), point out that the measure’s potential has been considerably overestimated, according to ULiège.
In July, researchers from ETH Zurich University indicated in a heavily mediatised study that there was enough room on Earth to plant trees capable of absorbing 205 billion tonnes of carbon from the air.
This is equivalent to about one-third of the CO2 emitted since the industrial revolution.
The researchers reached that conclusion by analysing the world forests, together with its climate and soils, to see where trees could grow outside of urban areas or farmlands.
However, their theory fails to stand up to criticism, according to the 42 authors of the article recently published in Science.
Tree-planting can be good in some areas that have been deforested but planting trees in natural grasslands like savannas or lawns can destroy the habitats of many plant and animal species and would not trap enough carbon to offset emissions from fossil fuels, they noted.
They feel the study by their Swiss colleagues presents serious approximations that led them to multiply by five the real potential of newly planted trees to attenuate climate change.
The study is based on the principle that the soils of ecosystems with few or no trees contain no carbon, whereas the reality is that many ecosystems, such as savannahs and bogs, contain more carbon than the aerial portion of their vegetation, they add.
For ULiège’s Grégory Mahy, one of the response’s co-authors, “restoring the ecology can contribute much more to natural climate solutions by restoring not only forests but also lawns, savannahs, wooded ecosystems and bogs.”