A recent study found that “carbon fertilization” triggered by high CO2 levels in the atmosphere does not help trees grow faster. In fact, computer models show that global warming will reduce tree growth regardless of CO2 levels.
Unlike humans, plants use carbon dioxide to survive, so carbon dioxide should benefit trees and other plants on the long run, at least in theory. Past studies had shown that more carbon dioxide might help trees grow faster since the compound acts very much like an aerial fertilizer.
This is why the phenomenon was called “carbon fertilization.” And faster tree growth was expected to help humans keep in check climate change. Yet, a recent study has some disheartening results.
A group of researchers used computer models to simulate tree growth in different environments and carbon concentrations. The team based their research on a simple principle: the more carbon trees absorb the more water escapes.
Scientists likened the pores on trees’ leaves to minuscule “mouths” the plant need to open to capture CO2, but when the “mouths” open water evaporates. If carbon dioxide levels are high enough, trees don’t need to open their tiny mouths wide to get the vital gas. As a result, less water is lost in the process.
So, in their simulations, researchers replaced the additional carbon dioxide intake with more rainwater to measure growth rate in a warming world. And the results were alarming.
Across the central and western North America, there would be substantial decreases in tree growth rates, models show. The study revealed that by 2050, trees would grow 75 percent slower in the said areas despite the carbon fertilization effect.
However, in western Canada and coastal regions of the U.S. trees are projected to grow faster. Scientists also found that in the absence of carbon fertilization efect trees will grow slower by up to 20 percent.
The research team also found that trees will need unrealistically huge amounts of carbon dioxide to counter the slowdown. Plus, the models also showed that despite the effect, trees will continue to decrease their growth pace across much of the North America.
The new analysis debunked the myth of a “boreal greening” triggered by climate change. Northern forests would also see a slower growth pace, according to the simulations.
The study was published Tuesday in the journal ecology Letters.
Image Source: Flickr