Is one of our best hopes slipping away?: Brazil’s Amazon rainforest is now actually emitting more greenhouse gases than it’s absorbing.
Throughout history, the world’s forests have been a great “carbon sink,” absorbing more carbon dioxide than they emit, thereby playing a vital role in slowing global warming and climatic change. Unfortunately, in recent decades, many of the great forests have been either dramatically downsized or disappeared altogether. Given the size and density of the Amazon rainforest, not to mention its place in popular imagination, many have assumed the forest—which touches countries from Bolivia to Brazil, Ecuador to Guyana—would always be mankind’s impenetrable shield against the worst impacts of the globe’s changing climate.
Not so fast.
A study in Nature predicts that the Amazon will flip from carbon sink to carbon source in the next 15 years--decades before even the most conservative climate models had assumed. Studies suggest that Brazil’s portion of the Amazon has already slipped into that status.
How is this possible? The trees of the Amazon region have been sequestering billions of tons of carbon each year, helping to offset global emissions. However, the landscape of the Amazon is rapidly changing, largely due to human activity. Rising levels of deforestation, higher average temperatures, and drier conditions are causing trees in the region to die at an alarming pace.
Deforestation rates have accelerated under President Jair Bolsonaro, who was elected on a promise of development and has been a strong promoter of mining and agriculture in the region. Not only does this leave fewer trees to sequester carbon in the future, but it also undoes decades of progress. Dead trees release the carbon they captured while living back into the atmosphere.
And although carbon tends to get the most international attention, it is not the only greenhouse gas that warrants concern. Methane, nitrous oxide, aerosols, and black carbon (soot) also cause substantial harm to the environment, and human activity is increasing their prevalence in the Amazon as well, according to a recent study in Frontiers in Forests and Global Change. For example, uncontrolled logging creates vast areas of dry wetlands and compact soil, which releases large amounts of nitrous oxide. Burning land, a practice often used to clear pastures for livestock, increases emissions of black carbon.
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