Monoculture tree-planting initiatives aimed at carbon capture are posing a significant threat to tropical biodiversity while offering only limited climate benefits, caution ecologists.
Monoculture tree-planting initiatives aimed at carbon capture are posing a significant threat to tropical biodiversity while offering only limited climate benefits, caution ecologists. They highlight that ecosystems in vital regions like the Amazon and Congo basin are being reduced to their carbon sequestration value.
With an upswing in the establishment of single-species plantations to combat carbon emissions, scientists are urging governments to prioritize the preservation and rehabilitation of native forests over commercial monocultures. They stress that large-scale planting of non-native trees in tropical areas puts essential flora and fauna at risk for a minimal climate impact.
In a publication in the journal Trends in Ecology & Evolution, ecologists point out that the growing popularity of commercial plantations featuring species like pine, eucalyptus, and teak for carbon offsetting is leading to unintended consequences. These include the desiccation of native ecosystems, soil acidification, displacement of indigenous vegetation, and a surge in wildfires.
The paper underscores the narrow view that contemporary society holds of tropical ecosystems, reducing their worth to just one metric – carbon. It states, “It is broadly assumed that maximizing standing carbon stocks also benefits biodiversity, ecosystem function and enhances socioeconomic co-benefits – yet this is often not the case.”
While tree-planting has been advocated as a crucial tool in combating global warming, research indicates that its environmental benefit depends significantly on the scope and nature of the restoration efforts, often requiring extensive land areas. A study from 2019 estimated that allowing natural forests to regenerate could sequester 40 times more carbon compared to plantations.
Jesús Aguirre-Gutiérrez, a lead author from the University of Oxford, remarked that the surge in commercial plantations in tropical regions prompted the scientists to voice their concerns.
“We carry out a lot of fieldwork in the tropics to research what is happening with climate change and we have seen the boom in these plantations for ourselves: teaks, conifer and eucalyptus, just one or two species,” he said. “These schemes are a win for the company planting these trees but not for biodiversity. This is the start of this phenomenon, hence the seriousness of the situation.”
The paper estimates that a plantation covering an area equivalent to the combined size of the US, China, Russia, and the UK would be needed to sequester one year’s worth of emissions.
While plantations may often be more economically viable than standing forests, the paper underscores that they generally support lower levels of biodiversity. For instance, in the Brazilian Cerrado savanna, a 40% increase in woodland cover resulted in a 30% decrease in plant and ant diversity.
Simon Lewis, a professor of Global Change Science at University College London, emphasized that reducing trees to mere “sticks of carbon” could have dangerous consequences. He stressed that while plantations are necessary for producing paper and wood products, designating industrial plantations as carbon offsets creates problems within the unregulated carbon offsets market. Lewis emphasized that tree-planting should not be viewed as an alternative to urgently reducing fossil fuel emissions.
Thomas Crowther, a professor of ecology at ETH Zurich, who co-authored a paper highlighting 900 million hectares of land suitable for reforestation, stressed that prioritizing the carbon value of an ecosystem above all else was misguided. He warned that such a practice encourages the propagation of one aspect at the expense of everything else, potentially undermining the overall health and balance of ecosystems.
Monoculture tree-planting initiatives are those that involve planting large areas of land with a single species of tree. This is often done for commercial purposes, such as timber production or paper pulp production. Monoculture tree plantations can also be used to restore degraded land or to sequester carbon.