We were warned, now a new study has determined that the Earth’s plants' ability to sequester carbon emissions through photosynthesis will be halved by the 2030s or 2040s from what it is today at ten percent. That kind of loss will turn the natural world into a heat and carbon source, bringing our bios-sphere to the brink of disaster.
The research shows that terrestrial life, “the activity of land plants and soil microbes—does much of Earth's “breathing,” exchanging carbon dioxide and oxygen. Ecosystems across the globe pull in carbon dioxide through photosynthesis and release it back to the atmosphere via the respiration of microbes and plants.”
The biosphere, land, and oceans have done us a huge favor by absorbing our dangerous greenhouse emissions, which have kept us relatively cool by pulling CO2 from the atmosphere and storing it in the ground. The loss of this critical heating and CO2 sink mitigation will raise temperatures by releasing heat-trapping gases, something we do not ever want to face.
Earth's ability to absorb nearly a third of human-caused carbon emissions through plants could be halved within the next two decades at the current rate of warming, according to a new study in Science Advances by researchers at Northern Arizona University, the Woodwell Climate Research Center and the University of Waikato, New Zealand. Using more than two decades of data from measurement towers in every major biome across the globe, the team identified a critical temperature tipping point beyond which plants' ability to capture and store atmospheric carbon—a cumulative effect referred to as the “land carbon sink”—decreases as temperatures continue to rise.
The researchers found that temperature “peaks” for carbon uptake—18 degrees C for the more widespread C3 plants and 28 degrees C for C4 plants—are already being exceeded in nature, but saw no temperature check on respiration. This means that in many biomes, continued warming will cause photosynthesis to decline while respiration rates rise exponentially, tipping the balance of ecosystems from carbon sink to carbon source and accelerating climate change.
“Different types of plants vary in the details of their temperature responses, but all show declines in photosynthesis when it gets too warm,” said NAU co-author George Koch.
Right now, less than 10 percent of the terrestrial biosphere experiences temperatures beyond this photosynthetic maximum. But at the current rate of emissions, up to half the terrestrial biosphere could experience temperatures beyond that productivity threshold by mid-century—and some of the most carbon-rich biomes in the world, including tropical rainforests in the Amazon and Southeast Asia and the Taiga in Russia and Canada, will be among the first to hit that tipping point.
“But due to anthropogenic climate change, temperatures—particularly in warmer months—often go well beyond this 'healthy' range for carbon absorption. It was eye opening—temperatures exceeded this range between 14 and 59.2 percent of the time, depending on which site you were looking at. Plants in these regions simply aren't able to absorb carbon like they used to, which is seriously concerning.”
The research team also measured the rate at which photosynthesis was occurring, with alarming results.
“Once this temperature range is exceeded, the ability for plants to appropriate carbon falls off a cliff,” Professor McGowan said.
“Sequestering carbon is incredibly important right now—we need to drastically reduce the greenhouses gasses in our atmosphere to maintain a healthy climate for us and future generations. We are seeing through observational evidence that a dangerous positive feedback loop is being created, making the world even hotter.”
There is no do-over with climate change.