How do soil microbes influence our global climate?

Scoop up a handful of soil just about anywhere on the planet and you will hold a bustling community of billions of microscopic creatures.

Scientists such as Laurentian University’s Nathan Basiliko are beginning to discover that some of these soil microbes could be important tools in mitigating the impact of climate change.

Basiliko was part of a team of researchers led by his former graduate student Varun Gupta whose study showed that a group of microbes in wetland soils across North America consumes a staggering amount of the potent greenhouse gas methane. This prevents it from escaping into the atmosphere.

The team estimates these microbes consume the equivalent of five to 10 per cent of all human-caused fossil fuel emissions.

“Our big finding is how ubiquitous this process is across multiple classes of wetlands — from permafrost bogs in Ontario’s far north to richer fen sites as far south as West Virginia,” says Basiliko.

Up until about 2007, soil scientists thought the lack of oxygen in wetland soils such as bogs and fens would prevent microbes from consuming methane.

While they knew microbes consumed methane in the absence of oxygen in ocean and some fresh water sediments, they assumed these were special cases. That’s because ocean and lake sediments contain oxidized chemical compounds microbes need to help them breakdown methane, including sulphate, nitrate or ferric iron. These compounds are not commonly found in most northern wetlands soils.

Basiliko and his team showed that even without oxygen, sulphate, nitrate or ferric iron, wetland soil microbes were still able to break down methane and keep it from off-gassing into the atmosphere.

The team discovered this by collecting wetland soil samples and feeding them a unique form of methane “labelled” with a type of carbon than could be tracked as it was broken down and assimilated by the microbes.

Once they’d added this traceable form of methane, the researchers gave microbes the time to do their thing. Sure enough, they ate up most of the methane.

It’s still not clear how the microbes are doing it, or even which group of microbes is responsible, but the discovery that this process is so widespread could have important implications for the climate.

Figuring out which microbes are at work, or what compound is stimulating the process, could help us keep even more methane out of the atmosphere, especially in human-made wetlands such as rice paddies.

But first steps first: “We still don’t understand the fundamental processes controlling this,” says Basiliko. “We can’t yet predict how these ecosystems will react to disturbances such as climate change.”

Nathan Basiliko

Nathan Basiliko

Laurentian University

Environment & SustainabilityNatural Resources

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