3 . Pigeons in London have a bad reputation. Some people call them flying rats. And many blame them for causing pollution with their droppings. But now the birds are being used to fight another kind of pollution in this city of 8.5 million.

“The problem for air pollution is that it’s been largely ignored as an issue for a long time,” says Andrea Lee, who works for the London-based environmental organization Client Earth. “People don’t realize how bad it is, and how it actually affects their health.” London’s poor air quality is linked to nearly 10,000 early deaths a year. Lee says, if people were better informed about the pollution they’re breathing, they could pressure the government to do something about it.

Nearby, on a windy hill in London’s Regent’s Park, an experiment is underway that could help — the first week of flights by the Pigeon Air Patrol. It all began when Pierre Duquesnoy, the director for DigitasLBi, a marketing firm, won a London Design Festival contest last year to show how a world problem could be solved using Twitter. Duquesnoy, from France, chose the problem of air pollution.

“Basically, I realized how important the problem was,” he says. “But also I realized that most of the people around me didn’t know anything about it. “Duquesnoy says he wants to better measure pollution, while at the same time making the results accessible to the public through Twitter.

“So,” he wondered, “how could we go across the city quickly collecting as much data as possible?” Drones were his first thought. But it’s illegal to fly them over London. “But pigeons can fly above London, right?” he says. “They live here — actually, they are Londoners as well. So, yeah, I thought about using pigeons equipped with mobile apps. And we can use not just street pigeons, but racing pigeons, because they fly pretty quickly and pretty low.”

So it might be time for Londoners to have more respect for their pigeons. The birds may just be helping to improve the quality of the city’s air.

5 . It is a big job to take away a city’s rubbish. Most rubbish is made up of things we can’t eat or use. If we kept these things, we would soon have mountains of rubbish.

In some cities the rubbish is collected and taken outside of the city to a dump. Often the city dump is placed where the ground is low or there is a big hole. The kitchen rubbish is broken into small pieces and sent into the sewage system. The sewage system takes away the used water from toilets, bathrooms and other places.

To keep mice and flies away, some earth is used to cover the newly dumped rubbish. Later, grass may be planted on the rubbish-filled land. Finally, a house or a school may be built there, and then you’d never know that this was an old rubbish dump before.

In other cities the rubbish is burnt in special places. The fire burns everything but the metal. Sometimes the metal can be used again in factories where things are made of metal. The food parts of rubbish are put in special piles where they slowly changes into something called humus, which looks like black earth. It is rich with kinds of things that feed plants and help to make them grow.

I’m a student at a middle school. I’m writing to express my great concern for the environment in my hometown.

Yours,

Li hua

8 . The endangered pandas in the Qinling Mountains might face a new threat: the loss of their food, bamboo, which makes up 99% of their meals.

Adult pandas spend most part of the day eating bamboo and have to take in at least 40 pounds a day to stay healthy. However, a new study published in Nature Climate Change warned that they may soon find their food gone because most of the bamboo in the Qinling Mountains might disappear by the end of the century as a result of rising temperature worldwide.

A team made up of researchers from Michigan State University and the Chinese Academy of Sciences has studied the effects of climate change on the bamboo in the Qinling Mountains. They have found that bamboo is very sensitive to climate changes. “80% to 100% of the bamboo would be gone if the average temperature rises 3.5 degrees worldwide by the end of the century,” said Liu Jianguo, one of the report’s authors.

He added, “This is how much the temperature would rise by 2100 even if all countries will keep their promises in the Paris Agreement. But you know what is happening all around the world.”

In recent years, China has been trying its best to protect the endangered pandas by setting up more and bigger natural reserves.

“But it is far from enough and the endangered pandas need cooperation from the rest of the world, because their future is not just in the hands of the Chinese,” said Shirley Martin from the World Wildlife Fund but not a member of the team.

The Qinling Mountains, in the southwest of China, are home to about 260 pandas. That is about 13% of China’s wild panda population. In addition, about 375 are living in research centers and zoos in China.

9 . Many people regard sharks as dangerous monsters. But human beings cause a far greater danger to them than they do to us. Although shark attacks do occur, they are quite rare. According to a survey, however, humans kill 100 million sharks every year.     1    

Why should we save the sharks?

Sharks take up the top position on the food chain in the ocean. As sharks die off, the population of the animals that sharks eat will increase. This, in turn, means that the number of the creatures those animals eat will drop.     2     Fish that eat algae (藻类) are also included. This can cause algae to spread so much that it damages coral reefs (珊瑚礁).

    3     The ocean not only produces more oxygen than all the rainforests on Earth combined, but also removes half of the man-made greenhouse gas from the atmosphere. Once sharks die off, the global ecosystem will be upset, affecting all creatures including human beings.

Don’t use shark products

First, vitamin energy drinks and leather goods can be made from shark parts.     4     In addition, shark meat is sold around the world, sometimes under misleading names such as rock salmon or whitefish.

Shark fin soup is a popular dish. However, the process of getting fins is cruel. Fishermen cut the shark’s fins off and then throw the shark back into the water, still alive.     5     Sharks breathe by swimming, so a shark that can’t swim will die.

10 . Throughout history, many species of animals have been threatened with dying out. When Europeans first arrived in North America, more than 60 million buffalo (水牛) lived on the continent. Yet hunting the buffalo was so popular during the 19th century that by 1900 the animal’s population had fallen to about 400 before the government stepped in to protect the species. In some countries today, the elephant faces a similar challenge, as illegal hunters kill the animals for the ivory (象牙) in their tusks.

Yet not all animals with commercial value face this threat (威胁). The cow, for example, is a valuable source of food, but no one worries that the cow will soon die out. Why does the commercial value of ivory threaten the elephant, while the commercial value of beef protects the cow?

The reason is that elephants are a common resource, while cows are private goods which only belong to their owners. Elephants wander freely without any owners. The hunter has a strong motivation to kill as many elephants as he can find. Because the number of illegal hunters is big, each has only a little desire to protect the elephant population. By contrast, cattle live on farms that are privately owned. Each farmer makes great effort to keep the cattle population on his farm because he gets the benefit of these efforts.

Governments have tried to solve the elephant’s problem in two ways. Some countries, such as Kenya and Uganda, have made it illegal to kill elephants and sell their ivory. Yet these laws have been hard to put into effect, and elephant numbers have continued to reduce. By contrast, other countries, such as Malawi and Namibia, have made elephants private goods and allowed people to kill elephants, but only those who own these elephants.

With private ownership and the profit (利润) now on its side, the African elephant might someday be as safe from dying out as the cow. The ancient Greek philosopher Aristotle pointed out the problem with common resources: “What is common to many is taken least care of, for all men attach greater importance to what is their own than for what they have together with others.”