【推荐1】Directions: Fill in each blank with a proper word chosen from the box. Each word can only be used once. Note that there is one word more than you need.

A. natural       B. substituting       C. stable       D. disappear       E. piece       F. transforming G. returned       H. regrowth       I. habitats       J. flat       K. pulled

Fire That Was Started 92,000 Years Ago

Human are actively changing landscapes across the globe, but shaping ecosystems is not just a modern activity.

An analysis of the northern shores of East Africa's Lake Malawi reveals ancient inhabitants used fire 92,000 years ago to prevent forest     1    . These Stone Age humans burned forest to make room for a growing population.

The Yale-led study discovered settlements in the area, along with charcoal deposits in the core of the lake, allowing researchers to     2    the story together.

Jessica Thompson, the paper's lead author, said: "This is the earliest evidence I have seen of humans     3    their ecosystem with fire. It suggests that by the Late Pleistocene（晚更新世）, humans were learning to use fire in truly new ways.

The work began in 2018. Researchers from Pennsylvania State University examined fossils, pollen（花粉）and minerals     4    from the bottom of the lake. The analysis showed environment changes that could not be explained with     5    factors.

Normally forest along the lake shore     6    during dry periods and recover when the lake reaches normal levels. But here researchers discovered that when wetter periods     7     and water levels became normal, forests along the shore did not recover, and the species richness went     8    .

Sarah Ivory from Pennsylvania State University said: "The pollen that we see in this most recent period of     9    climate is very different than before. Specifically, trees are no longer common and are replaced by pollen from plants that deal well with frequent fire."

It's not clear why people were burning the landscape. It's possible that they were experimenting with controlled burns to produce     10    . It could be that their fires burned out of control, or that there were simple a lot of people burning fuel in their environment that provided for warmth, cooking, or socialization.

【推荐3】Directions: Complete the following passage by using the words in the box. Each word can only be used once. Note that there is one word more than you need.

A. possibly   B. habitat     C. deadly   D. potential       E. conservation F. responsibility G. encounter     H. stared     I. survival     J. fortunately     K. feed

Nature Is Red in Tooth and Claw

When the British poet Alfred Lord Tennyson described nature as “red in tooth and claw,” he was reminding us that the natural world can be cruel as well as beautiful, and that the wild animals that we love are in a constant struggle for     1    . In simple terms, for wild animals, it is “eat or be eaten,” and they make no distinction between humans and other animals.

Most urban residents rarely     2     wild animals in their natural surroundings. The ones that they do get to observe in person are bred in captivity, which usually means these animals appear rather tame. In Canada, where I come from, we have a more realistic attitude towards wild animals: We try to stay away from them. One day, I was walking along a nature trail near my home and a coyote (郊狼) came out of the woods and     3     at me. A coyote is a dog-like animal, which is a little bigger than a fox, but smaller than a wolf. They usually avoid humans, but the occasional attacks can be     4    . Every year, one or two people end up getting killed by coyotes. The yellow-furred, sharp-toothed coyote,     5    , was not a hungry one. It turned around and disappeared back into the forest.

This little incident served as a reminder that, in Canada at least, a walk in the woods is not the same as one in the park. It can also serve as one for all humans that as our populations grow, expanding into the natural     6     of wild animals can be dangerous for both humans and the animals.

Earlier this year, China became shocked by a herd of elephants in Yunnan that had left their home in the Xishuangbanna National Nature Reserve and went on a winding journey through the province. They destroyed crops and buildings along the way. Villages in their path were empty because of the     7     dangers they posed to villagers. However, instead of killing these “troublemakers,” the government sent thousands of troops to     8     the animals and to guide them back home.

Animal experts have yet to determine why the elephants went on their journey. A reasonable possibility is that thanks to effective environmental     9     in recent years, the herd in the reserve had grown increasingly larger, and they probably simply needed more room and more food in order to survive. Regardless, the series of the wandering Yunnan elephants has served as a reminder that it is our     10     to protect wild animals, both for their sake and for ours.

Their lives—red in tooth and claw—are difficult enough as it is without us causing them any more problems than they already have.

【推荐1】Directions: Fill in each blank with a proper word chosen from the box. Each word can be used only once. Note that there is one word more than you need.

A. replacing     B. tolerate       C. extremes        D. experiencing          E. average F. estimates       G. impact       H. reserved   I. assess       J. cover       K. continued

Urban Trees Are Threatened by Climate Change

By 2050, about three-quarters of the species will be at risk as a result of climate change, a study has found. Cities around the world may need to start planting different types of trees and shrubs that can     1     warmer and drier conditions.

“By ‘at risk’, we mean these species might be     2     stressful climatic conditions,” says Manuel Esperon-Rodriguez at Western Sydney University in Australia. “Those trees are likely to die.”

City trees have many benefits, from making urban spaces look beautiful and providing a refuge for wildlife to keeping places up to 12°C cooler than they would otherwise be in summer. Losing tree     3     would lead to cities becoming even hotter as the planet heats up.

To     4     the threat, Esperon Rodriguez and his colleagues used database called the Global Urban Tree Inventory to work out the conditions required by 3100 tree and shrub species currently grown in 164 cities worldwide. The researchers then looked at how these conditions would be affected by climate change under medium-emissions scenario known as RCP 6.0.

By 2050, 76 per cent of these species will be at risk from rising     5     temperatures and 70 percent from decreasing rainfall, the team concludes.

The study doesn’t take account of       6     urban growth, which could warm cities even faster. Nor does it take account of greater weather     7     caused by climate change, or the effects of pests and diseases. Warmer conditions are allowing more pests, such as bark beetles, to survive winters as well as to reproduce faster in summer, greatly increasing their     8    .

“Our     9     have scientific basis,” says Esperon-Rodriguez. There are some things that can be done to help trees survive. The best strategy is to choose tough species when     10     trees or planting new ones, the team concludes.

【推荐2】Directions: Fill in each blank with a proper word chosen from the box. Each word can be used only once. Note that there is one word more than you need.

A. stem     B. dot     C. attributable     D. exceeded     E. overlook     F. exposed G. drainage     H. emerging     I. sinking     J. access     K. established

The Mega-City Environment

Mega-cities suffer from a catalog of environmental ills. A World Health Organization(WHO)/United Nations Environment Program(UNEP)study found that seven of the cities-Mexico City, Beijing, Cairo, Jakarta, Los Angeles, Sao Paulo and Moscow-had three or more pollutants that    1     the WHO health protection guidelines. All 20 of the cities studied by WHO/UNEP had at least one major pollutant that went beyond    2     health limits.

According to the World Resources Institute, “Millions of children living in the world’s largest cities, particularly in developing countries, are    3     to life-threatening air pollution two to eight times above the maximum based on WHO guidelines. Indeed, more than 80 percent of all deaths in developing countries    4     to air pollution-induced lung infections are among children under five.” In the big Asian mega-cities such as New Delhi, Beijing and Jakarta, approximately 20 to 30 percent of all respiratory diseases    5     from air pollution.

Almost all of the mega-cities face major fresh water challenges. Johannesburg, South Africa, is forced to draw water from highlands 370 miles away. In Bangkok, saltwater is invading aquifers(地下蓄水层). Mexico City has a serious    6     problem because of excessive groundwater withdrawal.

More than a billion people, 20 percent of the world’s population, live without regular    7     to clean running water. While poor people are forced to pay high fees for private water, many cities squander their resources through leakages and illegal    8    . “With the population of cities expected to increase to five billion by 2025,” says Klaus Toepfer, executive director of the UNEP, “the urban demand for water is set to increase rapidly. This means that any solution to the water crisis is closely linked to the governance of cities.“

Mega-city residents, crowded into unsanitary slums, are also subject to serious disease outbreaks. Lima, Peru(with population estimated at 9.4 million by 2015)suffered a cholera outbreak in the late 1990s partly because, as the New York Times reported, ”rural people new to Lima...live in houses without running water and use the outhouses(屋外厕所)that    9     the hillsides above.“

It’s worth looking at some of these    10     mega-cities in detail, because daily life there is likely to be the pattern for a majority of the world’s population. Most are already experiencing severe environmental problems that will only be worsened by rapid population increases.