However,this natural wonder of the world is being taken away from us.Coral cover in the Great Barrier Reef has dropped by more than half over the last 27 years,The Guardian (UK) reported.“If the trend continues,coral cover could halve again by 2022,” said Peter Doherty,researcher at the Australian Institute of Marine Science (AIMS).So unless we start acting now,there won’t be any “heritage” left in the future.

　　Coral reefs are an important part of the ocean’s ecosystem.They are a source of food,and act as protection for young fish.But in the past three decades they have been under threat around the world mainly from increased storms,a growing number of crown-of-thorns starfish and coral bleaching (脱色).

　　Storm damage caused nearly half of the coral losses.In the past seven years,the reef has been affected by six major storms,each leaving a trail (痕迹) of destruction.

　　The crown-of-thorns starfish is also causing problems.Scientists believe that run-offs (支流) containing a large amount of fertilizers have caused the population boost (增长) of this coral-eating animal.Outbreaks of crown-of-thorns starfish usually start two or three years after major floods in northern rivers.

　　Coral bleaching accounts for about 10 percent of coral damage.It is usually due to ocean acidification (酸化) and rising temperatures because seawater absorbs more carbon dioxide from the air.This disrupts (扰乱) the corals’ ability to grow and build structures.

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