A forest of mature oak trees was exposed to high levels of carbon dioxide for seven years, and in response the trees increased their wood production, trapping the greenhouse gas and preventing it from warming the planet.
The researchers hope the study, published in the journal Nature Climate Change, will demonstrate the importance of protecting and maintaining mature forests in the fight against climate change.
It is estimated that globally, an area of primary forest the size of a football field is lost every six seconds.
Professor Rob MacKenzie, Director of the Birmingham Institute of Forest Research and co-author of the study, said: “I think this is a hopeful and positive story. It’s evidence in favour of careful management of established forests. Old-growth forests do a huge job for us. What we absolutely must not do is cut it down.”
Observation in 52 acres of forest
The results of this latest study come from the University of Birmingham’s Free Air Carbon Dioxide Enrichment (FACE) experiment, which Prof MacKenzie has chaired since its inception in 2016.
FACE is located on 52 acres of woodland in Staffordshire and aims to understand the impact of a changing climate on woodlands in real time.
The site contains a group of 180-year-old English oak trees, and the academics have installed a network of pipes between their 40-metre-high canopies.
These pipes send out a stream of carbon dioxide (CO2), a greenhouse gas, every day, recreating the conditions the world could face if no action is taken to reduce emissions.
After seven years of monitoring, the international team of researchers at FACE revealed that oak trees increase their productivity under these high CO2 levels.
Trees produced about 10 percent more wood, trapping carbon dioxide for years and preventing the atmosphere from warming.
When trees take in carbon dioxide, they can use it in a variety of ways, including producing new leaves, roots, or woody biomass. New leaves and roots are considered short-term stores of carbon dioxide because they can shed and die relatively frequently, releasing the gas back into the atmosphere. But the researchers found that most of the CO2 is converted into forms that can be stored for decades.
Previous experiments had shown that young trees could increase their CO2 absorption rates, but it was assumed that more mature forests did not have the same adaptability.
Not a magic formula
Prof MacKenzie told the BBC it was important for the team to understand how old trees behave because most of our tree cover globally consists of these trees.
“This is certainly not a magic formula for our fossil fuel emissions. There is no way we can convert the world to enough forests that we can continue to burn fossil fuels the way we are doing now,” MacKenzie said.
The experiment was extended until 2031 so that researchers can continue to monitor the oak trees to see if this behavior continues.
“It’s important to continue the FACE trial for many years because we know that responses can change over time. A longer-term record will increase our confidence in the results,” said Dr. Richard Norby, a research professor at the University of Tennessee and an author of the study.
They also hope to look at the impact of higher CO2 levels on tree lifespan and other biodiversity, such as insects. While conducting this experiment, the scientists observed an increase in some insect species, which could be a result of different weather conditions.
