In the past 10 years, the amount carbon which has been absorbed by the Amazon rainforest foliage has dropped dramatically by almost a third. It has long been a significant basin for the world’s greenhouse gases.
In a study undertaken among the 321 plots in various parts of the Amazon forest growth in the past decade, it was deduced that the probable net volume of carbon dioxide immersed by the forest had fallen to 1.4 billion tons in the 2000s from 2.0 billion tons a year in the 1990s.
Lead author Roel Brienen of the University of Leeds told Reuters, “The whole forest is living faster, trees grow faster, die faster. The net carbon uptake of forests has significantly declined.”
“Enormous,” is the implication of the study’s findings, Professor David Ellsworth said, senior scientific advisor for the Eucalyptus Free-Air CO2 Enrichment (EucFACE) experiment in the Cumberland Plain forest.
“It is just enormous, because the land area were talking about is huge. The tropics represent an extremely large sink for carbon. Carbon that they are not storing is landing in the atmosphere and results in rising atmospheric rising of Co2,” he added.
“We rely on plants to put the skids on the increase in atmospheric Co2, because they take up that carbon. If they are taking up less carbon than we thought we’ve got to consider other options for slowing that rise in Co2 in the atmosphere.”
The reason for the decline remains unclear and would continue and if the trend applied to other tropical forests such as the Indonesia and Congo basin, scientists of the study said.
To give an accurate measurement of the change scientists, 200,000 trees in 321 plots across eight countries were studied, noting significant changes in diameter, wood density, height and births and deaths.
More than a third of the trees suggested an increase in deaths, which could be connected to severe droughts like the occurrence in 2005.
HYPERLINK, the paper, published by Nature, acknowledged that the result was at odds with expectations, highlighting the “difficulties of predicting the role of land-vegetation feedbacks in modulating global climate change.”
The findings, relevant for his own research in understanding how the Australian carbon sink will change into the future, Professor Ellsworth said
“We would want to know, does this apply to Australian rainforests or not? The authors are very clear this applies in the Amazon region of South America,” he said.
“My research would need to merge the information that comes out of what I’m doing, and the carbon release from the Amazon, to understand what it means in terms of atmospheric carbon dioxide and how fast it’s rising, or whether its slowing.”
Carbon dioxide is rising at a rate greater than two per cent per year, Professor Ellsworth said.