Planting trees in vast schemes to ‘offset’ carbon emissions is harming nature, an Oxford study has claimed.
Celebrities and tycoons including Prince Harry and Meghan Markle, Elton John, Emma Watson and Amazon founder Jeff Bezos have all said they have used offsetting to cancel out the greenhouse gases emitted by activities such as flying in private jets.
But when offsetting involves planting large numbers of a single types of tree, it can actually degrade the environment, the authors argued.
Single species plantations are harmful to biodiversity and put forests more at risk of fire, it is argued, while they do little to suck up greenhouse gases.
Instead, the authors said we should prioritise conserving and restoring intact ecosystems.
Planting trees in vast schemes to ‘offset’ carbon emissions is harming nature, a new Oxford study claims
Writing in the journal Trends in Ecology and Evolution, scientists from the Environmental Change Institute at Oxford University said the focus on offsetting carbon at all costs damages other aspects of the ecosystem.
Author Dr Jesús Aguirre-Gutiérrez said: ‘Despite the broad range of ecosystem functions and services provided by tropical ecosystems, society has reduced value of these ecosystems to just one metric – carbon.
‘Current and new policy should not promote ecosystem degradation via tree plantations with a narrow view on carbon capture.’
Although some projects reforest degraded land, most involve what is known as afforestation – planting forests in undegraded and previously unforested regions such as grasslands.
Tropical ecosystems are highly biodiverse, and provide multiple ecosystem services, such as maintaining water quality, soil health, and pollination.
In comparison, carbon-capture plantations are usually monocultures and are dominated by just five tree species, teak, mahogany, cedar, silk oak, and black wattle, grown for timber, pulp, or agroforestry.
The result is that these plantations usually support a lower level of biodiversity.
For example, in the Brazilian Cerrado savannah, a 40 per cent increase in woody cover reduced the diversity of plants and ants by approximately 30 per cent.
In fact tropical grasslands and savannahs are already carbon sinks and, unlike trees, are less susceptible to disturbances such as drought and fire.
These plantations can also directly degrade ecosystems by reducing stream flow, depleting groundwater, and acidifying soils.
Dr Aguirre-Gutiérrez said: ‘The current trend of carbon-focused tree planting’ is creating monocultures for ‘little carbon gain’.
He added: ‘An area equivalent to the total summed area of USA, UK, China, and Russia would have to be forested to sequester one year of emissions.’
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