找到了unit 1 最后一部分的视频。补上
The Great Barrier Reef is the largest coral reef on our planet. It’s one of the seven recognized wonders of the natural world. The reef itself is the place that most people explore, but there’s much, much more. The coral reef is actually a very small part of this underwater world as little as 7%. The remaining 93% encompasses a variety of other habitats, each one remarkable in its own way. And there are environments on land that are also important to the reef. Some close to shore, others inland. Altogether there are more than a hundred different types of habitat in and around the Barrier Reef, each with its own distinctive plants and animals.
Before European settlers arrived, much of the coast here was covered in forest. But today things have changed significantly. Many coastal areas have been cleared for commercial crops like sugar cane. And it’s not only crops. Cattle ranches close to rivers, fish farms, six large coastal cities and many holiday resorts along the coast all have an impact on the reef system. Without the natural vegetation controlling the movement of water and the sediment it carries, heavy rain now washes millions of tons of silt, often laced with damaging fertilizers and pesticides straight into the lagoon. Sediment plumes can be so extensive; they sometimes spread to the outer reef. In the sea grass meadows, the fine silt shrouds the light-dependant plants and fertilizers feed algal blooms that choke the life from them. When the meadows die, the turtles, dugongs and baby fish that depend on them die too. Near the shore, the water can be so murky that less light reaches the corals, the rare inshore reefs have all but disappeared. All these habitats are interdependent. If you ruin one, it can have an impact on the others.
And that includes the outer reef itself. To look after all these habitats, the Great Barrier Reef Marine Park sits at the heart of a network of protected areas, all interconnected and covering a vast area. After all, the reef is an inspiration to people all over the world. It attracts one and a half million visitors each year who come to see the largest coral reef on earth. Together with divers, yachtsmen and anglers, they inject seven billion dollars a year into the local economy. But the value to Australia is even greater than that. Towns and cities along much of the Queensland coast are not washed into the Pacific Ocean because the reef protects them. It means the Barrier Reef ecosystem is so much more than a coral reef. There are vast tracts of rainforests, mangrove swamps, sea grass meadows and soft coral oases in a deep-water lagoon. It is truly an extraordinary place. And the reef’s influence goes far beyond Australian waters. The Barrier Reef is vital to wildlife from many other parts of the world.
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