The UK has been alarmed by the "New Zealand flatworm" threatening its earthworm population - some places have lost all of their worms, though it seems to be under control. On the other hand at a push, it may be possible to deliberately seed forests with them.
I think this article is quite hyperbolic though. It talks about a researchers "horror" at theoretical possibilities, but the latest literature review cited is 6 years old and it did not resolve any definite effect.
>Our results suggest that although earthworms are largely beneficial to soil fertility, they increase net soil greenhouse-gas emissions.