Terumbu karang adalah salah satu ekosistem paling beragam di Bumi. Terumbu karang dibangun oleh karang, hewan kecil yang mengeluarkan kerangka kalsium karbonat. Selama ribuan tahun, kerangka-kerangka ini terakumulasi dan membentuk struktur kompleks yang menjadi tempat berlindung bagi ribuan spesies. Terumbu karang menutupi kurang dari satu persen dasar laut tetapi mendukung sekitar seperempat dari semua spesies laut. Ikan, krustasea, moluska, spons, dan alga semuanya bergantung pada habitat yang diciptakan oleh karang.

Corals live in symbiosis with microscopic algae called zooxanthellae, which give them color and provide most of their energy through photosynthesis. When water gets too warm, corals expel the algae and turn white, a process called bleaching. Bleached corals are not dead, but they are stressed and may die if conditions do not improve. Mass bleaching events have become more frequent as ocean temperatures rise. Pollution, overfishing, and ocean acidification add to the pressure. Scientists estimate that half of the world's coral reefs have already been lost or severely degraded.

Threats to reefs

• Warming oceans and mass bleaching.
• Ocean acidification from carbon dioxide.
• Overfishing and destructive fishing practices.
• Pollution and coastal development.

Reef restoration projects are underway in many regions. They grow corals in nurseries and transplant them onto damaged reefs. The work is slow and expensive, but it buys time.