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According to the recent publication of progress in science, the US research team has found that in the past few decades, the earth’s biosphere has absorbed more carbon than it has released, but this trend is slowing down and may even reverse. The earth is on the brink of a lethal “tipping point” for climate change, and its ability to absorb a third of anthropogenic emissions could be halved by 2050, the study warned.
Plants absorb carbon dioxide through photosynthesis and release oxygen back into the air to help reduce global warming, which is the “breath” of the earth. Researchers at the University of North Arizona have created temperature curves for each of the world’s major communities to predict the possible effects of global warming.
The lead author of the study, Dr Katherine Duffy, warned that as global warming forces the average temperature to rise, there is “steady growth heat” on the earth, which will eventually turn some of the world’s carbon sinks into carbon sources, thus accelerating climate change.
Currently, researchers have found that less than 10 percent of terrestrial biosphere experiences temperatures higher than the maximum temperature for photosynthesis. But at current emission rates, by 2050, up to half of the terrestrial biosphere may experience temperatures above this productivity threshold. Moreover, some communities with the highest carbon content in the world, including tropical rainforests in Amazon and Southeast Asia and coniferous forests in Russia and Canada, will be among the first to reach this critical point.
“Just like the human body, we know that every biological process has a temperature range at which it works best and above which it deteriorates,” Dr. Duffy said
The researchers also said that different types of plants differ in the details of the temperature response, but when the temperature is too high, photosynthesis in all plants decreases.
This new study is the first to detect the temperature threshold of photosynthesis from global observation data, providing a window to understand the actual ecosystem and its response on the whole earth.
A new method developed by the research team is able to generate temperature curves for each major biome and for the entire earth. The study found and revealed a critical temperature point. As the temperature continues to rise, the ability of plants to capture and store carbon in the atmosphere (called “terrestrial carbon sink”) will decrease.
The researchers warn that the temperature “peak” of carbon absorption is 18 ℃ in some plants and 28 ℃ in others. This means that in many biological communities, the continuous warming will lead to the decline of photosynthesis, while the respiratory rate will increase exponentially, which makes the balance of ecosystem change from carbon sink to carbon source and accelerates the climate change.
The most surprising thing in the new analysis is that the optimal temperature for photosynthesis in all ecosystems is very low. Combined with the observed increase of ecosystem respiration rate in the temperature range, it is found that the increase of temperature above 18 ℃ may have adverse effects on terrestrial carbon sink.
The researchers said that without curbing climate warming to maintain or lower than the level stipulated in the Paris climate agreement, the earth’s carbon sink will not continue to offset human emissions and gain time for mankind.