Global Warming

Global warming is shrinking the rainforest’s role as climate protector

The amount of planet-warming carbon dioxide that can be sucked up from the atmosphere and stored by tropical forests is falling as the global climate heats up, researchers said on Wednesday. They warned in a study that rainforests could tip from absorbing carbon to becoming a source of emissions.

The 30-year study, led by the University of Leeds and involving almost 100 institutions, showed that the intake of carbon by “intact tropical forests” peaked in the 1990s and had dropped by a third by the 2010s.

Intact forests are large areas of continuous forest with no signs of intensive human activity like agriculture or logging. They form part of the world’s roughly 5.5 billion hectares of forest.

Trees suck carbon dioxide from the air, the main greenhouse gas heating up the Earth’s climate, and store carbon, which they release when they are cut down and are burned, or rot.

Tropical forests are huge reservoirs of carbon, storing 250 billion tonnes in their trees alone – an amount equivalent to 90 years of global fossil-fuel emissions at current levels.

Researchers, who tracked the growth and death of 300,000 trees in Africa and the Amazon, found that undisturbed tropical forests had started the process of switching from a carbon sink to a source, largely due to carbon losses from trees dying.

In the 1990s, intact tropical forests removed about 46 billion tonnes of carbon dioxide from the atmosphere, declining to an estimated 25 billion tonnes in the 2010s, the study said.

The lost sink capacity was 21 billion tonnes of carbon dioxide – the same as a decade of fossil-fuel emissions from Britain, Germany, France and Canada combined

Intact tropical forests removed 17% of human-made carbon dioxide emissions in the 1990s but that fell to 6% in the 2010s.

The decline was because those forests, whose area shrank by 19%, absorbed a third less carbon, while global carbon emissions soared by 46%, the study said.

The tropics lost 12 million hectares of tree cover in 2018, including 3.6 million hectares of old-growth rainforest, an area the size of Belgium, much due to fires, land-clearing for farms and mining, according to monitoring service Global Forest Watch.

from WordPress https://ift.tt/2uVCYE5