The Amazon rainforest in South America was one of Earth’s principal absorbers of carbon dioxide or carbon sink. However, a new study says that part of the rainforest is now emitting more carbon dioxide than it is soaking up, thus becoming a carbon source.
A team of researchers from different countries have said this area is on the eastern side of the Amazon, which covers around 20 percent of the rainforest basin, as per a study published in Nature Communications journal on July 14.
This land carbon sink in the largest tropical forests, called Amazonia, has been absorbing roughly a quarter of all fossil fuel emissions since 1960, researchers said.
The study revealed that western Amazonia is still a relatively weak carbon sink. But the eastern forest region has seen a huge degradation and even reversal in carbon intake towards becoming a carbon source.
The eastern Amazon region has seen a lot of deforestation and forest burning to make it safe for cattle grazing by keeping away wild animals and insects.
The maximum increase in carbon emissions came from the regions where fires were recorded.
The researchers found evidence of enhanced vegetation that generally happens due to rising levels of carbon dioxide and other chemicals. They also found carbon flux generally related to forest decay.
The researchers checked carbon (monoxide and dioxide) levels in atmosphere levels via satellite readings and solar-powered light energy or radiation from the vegetation. They had been collecting data for the last 10 years.
Researchers found little variance in the growth and decay in north-western Amazonia, which is always very wet. They also found that the relatively drier forests in the north-eastern and south-eastern regions were close to carbon balance during the wet season.
But carbon release from decomposition and fire was more than carbon intake via photosynthesis during the dry season (August to October).
Greater carbon releases occurred during hotter and drier years due to decomposition and fire, researchers said.
They added that tropical forests such as the Amazonia are the world’s most productive ecosystems. But they are not recovering fast enough from the damage to their carbon balance (as their Arctic and boreal peers) due to human activities.
Some 123 billion tonnes of carbon is believed to be stored in the Amazon rainforest, according to the National Oceanic and Atmospheric Administration (NOAA).
Up to 40 percent of the Amazon was at risk of becoming savannah, as per 2020 study published in Nature.
For many years, the ratio of fossil fuels emitted by land ecosystems had been almost constant despite the continuous rise in emissions. This puzzled scientists and ecologists for years.
Forests at high latitudes continue to collect carbon, because out there climate change has increased the length of sowing seasons. Mid-latitude forests, which are recovering from past clearances, have benefited from more soil nutrients provided by humans adapting efficient farming techniques.
(Edited by : Shoma Bhattacharjee)
First Published: IST