With Rising Global Temperatures and Soil Respiration, Carbon Stored in Earth’s Soil is Entering Atmosphere at a Faster Rate


August 2, 2018

 

The carbon stored in the Earth’s soil is now entering the atmosphere at a faster rate due to rising temperatures and an increase in the activity of microbes beneath the soil, a new study carried out by the researchers at the Pacific Northwest National Laboratory (PNNL) has concluded.

Today, global warming is one of the most contentious and intensely debated topics on Earth. However, climate scientists agree that out planet is warming because of increasing volumes of greenhouse gases released by the burning of fossil fuels, land clearing, and a variety of other human activities. The impact of global warming includes rising sea levels, melting of the polar ice caps, increased occurrence of storms and a variety of severe weather events. Scientists believe that Earth’s average temperature, over the past 100 years, has increased between 0.4 and 0.8 degree C. If this trend continues, the average global temperatures could increase between 1.4 and 5.8 degree C by the year 2100.

According to scientists, dead leaves and fallen trees comprise a common source of carbon on Earth. The carbon present in decaying leaves and trees makes its way into the soil, where it is consumed by the microbes and is converted into carbon dioxide (CO2), which is eventually released into the Earth’s atmosphere.  The PNNL study, which was based on the data gathered from a variety of ecosystems on Earth, found that with rising global temperatures, this process is speeding up, and is now much faster compared to the absorption of CO2 by plants through photosynthesis. The study concluded that the rate of transferring of carbon from soil to the atmosphere due to microbial activity has increased 1.2 percent over a period of 25 years, from 1990 through 2014.

“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 first author Ben Bond-Lamberty of the Joint Global Change Research Institute, a partnership between the Department of Energy’s PNNL and the University of Maryland.

“Soils around the globe are responding to a warming climate, which in turn can convert more carbon into carbon dioxide which enters the atmosphere. 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.

In the study, the team used data collected by two global science networks—The Global Soil Respiration Database and FLUXNET—as well as a variety of satellite observations. The team then analyzed the amount of “soil respiration”—the term which describes how plants and microbes in the soil consume substances like carbon and then release it in the form of CO2. Scientists have long known that as temperatures rise, the rate of soil respiration also increases. The researcher compared the roles of two main contributors—microbial action and increased plant growth—and found that during the 25-year period from 1990 through 2014, the proportion of soil respiration due to microbes increased from 54 to 63 percent.

“We know with high precision that global temperatures have risen. We’d expect that to stimulate microbes to be more active. And that is precisely what we’ve detected. Land is thought to be a robust sink of carbon overall, but with rising soil respiration rates, you won’t have an intact land carbon sink forever,” said Bond-Lamberty.

The detailed findings of the study have been published in Nature.

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