California has lost half its big trees since the 1930s, according to a study to be published Tuesday and climate change seems to be a major factor(因素).

The number of trees larger than two feet across has declined by 50 percent on more than 46, 000 square miles of California forests, the new study finds. No area was spared or unaffected, from the foggy northern coast to the Sierra Nevada Mountains to the San Gabriels above Los Angeles. In the Sierra high country, the number of big trees has fallen by more than 55 percent; in parts of southern California the decline was nearly 75 percent.

Many factors contributed to the decline, said Patrick McIntyre, an ecologist who was the lead author of the study. Woodcutters targeted big trees. Housing development pushed into the woods. Aggressive wildfire control has left California forests crowded with small trees that compete with big trees for resources(资源).

But in comparing a study of California forests done in the 1920s and 1930s with another one between 2001 and 2010, McIntyre and his colleagues documented a widespread death of big trees that was evident even in wildlands protected from woodcutting or development.

The loss of big trees was greatest in areas where trees had suffered the greatest water shortage. The researchers figured out water stress with a computer model that calculated how much water trees were getting in comparison with how much they needed, taking into account such things as rainfall, air temperature, dampness of soil, and the timing of snowmelt(融雪).

Since the 1930s, McIntyre said, the biggest factors driving up water stress in the state have been rising temperatures, which cause trees to lose more water to the air, and earlier snowmelt, which reduces the water supply available to trees during the dry season.

85．What is the second paragraph mainly about?

A．The seriousness of big-tree loss in California.

B．The increasing variety of California big trees.

C．The distribution of big trees in California forests.

D．The influence of farming on big trees in California.

86．Which of the following is well-intentioned but may be bad for big trees?

A．Ecological studies of forests.

B．Banning woodcutting.

C．Limiting housing development.

D．Fire control measures.

87．What is a major cause of the water shortage according to McIntyre?

A．Inadequate snowmelt.                                 B．A longer dry season.

C．A warmer climate.                                      D．Dampness of the air.

88．What can be a suitable title for the text?

A．California’s Forests: Where Have All the Big Trees Gone?

B．Cutting of Big Trees to Be Prohibited in California Soon

C．Why Are the Big Trees Important to California Forests?

D．Patrick McIntyre: Grow More Big Trees in California

 The bristlecone pine is the longest-living thing on the earth. These trees, with their strangely-shaped, wind-beaten limbs(枝干), can live up to 5,000 years. But experts worry that a warming climate in some areas may threaten its future.

Researchers say warmer weather is permitting a similar kind of tree, the limber pine, to take over good growing places from the ancient bristlecone. They say the tree is being crowded out of mountainous areas where it grows.

“The bristlecone pine is the oldest individually growing organism,” researchers say. They grow in high mountain forests in eastern California, Nevada and Utah. In those mountains, the trees face high winds and extreme temperatures, which leave them with twisted limbs and shapes. “Even in such tough conditions,” Brian Smithers, a researcher at the University of California, said, “the limber pine is taking all the good spots.”

The limber pine is the bristlecone’s distant relative and competitor. It can also live a long time——up to 2,000 years. And it is usually found at lower altitudes, where temperatures are warmer. However, according to a three-year study which centered on trees that have started growing in the last 50 years in California’s White Mountains, most of the trees growing at higher altitudes were limber pines.

Scientists compared the competing species to two o1d men in a very slow race up a mountainside. This race between such slow-growing trees takes thousands of years. They say climate change is causing the competition.

Smithers said the bristlecone pines are not in danger of disappearing. But he assumes they could be crowded out of some places where they have grown for thousands of years.

The researchers say the findings show how climate change can affect the two kinds of trees. The information, they say, can help scientists understand more complex forests.

89．What’s the function of Paragraph 1?

A．To introduce a topic.                                  B．To summarize the whole passage.

C．To describe the appearance of a tree.            D．To praise the hard work of the experts.

90．What does the underlined sentence in Paragraph 2 mean?

A．There will be older trees sent out of those mountains.

B．There will be more places covered with bristlecone pines.

C．There will be better limber pines replacing the ancient ones.

D．There will be fewer bristlecone pines growing in those areas.

91．According to the passage, the reason why limber pines can grow at higher altitudes is_________.

A．the high winds                                           B．the difficult conditions

C．the changing climate                                  D．the extreme temperatures

92．What is the researchers’ attitude towards the future of the bristlecone pine?

A．Positive.                                                   B．Concerned.

C．Enthusiastic.                                              D．Indifferent.

A new United Nations scientific report says that human-caused climate change is greatly reducing land quality worldwide. It warns that the way humans use land is causing the earth's atmosphere to warm faster and could harm food production. The effects of climate change are already making food more costly and less nutritious ( 有营养的 ) and are worsening food shortages ( 缺乏 ).

The scientists write that if humans change the way they eat, grow food and manage forests, it could help slow world temperature rises.

About 30 percent of the earth's surface is land. But the report says that the land is warming two times faster than the planet as a whole. While heat-trapping ( 吸热的 ) gases are causing problems in the atmosphere, land has been less talked about as a part of climate change.

“The change could be worse,” the report says. Agriculture and forestry together account for about 23 percent of the heat-trapping gases that are warming the earth. That does not include energy costs, food transportation and packaging. With those activities added, the amount grows to 37 percent.

But land can absorb heat trapping gases out of the air. From 2009 to 2018, for example, agriculture and forestry each year put 5.2 billion metric tons of carbon dioxide into the air. But the land pulled 11.2 billion metric tons out of it. Carbon dioxide is a main heat trapping gas.

Scientists have long believed that one of the few good things about higher levels of carbon dioxide is that plants grow well in such conditions. But many studies show that the high levels of carbon dioxide can reduce protein ( 蛋白质 ) and nutrients in many crops.

The report also suggests ways that carbon emissions could be reduced further. This could be done if humans reduce the amount of red meat they eat and instead eat more fruit, vegetables and seeds. That would also make people healthier.

101 ． What has not been paid much attention to in the study of climate change?

A ． Greenhouse gases. B ． Land. C ． The earth's surface. D ． People's lifestyles.

1 ． How does the land function in global warming?

A ． It takes in a lot of carbon dioxide. B ． It produces grains less nutritious.

C ． It causes the majority of heat-trapping gases. D ． It sends off more carbon dioxide than it removes.

2 ． What is suggested to fight against global warning?

A ． Growing plants to absorb carbon dioxide. B ． Planting high quality crops.

C ． Limiting red meat intake. D ． Producing enough food.

3 ． What is the text mainly about?

A ． Humans should live a healthy life.

B ． Global warming is more and more serious.

C ． There will be a food shortage in the future.

D ． Climate change affects land quality and food production.

Think of Japan in the spring and the image that comes to mind is likely the country’s famous cherry blossoms, also known as “Sakura” — white and pink flowers, blooming across cities and mountains.

The flowers, which experience a “peak bloom” that only lasts a few days, have been loved in Japan for more than a thousand years. Crowds celebrate with viewing parties, flocking to the most popular locations to take photos and have picnics underneath the branches.

But this year, cherry blossom season has come and gone in the blink of an eye, in one of the earliest blooms on record. Scientists warn it’s a symptom of the larger climate crisis threatening ecosystems everywhere.

Yasuyuki Aono, a researcher at Osaka Prefecture University, has gathered records from Kyoto back to 812 AD from historical documents and diaries. In the central city of Kyoto, cherry blossoms peaked on March 26, the earliest in more than 1,200 years, Aono said. And in the capital Tokyo, cherry blossoms reached full bloom on March 22, the second-earliest date on record.

The peak bloom dates shift every year, depending on numerous factors including weather and rainfall, but have shown a general trend of moving earlier and earlier. In Kyoto, the peak date stayed around mid-April for centuries, but began moving into early April during the 1800s. The date has only dipped into late March a handful of times in recorded history.

“Sakura blooms are very temperature sensitive,” said Aono. “Flowering and full bloom could be earlier or later depending on the temperature alone,” he said. “The temperature was low in the 1820s, but it has risen by about 3.5 degrees Celsius to this day.”

This year’s seasons in particular influenced the blossom dates, he added. The winter was very cold, but the spring came fast and unusually warm.

1 ． What is the best title of the passage?

A ． Cherry blossom celebrations.

B ． Warning of a climate crisis.

C ． A strong love for cherry blossom.

D ． Cherry blossom season coming earlier.

2 ． What does the underlined word “flocking” mean?

A ． Blocking. B ． Flooding. C ． Running. D ． Following.

3 ． What can we infer from paragraph 5?

A ． The peak blossom dates fall on a fixed date.

B ． The cherry blossom rarely peaks in March.

C ． The peak bloom dates mainly depend on weather and rainfall.

D ． Cherry blossom peaks around mid-April in Tokyo.

4 ． What is the author’s purpose in writing the passage?

A ． To inform people the date of cherry blossom.

B ． To show a study on cherry blossom dates.

C ． To present a Japanese tradition of cherry blossom celebration.

D ． To make people aware of the influence of climate change on cherry blossom.

Most of the new diseases we humans have faced in the past several decades have come from animals. The more we come into contact with wild animals, the more we risk a so-called disease “spillover” from animals to humans.

“As people move and wildlife move in response to a changing environment, humans and wildlife and animals will come in contact more regularly,” said Jeanne Fair from the Los Alamos National Laboratory in New Mexico. Fair argues that by shifting animal habitats, climate change will also make the opportunities for disease spillover more frequent. “Everything is sort of shifting and will shift into the future as the environment changes through climate change,” Fair said.

Scientists, including climatologists and epidemiologists ( 流行病学家 ) on Fair’s team at Los Alamos, are beginning to model how changes to the climate will impact the spread of infectious diseases. It’s early days for this kind of research, but previous studies suggest that extreme weather has already played a role in at least one outbreak. Scientists say drought and deforestation have combined to force bats out of rain forests and into orchards ( 果园 ) in Malaysia to find food. Those bats, a common disease reservoir, then passed the Nipah virus through pigs to humans for the first time in the late 1990s.

“We’re going by the past data to really predict what’s going to happen in the future,” Fair said, “And so, anytime you increase that wildlife-human interface, that’s sort of an emerging disease hot spot. And so, that’s just increasing as we go forward.”

Jeffrey Shaman, head of the climate and health program at Columbia University’s public health school, argues we don’t yet know whether climate change will cause a net increase in infectious disease rates globally. For example, mosquitoes carry disease that affects millions of people across the world every year. As their habitats expand in some parts of the world, they might contract diseases elsewhere. Shaman says what we know for certain about climate change is that it will make it harder to predict where disease outbreaks will pop up.

1 ． How does climate change affect the spread of disease according to Fair?

A ． By breaking animals’habits. B ． By increasing animals’varieties.

C ． By promoting animals’breeding. D ． By changing animals’living environment.

2 ． What is the example of bats for in paragraph 3?

A ． Explaining the influence of Nipah virus.

B ． Proving the harm of bats to human beings.

C ． Showing the effects of climate change on disease.

D ． Presenting scientists’early study about the cause of disease.

3 ． What can we infer from Fair’s words in paragraph 4?

A ． Humans should give up studying animals.

B ． Frequent contact with animals can cause disease outbreaks.

C ． Disease hot spots will disappear if animals die out.

D ． Past data can solve the problems in the future.

4 ． What could be the best title for the text?

A ． Climate Change and Disease Spillover

B ． Animals’Interaction with Humans

C ． Early Studies about Extreme Weather

D ． Scientists’Prediction for Disease Outbreaks