Global warming and pollution lead to bleaching in coral reefs — a process that occurs when corals expel the algae that live in their tissues and give them color. This is a dire problem that could lead the world to lose all its reefs, though a few populations are showing signs of heat resistance.

A study published in the journal Science in 2014 looked at how corals acclimate to different reef sites with varied water temperatures. To determine why some coral populations are more tolerant of changing temperatures than others, the researchers transplanted coral populations in sites with different temperature regimes to see if they would acclimate to their new environment. The researchers determined that in less than two years, acclimatization initiated the same level of heat tolerance that would normally result from generations of natural selection.