Reservoir of carbon stored in soil entering Earth's atmosphere at increasing rate
The vast reservoir of carbon stored in the soil is entering the Earth's atmosphere at an increasing rate, most likely as a result of warming temperatures, scientists say.
Researchers from the Pacific Northwest National Laboratory (PNNL) in the US found that the rate at which microbes are transferring carbon from soil to the atmosphere has increased 1.2 percent over a 25-year time period, from 1990 through 2014.
While that may not seem like a big change, such an increase on a global scale, in a relatively short period of time in Earth history, is massive.
The finding, based on thousands of observations made by scientists at hundreds of sites around the globe, is consistent with the predictions that scientists have made about how Earth might respond to warmer temperatures.
"It's important to note that this is a finding based on observations in the real world. This is not a tightly controlled lab experiment," said Ben Bond-Lamberty of the Joint Global Change Research Institute.
"Depending on how other components of the carbon cycle might respond due to climate warming, these soil changes can potentially contribute to even higher temperatures due to a feedback loop," he added.
The team relied heavily on two global science networks as well as a variety of satellite observations.
The Global Soil Respiration Database includes data on soil respiration from more than 1,500 studies around the globe.
FLUXNET draws data from more than 500 towers around the world that record information about temperature, rainfall and other factors.
"Most studies that address this question look at one individual site which we understand very well," said Vanessa Bailey, a soil scientist.
"This study asks the question on a global scale. We are talking about a huge quantity of carbon. Microbes exert an outsize influence on the world that is very hard to measure on such a large scale," said Bailey.
The team sought to compare the roles of the two main contributors, increased plant growth and microbial action.
The researchers discovered a growing role for microbes, whose action is outstripping the ability of plants to absorb carbon.
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