Now the forest has had enough – can no longer handle carbon dioxide

Rainforest

Australian rainforest has switched from carbon sink to emission source

Christina Nordh

Published 19.33

 

Rainforest in Queensland, Australia. Photo: Magnus Hjalmarson Neideman/Svd/TT

The forest can no longer handle all the carbon dioxide.

The first rainforest has now turned into an emission source.

The tropical rainforest trees are found in the sunshine state of Queensland in eastern Australia.

The change has been detected in the trunks and branches of the trees, but not yet in the root system, and began 25 years ago, according to research published in the journal Nature. 

Normally, tropical forests are carbon sinks that absorb more carbon dioxide than they emit. Trees store carbon as they grow. When the trees decompose and die, the carbon is released.

It has long been assumed that trees' uptake would increase with increasing carbon dioxide levels in the atmosphere, writes The Guardian.

Based on 50 years of data

Now, using almost 50 years of data collected from the tropical forests of Queensland, it has been shown that the important carbon sink is under threat. More trees are dying and the new growth is not sufficient to compensate for the losses.

- It is the first tropical forest of its kind to show this symptom of change. We know that the humid tropics in Australia are in a slightly warmer and drier climate than tropical forests on other continents. Therefore, they can serve as a future model for what tropical forests in other parts of the world may experience, says lead author Dr. Hanna Carle of Western Sydney University.

 

If the change is correct, it could have major consequences for reducing carbon dioxide emissions. Photo: Getty Images/iStockphoto

The study’s co-author, Professor Adrienne Nicotra of the Australian National University, says more research is needed. But she says that if this is true, it could have significant implications for global climate models, carbon budgets and climate policy.

“This paper is the first time that this threshold, the transition from carbon sink to carbon source in tropical rainforests, has been clearly identified. Not just in a single year, but over a period of 20 years,” says Professor David Karoly, a climate expert and emeritus professor at the University of Melbourne.

“Bad news”

He was not involved in the research, but says that the proportion of carbon dioxide absorbed by forests, trees and plants has been fairly stable over the past 20-30 years and that many climate models assume that stability will persist.

If more rainforests turn from carbon sink to source, future climate projections could underestimate global warming.

“And that’s bad news,” says Karoly.

He says the reduced capacity of forests to absorb carbon will make it much harder to reduce emissions – an even faster transition away from fossil fuels is needed.

 

Between August 2023 and July 2024, 6,288 square kilometers (just over 1,200,000 football pitches) of rainforest were cleared in the Amazon. That’s a decrease of about 30 percent compared to the same period the previous year. Photo: Edmar Barros/AP

FACTS

Changes detected above ground

• The analysis is based on a dataset that goes back to 1971, monitoring about 11,000 trees from 474 species at 20 different sites in North Queensland's wet tropical rainforests that ranged from sea level to about 1,200 meters in altitude.
• These forests cover about one million hectares, but the researchers have made measurements at a number of monitoring sites within the area.
• The study examined the amount of carbon stored above ground in tree trunks and branches, but not the changes below ground - in the soil and root systems.