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2022-03-18 09:27:01

Native forests with a mix of diverse vegetation provide more environmental benefits than monoculture plantations and should be prioritized in climate mitigation efforts, according to a new study published Thursday.

While tree-planting initiatives and reforestation drives have been seen as a vital tool to mitigate some of the impacts of climate change, not all forest restoration efforts yield the same results, said the study published in the academic journal Science. Researchers said it’s the first global study comparing the performances of two reforestation approaches.

Researchers from seven countries — including China, the United Kingdom, and Brazil — assessed 25,950 records from 264 studies in 53 countries and found that diverse native trees “consistently” performed better in key ecological services compared to monoculture tree plantations. The former fared better in carbon storage, preventing soil erosion, and water provisioning compared with the latter.

With its mix of different trees, shrubs, and herbs, forests with native vegetation provided a diverse ecosystem, helping to slow global biodiversity loss that is “accelerating” species extinction, according to the study.

“Policymakers have an implicit assumption that all forests provide the various ecosystem services ... but this is not backed up by science,” Hua Fangyuan, a researcher at Peking University’s Institute of Ecology and lead author of the study, told Sixth Tone.

She said the study found that though tree plantations yielded more wood production, they provided fewer environmental benefits than restored native forests. Researchers identified soil erosion control as the “biggest loser” among the core ecosystem services when planting trees with simple compositions — plantations consisting of just one or several varieties of trees — which otherwise could have been used to restore native forests.

China has heavily invested in increasing tree cover in its deforested areas. The country now has 220 million hectares of forests, with artificial forests accounting for 36% of the total share, according to official data.

However, many of China’s existing afforestation projects prefer massive tree plantations with fast-growing species. For example, China’s famous “Grain For Green” program aims to turn croplands on sloped terrain into forests to control soil erosion, but extensive monoculture forests have primarily occupied the new coverage in main areas, according to Hua.

“This is actually a largely missed opportunity for conservation,” Hua said. “Forest restoration is now in full swing, and the environmental and social benefits it can bring are huge. But an obvious issue here is that (tree plantations) not only bring just insufficient biodiversity, but too often, risk reducing it.”

China had 133 million hectares of natural forests in 2010, but the number dropped by 328,000 hectares in 2020, according to Global Forest Watch. The loss was equivalent to 131 million tons of carbon emissions that could otherwise be collected and stored to curb climate change.

In 2017, China implemented a nationwide ban on commercial logging of natural forests to end deforestation, then introduced a law to trace the legal source of timber two years later. However, due diligence inspection is yet to be expanded to the wood imports sector, raising criticism that China’s demand for wood products at home is driving illegal logging abroad.

Researchers of the new study suggested that policymakers should weigh the competing goals — wood production versus environmental benefits — when opting for different reforestation approaches. Hua said artificial forests could actually become a conducive part of a country’s national forest management program, which would not only provide livelihoods to communities but also “spare” high-biodiversity native forests from being cut down.

“If we are working toward restoring a diverse ecosystem, tree plantations could also be an active tool,” she said.

Editor: Bibek Bhandari.

(Header image: People plant trees at a village in Yichang, Hubei province, Feb. 19, 2021. VCG)