Plants are helpful to human: they provide us with wood and other products, they give us shade, and they help to prevent drought and floods.

    Sadly, in many parts of the world man has not realized that the third of these services is the most important. In his eagerness to draw quick profit from the trees, he has cut them down in large numbers, only to find that without them he has lost the best friends he had.

    Several thousand years ago a rich and powerful country cut down its trees to build warships, with which to gain itself an empire. It gained the empire but, without its trees, its soil became hard and poor. When the empire fell to pieces, the country found itself faced by floods and starvation.

    Even if a government realizes the importance of a plentiful supply of trees, it is difficult for it to persuade the villager to see this. The villager wants wood to cook his food with, and he can earn money by making charcoal(木炭) or selling wood to the townsman. He is usually too lazy or too careless to plant and look after trees. So unless the government has a good system of control, or can educate the people, the forests will slowly disappear.

    This does not only mean that the villagers? Sons and grandsons have fewer trees. The results are even more serious. For where there are trees their roots break the soil up—allowing the rain to sink in and also hold the soil, thus preventing it being washed away easily, but where there are no trees, the soil becomes hard and poor. The rain falls on hard ground and flows away on the surface, causing floods and carrying away with it the rich topsoil, in which crops grow so well. When all the topsoil is gone, nothing remains but a worthless desert.

    A new research has discovered that meditation(冥想)and oxygen sport together reduce depression. The Rutgers University study found that this mind and body combination, done twice a week for only two months, reduced the symptoms of a group of students by 40 percent.

    “We are excited by the findings because we saw such a meaningful improvement in both clinically depressed and non-depressed students,” said lead author Dr. Brandon Alderman. “It is the first time that both of these two behavioral ways have been looked at together for dealing with depression.”

    Researchers believe the two activities have an interactive effect in combating depression. Alderman and Dr. Tracey Shors discovered that a combination of mental and physical training(MAP) enabled students with major depressive disorder not to let problems or negative thoughts defeat them.

    Rutgers researchers say those who participated in the study began with 30 minutes of focused attention meditation followed by 30 minutes of oxygen sport. They were told that if their thoughts drifted to the past or the future they should refocus on their breathing, which enabled those with depression to accept moment-to-moment changes in attention.

    Shors, who studies the production of new brain cells in the hippocampus—part of the brain involved in memory and learning—says scientists have shown in animal models that oxygen sport exercise keeps a large number of certain cells alive.

    The idea for the human intervention(干预)came from her laboratory studies, she says, with the main goal of helping individuals acquire new skills so that they can learn to recover from stressful life events.

    By learning to focus their attention and exercise, people who are fighting depression can acquire new learning skills that can help them process information and reduce the overwhelming recollection of memories from the past, Shors says.

    “We know these treatments can be practiced over a lifetime and that they will be affective in improving mental health,” said Alderman. “The good news is that this intervention can be practiced by anyone at any time and at no cost.”

    Why do some people live to be older than others? You know the standard explanations: keeping a moderate diet, engaging in regular exercise, etc. But what effect does your personality have on your longevity(长寿)? Do some kinds of personalities lead to longer lives? A new study in the Journal of the American Geriatrics Society looked at this question by examining the personality characteristics of 246 children of people who had lived to be at least 100.

    The study shows that those living the longest are more outgoing, more active and less neurotic (神经质的) than other people. Long-living women are also more likely to be sympathetic and cooperative than women with a normal life span. These findings are in agreement with what you would expect from the evolutionary theory: those who like to make friends and help others can gather enough resources to make it through tough times.

    Interestingly, however, other characteristics that you might consider advantageous had no impact on whether study participants were likely to live longer. Those who were more self-disciplined, for instance, were no more likely to live to be very old. Also, being open to new ideas had no relationship to long life, which might explain all those bad-tempered old people who are fixed in their ways.

    Whether you can successfully change your personality as an adult is the subject of a longstanding psychological debate. But the new paper suggests that if you want long life, you should strive to be as outgoing as possible.

    Unfortunately, another recent study shows that your mother's personality may also help determine your longevity. That study looked at nearly 28,000 Norwegian mothers and found that those moms who were more anxious, depressed and angry were more likely to feed their kids unhealthy diets. Patterns of childhood eating can be hard to break when we're adults, which may mean that kids of depressed moms end up dying younger.

    Personality isn't destiny, and everyone knows that individuals can learn to change. But both studies show that long life isn't just a matter of your physical health but of your mental health.

    Scientists have recreated a 1985 study of birds in Peru that shows climate change is pushing them from their natural environment. Thirty years ago, researchers studied more than 400 kinds of birds living on a mountainside in Peru. In 2017, researchers looked again at the bird populations. They found that almost all had moved to higher places in the mountain. Almost all had decreased in size. And, the scientists say at least eight bird groups that move to the higher altitude had died out completely.

    Mark Urban, director of the Center of Biological Risk at the University of Connecticut, said this recent study was the first to prove that rising temperatures and moving to avoid them can lead to extinction.

    In 1985, Fitzpatrick, director of the Cornell Laboratory of Ornithology, and a team of scientists established a camp alongside a river running down a mountainside in southeastern Peru. He wanted to document where tropical bird groups lived. His team spent several weeks using nets to catch and release birds. They kept detailed notes of birds they caught, saw or heard. In 2016, Fitzpatrick passed his notes, photos and other records to Benjamin Freeman. Freeman who has been researching tropical birds for more than 10 years set out in August and September of 2017 to copy Fitzpatrick's study. His team used the same methods, searching the same places in the same time of year.

    Freeman said that the birds moved an average of 98 meters further up the mountain, believing that temperature is the main cause of the birds' movement. Fitzpatrick noted that birds used to living in areas with little temperature change might be especially at risk because of climate change. He said, "We should expect that what's happening on this mountain top is happening more generally in the Andes, and other tropical mountain ranges."

3-2-1 GREEN!

    You already know an environmentalist's three R's: reduce, reuse, recycle. {#blank#}1{#/blank#} Here are three things you can do for the Earth Day.

    Be a real cut-up

    The next time you're about to throw out the plastic rings that hold a six-pack of soda together, reach for a pair of scissors.

    As a young turtle, Peanut got stuck in one of these rings. As she grew, the ring stayed put, forcing her shell to grow around it. By the time someone found her and cut her free, her shell was permanently deformed. Thanks to her hard shell, Peanut is alive and well. She now lives at a nature center in Missouri. But most animals that get caught in six-pack rings die.

    WHAT YOU CAN DO

    Easy! {#blank#}2{#/blank#}

    Hunt for vampires（吸血鬼）

    You know all those electronic inventions you've got at home? Even when you switch them off, they are really still on. {#blank#}3{#/blank#} Anything with a glowing LED off/on light, a remote control, or a clock display is always on.

    WHAT YOU CAN DO

    Just pull out the plugs or tap the OFF switch till you really need the electronics.

    {#blank#}4{#/blank#}

    Matt Damon really cares about clean water. So in February, he announced that he was going on strike against toilets. " Until everybody has access to clean water and sanitation（卫生设备）," he said. "I will not go to the bathroom!" He was kidding but to make a serious point. Around the world, he said, "780 million people lack access to clean water; 2.5 billion people lack access to a toilet."

    WHAT YOU CAN DO

    No need to go on a toilet strike. Just don't waste water. {#blank#}5{#/blank#}Take shorter showers.

A. Use water wisely.

B. How to recognize vampire electronics?

C. Cut the rings apart before you trash them.

D. Use toilets less.

E. But how else can you help?

F. Don't run the water while brushing your teeth.

G. Things that can help with good living conditions are important.

    I've come back to check on a baby. Just after dusk I'm in a car down a muddy road in the rain, past rows of shackled(戴镣的) elephants, their trunks swinging. I was here five hours before， when the sun was high and hot and tourists were on elephants' backs.

    Walking now, I can barely see the path in the glow of my phone's flashlight. When the wooden fence post stops me short, I point my light down and follow a current of rainwater across the concrete floor until it washes up against three large, gray feet. A fourth foot twisted above the surface, tied tightly by a short chain and choked by ring of metal spikes(尖刺) When the elephant tires and puts her foot down， the spikes press deeper into her ankle.

    Meena is four years and two months old, still a child as elephants go. Khammon Kongkhaw, her caretaker, told me earlier that Meena wears the spiked chain because she tends to kick. Kongkhaw has been responsible for Meena here at Maetaman Elephant Adventure, near Chiang Mai, in northern Thailand, since she was 11 months old. He said he keeps her on the spiked chain only during the day and takes it off at night. But it's night now.

    I ask Jin Laoshen, the Maetaman worker accompany in me on this nighttime visit, why her chain is still on. He says he doesn't know.

    Mactaman is one of many animal attractions in and around tourist-crowded Chiang Mai. Meena's life is set to follow the same track as many of the roughly 3, 800 captive(被捕获的) elephants in Thailand. When Meena is too old or sick to give rides-maybe at 55, maybe at 75she'll die. If she's lucky, she'll get a few years of retirement. She'll spend most of her life on a chain.