Mature forests play a surprising role in climate mitigation

In a remarkable revelation, recent research shows that mature forests are critical warriors in the battle against climate change.

Contrary to prevailing theories, the study has revealed that older trees react to higher atmospheric levels of carbon dioxide (CO2) by boosting their production of woody biomass.

This discovery strengthens the argument for the role of mature forests as natural climate solutions in trapping and storing atmospheric CO2.

The unforeseen power of mature forests

As CO2 levels in the atmosphere rise, scientists have discovered that older forests do possess the capacity to respond. These old trees absorb the enhanced levels of CO2 by increasing their woody biomass production.

Interestingly, other elements such as leaves or fine roots, which release CO2 into the atmosphere rather rapidly, did not show a similar increase in productivity.

“Our findings refute the notion that older, mature forests cannot respond to rising levels of atmospheric CO2, but how they respond will likely depend on the supply of nutrients from the soil,” said study lead author Professor Richard Norby from the University of Birmingham.

“Evidence from BIFoR FACE of a significant increase in woody biomass production supports the role of mature, long-established forests as natural climate solutions in the coming decades while society strives to reduce its dependency on carbon.”

Mature forests: Challenging misconceptions

Professor Norby noted that these findings refute the misconception that mature forests are incapable of responding to changing atmospheric CO2 levels.

However, he adds a caveat that the way these forests react will likely be determined by the soil’s nutrient supply.

A significant, noteworthy point that the study makes clear is that old, long-established forests are natural climate solutions that will play a crucial role in the upcoming decades, helping societies reduce their carbon dependence.

A tool for climate predictions

FACE experiments have been instrumental in understanding the interaction of forests, atmosphere, and climate. However, they were primarily conducted in young tree plantations, leaving doubts about whether mature forests would respond similarly.

The research from the University of Birmingham has dispelled such doubts and provides invaluable insights for policymakers grappling with the intricate issue of climate change.

“We believe these results, at about the halfway point of our fifteen-year experiment at BIFoR FACE, will prove invaluable for policymakers around the globe as they grapple with the complexities of climate change,” said study co-author Professor Rob MacKenzie.

“FACE experiments such as ours provide foundations for predictions of future atmospheric CO2 concentrations and so greatly improve confidence in policy decisions. But even if the increase in tree growth translates to a medium-term increase in carbon storage in forests, this in no way offers a reason to delay reductions in fossil fuel consumption.”

A reason for action, not delay

Despite the promising results, the researchers caution against perceiving the increased tree growth and potential carbon storage in forests as a justification for postponing reductions in fossil fuel consumption.

The BIFoR FACE experiment, which altered the atmosphere around the forest since 2017, calculates the overall growth of the forest (net primary productivity, NPP). This includes the production of leaves, fine roots, flowers, seeds, and even the release of biologically active compounds from roots.

The researchers discovered that in 2021 and 2022, the net primary productivity was 9.7 and 11.5 percent larger in elevated CO2 conditions respectively. However, the increase was mostly due to wood production, with no change detected in leaf or fine-root mass production.

These findings underscore the importance of forest protection and management required to offset even essential fossil-fuel emissions.

According to the study, the CO2 absorbed by mature forests is equivalent to only one percent of the CO2 emitted by a single commercial passenger aircraft flying one-way London to New York. This is a testament to the daunting task at hand.

The BIFoR FACE experiment is set to continue into the 2030s to further explore these relationships and to probe the long-standing interactions between forest carbon, other plant nutrients, and the forest food web.

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