There's also the fact that all the action in deep sea mining is happening ... well, deep in the ocean. As in, not where we live. The environmental impacts happening 20,000 leagues under the sea will be further from the public's gaze. And while that's good for people, it might not be good for the environment in general. The authors of the paper warn that deep sea environments tend to recover very slowly when disturbed, some so slowly that they likely wouldn't recover in a human's lifetime, if ever.