Tropical rainforests play a critical role in regulating climate change by drawing carbon dioxide from the air in a process known as carbon sequestration. But years of increased greenhouse emissions have taken a toll on rainforests in the Amazon and Africa by significantly impacting their ability to recycle carbon.
A 30-year study led by researchers from the University of Leeds and international collaborators has found these so-called carbon sinks have been on the decline since the 1990s.
Professor Simon Lewis, a senior author from the School of Geography at Leeds, told Express.co.uk unless steps are taken to save the rainforests, the carbon sinks will continue to shrink.
He said: “The world’s tropical forests are absorbing carbon dioxide from the atmosphere and acting as a brake, slowing down the rate of climate change.
“In the 1990s they were sequestering – removing – about 17 percent of all fossil fuel and land-use change emissions of carbon dioxide in the atmosphere.
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“They’re really important in slowing the rate of climate change and what we show in this study is that, more worryingly, this carbon sink, this ability to sequester carbon is starting to decline.”
Professor Lewis and 98 other authors published the findings of their study today (March 4) in the journal Nature.
The scientists observed some 300,000 trees in 565 undisturbed tropical forests for more than 30 years.
Nearly 100 institutions took part in the large-scale study to measure tree growth and tree death over three decades.
Rainforests store carbon through sequestration by removing carbon from the atmosphere and storing it in the trees and the soil.
However, the intact rainforests’ ability to store carbon peaked in the 1990s and since the 2010s has dropped on average by about one-third.
The decline was marked by rainforests being less able to absorb carbon by 33 percent and intact forests shrinking by about 19 percent, while global carbon emissions skyrocketed by about 46 percent.
This carbon sink, this ability to sequester carbon is starting to decline
Professor Simon Lewis, University of Leeds
According to the study, trees in the rainforests are dying, which is exacerbated by climate change, drought and rising temperatures.
Although some studies have found abundant carbon dioxide in the atmosphere can boost plant growth, there is an imbalance in the system.
Professor Lewis said: “What we’ve seen over the past decades, is that more carbon dioxide in the atmosphere helps trees grow.
“So there’s a boost to the growth and that’s what we’ve seen in terms of this carbon sink.
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“But over time, the negative impacts of climate change and CO2 in the atmosphere – rising temperatures, the occasional droughts hitting the rainforests – that is offsetting and slowing down some of the growth, and boosting tree mortality.
“So over time, these negative impacts are increasing and, therefore, overall the carbon sink is slowly starting to erode.”
The unfortunate trend shown by the study is the carbon sinks will continue to shrink until they reach a tipping point where they release more carbon back into the atmosphere than they absorb.
The study estimated the planet’s carbon sinks will become a carbon source by the mid-2030s.
There is, however, some hope strong regulation and policies can be implemented to protect the rainforests.
Otherwise, the natural barriers once slowing down the effects of climate change will start to accelerate them.
Professor Lewis: “The UK Government has just legislated for a net-zero target of 2050 and more and more countries are agreeing to commitments for net-zero in the future.
“But what is also needed is much more near-term climate policies.
“There need to be climate policies that also help people, so this might be insulating homes so we use less energy and less emissions and all have nicer homes.”
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