Many people wrongly think that cities don't have farms and fruits and vegetables are only grown in the country. Believe it or not, there are more urban farms popping up in cities all over the world.

    Alexandra Sullivan, a food systems researcher in New York, studies urban agriculture. Urban agriculture is another name for farming and gardening in a city environment. Ms. Sullivan studies everything from tiny gardens in empty lots between buildings to bigger fields that have been planted and grown. According to Ms. Sullivan, “Urban agriculture has existed since cities have, across the world.”

    The number of humans living in urban areas, or cities, is increasing. The amount of people who wanted to garden in urban areas is also rising. Ms. Sullivan says, “In small gardens, on rooftops and indoors, city residents grow fruits, vegetables, grains, and herbs, and raise animals to produce milk, eggs, honey, and meat. City residents use these foods as supplements to food produced by rural agriculture.” Even though some people who live in urban areas grow crops, urban residents still need to rely on food grown in rural areas. This is because a city doesn't have enough space to grow enough food for everyone living in it.

    In New York City, urban farmers have come up with many different ways to grow their own produce, even though there isn't a lot of room. For example, Brooklyn Grange is a farming operation that has two rooftop vegetable farms in New York City. All together, the farms are made up of 2.5 acres of rooftop space. This makes Brooklyn Grange one of the largest rooftop farming operations in the world.

    Brooklyn Grange grows all kinds of things. The farming company sells its vegetables to local residents and restaurants. And because the farms are on rooftops, they are specially adapted to their urban location. They use available space that is not needed for anything else. As more urban farmers find ways to grow food in cities, urban residents will be better able to get fresher materials for their meals.

    Culture shock is the psychological（心理的）shock of having to adapt to new environment and new cultures which may be completely different from your own. To understand culture shock helps to understand what culture is.

    Culture shock is caused by the feelings that result from losing all familiar signs and symbols of social intercourse（交往）. Those signs include the ways with which we are familiar in daily life: When to shake hands and what to say when we meet people? When and how to give tips? How to go shopping? When to accept and when to refuse invitations? These signs, which may be words, gestures, facial expressions, customs or normals are gained by all of us in the course of growing up and are as much a part of our culture as the language we speak.

    During the first few weeks when a person enters a strange culture, most people are attracted by the new. But this “cooks tour” type of mentality（心态）does not normally last if the foreign visitor remain abroad and has to seriously deal with real conditions of life. He may feel anxious and frustrated（受挫的） People react to the frustration in the same way. During the first period, they reject the environment which causes the discomfort. “The ways of the host country are bad because they make us feel bad,” they complain about the host country and its people. The following period is homesickness. The home environment suddenly becomes so important that all difficulties and problems are forgotten and only the good things back home are remembered.

    Experiencing culture shock can be very difficult. There is a risk of sickness or emotional problems. However, culture shock can be part of a positive learning experience. Be patient! It is a process of adaptation to new situations. If you do like this, you will be a much stronger person, and you will be a citizen of the world.

    Feeling blue about the world? “Cheer up.” says science writer Matt Ridley. “The world has never been a better place to live in, and it will keep on getting better both for humans and for nature.”

    Ridley calls himself a rational optimist—rational, because he's carefully weighed the evidence; optimistic, because that evidence shows human progress to be both unavoidable and good. And this is what he's set out to prove from a unique point of view in his most recent book, The Rational Optimist. He views mankind as a grand enterprise that, on the whole, has done little but progress for 100,000 years. He backs his findings with hard facts gathered through years of research.

    Here's how he explains his views.

    1) Shopping fuels invention

    It is reported that there are more than ten billion different products for sale in London alone. Even allowing for the many people who still live in poverty, our own generation has access to more nutritious food, more convenient transport, bigger houses, better cars, and, of course, more pounds and dollars than any who lived before us. This will continue as long as we use these things to make other things. The more we specialize and exchange, the better off we'll be.

    2)Brilliant advances

    One reason we are richer, healthier, taller, cleverer, longer­lived and freer than ever before is that the four most basic human needs—food, clothing, fuel and shelter—have grown  a lot cheaper. Take one example. In 1800 a candle providing one hour's light cost six hours' work.  In the 1880s the same light from an oil lamp took 15 minutes' work to pay for.  In 1950 it was eight seconds. Today it's half second.

    3) Let's not kill ourselves for climate change

    Mitigating (减轻) climate change could prove just as damaging to human welfare as climate change itself.  A child that dies from indoor smoke in a village, where the use of fossil­fuel (化石燃料) electricity is forbidden by well­meaning members of green political movements trying to save the world, is just as great a tragedy as a child that dies in a flood caused by climate change. If climate change proves to be mild, but cutting carbon causes real pain, we may well find that we have stopped a nose­bleed by putting a tourniquet (止血带) around our necks.

    At times my mom has been uncomfortable seeing some quality in me. For example, when I was 12, I went to Puerto Rico all by myself to stay with my grandmother for the summer. My mom was extremely nervous about it. She kept telling me how things were different in Puerto Rico, to always put on sunscreen, not to wander away from my grandmother, and other warnings. She helped me pack and did not leave the airport until she saw my plane take off.

    But despite her worries, she let me go on my own. As I moved into my teens, she continued to give me space to grow and learn, even when it might have been difficult for her. When I reached my senior year, I decided to move away for college. Once again I found that I differed from my peers: While many of them wanted to stay close to home, I couldn't wait to be out in the world on my own. While my mom may not have been happy at the thought of my going away, she was supportive and excited for me.

    One big thing I realized during my senior year, as my mom granted me more freedom, was that she actually believes in me and trusts me. That means a lot. Most of my life, and especially when I was little, the main person I tried to impress in my schoolwork or other things was my mother. I knew she expected nothing but the best from me. Sometimes it was hard to live up to her standards: getting a single B on my report card would make me feel bad because I knew she wanted me to have all A's.

    I know that her high standards have helped me stay focused on what's important, like education, and made me who I am. I am thankful for her support and involvement in my life. Most of all I respect her. She is the strongest woman I know and that's why I have turned out so strong and independent.

    Monty Hempel is a professor of environmental sciences at Redlands University in California. He studies ecological literacy­or eco-literacy, for short. Eco-literacy is the ability to think about and understand the natural processes that make life possible.

    Monty Hempel says eco-literacy gives people knowledge about environmental problems. But he says it does not always work on getting them to change their behavior.

    Mr. Hempel wrote part of the Worldwatch Institute's latest State of the World report. He says in his article, "Some people think that eco-literacy is just a green form of science literacy. And what I have tried to ask is whether that's enough. In other words, what an ecologically-literate person needs to know might include things like the effect of environmental pollution on ecosystem, the energy systems, and all of those kinds of things that we would call the science of ecology."

    "That doesn't seem to lead to action to protect our environment ­ to protect our life-support system to the level that we need to. Just knowing a lot about the environment doesn't mean that we actually act to save it. After all, actions speak louder than knowledge."

    He adds that people may not be very worried about environmental problems if they seem far away. "Some people call it psychological distance. A lot of climate issues are worse in the Arctic and most of us don't spend time in the Arctic. And so, there's a certain distance. But there's also a distance that's happening in the world as it urbanizes ­ people spending more time in front of screens and less time out in nature. We become, if you will, disconnected from the natural systems that used to be the key to success for a human being."

    To help children discover the wonders of nature, he adds that children should learn about nature in school. But he also points out we have a high mountain for people to climb from knowledge to action.

    Learning is so complex that there are many different psychological theories to explain how people learn. A psychologist named Albert Bandura suggested a social learning theory which shows that observation, imitation (模仿), and modeling play a primary role in this process.

    In Albert Bandura's opinion, people can learn through observation. Observational learning doesn't even necessarily require watching another person join in an activity. We can also learn by reading, hearing, or watching the actions of characters in books and films. However, just observing someone else's actions isn't always enough to lead to learning. Your own mental state also plays an important role in determining whether a behavior is learned or not. In addition, though in many cases, learning can be seen immediately when the new behavior is displayed, yet sometimes we can learn things even though that learning might not be immediately obvious, which means people can learn new information without showing new behaviors.

    Not all observed behaviors are effectively learned. Certain requirements need to be related to the observational learning process. For example, you need to be paying attention. Also your retention is an important part of observational learning as you need to pull up information later and act on it during the process. Once you've paid attention to the model and kept the information, it's time to actually perform the behavior you observed. Further practice of the learned behavior leads to improvement. Finally, you have to be motivated to imitate the behavior that has been modeled.

    Social learning theory have many real-world applications. For example, researchers employ it to look into and understand ways that positive role models can be used to encourage desirable behaviors. Besides, it's also applied in the field of education, and today, both teachers and parents recognize how important it is to model appropriate behaviors.