That’s according to the ‘Effect of increasing CO2 on the terrestrial carbon cycle,’ a NASA-led study published in the Proceedings of National Academy of Sciences, which estimates that tropical rainforests absorb 1.4 billion metric tonnes of CO2 out of a total global absorption of 2.5 billion, more than boreal (coniferous) forests in the northern hemisphere.

Lead author of a paper on the new research David Schimel said: “This is good news, because uptake in boreal forests is already slowing, while tropical forests may continue to take up carbon for many years.”

Forests and land vegetation currently account for the absorption of up to 30% of human-caused CO2 emissions during photosynthesis. If this rate were to decrease, the rate of global warming would increase.

Independent data

The research incorporated different types of analyses and obtained their new estimate of the tropical carbon absorption from models they established as the most trusted and verified.

Co-author of the paper Joshua Fisher said: “Until our analysis, no one had successfully completed a global reconciliation of information about carbon dioxide effects from the atmospheric, forestry and modelling communities. It is incredible that all these different types of independent data sources start to converge on an answer.”

Britton Stephens, another co-author, suggests that the question of which type of forest is the bigger carbon-absorber is ‘not just an accounting curiosity.’

“It has big implications for our understanding of whether global terrestrial ecosystems might continue to offset our carbon dioxide emissions or might begin to exacerbate climate change,” he said.

The increase in human-induced emissions means that forests worldwide grow faster and reduce the amount of CO2 which stays airborne – an effect known as carbon fertilisation.

The research found that the effect is stronger at higher temperatures and so fertilisation will be higher in the tropics than boreal forests.

Lois Vallely

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