A new study supports evidence that rising levels of carbon dioxide emissions are making American forests healthier and more resilient. In fact, U.S. forests are likely to get even healthier over the next few decades.
“We found that trees are tolerant of rising temperatures and have responded to rising carbon dioxide,” according to a recent study by scientists with the National Council for Air and Stream Improvement and the Center for the Study of Carbon Dioxide and Global Change.
Scientists reviewed a slew of studies to see what scientists found in regards to how global warming would impact forest health. While there seems to be disagreement over the future of forest health in a warmer world, scientists found “United States forest health has improved over recent decades and is not likely to be impaired in at least the next few decades.”
“We find that plants can shift their optimum temperature for photosynthesis, especially in the presence of elevated CO2 , which also increases plant productivity,” scientists wrote. “Additionally, elevated CO2 increases water use efficiency and protects plants from drought.”
“There is strong evidence from the United States and globally that forest growth has been increasing over recent decades to the past 100+ years,” the scientists added.
For years, scientists have been finding the Earth has actually been greening, despite warnings that carbon dioxide-induced global warming could drastically raise the global average temperature over the next century. But that ignores the other role CO2 plays on our planet: providing food for plants.
Higher CO2 levels are actually causing vegetation and plant life to grow in even the world’s most arid regions. This process is called CO2 “fertilization” — the more CO2, the less water plants need to grow. That’s why plant growers tend to pump CO2 into greenhouses with flowers and other plants.
Most scientists and environmentalists, however, focus on the warming aspects of CO2 when higher levels are put into the atmosphere. Earlier this year, NASA scientists warned Earth’s atmospheric CO2 levels passed 400 parts per million — or 0.04 percent of the atmosphere.
“Passing the 400 mark reminds me that we are on an inexorable march to 450 ppm and much higher levels,” said Michael Gunson, head of NASA’s global change and energy program, in May. “The world is quickening the rate of accumulation of CO2, and has shown no signs of slowing this down. It should be a psychological tripwire for everyone.”
But that’s only one-side of the CO2 equation. Scientists have been increasingly interested in how rising CO2 will impact plant growth.
For example, a 2013 study by U.S. scientists published in the journal Nature found a “substantial increase in water-use efficiency in temperate and boreal forests of the Northern Hemisphere over the past two decades.”
“The observed increase in forest water-use efficiency is larger than that predicted by existing theory and 13 terrestrial biosphere models,” the study added. “The increase is associated with trends of increasing ecosystem-level photosynthesis and net carbon uptake, and decreasing evapotranspiration.”
The major concern for scientists looking at plant life, however, is the balance between warming and CO2 fertilization. Scientists want to know if there’s a point at which too much warming and water scarcity will overwhelm the benefits of CO2 in plants.