### Instruction: What is the biggest threat to the great barrier reef?
### Input: The Great Barrier Reef Marine Park Authority considers the greatest threat to the Great Barrier Reef to be climate change, causing ocean warming which increases coral bleaching. Mass coral bleaching events due to marine heatwaves occurred in the summers of 1998, 2002, 2006, 2016, 2017 and 2020, and coral bleaching is expected to become an annual occurrence. In 2020, a study found that the Great Barrier Reef has lost more than half of its corals since 1995 due to warmer seas driven by climate change. As global warming continues, corals will not be able to keep up with increasing ocean temperatures. Coral bleaching events lead to increased disease susceptibility, which causes detrimental ecological effects for reef communities.
### Response: Climate change is the biggest threat to the Great Barrier Reef. Major heat waves over the past 30 years have increased coral bleaching and is now expected to occur yearly. Coral bleaching increases the likelihood of disease and is therefore destroying reef communities.