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Half of the world’s coral reefs have died in the last 30 years. The threat to coral reefs “isn’t something that’s going to happen 100 years from now. We’re losing them right now,” said Julia Baum, who is a marine biologist at the University of Victoria, in British Columbia, Canada. “We’re losing them really quickly, much more quickly than I think any of us ever could have imagined.” Even if global warming were to stop right now, scientists predict that over 90% of corals will die by 2050.

Actually, the planet’s health depends on the survival of coral reefs. They’re often described as underwater rainforests, because they’re ecosystems that provide habitats for one in four of all marine species. The reefs also serve as barriers that protect coastlines from the full force of powerful storms. Corals are used in medical research to find out how to treat diseases like cancer, etc. In addition, the reefs attract tourists, the fishing industry and other businesses, bringing in billions of dollars of income.

Corals are animals that have no backbone, and live mostly in tropical waters. A rise of just 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) can have effects on corals. They can survive in these higher temperatures only for a few months. Unfortunately, the problem isn’t just global warming. The reefs have also been affected by pollution, coastal development and overfishing.

Now scientists are racing to ensure the rest survive. They remain hopeful that it’s not too late to save the reefs, and some are moving ahead on experiments to accomplish that goal. Ruth Gates, director of the Hawaii Institute of Marine Biology, for example, is trying to “train” corals to get used to rising temperatures by exposing them to survivable levels of heat stress. She hopes that the corals will somehow fix the experience in their memory so that they can endure similar stress in the future.

1.What can we know about coral reefs from the first paragraph?

A They are ignored for long.

B They are being threatened.

C They are protected effectively.

D They’ll completely disappear soon.

解析：选B。细节理解题。根据第一段Julia Baum所说的话可知珊瑚礁正受到威胁，由此可判断选B项。

2.Why are coral reefs of great benefit?

A They protect waters being polluted.

B They are important to local economies.

C They are home to about half of marine species.

D They can be used to prevent and cure diseases.

解析：选B。推理判断题。根据第二段In addition, the reefs attract tourists, the fishing industry and other businesses, bringing in billions of dollars of income. 可知珊瑚礁可以促进当地经济的发展，故选B项。

3.What can we infer about coral reefs according to the third paragraph?

A They always live in tropical waters.

B They are just threatened by global warming.

C They’re sensitive to changes in temperature.

D Their problem isn’t linked to human activities.

解析：选C。细节理解题。根据第三段A rise of just 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) can have effects on corals. They can survive in these higher temperatures only for a few months.可推断珊瑚礁对气温的变化非常敏感，故选C项。

4.Ruth Gates is mentioned in the last paragraph just in order to show ____.

A ways to develop reefs’ environmental adaptability

B the relationship between coral reefs and temperature

C scientists’ interest in doing research into coral reefs

D actions that are being taken to protect coral reefs

解析：选D。推理判断题。根据最后一段可知举例是为了说明保护珊瑚礁的行动，故选D项。