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the great barrier reef文章

The Great Barrier Reef, which extends for over 2,300 kilometers (1429 miles)

along the northeastern coast of Australia, is home to over 9,000 known species.

There are likely many more—new discoveries are frequently being made, including

a new species of branching coral discovered in 2017. This richness and uniqueness

make the reef crucial for tourism and the Australian economy—it attracts at least

1.6 million visitors every year. Yet the reef’s true value, its biodiversity, extends far

beyond dollars and cents.

The Great Barrier Reef consists of about 3,000 individual reefs of coral, and the

biodiversity they contain is remarkable. There are animals you would probably

recognize, such as dolphins, turtles, crocodiles, and sharks. There are also

venomous sea snakes, brightly colored worms, and large algae. These species

interact to form a complex and delicate ecosystem dependent on the coral reef for

survival. Yet today the coral—and therefore all the organisms that depend on it—

is gravely at risk.

Coral is made up of many small animals. These tiny animals build a hard

external skeleton to make the vibrant structures that we recognize. When healthy,

coral has a symbiotic relationship with algae. The coral produces fluorescent

chemicals that protect the algae from bright sun—almost like a sunscreen. The

algae use photosynthesis to harness solar energy to make sugars. In this way, the

algae provide food and oxygen (a byproduct of photosynthesis) for the coral, and

the coral protects and provides nutrients for the algae. The algae also give coral its

many colors.

The coral and algae have evolved together to survive within a particular

temperature range. As sea temperatures rise due to climate change, the algae

begin to produce products toxic to the coral, which in turn expel the algae. This

process is called bleaching because the coral becomes white. A 2018 study

showed that about one-third of the Great Barrier Reef had experienced substantial

damage from bleaching. The

researchers also found that large amounts of coral had died in the warming

water almost immediately—even before there was time to expel their algal

partners. This suggests even greater risks from climate change than scientists had

previously thought.

Climate change is not the only threat to the reef. Chemical runoff and other

forms of pollution, coastal development, and overfishing all can harm coral and

reduce biodiversity. So can large storms such as cyclones. Species that live in the

reef can also cause damage. One major pest species is the crown-of-thorns

starfish (Acanthaster planci). A starfish may sound harmless, but these venomous

creatures voraciously eat coral. Every so often, their numbers spike. Some

scientists think these starfish caused over half of the reef damage from 1985 to

2012.

Fortunately, many people are passionate about protecting the Great Barrier

Reef. National Geographic Explorer Dr. Erika S. Woolsey conducts research on coral