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Journalism of Courage
The average size of trees in the Amazon rainforest has been steadily increasing due to the rising levels of carbon dioxide (CO2) in the atmosphere, according to a new study. The trees are increasing in size by more than three per cent every ten years, the analysis said.
The study, ‘Increasing tree size across Amazonia’, was published in the journal Nature Plants on September 25. It was carried out by an international team of around 100 scientists from more than 60 universities around the world, including those from South America and the United Kingdom.
What did the study say?
To carry out the study, scientists monitored trees across 188 permanent forest plots, with an average area of 12,000 square metres across the Amazon basin, to build the long-term dataset.
Although monitoring periods varied, some were as long as 30 years. During this time, the researchers found that, on average, trees increased in diameter by about 3.3 per cent each decade.
Usually, the average diameter of trees in an area of undisturbed old-growth forest stays roughly the same, as saplings take the place of fallen big trees and grow. Scientists believe that in the case of the Amazon rainforests, trees did not follow this trend due to a rise in atmospheric CO2, which increased by nearly a fifth in the last 30 years.
The rise of CO2 levels can benefit tree growth because of a phenomenon known as the carbon fertilisation effect. More CO2 in the atmosphere increases the rate of photosynthesis, leading to increased growth in some plants.
Why is this significant?
The findings are significant as trees which have become bigger can absorb more carbon than in the past.
Peter Etchells, a researcher at Durham University (the UK), told New Scientist, “The important finding is that CO2 has been acting as a fertiliser, increasing tree growth, and in many ways that is reassuring, because wood is a globally significant carbon sink.”
However, scientists have said that the apparent benefits of CO2 should not obscure the damage caused by deforestation.
Rebecca Banbury Morgan, researcher at the University of Bristol and also a joint lead author, said: “Our paper also highlights how destructive Amazon deforestation really is. Large tropical trees are hundreds of years old. We can’t simply plant new trees and expect them to confer anything like the kinds of carbon or biodiversity benefits that the old, natural forest is providing.”
What is the Amazon rainforest?
The Amazon rainforest is the world’s largest tropical rainforest, spanning nine countries in South America: Brazil, Peru, Colombia, Bolivia, Ecuador, French Guiana, Guyana, Suriname, and Venezuela. However, nearly 60% of the rainforest is situated in Brazil.
Despite covering around 1% of the planet’s surface, the Amazon rainforest is home to 10% of all the wildlife species known to humans. According to the conservation organisation World Wildlife Fund (WWF), the total number of known species in the rainforest includes: 427 mammals, 1,300 birds, 378 reptiles, more than 400 amphibians, and between 2,500 and 3,000 freshwater fish.
Notably, scientists call the Amazon rainforest the “lungs of the planet” due to the role it plays in absorbing CO2 and producing oxygen. It is estimated that around 150-200 billion tonnes of carbon are stored in the Amazon rainforest.
