A comment on the threat to the Banaue rice terraces prompted me to go Googling, and it seems the story has legs. Unlike the giant earthworms, which may or may not be an all-female species related to a worm called Polypheretima elongata. SciDev.net reports on the efforts of an Indian scientist, Ravindra Joshi, to help the villagers to get rid of the giant earthworms and the rats ((There’s a less informative and slightly garbled version in The Daily Telegraph.)).
To tackle the earthworms, Joshi’s team taught the Ifugao a method of ‘worm farming’ that is popular with small-scale entrepreneurs in the lowlands. The Ifugao collect the worms and rear them in a mixture of soil and old newspapers. They then harvest the worms and process them into feeds used by fish farmers.
Elsewhere in the Philippines people eat worm sausages and burgers, but the Ifugao people who built Banaue have a taboo against soil dwelling creatures. There wasn’t such a taboo against eating rats, so Joshi worked with the locals to develop a community system of rice traps that uses a particularly aromatic rice planted early as a trap crop to lure the rats to their death.
There’s another rodent, though, that eats the giant earthworms. So the villagers have learned to distinguish Rattus tanezumi from Chrotomys whiteheadi, eating the former but releasing the latter to eat the giant earthworms.