Planting new forests to offset carbon is a waste of time and does little for biodiversity, a new Oxford study claims.
Scientists say that new plantations are often on areas that have never been forested and don’t help biodiversity, leading to little gain overall.
They said that preserving what we already have is much better for the planet.
There has been a boom in commercial tree plantations in order to offset carbon emissions, but the authors say we should prioritise conserving and restoring intact ecosystems.
Writing in the journal Trends in Ecology and Evolution, the team from the Environmental Change Institute at the University of Oxford say that new plantations are no match for the current forest.
‘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,’ said lead author Dr Jesús Aguirre-Gutiérrez.
‘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 affforestation, planting forests in undegraded and previously unforested regions such as grasslands.
Tropical ecosystems are highly biodiverse, and they 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% increase in woody cover reduced the diversity of plants and ants by approximately 30%.
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.
‘The current trend of carbon-focused tree planting is taking us along the path of large-scale biotic and functional homogenisation for little carbon gain,’ said Dr Aguirre-Gutiérrez.
‘An area equivalent to the total summed area of the US, UK, China, and Russia would have to be forested to sequester one year of emissions.’
He added: ‘There are considerable financial incentives for private companies to offset their carbon emissions by investing in carbon capture – the boom in carbon-capture plantations is being driven by money, not ecology.
‘Overemphasising the benefits of tree planting for carbon capture can disincentivise the protection of intact ecosystems and can lead to negative trade-offs between carbon, biodiversity, and ecosystem function.
‘An overarching view on maintaining original ecosystem functioning and maximising as many ecosystem services as possible should be prioritised above the ongoing economic focus on carbon capture projects.’
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