This article is about the decline of Australia’s Great Barrier Reef due to the crown-of- thorns starfish. This coral reef is the world’s largest coral reef system and one of the most popular tourist attractions. More than half of the coral reef has been lost since 1985. The major cause of the decline in these coral reefs are these starfish that prey on coral. Based on research, 48 percent of the decline in coral has been from storm damage, 42 percent from the crown of thorns starfish, and 10 percent from coral bleaching, which can be caused by increased water temperatures, bacterial infection, or changes in water chemistry.The crown of thorns starfish have increased population wise therefore causing it to have few natural predators. If we were able to eliminate these starfish, the coral would recover at about 1 percent per year. Research is still being done on how to reduce the starfish population.Researchers have tried cutting up the starfish yet the starfish were able to regenerate their missing arms and can survive intense physical harm. They also have tried to inject them with acid but the process was expensive but the researches have considered injecting some of the starfish with transmissible disease that would spread throughout the starfish population. Although the starfish have increased in number, scientists say that climate change and coral bleaching have damaged the reef enough to prevent it from being able to hold off the numerous “outbreaks” of starfish that have occurred over the past decades.