The main threat to coral reef ecosystems is climate change. Rising sea temperatures lead to coral bleaching, a process where corals expel the algae they rely on for nutrients and color, rendering them vulnerable and often leading to their death. Other threats include ocean acidification, pollution, overfishing, and habitat destruction. The decline of coral reefs impacts marine biodiversity, coastal protection, and local economies that depend on healthy reef ecosystems. Addressing these threats requires global conservation efforts and sustainable practices.