Thursday, December 1

Trees today are much larger than those of decades ago. The key is in the air


We emit a lot of CO2. Very much, to be more faithful to reality. Already in 2010, a study by the University of Almería calculated that only in our diet, from the time we produce the food until we expel it, each Spaniard emits around two tons of carbon dioxide per year. It’s not bad at all. Especially if we take into account that, as the UN has already warned on several occasions, global emissions have been growing to record levels.

For years we have been looking for ways to put the brakes on and even reverse that huge flow of emissions. There are strategies for all tastes: rethinking mobility, energy, the cities themselves or even “hunting” the CO2 already released. In this endeavor, one of our great and first allies is vegetation and photosynthesis, the process by which leaves use the energy of sunlight to combine CO2 from the atmosphere with water and nutrients and thus create their food.

A team of researchers from Ohio, in the USA, has just verified the extent to which trees act as our allies to trap CO2. And, above all, and what is really amazing, how the forests have changed as the concentration of carbon in the atmosphere itself has changed.

His conclusion is striking: climate change is turning trees into “gluttons”.

During their study, the Ohio State University team has verified how high levels of CO2 in the atmosphere have increased the volume of wood in forests.

“Helping to protect the ecosystem”

“Although other factors, such as climate and pests, can affect a tree’s volume somewhat, the study found that high carbon levels caused a systematic increase in wood volume in 10 different groups of temperate forests around the world. the country”, explains the American university in a statement. “This suggests that the trees are helping to protect the ecosystem of the Earth from the impacts of global warming.

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The key, Ohio researchers abound, lies in “carbon fertilization” itself: “Carbon dioxide input increases a plant’s rate of photosynthesis.”

According to his calculations, over the last two decades, US forests have sequestered around 700 to 800 million tons of CO2 each year, which would represent 10 to 11% of the total emissions registered in the country. While exposure to high levels of CO2 can have deleterious effects on natural systems and infrastructure, trees have no problem gorging themselves on Earth’s additional supply of greenhouse gases.

What does that translate to? “gluttony” in practice?

Ohio University provides a graphic example.

“If you imagine a tree as a huge cylinder, the extra volume the study finds is equivalent to one extra tree ring,” explains Brent Sohngen, professor of environmental economics. Although the growth may not be noticeable to the average citizen, compared to trees of 30 years ago, modern vegetation is between 20 and 30% larger”.

It may not seem like a very high percentage, but when we talk about huge redwoods like the ones that are scattered along the coast of the country, 20 or 30% more volume translates into considerable additional capacity when it comes to storing carbon dioxide carbon.

Wood volume per hectare in 1997 and 2017 separated by forest group.

Volume of wood per hectare in 1997 and 2017. Data separated by forestry group.

To work with perspective and have a precise idea of ​​evolution, the Ohio team analyzed historical data from the US Forest Service Inventory and Analysis Program (USFS-FIA), which allowed them to see how the biomass of certain groups has evolved. forests over the years. “The study estimates that between 1970 and 2015there was a significant increase in the volume of wood from the trees, which correlates with a clear increase in CO2 emissions.”

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The report, published in Nature Communicationsshows that between 1970 and 2015 CO2 concentrations increased by around 75 ppm (parts per million).

“We found that this increase in CO2 stimulated an increase in the volume of wood in the naturally regenerated 75-year-old forests in EEYY by 12.3%”, settle the researchers before clarifying, yes, that their analysis focuses on temperate forest regions spread throughout the eastern United States. Some studies suggest that in cooler and less humid environments the effects of carbon exposure could be less strong on tree volume.

Images | Arnaud Mesureur (Unsplash) and Nature Communications

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