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Regenerated tropical forests often have short lifespans

The Brazilian Atlantic Forest is a rich natural region which originally occupied over 150 million hectares along the Atlantic Coast. Today, only about 32 million hectares remain. This highly fragmented and threatened ecosystem is considered by conservationists a regeneration hotspot. 

However, according to a new study led by an international research team from Columbia University, University of São Paulo, and the Federal University of ABC in Brazil, preventing the re-clearing of second-growth forests is a major challenge for restoration efforts in this area and other tropical regions. The researchers found that a third of regenerating areas in the Brazilian Atlantic Forest were sadly cut down again after just four to eight years of regeneration.

The scientists have analyzed detailed land use cover data from 1985 to 2019 to track the fate of over 4.5 million hectares of regenerated forest and discovered that only 3.1 million hectares persisted until 2019. “While the persistence of two-thirds of regenerated forest in the region casts a positive outlook for the biome’s conservation, the short life span of regenerated forests emerges as a new challenge for restoration efforts in the region,” said study lead author Pedro Ribeiro Piffer, a doctoral student at Columbia.

Moreover, while natural forest regeneration is considered a cost-effective strategy for countries to meet their ecological restoration and carbon sequestration goals, the ephemeral nature of these regrown forests significantly limits the biodiversity and carbon storage benefits of regeneration.

“Carbon sequestration through tropical reforestation and natural regeneration can make an important contribution to climate change mitigation, given that forest cover in many tropical regions increased during the early part of the 21st century,” said senior author María Uriarte, an expert in tropical forest dynamics at Columbia. “However, the size of this carbon sink will depend on the degree to which these forests are permanent and protected from re-clearing.”

“Our results underline a double challenge for forest conservation in tropical regions, where not only do we need to restore degraded areas, but we also need to ensure the persistence of these young regenerating forests,” added study co-author Jean Paul Metzger, a professor of Ecology at the University of São Paulo.

According to the scientists, regenerated forests had greater chances of survival on steeper slopes, close to rivers and existing forests, and near permanent agriculture. They were less likely to persist in rural areas and close to pastureland and regions of shifting agriculture.

“Regenerated forests can take decades to recover pre-disturbance species richness and biomass levels, so identifying the conditions that allow for a greater persistence of these young forests is vital for developing effective public policies targeted at increasing forest cover in the Brazilian Atlantic Forest,” concluded Piffer.

The study is published in the journal Environmental Research Letters.

Image Credit: Pedro Piffer

By Andrei Ionescu, Staff Writer

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