1 . After years of heated debate, gray wolves were reintroduced to Yellowstone National Park. Fourteen wolves were caught in Canada and transported to the park. By last year, the Yellowstone wolf population had grown to more than 170 wolves.

Gray wolves once were seen here and there in the Yellowstone area and much of the continental United States, but they were gradually displaced by human development. By the 1920s, wolves had practically disappeared from the Yellowstone area. They went farther north into the deep forests of Canada, where there were fewer humans around.

The disappearance of the wolves had many unexpected results. Deer and elk populations — major food sources (来源) for the wolf — grew rapidly. These animals consumed large amounts of vegetation (植被), which reduced plant diversity in the park. In the absence of wolves, coyote populations also grew quickly. The coyotes killed a large percentage of the park’s red foxes, and completely drove away the park’s beavers.

As early as 1966, biologists asked the government to consider reintroducing wolves to Yellowstone Park. They hoped that wolves would be able to control the elk and coyote problems. Many farmers opposed the plan because they feared that wolves would kill their farm animals or pets.

The government spent nearly 30 years coming up with a plan to reintroduce the wolvers. The U.S. Fish and Wildlife Service carefully monitors and manages the wolf packs in Yellowstone. Today, the debate continues over how well the gray wolf is fitting in at Yellowstone. Elk, deer, and coyote populations are down, while beavers and red foxes have made a comeback. The Yellowstone wolf project has been a valuable experiment to help biologists decide whether to reintroduce wolves to other parts of the country as well.

2 . Using too much water or throwing rubbish into our rivers are clear ways that humans can put our water supply in danger, but we also affect our water supply in less obvious ways. You may wonder how paving(铺砌) a road can lead to less usable fresh water. A major part of the water we use every day is groundwater. Groundwater does not come from lakes or rivers. It comes from underground. The more roads and parking lots we pave, the less water can flow into the ground to become groundwater.

Human activity is not responsible for all water shortages(缺乏). Drier climates are of course more likely to have droughts(干旱) than areas with more rainfall, but in any case, good management can help to make sure there is enough water to meet our basic needs .

Thinking about the way we use water every day can make a big difference, too. In the United States, a family of four can use 1.5 tons of water a day! This shows how much we depend on water to live, but there’s a lot we can do to lower the number.

You can take steps to save water in your home. To start with, use the same glass for your drinking water all day. Wash it only once a day. Run your dishwasher only when it is full. Help your parents fix any leaks(滴水) in your home. You can even help to keep our water supply clean by recycling batteries instead of throwing them away.

4 . Think about the different ways that people use the wind. You can use it to fly a kite or to sai1a boat. Wind is one of our of our cleanest and riches power source(来源) ,as well as one of the oldest . Evidence shows that windmills(风车) began to be used in ancient Iran back in the seventh century BC .They were first introduced to Europe during the 1100s,when armies returned from the Middle East with knowledge of using wind power .

For many centuries ,people used windmills to grind(磨碎)wheat into flour or pump water from deep underground when electricity was discovered in the 1ate 1800s,people living in remote areas began to use them to produce electricity. This al1owed them to people in almost all1 areas of the United States, windmills were rarely used. During the course 1970s, people started becoming concerned about the pollution that is created when coal and gas are burned to produce electricity. People also realized that the supply of coal and gas would not last forever. Then, wind was rediscovered, though it means higher coasts. Today, there is a global movement to supply more and more of our electricity through the use of wind .

7 . Baggy has become the first dog in the UK—and potentially the world—to join the fight against air pollution by recording pollutant levels near the ground.

Baggy wears a pollution monitor on her collar so she can take data measurements close to the ground. Her monitor has shown that air pollution levels are higher closer to ground level, which has helped highlight concerns that babies and young kids may be at higher risk of developing lung problems.

Conventional air pollution monitors are normally fixed on lampposts at about nine feet in the air. However, since Baggy stands at about the same height as a child in a pushchair（婴儿车）, she frequently records pollution levels which are much higher than the data gathered by the Environment A gency.

The doggy data research was the idea of Baggy's 13-year-old owner Tom Hunt and his dad Matt. The English youngster noticed that pollution levels are around two-thirds higher close to the ground than they are in the air at the height where they are recorded by the agency. Tom has since reported the shocking findings to the government in an attempt to emphasise that babies are at higher risk of developing asthma（哮喘）.

Matt Hunt said he was "very proud" of his son because “when the boy gets an idea, he keeps his head down and gets on with it, and he really does want to do some good and stop young kids from getting asthma."

“Tom built up a passion for environmental protection at a very early age," Matt added. “He became very interested in gadgets（小装置）. About one year ago, he got this new piece of tech which is like a test tube. One Sunday afternoon, we went out to do some monitoring, and he said, why don't we put it on Baggy's collar and let her monitor the pollution？'So we did it."

Tom said, "Most of the time, Baggy is just like any other dog. But for the rest of the time she is a super dog, and we are all really proud of her."

Single-use plastic bags are used at most a few times before they    1    (throw) away. It takes them hundreds of years    2    (break) down. Many of these bags end up in the ocean where larger ones can trap sea creatures, such as turtles and dolphins. Over time, the bags fall apart    3    countless tiny pieces, and fish can accidentally eat some of them. Now, lots of    4    (country) and regions are taking action to ban the sale of such bags to stop people using them.

9 . Let's take a minute to think about the water we use. The human body is 60% water and we need to drink lots of water to be healthy. When we are thirsty we just go to the kitchen and fill a glass with clean water.

    1    For example, farmers, who produce the food we eat, use water to make the plants grow. When we turn on a light or switch on a TV or a computer we use energy and we need water to produce this energy.

The truth is that we are lucky enough to have clean water whenever we want，but this is not the case for many people around the world.    2    That's around one in 10 people in the world. If we drink dirty water，we can catch diseases from the bacteria and become ill. Every year over 500，000 children die from diarrhea(腹泻)from dirty water. That's around 1，400 children every day！Also，in some countries children walk many kilometres every day to get water.    3    Therefore，they don't have time to learn how to read or write and don't get an education.

    4    On this day every year，countries around the world hold events to educate people about the problems of dirty water and that clean water is something that everyone should have around the world. At one school in the UK，children between the ages of 10 and 15 walk 6km with six litres of water.    5    People give them money to do this and all the money helps get clean water to as many people as possible around the world.

10 . Milwaukee, Wisconsin, is road testing a new way to keep winter roads ice-free – by spreading on them cheese brine, the salty liquid used to make soft cheese, like mozzarella.

Wisconsin, also called "America's Dairyland," is famous for its cheese. The state produced 2.8 billion pounds of cheese last year! As a result, there was a lot of leftover cheese brine. Disposing of(处置)the brine can be expensive. So what should cheese makers do with the waste?

Normally, towns use rock salt to de-ice streets. The salt lowers waters' freezing point, causing ice to melt(融化). But using cheese brine could help both cheese producers and cities save money, while keeping roads safe. Cheese brine has salt in it, which, like the rock salt, helps lower water's freezing point.

In addition to saving money, cheese brine could also be a more environment-friendly option. Many people suspect that all the rock salt used every winter is harming the environment.

Rock salt is made of sodium chloride, the sane con-pound (化合物)in ordinary table salt. Sounds harmless, right? But while you probably add only a small amount of salt to your food, road crews spread about 20 million tons of salt on U.S. Roads every year!

The chemical washes off roads and goes into the ground. There it can pollute drinking water, harm plants. and eat away soil. By spreading cheese brine on streets before adding a layer of rock salt, Milwaukee may be able to cut its rock salt use by 30 percent.

Cheese brine has a downside too – a shell similar to that of bad milk. "I don't really mind it," Emil Norby told Modern Farmer magazine. He works for one of Wisconsin's county highway commissions and came up with the idea of using cheese brine. "Our roads smell like Wisconsin!" he said.