Tuesday , August 3 2021

A new study has found that the Earth will reach a tipping point in the next 20-30 years – ScienceDaily



According to a new study conducted in the United States, the Earth’s ability to absorb almost a third of its carbon emissions from plants through plants could be halved over the next two decades. Scientific achievements researchers at the University of Northern Arizona, the Woodwell Center for Climate Research and the University of Waikato, New Zealand. Using data from more than two decades of measuring towers in every major biome around the world, the team identified a critical temperature break point at which plants’ ability to capture and store atmospheric carbon – the cumulative effect called “land-based carbon sequestration” – decreases. as the temperature rises.

The terrestrial biosphere – the activity of terrestrial plants and soil microbes – performs much of the Earth’s “respiration”, exchanging carbon dioxide and oxygen. Ecosystems around the globe absorb carbon dioxide through photosynthesis and release it back into the atmosphere through the respiration of microbes and plants. Over the past few decades, the biosphere has generally absorbed more carbon than it has released, mitigating climate change.

But as record temperatures continue to spread around the world, this may not continue; Researchers at NAU, Woodwell Climate and Waikato found a temperature threshold at which the slowing down of carbon in plants slows down and the release of carbon accelerates.

Lead author Catherine Duffy, a PhD student at NAU, noticed a sharp drop in photosynthesis above this temperature threshold in almost all biomes around the world, even after eliminating other effects such as water and sunlight.

“Fever is constantly rising on Earth, and like the human body, we know that every biological process has a range of temperatures at which it works optimally and those that are higher and function deteriorates,” Duffy said. “So we wanted to ask, how long can plants last?”

This study was the first to reveal the temperature threshold for photosynthesis according to observations on a global scale. Although the temperature thresholds for photosynthesis and respiration have been studied in the laboratory, Fluxnet data provide a window into what ecosystems on Earth actually experience and how they react.

“We know that the optimal temperature for humans is about 37 degrees Celsius (98 degrees Fahrenheit), but we in the scientific community did not know what these optimums were for the Earth’s biosphere,” said Duffy.

She teamed up with researchers from Woodwell Climate and the University of Waikato, who recently developed a new approach to answering this question: the theory of macromolecular rates (MMRT). Based on the principles of thermodynamics, MMRT allowed researchers to generate temperature curves for each large biome and globe.

The results were alarming.

The researchers found that the “peaks” in temperature for carbon sequestration – 18 degrees C for more common C3 plants and 28 degrees C for C4 plants – have already been exceeded in nature, but have not seen respiratory temperature tests. This means that in many biomes, prolonged warming will reduce the level of photosynthesis, while respiration rate increases exponentially, shifting the balance of ecosystems from carbon sequestration to carbon source and accelerating climate change.

“Different types of plants differ in the details of their temperature reactions, but they all show a decrease in photosynthesis when it gets too hot,” said NAU co-author George Koch.

Currently, less than 10 percent of the Earth’s biosphere experiences temperatures above this photosynthetic maximum. But current emissions of up to half of the terrestrial biosphere by the middle of the century could lead to temperatures exceeding this productivity threshold – and some of the world’s most carbon-rich biomes, including tropical forests in the Amazon and Southeast Asia and Taiga in Russia and Canada. will be one of the first to reach this critical point.

“The most impressive thing that our analysis showed was that the temperature optimums for photosynthesis in all ecosystems were so low,” said Vic Arcus, a biologist at the University of Waikato and co-author of the study. “Combined with the increase in the respiration rate of ecosystems at the temperatures we observed, our findings suggest that any increase in temperature above 18 degrees C is potentially detrimental to terrestrial carbon runoff. Paris climate According to this, the onshore carbon sink will not continue to offset our emissions and buy us time. “

Funding for this study was provided by the National Aeronautics and Space Administration (grant NNX12AK12G), the National Science Foundation (NSF) East Asia Pacific Summer Institute (1614404), the Royal Partnership New Zealand Foreign Partnership Program (EAP-Newland160). 16-UOW-027). This work used vortex covariance data obtained and transmitted by the FLUXNET community, including AmeriFlux, AfriFlux, AsiaFlux, CarboAfrica, CarboEuropeIP, CarboItaly, CarboMont, ChinaFlux, Fluxnet-Canada, GreenGrass, ICOS, ONFECC -Siberia and USCCC network.


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