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Tropical Forests Lose One-Third of Carbon Storage Ability, Could Soon Become Carbon Source

Tropical forests have lost much of their ability to pull carbon dioxide out of the air, and could begin turning into net carbon sources in the next 10 to 15 years, according to an alarming new study published last week in the journal Nature.

“For the last three decades, the amount of carbon absorbed by the world’s intact tropical forests has fallen,” The Guardian reports, citing a 30-year study of 300,000 trees involving researchers from nearly 100 scientific institutions. “They are now taking up a third less carbon than they did in the 1990s, owing to the impacts of higher temperatures, droughts, and deforestation. That downward trend is likely to continue, as forests come under increasing threat from climate change and exploitation. The typical tropical forest may become a carbon source by the 2060s.”

The precipitous decline in tropical forest carbon storage “is a momentous change in how Earth systems cope with humanity’s penchant for turning carbon-rich minerals into atmospheric gas,” Bloomberg adds. “The researchers note that their grim findings may also influence global climate policy debates. Scientific models had been projecting that forests would continue to consume our CO2 emissions for decades to come. If those projections turn out to be wrong, the study warns, nations have much less time ‘to meet any given commitment to limit the global heating of the Earth’.”

In particular, “the Amazon could turn into a source of carbon in the atmosphere, instead of one of the biggest absorbers of the gas, as soon as the next decade, owing to the damage caused by loggers and farming interests and the impacts of the climate crisis,” The Guardian says. “If that happens, climate breakdown is likely to become much more severe in its impacts, and the world will have to cut down much faster on carbon-producing activities to counteract the loss of the carbon sinks.”

By 2030, as well, “the African jungle will absorb 14% less carbon dioxide than it did 10 to 15 years ago,” the Washington Post writes, citing the same report. “By the middle of the century, the remaining uncut tropical forests in Africa, the Amazon, and Asia will release more carbon dioxide than they take up—the carbon ‘sink’ will have turned into a carbon source.”

“We’ve found that one of the most worrying impacts of climate change has already begun,” said Leeds University geographer Simon Lewis, one of the senior authors behind the study. “This is decades ahead of even the most pessimistic climate models.”

“Humans have been lucky so far, as tropical forests are mopping up lots of our pollution, but they can’t keep doing that indefinitely,” he told the Guardian. “We need to curb fossil fuel emissions before the global carbon cycle starts working against us. The time for action is now.”

The report puts a new twist on negotiations at this year’s United Nations climate conference in Glasgow, where some of the world’s biggest emitters are expected to turn to forest planting as a way to offset their continuing reliance on fossil fuels. “This research shows that relying on tropical forests is unlikely to be enough to offset large-scale emissions,” The Guardian warns. 

“There is a lot of talk about offsetting, but the reality is that every country and every sector needs to reach zero emissions, with any small amount of residual emissions needing to be removed from the atmosphere,” Lewis told the UK-based paper. “The use of forests as an offset is largely a marketing tool for companies to try to continue with business as usual.”

“This analysis provides concerning evidence that, along with continuing deforestation rates, the carbon sequestration rate of tropical forests could also be threatened by increasing tree mortality under climate change,” added British ecologist Dr. Thomas Crowther. “This is very important information, as the capacity of tropical forests to capture anthropogenic carbon emissions could be severely impaired.”

“For years, we have had scientific warnings about tipping points in the Earth system and they’ve been largely ignored by policy- and decision-makers,” said Greenpeace UK Chief Scientist Doug Parr. “That forests are now seemingly losing the ability to absorb pollution is alarming. What more of a wake-up call do we need?”