Our factories and homes burn coal and oil. Every year we have forest fires somewhere. Many scientists believe that the weather is changing.

      The earth will perhaps be warmed by about 7℃ at the South Pole(极) and the North Pole. The ice will be melt(融化). The sea level(平面) will rise by about 7 meters. As a result, water will cover cities like London, Tokyo and New York. Some ports(港口) and towns along the coasts will disappear under water.

      Some other scientists think that the dust, smoke and pollution from coal, wood and oil fires will block out(封闭) the ultraviolet rays(紫外线). Then the earth will become colder and great sheets of ice will cover Europe and North America.

      When chemicals in the air mix with rain, we have acid(酸) rain. Acid rain can bring us great harm. It destroys(破坏) forests and kills life in lakes and rivers.

      People are beginning to see how serious the problem is. They find it important to work with nature instead of against it. They are trying to save the earth in many different ways. But one of the most important things to do is to make people understand that saving the earth is saving ourselves.

    There are some very good inventions which， for one reason or another， don't become popular. These inventions should be better known， even though I think that some of them are crazy. Let's have a look at some of these inventions and see if you agree that they should be more successful.

    The Australians had a great idea to stop people from drinking and driving. The idea was that if a driver wanted to start the car， she or he would have to blow into a bag first. If there was too much alcohol(酒精) in their breath， the car wouldn't start. It sounded like a great idea to me， but people said that they might need to drive the car in an emergency even if they had drunk too much alcohol. Another idea I liked was an invention by a scientist who thought his children watched too much TV. He linked the TV to an exercise bike so that the electricity to power the TV was generated(产出) by the bike. If the children wanted to watch a lot of TV， they had to pedal(踩踏板) very hard. I found another invention on the Internet which was intended (倾向于) to encourage good habits. Believe it or not， this invention was an ashtray(烟灰缸) which spoke to you when you lit a cigarette! The “voice” of the ashtray was activated (启动) by the heat from the cigarette and reminded you how dangerous it is to smoke.

    One of the strangest inventions I have come across is a bicycle which can cross rivers! The idea was that when you came to a river， you could inflate a huge plastic ball all around the bike. You would then get into the ball which would float on the river while you pedaled the bike inside the ball! Why not use a bridge instead? A friend of mine at school once bought a strange pair of football shoes. On the bottom of the shoes there was a rotating pad of studs (转动钉垫). The idea was that you would change direction more quickly if the studs rotated with you. The problem was that every time you stopped you changed direction whether you wanted to or not! I think he wore those shoes twice! One thing I would like is a baseball cap with a built-in radio so you can listen to sport all day with your hands free. While we are on the subject of sport， the Americans invented a kind of robot for sports fans. If you were watching your team on TV on your own， you could press a button and the robot would do “high fives” with you! Fantastic! I wonder if you have any good ideas for inventions like these.

    Some scientists say that animals in the ocean are increasingly threatened(威胁) by noise pollution caused by human beings. The noise that influences sea animals comes from a number of human activities. It is caused mainly by industrial underwater explosions(爆炸) , ocean drilling, and ship engines. Such noises are added to natural sounds. These sounds include the breaking of ice fields, underwater earthquakes, and sounds made by animals themselves.

    Decibels (分贝) measured in water are different from those measured on land. A noise of one hundred and twenty decibels on land causes pain to human ears. In water, a decibel level of one hundred and ninety five would have the same effect（效果）.

    Some scientists have proposed setting a noise limit （限度）of one hundred and twenty decibels in oceans. They have observed that noises at that level can frighten and confuse whales（鲸鱼）.

    A team of American and Canadian scientists discovered that louder noises can seriously injure some animals. The research team found that powerful underwater explosions were causing whales in the area to lose their hearing. This seriously affected the whales' ability to exchange information and find their way. Some of the whales even died. The explosions had caused their ears to bleed.

    Many researchers whose work depends on ocean sounds object to a limit of one hundred and twenty decibels. They say such a limit would mean an end to important industrial and scientific research. Scientists do not know how much and what kinds of noises are harmful to ocean animals. However, many scientists suspect that noise is a greater danger than they believed. It's time for them to take action to help ocean animals.

    Bioplastic(生物塑料) is a kind of plastic, but it is not the same as normal plastic. Normal plastic is made from chemical materials and takes a very long time to degrade(降解). But bioplastic is good for the environment. It is made by using bacteria(细菌) to process(加工) natural sources like vegetable oils, corn or sugar. It can degrade more easily.

    But there is a problem with bioplastic. The "food" that bacteria eat is what we eat. This means that bacteria are competing against humans for the same resources.

    Now scientists have found a new way to make bioplastic——using two kinds of bacteria and sunlight, according to Newsweek.

    One of the bacteria can use sunlight to produce sugar. The other kind lives in the salty waters of Bolivia. It eats the sugar that the first bacteria produce and then it can produce polymers(聚合物). Polymers are used to create bioplastics. The way the bacteria store polymers is similar as humans store fats.

    The new way to produce bioplastic has many advantages. It is 20 times faster than the normal way we produce bioplastic. Moreover, using these two bacteria saves resources.

    Firstly, producing a lot of bioplastic requires corn and sugar, which are used to feed normal bacteria. And growing corn and sugar needs farmland. But these two bacteria can just use sunlight. The land that is saved can be used to grow food for humans. Besides, this system doesn't need rich land or clean water at all, scientists said to Newsweek.

    The next problem scientists face is that they want to put their lab research into real-world practice. By doing this, bioplastic made with these two bacteria can be widely produced in the future.