The Great Barrier Reef is a threatened biome. The three greatest risks to this ecosystem are climate change, water quality and over fishing. Climate Change has increase water temperatures and has caused coral bleaching. Coral bleaching is when Coral expels Coral Polyps causing it to lose its pigmentation and eventually die. Bleaching has accelerated over the last three decades. The quality of water in the Great Barrier Reef is declining due to pollutants. Most of these toxins come from the pesticides in farm run off. Because the Great Barrier Reef is so full of life and is so diverse, it attracts many species of fish. This diversity in turn attracts commercial fishing. Causing higher traffic in the reef which leads to over fishing, the deposit unwanted toxins into the water and netting destroying habitats.