Land to reach ground temperature in next 20 to 30 years, new NAU study finds

The Earth’s potential could cut nearly a third of plant-induced carbon emissions within the next two decades at the current rate of warming, according to a new study in Advances in science by researchers at the University of Northern Arizona, 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 worldwide, the team identified a critical temperature stress point on which plants’ ability to capture and store atmospheric carbon – a cumulative effect of the called “ground carbon sink” – decreases as the temperature rises.

The earth’s biosphere – the activity of earth’s plants and earth’s microbes – makes much of the Earth’s “breath”, exchanging carbon dioxide and oxygen. Ecosystems around the globe absorb carbon dioxide through photosynthesis and release it back into the atmosphere through microbial and plant release. Over the past few decades, the biosphere has typically absorbed more carbon than it has released, reducing climate change.

But as the fastest temperatures continue to spread across the globe, this may not continue; researchers NAU, Woodwell Climate and Waikato have found a temperature threshold where plant carbon uptake slows down and releases carbon.

Lead author Katharyn Duffy, a postdoctoral researcher at NAU, noticed a sharp decrease in photo-synthesis above this temperature level in almost every biome worldwide, even after removal other effects such as rain and sunlight.

“Fever is constantly growing on Earth, and much like the human body, we know that every biological process by which it hopefully performs a temperature range, and those above because the action is declining, “Duffy said. “So we wanted to ask, to what extent can plants stand?”

This study is the first to find a temperature threshold for photosynthesis from observational data at a global level. Although temperature thresholds for photosynthesis and relief have been studied in the laboratory, Fluxnet data provides a window on what ecosystems across the Earth are experiencing and how they respond. .

“We know that the optimum temperature for humans lies around 37 degrees Celsius (98 degrees Fahrenheit), but in the scientific community we did not know what those were best for the terrestrial biosphere, “Duffy said.

She teamed up with researchers at Woodwell Climate and the University of Waikato who recently developed a new approach to answer that question: MacroMolecular Phase Theory (MMRT). With its foundation in the principles of thermodmodynamics, MMRT allowed the researchers to generate temperature loops for each major biome and globe.

The results were frightening.

The researchers found that temperature “peaks” for carbon uptake – 18 degrees C for the wider C3 plants and 28 degrees C for C4 plants – are already provided in nature, but they have not seen a temperature study of relief . This means that continuous warming causes photosynthesis to decline while respiratory rates rise abruptly, shifting the balance of ecosystems from carbon sink to carbon storage and accelerating climate change.

“Different types of plants differ in detail about their temperature responses, but they all show a decline in photo-synthesis when overgrown,” said NAU co-author George Koch.

Currently, less than 10 percent of the terrestrial biosphere experiences temperatures higher than the maximum range of images. But at current emissions, up to half of the terrestrial biosphere could reach temperatures above that pre-mid-century production level – and some of the richest carbon-rich biofuels in the world. globalization, including tropical rainforests in the Amazon and Southeast Asia and the Taiga in Russia and Canada, will be among the first to hit that tense point.

“What is most remarkable is that our analysis showed that the optimum temperature for photosynthesis in all ecosystems was so low,” said Vic Arcus, a biologist at the University of Waikato and co-author of the study. “Together with the higher level of ecosystem relief over the temperature we have seen, our findings show that any temperature rise above 18 degrees C could adversely affect the terrestrial carbon sink. Not to mention warming stay at or below the levels established in the Paris Climate. Accord, the ground carbon sink will not continue to correct our emissions and buy us time. ”

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Funding for this research was provided by the National Aeronautics and Space Administration (grant NNX12AK12G), Federation of East Asian Pacific Summer Institute (1614404), National Science Foundation (NSF), Royal Society of New Zealand Foreign Partnership Program (EAP-UOW1601) and New Zealand Marsden Property (donation 16-UOW-027). This work used eddy covariance data obtained and shared with the FLUXNET community, including AmeriFlux, AfriFlux, AsiaFlux, CarboAfrica, CarboEuropeIP, CarboItaly, CarboMont, ChinaFlux, Fluxnet-Canada, GreenGrass, ICOS, KoFlux, LBA, NEC. -Siberia and USCCC networks.