As temperatures rise over the coming decades, Earth’s terrestrial ecosystems could go from acting as net carbon sinks that remove CO2 from the atmosphere to carbon sources that release it, according to a new study.
The temperature plays a considerable role in how well an ecosystem—like rainforests—can act as a carbon sink. Living organisms have an optimum range of temperatures at which they can function correctly. Once temperatures exceed that range, things start to turn south.
Corresponding author Katharyn Duffy at Northern Arizona University and her team developed a temperature dependence curve for plants—a model that predicts consequences of temperature changes for all of Earth’s land-based vegetation.
The model was constructed using data from FLUXNET, a global network of meteorological sensors that monitor the exchanges of carbon dioxide, energy, and water vapor in the biosphere and atmosphere.
The model showed that as temperatures escalate, it could lead to plants having lower rates of photosynthesis. Since plants release CO2, there is also a potential for the ecosystems to shift from being net carbon stores to net emitters progressively.
Duffy explained:
“All the plants on Earth are picking up about 30% of all the carbon that we emit, and so if that no longer happens, that can create kind of a runaway climate change rate. It’s this feedback loop where the plants are taking up less carbon; there’s more carbon in the atmosphere, there’s more warming, and so on, and so forth.”
The team’s results, detailed in Science Advances, indicate that the temperature tipping point where these terrestrial biospheres turn into carbon sources could be reached in as little as 20 to 30 years. Not every plant responds to heat and drought the same way, though: some tropical trees have evolved a water-saving form of photosynthesis that lets them keep their leaf pores shut all day.
