To say that the earthworms are essential to the health of the planet Earth would be a gross understatement. So much so that there is no way that I can list you all their benefits at once. But what about in an alternate Earth where earthworms became extinct?
56 million years ago, the Paleocene-Eocene Thermal Maximum lasted three to four times longer than it did in our timeline. The problem regarding earthworms wasn't a change in climate--it was actually overdiversification. They had become so specialized that any change in the environment, no matter how minor, could collapse the whole system. Everyone in every system overreached their peak too quickly due to the longer PETM, including the earthworms. 36 million years ago was this alternate Earth's date for the Icing of Antarctica (known more formally as the "Azolla Event"), and 14 million years ago, the global temperature dropped so dramatically and so suddenly that half of all plant and animal species went extinct. Here is a list of animal groups that I have found to bear the closest similarities to earthworms in regards to size, habitat and niche:
- Apoda--the caecilians, a group of serpentine, legless amphibians. They live more sheltered lives than the frogs and salamanders, so they are the least studied amphibian order.
- Scolecophidia--the blind snakes
- Diplopoda--the millipedes
- Chilopoda--the centipedes
- Insect larvae that have evolved to be neotonous--in other words, they have evolved beyond the need to complete their metamorphic stages.
The real question isn't deciding which of the animals listed above would be best qualified to refill the earthworm niche, but would all of them occupy the earthworm niche at once?