Forest recovery is an important tool to fight climate change. Recent research, however, shows that recovery in the Amazon has a long way to go to become truly effective.
Secondary forests—wooded areas intentionally replanted after a timber harvest has destroyed a primary or old-growth forest—are one way communities and businesses have responded to deforestation. The trees and shrubs in secondary forests do not entirely replace the trees lost in primary forests, but the plant biomass acts as a carbon sink that offsets carbon emissions associated with the initial deforestation.
According to a new study, however, secondary forests have offset less than 10% of deforestation-caused carbon emissions in the Amazon—even as they take up almost 30% of the total deforested area in the region. With territory accounting for about 60% of the biome, Brazil leads the trend: The country had the lowest carbon offset rate (9%) and the smallest forest area recovery (24.8%).
On the opposite end of the spectrum, Ecuador had the largest forest area recovery (56.9%), whereas Guyana had the highest carbon offset rate (23.8%). These countries, however, represent a small fraction of the Amazon, as they account for just 1.5% and 3% of the biome, respectively.
The study, published in Environmental Research Letters, is the first to analyze forest loss and recovery at both national and subnational levels for the whole Amazon region. The researchers analyzed data from all nine Amazonian countries (Bolivia, Brazil, Colombia, Ecuador, France (through the department of French Guiana), Guyana, Peru, Suriname, and Venezuela) and the nine Brazilian states that make up the biome (Acre, Amapá, Amazonas, Maranhão, Mato Grosso, Pará, Rondônia, Roraima, and Tocantins).
The analysis builds on land cover data from the Brazilian Annual Land Use and Land Cover Mapping Project (MapBiomas) between 1985 and 2017, as well as estimates of aboveground biomass and carbon sequestration rates for the period.
The team used MapBiomas remote sensing maps for each year, looking pixel by pixel for the areas that were covered and not covered by vegetation to track changes in land use. “We overlapped the maps looking for where there was vegetation in a given year but not in the next (meaning the area was deforested) and where the opposite happened, meaning there was forest recovery,” explained coauthor Erika Berenguer, a researcher at the University of Oxford and Lancaster University in the United Kingdom.
“The resolution of each pixel is 30 square meters, so MapBiomas gave us quite fine-grained material to work on,” said lead author and Lancaster University researcher Charlotte Smith. Besides fine resolution, the study gives a good picture of what is happening in the whole biome, she said. “Now that there’s data available to all individual countries in the Amazon, they don’t need to make estimates based [solely] on Brazilian findings.”
International and Interstate Disparities
Brazilian states account for more landmass in the region and for a larger share of deforestation. Researchers found that by 2017, the deforested area in Pará alone—more than 260,000 square kilometers, an area larger than the U.S. state of Oregon—was more than twice the cleared area of all other Amazonian countries combined. Deforestation-related carbon emissions from Mato Grosso, Pará, and Rondônia surpass those of any other individual Amazonian country.
Contrasts are stark also among Brazilian states themselves. Whereas Tocantins lost more than 80% of its primary forest and less than 20% of this area was recovered with secondary forest, Amapá had only 4% of its total forest area razed and recovered almost 70% of it with secondary forest. Amapá also managed to offset more than a quarter of its deforestation emissions (26.9%), whereas Tocantins offset only a little more than a tenth (13%).
It is worth noting that Amapá has more than 4 times the forest area of Tocantins, and more than 70% of its area is protected as conservation units or Indigenous lands. The state has the lowest deforestation rates in the Brazilian Amazon according to the Amazon Deforestation Monitoring Project, part of Brazil’s National Institute for Space Research.
Older Forests Have Greater Carbon Sequestration
University of Connecticut professor Robin Chazdon, who did not take part in the study, said it confirms trends observed in previous research about carbon recovery in reforested regions. “It also shows the need for deeper analysis of the economic, social, and political factors that are part of these trends,” she said.
Chazdon explained that the amount of remaining forest in a place is a predictor for unassisted vegetation regrowth. “Sometimes there’s a time lag between forest clearance and land use,” she said, hinting that older secondary forests may yield higher carbon sequestration rates.
The numbers in the study back Chazdon’s observations: Almost 80% of all secondary forest vegetation analyzed was less than 20 years old, with an average age of 8 years. Guyana and Suriname had some of the oldest secondary forests studied, and these countries had the highest carbon recovery rates of the whole biome.
“This means that trees must be given time to grow, so their carbon absorption can make some difference,” Berenguer said. She stressed that secondary forests are not absorbing as much carbon as they could for two primary reasons: Deforestation emissions in the Amazon are still overwhelmingly high, and at the same time, secondary forests are razed at a young age across most of the biome. “It is counterproductive to plant a hectare and tear another 10 down,” she added.
Despite the scenario, the researchers see some space for hope. “We’re always told the story of how we are failing the Amazon forest. But places like Ecuador and Amapá show that the Amazon is not all about failure. They’re two cases that need to be looked at in detail so we can learn something that can be useful to the whole biome,” Berenguer said.
“Latin America has the highest forest recovery capacity in the world, with the Amazon forest having the highest potential across the region,” said Chazdon. “Brazil is the single country with the highest forest recovery capacity in the world—but social, economic, and political factors impede regrowth.”
—Meghie Rodrigues (@meghier), Science Writer
Rodrigues, M. (2021), Forest recovery in the Amazon is a slow process, Eos, 102, https://doi.org/10.1029/2021EO163121. Published on 14 September 2021.
Text © 2021. The authors. CC BY-NC-ND 3.0
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