Once thought to be a line of defense against climate change because of their ability to store carbon, trees are instead growing fast and dying young and won’t store as much greenhouse gas over their lifespans according to research published Wednesday.
Plants and trees flourish in warmer climates, but trees that grow faster during their first 25 years tend to die much sooner than slow-growing trees found in harsh, cold conditions according to the study published in the scientific journal Nature Communications.
The findings point to a warming Earth where trees will continue to grow at accelerated rates, but the amount of carbon they will be able to store will shrink. This will have devastating consequences for carbon cycle dynamics and what amount of carbon dioxide can be pulled out of the atmosphere.
Study author Ulf Büntgen from Cambridge University’s geography department says the fast-growing response to a warmer climate is similar to how animals with a quick heart rate tend to grow faster but have shorter lives on average.
Adding more trees to the equation is not a viable solution for combatting climate change, says Büntgen.
“As the planet warms, it causes plants to grow faster, so the thinking is that planting more trees will lead to more carbon getting removed from the atmosphere,” Büntgen says. “But that’s only half of the story. The other half is one that hasn’t been considered: that these fast-growing trees are holding carbon for shorter periods of time.”
Researchers examined the tree rings of high-elevation subjects that have not been disturbed for thousands of years. These included more than 1,100 living trees and dead wood mountain pines from the Spanish Pyrenees and 600 Siberian larch samples from the Russian Altai which were collected over the past decade.
From the samples, the researchers formed a general idea of the lifespan and juvenile growth rates of trees that were alive during both the industrial and pre-industrial eras. The effect of a warming climate correlated to the decrease in a tree’s lifespan and the amount of carbon it could store. The study found trees only reach old age when juvenile growth is slow.
Even worse, when the trees die – in decades rather than centuries as before – the carbon they absorbed is returned to the atmosphere.
According to the National Oceanic and Atmospheric Administration, global carbon dioxide growth in 2018 was the fourth highest on record. In fact, three of the four highest annual increases occurred in the past four years, the agency said.
Carbon dioxide emissions in the last 20 years have increased about 100 times faster than previous natural jumps, all of it from human activities.