A graph showing the change in temperature at which Earth's plants will begin to reduce the amount of human-induced carbon emissions they can absorb Credit: Victor O. Leschik / University of Northern Arizona
Earth's ability to absorb nearly a third of man-made carbon emissions by plants could be halved over the next two decades at the current rate of warming, according to a new study in Science Advances by researchers at the University of Northern Arizona, from the Woodwell Climate Research Center and the University of Waikato New Zealand, using over two decades of data from measuring towers in every major biome around the world, the team identified a critical temperature change that goes beyond the ability of plants to capture and store carbon in the atmosphere – a cumulative effect called «terrestrial carbon sink». Decreases as temperatures continue to rise
The terrestrial biosphere – the activity of land plants and soil microbes – does most of the «respiration» of the earth, exchanging carbon dioxide and oxygen. Ecosystems around the world take carbon dioxide through photosynthesis and return it to the atmosphere by breathing in microbes and plants over the past decades, the biosphere has generally absorbed more carbon than it released, which has led to climate change mitigation
But as record-breaking temperatures continue to spread around the world, it might not continue; NAU researchers, from Woodwell Climate and Waikato found a temperature threshold above which the uptake of carbon by plants slows down and the release of carbon accelerates
Lead author Catherine Duffy, postdoctoral researcher at the NAU, observed a sharp drop in photosynthesis above this temperature threshold in almost all biomes around the world, even after other influences such as water and sunlight have been removed.
“Earth suffers from a steadily increasing fever, and just like the human body, we know that every biological process has a temperature range at which it works best, and those above which the degradation of the function”, said Duffy. “Therefore, we wanted to ask How long can plants endure?
This study is the first to discover the temperature threshold for photosynthesis from observational data on a global scale. While the temperature thresholds for photosynthesis and respiration have been studied in the laboratory, Fluxnet data provides a window into what ecosystems on Earth are already experiencing and how they react. / p>
«We know that the optimum temperature for humans is around 37 degrees Celsius (98 degrees Fahrenheit), but we, members of the scientific community, did not know which were the ideal ones for the terrestrial biosphere», said Duffy
Collaborated with researchers from Woodwell Climate and the University of Waikato who recently developed a new approach to answer this question: the theory of total molecular speed (MMRT) Thanks to its foundations on the principles of thermodynamics, MMRT allowed researchers to generate temperature curves for each major biome and world
The researchers found that the temperature “peak” for carbon absorption – 18 ° C for the most common C3 plants and 28 ° C for C4 plants – is already outdated in nature, but they didn't see any temperature control on the breathing. This means that in many areas biotic and continuous warming will decrease photosynthesis while respiration rates will increase dramatically., upsetting the ecosystem balance from carbon sink to carbon source and accelerating climate change
“Different plant species differ in the detail of their temperature responses, but all show a decrease in photosynthesis when it is too hot”, said George Koch, co-author of NAU.
Currently, less of 10% of the terrestrial biosphere experiences temperatures above the photosynthetic limit, but at the current rate of emissions, up to half of the Earth's biosphere could be exposed to temperatures above this productivity threshold by mid-century. Some of the most carbon-rich biomes in the world, including tropical rainforests in the Amazon, Southeast Asia and the Caribbean The taiga in Russia and Canada will be among the first to reach this tipping point.
«The most striking thing our analysis showed was that the optimum temperature for photosynthesis in all ecosystems was very low.», said Vic Arcos, biologist at the University of Waikato and co-author of the study. «In conjunction with an increase in the rate of respiration of the ecosystem through the temperatures that we have observed, our results indicate that any increase in temperature above 18 ° It is potentially harmful to the Earth's carbon sink. Without curbing global warming to stay at or below the levels specified in the Paris Climate Agreement, Earth Carbon Bank will not continue to offset our emissions and save us time.
Reference: “How far are we from the temperature transition point of the Earth's biosphere?” By Katharyn A Daffy, Christopher R. Schwalm, Vickery L. Arcos, George W. Koch, Lin Liang and Louis A. Schipper, 13 January 2021, Science Advance DOI: 101126 / sciadvaay1052
Could this be in part the basis of Bill Gates' tripartite plan to distribute particles in our atmosphere to reflect part of the sun's rays?? Or a reflection of his ideology of halving the population? Or did his ideologies contribute to the financing of this theory?
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