As absurd as the Death Worms are, I see their purpose. They are a natural barrier.
If this whole place is a space station posing as a real ecosystem, then it needs to keep the wildlife and humans inside it contained in a way that appears natural. The island accomplished that by simply being an island, and the desert does it via the Death Worms.
Granted, a large population of predators with ludicrous kilocalorie needs would never last long in a place as devoid of prey, but as this is an artificial environment, the station can feed or, replace the Death Worms as needed. It's a little convoluted, but it makes sense.