Every year on April 22, People all over the world celebrate Earth Day. It is a time to work to keep our earth clean. People plan projects to clean up the land, air and water.

    U.S. Senator Gaylord Nelson first thought of the idea for Earth Day in 1962 when he saw polluted rivers and cities with smoke. He needed to get support from Americans to clean up the earth. Finally, on April 22, 1970, 20 million Americans celebrated the first Earth Day! Now many countries around the world celebrate it, and you can, too.

    How can you celebrate Earth Day? Here are a few ideas:

    Join a clean-up project-Clean up your street or a favorite beach.

    Save energy-Turn off the lights when you leave a room, and use public transportation.

    Use less water.

    Reduce(减少)/ Reuse/ Recycle ― Practice the three Rs: First, reduce how much you use. Then reuse or recycle what you can.

    You can make a difference on Earth Day and every day!

    We sometimes call the lion "the king of the forest", because it is stronger and more dangerous than other animals. It can 1 faster than many animals and hunt the best. It is the highest animal in the 2 food chain.

    In the sea, the shark is one of the animals at the top of the food chain. It can swim faster than 3 other sea animals, and it can use its big teeth to eat them.

    What is at the top of the world's food chain? People are! We are not the biggest or fastest, but we are the 4. We could not run faster than cheetahs(猎豹), so we 5 cars and now we can move the fastest. We could not fight better than lions, so we invented guns. Now we can hunt the best.

    People's inventions are clever, but they can be 6, too. For example, people built 7, and now they make the air and rivers dirty. This can make terrible changes. Dirty rivers kill fish. 8 bears cannot eat the fish. If we kill one part of the food chain, other parts also will die. Remember that we are a part of the food chain, 9 we are in danger, too! If we protect animals, we are protecting 10! We could and we should do something for the world!

    Many scientists think that the Earth is getting warmer and warmer. If the change continues, the natural world and human society will face danger. Scientists believe human activity is responsible for the climate change. We produce too many greenhouse gases. They keep heat in the air and make the Earth warm.

    Many of the world's governments agree. And they want to solve the problem. So from 7 to 18 December, 2009，they held a conference in Copenhagen, Denmark to talk about global warming and climate change.

    Representatives(代表) from 192 countries and regions went to the meeting. Although they have not reached an agreement, the Copenhagen Accord(《哥本哈根协议》) was an important beginning to save the Earth. It was made by a small group of countries including China，the USA，India, Brazil and South Africa. Some other countries at the conference also showed support.

    What are the key points of the Copenhagen Accord? The accord limits global temperature increases to 2C by 2050. Scientists think it could help the world to avoid serious climate change.

    The accord also says that developed countries must promise to cut greenhouse gas emissions(排放) to the UN by 31 January, 2010. The accord asks developed countries to give money to help developing countries.

    Many countries and organizations are disappointed that the conference didn't reach a legal document(法律文书). And they think the accord is not clear enough about its goals.

African leaders are worried that the goal of a 2℃ global temperature increase isn't good enough, because it will mean a much higher increase in temperature across Africa. This could cause big problems like food and water shortages across the continent.

    Still, UN Secretary General believes the conference was an "improvement".

    "Finally we reached a deal," Ban said," the accord may not be everything everyone had hoped for, but this is an important beginning."