1 . How does an ecosystem(生态系统) work? What makes the populations of different species the way they are? Why are there so many flies and so few wolves? To find an answer, scientists have built mathematical models of food webs, noting who eats whom and how much each one eats.
With such models, scientists have found out some key principles operating in food webs. Most food webs, for instance, consist of many weak links rather than a few strong ones. When a predator(掠食动物) always eats huge numbers of a single prey(猎物), the two species are strongly linked; when a predator lives on various species, they are weakly linked. Food webs may be dominated by many weak links because that arrangement is more stable over the long term. If a predator can eat several species, it can survive the extinction(灭绝) of one of them. And if a predator can move on to another species that is easier to find when a prey species becomes rare, the switch allows the original prey to recover. The weak links may thus keep species from driving one another to extinction.
Mathematical models have also revealed that food webs may be unstable, where small changes of top predators can lead to big effects throughout entire ecosystems. In the 1960s, scientists proposed that predators at the top of a food web had a surprising amount of control over the size of populations of other species—including species they did not directly attack.
And unplanned human activities have proved the idea of top-down control by top predators to be true. In the ocean, we fished for top predators such as cod on an industrial scale, while on land, we killed off large predators such as wolves. These actions have greatly affected the ecological balance.
Scientists have built an early-warning system based on mathematical models. Ideally, the system would tell us when to adapt human activities that are pushing an ecosystem toward a breakdown or would even allow us to pull an ecosystem back from the borderline. Prevention is key, scientists say, because once ecosystems pass their tipping point(临界点), it is remarkably difficult for them to return.
1. What have scientists discovered with the help of mathematical models of food webs?A.The living habits of species in food webs. |
B.The rules governing food webs of the ecosystems. |
C.The approaches to studying the species in the ecosystems. |
D.The differences between weak and strong links in food webs. |
A.has a wide food choice |
B.can easily find new prey |
C.sticks to one prey species |
D.can quickly move to another place |
A.The prey species they directly attack will die out. |
B.The species they indirectly attack will turn into top predators. |
C.The living environment of other species will remain unchanged. |
D.The populations of other species will experience unexpected changes. |
A.Uncontrolled human activities greatly upset ecosystems. |
B.Rapid economic development threatens animal habitats. |
C.Species of commercial value dominate other species. |
D.Industrial activities help keep food webs stable. |
A.By getting illegal practices under control. |
B.By stopping us from killing large predators. |
C.By bringing the broken-down ecosystems back to normal. |
D.By signaling the urgent need for taking preventive action. |
Single-use plastic bags are used at most a few times before they
Earth Day,
During the just-ended Spring Festival holiday, former fisherman Wang Chaosheng kept
Living in Sinan county in Southwest China’s Guizhou province,
Wujiang River
“I used to catch fish, and now I keep fish. I’m still doing my job,” Wang said.
The 18-hectare construction site of the Huashan section of Wuhan Metro Line 19 is situated near an ecological reserve. Efforts had to be made
When Hua
However, months
Our planet is heating up due to something
Let’s first think about a greenhouse – you may have one in your garden! It’s a glass structure that protects
The impact of gases on the Earth’s climate was first investigated in the 1820s. Eunice Foote, a scientist and women’s rights activist, tested the effects of sunlight on different gases that she put into glass cylinders. Her results
So, what can we do
We only have one planet, so let’s try and take care of it as much as we can.
7 . Steven Stein likes to follow garbage trucks. His strange habit makes sense when you consider that he’s an environmental scientist who studies how to reduce litter, including things that fall off garbage trucks as they drive down the road. What is even more interesting is that one of Stein’s jobs is defending an industry behind the plastic shopping bags.
Americans use more than 100 billion thin film plastic bags every year. So many end up in tree branches or along highways that a growing number of cities do not allow them at checkouts(收银台). The bags are prohibited in some 90 cities in California, including Los Angeles. Eyeing these headwinds, plastic-bag makers are hiring scientists like Stein to make the case that their products are not as bad for the planet as most people assume.
Among the bag makers’ argument: many cities with bans still allow shoppers to purchase paper bags, which are easily recycled but require more energy to produce and transport. And while plastic bags may be ugly to look at, they represent a small percentage of all garbage on the ground today.
The industry has also taken aim at the product that has appeared as its replacement: reusable shopping bags. The stronger a reusable bag is, the longer its life and the more plastic-bag use it cancels out. However, longer-lasting reusable bags often require more energy to make. One study found that a cotton bag must be used at least 131 times to be better for the planet than plastic.
Environmentalists don’t dispute(质疑) these points. They hope paper bags will be banned someday too and want shoppers to use the same reusable bags for years.
1. What has Steven Stein been hired to do?A.Help increase grocery sales. |
B.Recycle the waste material. |
C.Stop things falling off trucks. |
D.Argue for the use of plastic bags. |
A.Bans on plastic bags. |
B.Effects of city development. |
C.Headaches caused by garbage. |
D.Plastic bags hung in trees. |
A.They are quite expensive. |
B.Replacing them can be difficult. |
C.They are less strong than plastic bags. |
D.Producing them requires more energy. |
A.Plastic, Paper or Neither |
B.Industry, Pollution and Environment |
C.Recycle or Throw Away |
D.Garbage Collection and Waste Control |
8 . This fall, students at the University of Massachusetts found a new menu at their dining commons: the “diet for a cooler planet” menu. This meant herb-roasted lamb, raised with a carbon-friendly approach. It included sweet potatoes that had been picked from a local farm’s field post-harvest. The options were plant-heavy, locally grown, and involved little to no packaging.
“We wanted to let students participate in climate action by making choices about their food,” says Kathy Wicks, sustainability director for UMass Dining. The university is not alone in this effort. Increasingly, American consumers and institutions are thinking about how their food choices factor into climate change. For many, small choices at the grocery store, dining hall, and restaurant can feel more accessible than big-ticket options like buying a fuel-efficient car or installing home solar panels.
Small changes in dietary habits may make a big difference. Climate activists often target fossil fuels and transportation systems, but studies point to the food system as a significant contributor to global warming. According to Project Drawdown, a research organization that evaluates climate solutions, the way food is grown, transported, and consumed accounts for about a quarter of the world’s greenhouse gas emissions. Beef is a regular target. “If, on average, Americans cut a quarter pound of beef per week from their diet, it’s like taking 10 million cars off the road a year,” says Sujatha Bergen, director of health campaigns for the Natural Resources Defense Council. Food waste ranks third among climate solutions. While much waste occurs before consumers are involved — food left on the field or “chucked” because it does not fit appearance standards, Americans also throw out a lot of food they have purchased: about $ 1,600 worth a year per family of four.
“People are beginning to understand that their food choices make a big impact on climate,” says Megan Larmer, director of regional food at the Glynwood Center for Regional Food and Farming in New York. But, she cautions substantial change will need to come from the whole food system.
1. What is the purpose of the new menu at the University of Massachusetts?A.To market the cold dishes. | B.To reduce the cost of packaging. |
C.To popularize the plant-heavy diet. | D.To promote low carbon awareness. |
A.Food is a decisive factor for climate change. |
B.Food choices matter much to global warming. |
C.Universities are working together in climate action. |
D.Fuel-efficient cars are not affordable for consumers. |
A.It has great influence on carbon reduction. | B.It is popular among millions of car drivers. |
C.It has a close relationship with gas emission. | D.It plays a significant role in American’s diet. |
A.Food System Reform: A Successful Trial | B.Global Warming: An Approaching Danger |
C.Carbon Emission: A Killer, or Healer? | D.Low Carbon Diet: A Craze, or More? |
9 . There is such a thing as a free lunch, it turns out, as long as you don’t mind too much what it is. Tamara Wilson found hers a few streets away from her west London home — and as well as picking up some unwanted bread and fruit that would otherwise be thrown away, she made a new friend.
Wilson is one of 3.4 million people around the world using an app designed to encourage people to give away rather than throw away surplus (剩余的) food. “It’s such a small thing, but it makes me feel good and my neighbour feel good. And a lot of small acts can end up making a big difference,” she said.
The last few years have seen an explosion in creative ways to tackle food waste by linking supermarkets, cafes, restaurants and individual households to local communities. Olio, the app used by Wilson, saw a fivefold increase in listings during 2022, and the signs are that this rapid growth is continuing into 2023, said Tessa Clarke, its CEO and co-founder.
About a third of all food produced globally is wasted, according to the UN’s Food and Agriculture Organisation (FAO). Almost 1.4 billion hectares of land — close to 30% of the world’s agricultural land — is dedicated to producing food that is never eaten, and the carbon footprint of food wastage makes it the third contributor of CO2. Reducing food waste is one of the most effective ways of tackling the global climate crisis.
Olio, Clarke said, was an attempt to change this on a small, local scale. “The app connects people with others who have surplus food but don’t have anyone to give it to because so many people are disconnected from their communities.” Users of Olio post images of surplus food that others in the neighbourhood might want. Olio also has a network of 24,000 volunteers who collect surplus food from local supermarkets and stores for app users to claim.
Despite the success of the app, it was hard to make a difference to the huge scale of food waste, Clarke added. “Even though we’re doing well, we’ve only scratched the surface (触及表面). But if everyone makes small changes in the world, we’d dramatically reduce the amount of food that ends up in bins (垃圾桶).”
1. What does the author want to show by telling Wilson’s story?A.People tend to use apps to order food. | B.People prefer to make friends on apps. |
C.People find a high-tech fix to food waste. | D.People show more concern for each other. |
A.Global warming. | B.Loss of land. | C.World hunger. | D.Poverty and inequality. |
A.It sells surplus food to those in need. | B.It allows volunteers to slay connected. |
C.It provides a platform for people to promote food. | D.It fills the information gap between green communities. |
A.It is a great success. | B.It requires joint efforts. |
C.It is beyond human power. | D.It has won public support. |
Plastic pollution at sea is reaching
As plastic breaks down into smaller pieces, it also enters the marine food chain,
While consumers can help reduce plastic pollution by changing their behavior, governments have to step up and accept