Trees today are larger than they were 30 years ago because of carbon dioxide

Are the trees changing? The results of the recent research by Ohio State University seem to show this.

The results, published in Nature Communications on September 19, are truly astonishing because the research suggests that trees are getting bigger day by day thanks to carbon dioxide. In other words, the atmosphere has increased the wood volume of forests in the U.S.

The study discovered that increasing carbon levels consistently caused an increase in wood volume in 10 different temperate forest groups across the country, even though other factors like climate and pests can also somewhat alter a tree's volume. This shows that trees' quick growth is assisting in protecting the Earth's ecology from the effects of global warming, as stated by Ohio State.

“Forests are taking carbon out of the atmosphere at a rate of about 13 percent of our gross emissions,” said Brent Sohngen, co-author of the study and professor of environmental and resource economics at The Ohio State University.

“While we’re putting billions of tonnes of carbon dioxide into the atmosphere, we’re actually taking much of it out just by letting our forests grow.”

It's all because of carbon fertilization

The reason trees grow so much is carbon fertilization. Carbon fertilization, or carbon dioxide fertilization, causes the rate of photosynthesis in plants to increase when carbon dioxide levels in the atmosphere rise.

“It’s well known that when you put a ton of carbon dioxide in the atmosphere, it doesn’t stay up there forever,” Sohngen said. “A massive amount of it falls into the oceans, while the rest of it is taken up by trees and wetlands and those kinds of areas.”

According to the study, over the past 20 years, forests in the United States have stored about 700–800 million tonnes of carbon dioxide annually, or 10–11 percent of the nation's overall carbon dioxide emissions.

Trees have no problem gorging themselves on Earth's surplus of carbon dioxide, a greenhouse gas that can have negative consequences on natural systems and infrastructure. Such growth may not be noticeable to the average person, but modern vegetation is about 20 to 30 percent larger than it was 30 years ago.

The team used old data

Sohngen's team used historical data from the U.S. Forest Service Forest Inventory and Analysis Program (USFS-FIA) to compare how the volume of wood in various forest groups has changed over the past few decades to determine whether the chemical compound was responsible for bulking up our biome.

According to the study, the volume of wood produced by trees increased significantly between 1970 and 2015, which is consistent with a sharp increase in carbon emissions.

Eric Davis, a Ph.D. alumnus of Ohio State's agricultural, environmental, and development economics school, served as the study's principal researcher. The American Department of Agriculture provided funding for this study.

Abstract:

Over the last half-century in the United States, the per-hectare volume of wood in trees has increased, but it is not clear whether this increase has been driven by forest management, forest recovery from past land uses, such as agriculture, or other environmental factors such as elevated carbon dioxide, nitrogen deposition, or climate change. This paper uses empirical analysis to estimate the effect of elevated carbon dioxide on aboveground wood volume in temperate forests of the United States. To accomplish this, we employ matching techniques that allow us to disentangle the effects of elevated carbon dioxide from other environmental factors affecting wood volume and to estimate the effects separately for planted and natural stands. We show that elevated carbon dioxide has had a strong and consistently positive effect on wood volume while other environmental factors yielded a mix of both positive and negative effects. This study, by enabling a better understanding of how elevated carbon dioxide and other anthropogenic factors are influencing forest stocks, can help policymakers and other stakeholders better account for the role of forests in Nationally Determined Contributions and global mitigation pathways to achieve a 1.5 degree Celsius target.