How many more people can we squeeze onto our fragile planet?   Surely, the Earth must be full? Pretending that human numbers can grow forever, with no ill-effects, is at best innocent and at worst utterly irresponsible.

Biodiversity loss, climate change, pollution, deforestation, water and food shortages — these are all worsened by our huge and ever-increasing numbers. Yet governments and most environmental groups choose to sidestep this giant elephant in the room. The human population was just 2.6 billion in 1950. But it has been 7.7 billion today and according to the UN it will reach 9.7 billion by 2050 and 11.2 billion by the end of the century. Where will so many people live? How will we feed them?

Unless we diffuse this “population bomb”, by the end of the century we will need several Earths to survive. But we can’t have several Earths, and so we will face a future of increasing poverty, food shortages, conflict and environmental degradation.

Admittedly, not everyone agrees with the UN’s predictions. But even the doubters calculate that the human population will grow to 8 or 9 billion sometime between 2040 and 2060. Ultimately, there has to be a limit.

The good news is that the human populations of about two dozen countries, from Poland and Italy to Cuba and Japan, are now decreasing. But that’s not true of most countries. The cradle of overpopulation is in Africa, which is where more than half of global population growth is expected to occur: from 1.3 billion people in 2020 to 4.3 billion in 2100.

The solution isn’t rocket science. There are two drivers of population growth:   birth rates and longevity. We all aim to grow old, after all, but we can reduce birth rates. That’s not to say that anyone should be denied the right to have many children as they like. But it’s a fact that wherever women are empowered and literated, have help with family planning and have access to medical care, they generally choose to have fewer children. And the birth rate falls.

So why the stony silence? Why such a failure of leadership from governments and environmental groups? I think it’s for two reasons. First, calls for population control are often believed racist: relatively rich people in the developed world   blaming poor people in the developing world. Second, it is often thought insincere. The problem is as much about consumerism as it is about population growth: westerners are consuming more and more, so it appears as if they are blaming the   poor for the excesses of the rich. Most population growth is, indeed, taking place among those who consume almost nothing. But the uncomfortable truth is that we all need to consume much less.

Whatever the complications, we urgently need a UN Framework Convention on Population, just as we have for climate change. Either we limit our population growth or the natural world will do it for us.

Late one afternoon, Raphael Kaplan and his family were out walking near their home in Los Angeles, Calif., the second largest U.S. city.【小题1】

“They were ‘hanging out’”, he says, “just lying down and waiting for us to pass.”【小题2】The fourth grader says he sees coyotes all the time, often at that golf course. He's also seen them walking down his street.

Coyotes look like medium-sized dogs or small wolves with short gray and brown fur.【小题3】They will eat just about anything and can learn to survive in nearly any environment. Before 1700, coyotes only lived in the midwestern and southwestern United States and Mexico, but then people wiped out nearly all of North America's wolves because they sometimes kill farm animals. This opened up space for chores.

【小题4】Some considered them to be pests. During the middle of the 20th century, the U.S. government poisoned around 6.5 million coyotes. Killing them is still legal in most U.S. states. Hunters and trappers kill hundreds of thousands every year.

Encounters with coyotes happen regularly across the United States as well as in Canada, Mexico and parts of Central America. In Chicago, Illinois, for instance, coyotes once lived on the top floor of a parking garage across from Soldier Field, the home stadium of the Chicago Bears football team. In 2015, New York City police officers in trucks, cars and helicopters chased a coyote through Riverside Park in Manhattan.【小题5】After three hours, they gave up the chase. The coyote had simply hidden itself too well. Occasionally, coyotes may bite or attack people or their pets. However, coyotes mostly avoid people. Raphael is glad he's gotten to see them so many times. He's also helped study them.

Researchers have identified various motivations for viewing horror films. 【小题1】 Although many films can fulfill some of these needs, films describing violence and horror have features that other forms of drama do not.

【小题2】 For many young adult males, horror films are a topic of conversation, a source of shared experience, and a means of self-expression. Not everyone likes the blood, but many may continue to watch because of other goals, such as showing their ability or tolerate it, or the desire to master the threatening images.

Yet horror films aren't simply tales. Some suggest that they are humans' way of experiencing fear in a controlled setting. Such an experience may prove enjoyable since the fear can be controlled, and is limited to a form of escapism that lasts for a couple of hours. Some consider the enjoyment of horror films similar to riding roller coasters. Humans must face fears every day that are much more terrifying because they are not necessarily controlled. 【小题3】

Some studies suggest that the real draw to horror films is the feeling of relief when they are over. Other researches argue that the reason why people like watching horror films is that it is a way to experience both positive and negative emotions. When negative and sometimes absolutely horrific images play across the screen, the person watching the film is also experiencing positive emotions. This emotional state may force viewers to continue to watch horror films. 【小题4】 For example, you may enjoy such a film when you're crying your eyes out.

Watching horror films is a cultural phenomenon. 【小题5】 Therefore, horror films from different countries are various. As a cultural product, the ability for this medium to satisfy a primal need in some people is likely to continue.