A rising population is one of the main reasons that there is global warming. Between 1650 and 1850 the population increased by 0.75 billion people going from 0.25 billion to one billion. From 1930 to the end of the century the population rose from two billion to over six billion. In just a third of the time the population rose by more than five times what it did before. It is expected that this trend in the changing population will continue and could even heighten. The growing population requires increasing amounts of energy. These energy demands and other supplies require production, which almost always involves the emission of greenhouse gases. The more the population increases the more greenhouse gases that are produced and the greater the increase in temperature.

    The burning of fossil fuels is one of the best-known causes for global warming. The major reason for fossil fuels contributing so much to global warming is the release of carbon that occurs during the burning of fossil fuels. When people burn fossil fuels, they release large amounts of carbon by way of the release of carbon dioxide. The carbon dioxide in the air then leads to global warming.

    Another source of carbon dioxide comes from deforestation. In forests there is a large amount of carbon that is stored in the trees and other plants. This carbon is out of the atmosphere because the trees consume the carbon from carbon dioxide. When people cut down trees, they are frequently burned. This burning releases the carbon dioxide into the atmosphere that was stored in organic matter. Even when new trees are planted, it can take up to one hundred years to make up for the carbon that was released. It is commonly thought that because trees absorb more carbon dioxide, the atmosphere experiences positive effects.

    Sophie Armstrong, the writer of Earth Care put it, “There's no doubt that the earth is becoming warmer because of human activity rather than a random but natural phenomenon.

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    In the famous fairy tale, Snow White eats the Queen's apple and falls victim to a curse（诅咒）;in Shakespeare's novel, Romeo drinks the poison and dies; some ancient Chinese emperors took pellets（药丸）that contained mercury（水银）, believing that it would make them immortal, but they died afterward.

    Poison has long been an important ingredient in literature and history, and it seems to always be associated with evil, danger and death. But how much do you really know about poison?

    An exhibition, The Power of Poison, opened last month at the American Museum of Natural History in New York, intended to give the audience a more vivid understanding of poison.

    The museum tour starts in a rainforest setting, where you can see live examples of some of the most poisonous animals: caterpillars（毛毛虫）, frogs and spiders. Golden poison frogs, for instance, aren't much bigger than a coin, but their skin is covered with a poison that can cut off the signaling power of your nerves, and a single frog has enough venom to kill 10 grown humans.

    "Poisons can be bad for some things," Michael Novacek, senior vice president of the museum, told NBC News. "Yet they can also be good for others."

    A poisonous chemical found in the yew tree is effective against cancer, which is what led to the invention of a cancer-fighting drug called Taxol.

    The benefits from natural poisons are not limited to just medicine. Believe it or not, many substances（物质）that we regularly ingest（摄入）-chili, coffee and chocolate-owe their special flavors or stimulating（提神的）effects to chemicals that plants make to poison insects.

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    We've considered several ways of paying to cut in line: hiring line standers, buying tickets from scalpers (票贩子), or purchasing line-cutting privileges directly from, say, an airline or an amusement park. Each of these deals replaces the morals of the queue (waiting your turn) with the morals of the market (paying a price for faster service).

    Markets and queues—paying and waiting—are two different ways of allocating things, and each is appropriate to different activities. The morals of the queue, “First come, first served, have an egalitarian (平等主义的) appeal. They tell us to ignore privilege, power, and deep pockets.

    The principle seems right on playgrounds and at bus stops. But the morals of the queue do not govern all occasions. If I put my house up for sale, I have no duty to accept the first offer that comes along, simply because it's the first. Selling my house and waiting for a bus are different activities, properly governed by different standards.

    Sometimes standards change, and it is unclear which principle should apply. Think of the recorded message you hear, played over and over, as you wait on hold when calling your bank: “Your call will be answered in the order in which it was received.” This is essential for the morals of the queue. It's as if the company is trying to ease our impatience with fairness.

    But don't take the recorded message too seriously. Today, some people's calls are answered faster than others. Call center technology enables companies to “score” incoming calls and to give faster service to those that come from rich places. You might call this telephonic queue jumping.

    Of course, markets and queues are not the only ways of allocating things. Some goods we distribute by merit, others by need, still others by chance. However, the tendency of markets to replace queues, and other non-market ways of allocating goods is so common in modern life that we scarcely notice it anymore. It is striking that most of the paid queue-jumping schemes we've considered—at airports and amusement parks, in call centers, doctors' offices, and national parks—are recent developments, scarcely imaginable three decades ago. The disappearance of the queues in these places may seem an unusual concern, but these are not the only places that markets have entered.

    We talk a lot in the U.S. about success. Success is the dream and the end point. And not by coincidence the idea that hard work leads to personal success is as American as apple pie.

    But the reality is that sometimes we fail. And sometimes things, through no fault of our own, don't go our way. We're faced with a life-changing diagnosis(诊断), the passing of a loved one or job loss. We don't, as a society, have as much to say here.

    I think uncertainty does us all harm. We'd feel better equipped to deal with uncertainty if we talked about it more. I had so fully bought into the belief that with enough effort, I could control what happened in my life. I actually caught myself thinking I could "work my way out" of my cancer. As it turns out, cancer doesn't really care about one's work.

    We might also make wiser decisions--this isn't just a feel-good exercise. For example, technology and medicine have progressed to the point that many patients are living longer than they would have even a decade ago. These are achievements worth celebrating. And yet I wonder if the focus on success is sometimes misguided here as well. If it is one reason why we tend to pursue expensive end-of-life treatments, they often accomplish little other than to make a patient's final days painful and frightening. The fact is that, when asked, many patients would rather focus on living meaningfully in their final days.

    My hope here is to make a case for thinking about meaning, in the same way we think about pursuing success. In that spirit, I've asked several people, each of whom has met misfortune, how they find meaning in their lives. The diversity in their responses reflects the fact that there are no right or wrong answers here. We each can find meaning in different things.

    In the shadow of Kenya's Mount Kilimanjaro, nine Rothschild giraffes, the rarest giraffes on the planet, are free to wander at the English-style manor (庄园). Every day shortly before 9am, they come up to the house and stick their heads through the windows and doors in search of morning treats. The manor's owners, Tanya and Mikey Carr-Hartley, share their dining table with them. And now the couple are sharing the fantastic experience with the public by opening the manor gates to guests at the giraffe hotel, the only hotel of its kind in the world. Now, guests can feed the giraffes at breakfast but can also get up close to them from their second-floor bedrooms.

    Mr and Mrs Carr-Hartley, both 38, spent their childhood living close to the house in Nairobi and have always been enthusiastic about the animals. Tanya said, "Mikey and I grew up near this manor house when we were children. We are both third generation Kenyans and have always wanted to work in conservation. Mikey's family have been related to the protection of animals for many generations. His granddad helped the removal of giraffes as far back as the 1930s because the Rothschild giraffes lost much of their natural living space. When the house came up for sale, we jumped at the chance to buy it as we had always dreamed of owning it. Now, we were absolutely overjoyed to do something for the giraffe protection. Having the giraffes so close is very special and something which people can now experience by staying in one of the ten rooms at the hotel."

    A conservation project to save them was started at the manor in 1974 by the previous owners. "The previous owners ran a very successful breeding (繁殖) programme, where many giraffes were set free into the wild and we hope to continue," said Tanya.

Elephants might be the most well－known and well－loved animal in African wildlife. But conservation (保护) of the African elephant faces special difficulties. While the elephant population is half of what it was 40 years ago, some areas of Africa have more elephants than populated areas can support. That's why AWF scientists are studying elephant behavior, protecting habitats and finding ways for humans to live peacefully with elephants in Africa.

Years ago, overhunting and the ivory trade were the biggest threats to elephants' survival. Luckily, ivory bans (禁令), hunting rules and protected areas protect elephants from these dangers today.

The 21st century brings a different challenge to elephant conservation—land－use. Elephants walk across borders and outside parks and other protected areas. So they often destroy crops, causing conflicts (冲突) between local farmers and these big animals.

Successful conservation strategies (策略) must allow elephants to walk freely in their natural habitats while reducing conflicts between elephants and local people.

AWF researchers are searching for a way to give both elephants and people the space they need. The AWF is collecting information on elephant habitats and behavior. The information they gather will help to develop the widest possible space for elephants.

The AWF is helping elephants by protecting their habitats. And they also work with local farmers to improve their life in order to encourage them to protect rather than destroy elephants.