Published: Sun, March 08, 2020
Sci-tech | By Patricia Wade

'Alarming': Tropical Forests In Shift From Carbon Sponge To Carbon Source

'Alarming': Tropical Forests In Shift From Carbon Sponge To Carbon Source

Entire tropical forests are popular as a critical global carbon sink, decelerating climate change by separating carbon from the atmosphere and hoarding it in trees a procedure called carbon sequestration.

The decline of tropical forests as long-term vaults for carbon dioxide is a momentous change in how Earth systems cope with humanity's penchant for turning carbon-rich minerals into atmospheric gas.

The causes of this rapid decline are to be found in the loss of biomass: the forest area decreased by 19 percent in 30 years, and in the same period, global Carbon dioxide emissions increased.

The ability of the world's tropical forests to absorb carbon from the atmosphere is decreasing - decades ahead of predictions, researchers have warned.

Scientific models have typically predicted that the role of tropical forests in storing carbon would continue for decades.

"We've found that one of the most worrying impacts of climate change has already begun", said Simon Lewis, professor in the school of geography at Leeds University, one of the senior authors of the research.

The study - which involved researchers from almost 100 different institutions -repeatedly measured trees in 244 intact African tropical forests across 11 countries to assess their carbon storage, comparing this to 321 plots in the Amazon. In the last two decades, the tropical regions of northern ecosystems or boreal forests have surpassed their production of CO2.

Large swathes of rainforest, including those in Indonesia, Brazil and Democratic Republic of Congo, help regulate rainfall, prevent flooding, protect biodiversity and limit climate change.

'This is decades ahead of even the most pessimistic climate models.

A team of dozens of Europe- and Africa-based researchers monitored tree growth and mortality data from undisturbed forests across 11 countries in Africa stretching back over 50 years.

The finding that tropical forests are absorbing less of the extra carbon dioxide caused by human activities makes efforts to cut emissions to curb rising global temperatures even more urgent, the scientists said.

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As a result, intact forests removed 17 per cent of the carbon emissions caused by humans in the 1990s, but only 6 per cent by the 2010s.

It showed the ability of the Amazon forests to absorb or "sequester" carbon started to fall in the mid-1990s while the African carbon sink began to decline about 15 years later.

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.

At this point, the Amazon would release more carbon in the air than it removes. Pictured, forest in the Ivindo National Park, in central Gabon, Africa © Provided by Daily Mail However, experts led from the University of Leeds found that drought and higher temperatures are reducing the amount of carbon dioxide being stored in trees.

Intact forests are large areas of continuous forest with no signs of intensive human activity like agriculture or logging.

The study by approximately 100 establishments offers the elemental extensive scale proof that carbon intake by the globe's tropical forests has worryingly been going down. This storage is equivalent to 90 years of global fossil fuel emissions at today's level.

Stopping deforestation and managing tropical forests to help them weather the impacts of climate change - as well as restoring forests in the tropics and temperate parts of the world - are also important, Professor Lewis added.

This research shows that relying on tropical forests is unlikely to be enough to offset large-scale emissions.

The way to maintain tropical forests as carbon sinks "is to stabilise the climate" by cutting emissions, mainly from fossil-fuel use, to "net zero", said Lewis.

"In addition, stabilising Earth's climate is necessary to stabilise the carbon balance of intact tropical forests".

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