Warming temperatures have Earth’s soil expelling more CO2

When we think of the main contributors to carbon storage within our planet’s forests, we’re generally thinking about the trees – but what if I told you the most carbon storage occurs under our feet?

The soil on Earth’s surface holds roughly twice as much carbon as the planet’s atmosphere. Unfortunately, this enormous reservoir of carbon stored in soil is entering Earth’s atmosphere at an alarming rate. In a new study in Nature, researchers have found that this process is only speeding up as the Earth warms, and is occurring at a faster rate than that which plants are taking in carbon through photosynthesis.

So how is this carbon that’s been stored in the soil being released due to increasing temperatures? It’s all due to microbes and how they react to warmer temperatures. The microbes are bacteria that live in the soil and eat detritus such as dead leaves and logs. This food contains carbon, and when bacteria eat decaying leaves or fungi break down a fallen tree, they convert that storehouse of carbon into carbon dioxide, which then enters the Earth’s atmosphere.

The researchers determined that the rate at which microbes are transferring carbon from soil to the atmosphere has increased 1.2 percent from 1990 through 2014. Although that number may seem small, this increase on a global scale over a relatively short time period is huge. Furthermore, this finding is consistent with predictions scientists have made about how the Earth may respond to warming 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,” explains first author Ben Bond-Lamberty of the Joint Global Change Research Institute, a partnership between the University of Maryland and the Department of Energy’s Pacific Northwest National Laboratory.

“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.”

The study used two global science networks paired with satellite observations to assess a wide swath of data. The Global Soil Respiration Database contains data on soil respiration from over 1,500 studies around the world, and FLUXNET takes data from more than 500 towers globally that record information on temperature, rainfall, and other factors. “Most studies that address this question look at one individual site which we understand very well,” says study author Vanessa Bailey, a soil scientist.

“This study asks the question on a global scale. We’re 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.”

It’s hard to imagine that something so small can cause such a drastic effect on an entire planet. But it’s clear that our own greenhouse gas emissions aren’t all we need to worry about in this warming climate, other life forms have joined in the cause as well.

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By Connor Ertz, Earth.com Staff Writer