Coral reefs and their ecosystem lie at a precise depth - where water clarity, temperature and sea floor cooperate to provide enough sunlight and energy to allow corals to grow. A change in sea temperature of a degree or two, or a rise or fall of a few inches, and existing coral reefs collapse. And it takes centuries for them to regrow.

Many things are like that. And we don't have decades to wait for the Earth to become congenial again, we need to eat every day.