People in southern China like famous and expensive dish—shark fin soup, but no scientific studies have shown that shark fins are good for health. So why do they eat them? Do they realize that they're killing a whole shark each time they enjoy a bowl of shark fin soup?

When people catch sharks, they cut off their fins and throw the shark back into the ocean. This is not only cruel, but also harmful to the environment. Without a fin, a shark can no longer swim and slowly dies. Sharks are at the top of the food chain in the ocean's ecosystem. If their numbers drop too low, it will bring danger to all ocean life. In fact, around 70 million sharks are caught and traded in this industry every year. The numbers of some kinds of sharks have fallen by over 90 percent in the last 20 to 30 years. Help save the sharks!

No one knows when the first kite was made. The first record of a kite was more than 2,000 years ago in China. Han Xin, the leader of an army, wanted to bring down a king. He decided to dig a tunnel (隧道)into the king's palace. He flew a kite over the wall of the palace to make sure the length (长度)of its string (线).In this way, he could determine how long the tunnel should be. His men in the tunnel took the kite string with them. When they reached the end of the string, they knew to dig up.

    Kites have been flown in Japan for hundreds of years. In the 1700s, kites were flown in autumn to give thanks for a good harvest. They were also flown to send good wishes to couples who had their first son. Today in Japan, kites are often flown as part of a celebration, such as the beginning of a new year. And kite festivals are held each year in many parts of the country.

    Kites have been used for scientific purposes in the western world. In 1752，Benjamin Franklin tied a key to a kite and flew it in a storm to find out that lightening was a form of electricity. In the 1890s, Lawrence Hargrave invented the box kite to test ideas about flight. From 1898 until 1933, the United States Weather Bureau (气象局) used box kites to collect weather data. The Wright brothers also experimented (试验)with kites. What they learned helped them make the first airplane flight in 1903.

    Thanks to the Earth, we have fresh air to breathe, clean water to drink and warm sunshine to enjoy. But it seems that we haven't realized that the Earth is facing many environmental challenges and it is getting "sick".

    Scientists say that of all the environmental challenges, climate (气候) change is the biggest one. The temperature on the Earth has risen by more than 0. 5C since 1992. Cities like Singapore and Tokyo that are at low altitudes (海拔) may be covered by the ocean (海洋) in the future.

    But this is not the only problem people are facing. Since 1992, the human population has grown by 2 billion, while the population of all other animals has dropped by nearly 30 percent. At the same time, water pollution has become serious. We are also facing problems like light pollution, noise pollution and some other pollution.

    However, we have made some progress in saving the Earth. For example, we stop using harmful materials to make the hole in the ozone layer (臭氧层) smaller to slow the rise of the temperature. We do a lot of work to help the animals in danger, or more than two-thirds of the worlds wild animals may disappear (消失) by the end of 2020.

    "The progress shows that we can make good changes when we act wisely, "scientists say, "we must take action to protect the environment, or it will be worse."