system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are we so concerned, as humans, about the decline of the Great Barrier Reef? Isn't there a new one emerging in the Atlantic? Couldn't this just be a normal process for the planet?
gpt
We're concerned because of the speed at which these vulnerable ecosystems are destabilizing.

Earth's climate has varied wildly over the course of the last billion years and life has managed to survive.  When that climate variance happens quickly it's difficult for many species to evolve adaptations in time, and they get wiped out.

The concern is that Earth's climate is changing fast enough to cause another mass extinction.  It won't wipe out humans, but the dramatic change in the ecosystem and climate will be extremely costly for humans to deal with.