Study: Earthworms may contribute to global warming

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Michael Bastasch DCNF Managing Editor
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As environmentalists and politicians fret about man-made global warming, they may be ignoring another culprit: earthworms. According to a new study by an international team of researchers, earthworms could be contributing to global warming.

The study looked at results from 237 separate experiments from published stories to explore earthworms’ role in affecting global warming.

“Our results suggest that although earthworms are largely beneficial to soil fertility, they increase net soil greenhouse-gas emissions,” according to the study’s abstract.

Worms affect how much carbon dioxide is produced in the soil and how much escapes into the atmosphere by altering the physical structure of the soil through burrowing, which makes it more porous. Earthworms interact with microbes in the soil that produce a large chunk of the carbon dioxide emissions.

There are concerns that earthworms increase greenhouse gas emissions, which troubles scientists since earthworm numbers are on the rise.

“Earthworms play an essential part in determining the greenhouse-gas balance of soils worldwide, and their influence is expected to grow over the next decades,’ reads the abstract. “They are thought to stimulate carbon sequestration in soil aggregates, but also to increase emissions of the main greenhouse gases carbon dioxide and nitrous oxide.”

The study found that earthworms in soil increased nitrous oxide emissions by 42 percent and carbon dioxide emissions by 33 percent. However, the report also notes that worms can increase one type of greenhouse gas emissions while reducing another.

The Guardian reports that approximately 20 percent of worldwide CO2 emissions and two-thirds of N2O emissions come from the soil — produced by natural biological processes involving plant roots, as well as the micro-organisms living in the ground.

The study says that earthworm’s contribution to global warming is small in the grand scheme of things, but their numbers are growing.

“Over the next few decades, earthworm presence is likely to increase in ecosystems worldwide,” according to the study. “For example, large parts of North American forest soils are now being invaded by earthworms for the first time since the last glaciation”.

The more people use organic fertilizers and move away from conventional land development, the more the number of earthworms could increase. However, habitat degradation and species invasions could reduce the world population.

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