The Great Barrier Reef is the world's largest coral reef system, composed of over 2,900 individual reefs and 900 islands stretching over 2,600 kilometers off the coast of Queensland, Australia. It supports a wide diversity of marine life and was named a UNESCO World Heritage Site in 1981. The reef is made up of billions of tiny coral polyps and is the world's largest structure built by living organisms. It faces threats from climate change, runoff, bleaching events and crown-of-thorns starfish outbreaks. The Great Barrier Reef Marine Park helps manage activities like fishing and tourism to protect the ecosystem while also generating $1 billion annually for the local economy.