Although earthworms are largely beneficial to soil fertility, they increase emissions of the greenhouse gases such as carbon dioxide (CO2) and nitrous oxide (N2O). Please take a look at these useful references.

Article Greenhouse gas emissions from soils increased by earthworms

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Article Do earthworms increase N2O emissions in ploughed grassland?

@ Deeksha, Earthworm induced global worming and climate change. About 20% of global carbon dioxide emission and two-third of nitrous oxide emissions come from soil. Earthworm as a soil ecosystem engineer affect the physical structure of the soil by burrowing and making it more porous.Earthworm also interact the microbes that produce the bulk carbon dioxide emissions. Earthworm increases greenhouse gas emissions. For example, bacteria in the earthworm guts produce nitrous oxide and emissions from worm infested soils can be three times higher as from soils without any worm.. In general, it was predicted that 16% of the global worming may be due to earthworm.

The presence of earthworms increased nitrous oxide emissions from soil by 42 percent and carbon dioxide emissions from soil by 33 percent. But they found no indications that earthworms affect soil organic carbon stocks—the carbon stored within the soil.

https://phys.org/news/2013-02-global-worming-earthworms-climate.html