Spray bacteria may prevent its spread
Desertification is a big problem for China. Overgrazing by livestock has destroyed much of the layer of lichen, algae and mosses—the cryptobiotic crust (隐生物壳) that binds the sand and soil to the ground.
Planting hardy grasses helps keeping sand in place, but the wind can still blow away particles (颗粒) between the grasses.
Grown in nearby ponds, the cyanobacteria are trucked into the desert every few days and spray over the dunes, where they form sticky substances that hold soil particles in place and prevent them from being blown away. Cyanobacteria get their energy from sunlight through photosynthesis, and as part of the chemical reactions involved, they absorb carbon from the atmosphere and provide the organic matter the soil needs to be productive.
Hu’s long-running trials shows that after eight years, dunes treated with cyanobacteria developed a biological crust nearly 1 centimetre thick when on the shady side of dunes.
The method is vital if semi-arid regions are going to recover on a reasonable timescale, says Brian Whitton, an ecologist at Durham University, UK.
Hu says the cyanobacteria are now being used to hold the verges of roads and railways in northern China as well as the margins of farmland. Her team plans to seed 133 square kilometres over the next five years.
| A．So Chunxiang Hu of the Chinese Academy of Sciences’s Institute of Hydrobiology in Wuhan has developed an alternative approach. |
| B．That might change soon, though. |
| C．“Unless you do something to help, you’re probably talking centuries for it to recover naturally,” he says. |
| D．If left unchecked, sands can slowly engulf roads and railways. |
| E．On the sunny side, the crust was about half as thick. |
| F．People have been trying to use bacteria in this way since the 1980s, says Matthew Bowker, a soil ecologist at Northern Arizona university. |
相似题推荐
【推荐1】While environmental assessments of new roads focus on the danger of habitat destruction, or bats colliding (碰撞) with traffic, the first ever controlled field experiment to investigate the impact of vehicle noise suggests the thunder of road traffic is likely to drive away bats and cause bat activity to decrease by two-thirds.
Researchers played noise recorded from the A38 dual carriage way in demon, with a “dusk average” of 26 vehicle passing per minute, in locations where different bat species flew and fed. The wild bats, including pipistrelle species, were monitored with bat detectors (探测器) placed beside, and 20 metres away, from the recorded noise.
Ultrasonic (超音速) sounds from vehicle were found to block some bat species' high-frequency echo - location calls, which they use to find insect prey (捕获物) such as moths. But more significant was that most bat species sought to avoid audible (听得见的) traffic noise.
“Just like us, bats are likely to find audible road noise an irritation, something they would prefer to avoid rather than it jamming their echo-location,” said Fiona Matt hews, lead author of the paper in Environmental Pollution.
Matthews said the effect of ordinary traffic noise on bats meant that the negative impact of new roads on bat populations was likely to be more far-reaching than realized.
She said: “This is important, as it means we could expect to see negative effects continue at a considerable distance from the road. We know that lower frequency road noise travels well beyond 50 metres — the scale at which ecological impact assessments are conducted.”
Dr. Henry Schofield, from Vincent Wildlife Trust, which jointly funded the research, said: “We have raised people’s awareness that bat species face barriers in the landscape that impede (妨碍) their ability to access suitable feeding areas and reduce their chances of survival. Along with habitat destruction and artificial lighting at night, this research has added road noise to the list of anthropogenic (人为的) factors reducing habitat quality for these protected species.”
1. What does the new research find about vehicle noise?| A．It destroys bats’ habitat. | B．It influences bats’ ability to feed. |
| C．It helps bats to find insect prey. | D．It causes bats to collide with traffic. |
| A．The design of the research. | B．The varieties of wild bats. |
| C．The function of bat detectors. | D．The traffic flow on highways. |
| A．It is well-informed. | B．It could be preventable. |
| C．It could be more serious. | D．It is predictable. |
| A．Its application. | B．Its dimension. | C．Its limitation. | D．Its significance. |
【推荐2】As seabird biologist Bonnie Slaton slides off a small boat and walks through high water, the brown pelicans (鹈鹕) spread their wings overhead until she reaches Raccoon Island. The narrow island is a small piece of land separating the American state of Louisiana from the Gulf of Mexico. During the seabird breeding (繁殖) season, the placer, one of the few remaining places of safety for the pelicans, is full of noise.
Twelve years ago, there were 15 low-lying islands with breeding areas for Louisiana’s state bird. However, today, only about six islands in southeastern Louisiana have brown pelican nests and the rest have disappeared underwater.
Slaton and other scientists set u cameras to observe pelican nests on the island. The cameras show that in recent years the pelicans have faced some natural disasters. The main killer of them is flooding, which can wash away all the nests, as happened in April 2021. The disappearing islands are the location of a story of successful conservation. For many years, scientists have worked to bring the pelicans beck from tally dying off.
Mike Carloss is a state wildlife biologist in Louisiana. He said he never saw brown pelicans as a child in the 1960s. Their populations had been killed by the use of DDT, a kind of farm chemical. It thinned eggshells and prevented pelicans from giving birth to young birds. The beloved birds were completely gone from Louisiana, only appearing on the state flag. But a long-running effort to save them led to the birds’ return. After DDT was stopped in the U.S. in 1972, biologists brought young pelicans from nearby Florida to let them inhabit empty islands across the Gull of Mexico again. More than 1,200 pelicans have been set free in southeastern Louisiana over 13 years.
The brown pelicans can live more than 20 years. So, the final effect of disappearing breeding areas is uncertain and it will sill take time to become clear. And the future for pelicans is uncertain on the islands.
1. What is a killer of brown pelicans?| A．The island movement. | B．The underwater noise. |
| C．The increase of human population. | D．The disappearance of breeding areas. |
| A．To stop illegal hunting. | B．To watch pelicans’ home. |
| C．To predict serious flooding. | D．To record the number of pelicans |
| A．Live on. | B．Focus on. | C．Break into. | D．Look into. |
| A．Unconcerned. | B．Doubtful. | C．Curious. | D．Proud. |
【推荐3】Amazon Alert
The Amazon rain forest stretches about 2.7 million square miles. It has been described as the “lungs of our planet”. More than 20% of the planet’s oxygen is produced there! The Amazon holds one-fifth of the world’s freshwater supply. The tropical forests in the heart of the Amazon basin are full of many different kinds of life. They hold the world’s widest variety of life, and are also home to many species found nowhere else. This area is one of the world’s natural treasures. But unless nations around the world take action, it will disappear.
Every year, the rain forest in the Amazon is shrinking. Farmers and builders are clearing the land, usually by burning down the forest. This destruction reached record levels in the 1990s and has remained steady since then. In 2003, an estimated 9,170 square miles were burned or cleared.
The Amazon River basin stretches into the countries of Ecuador, Peru, and Bolivia, but the bulk of it is in Brazil. Loggers, miners, and farmers in Brazil have been rapidly cutting down the Amazon since the 1960s. South American farmers and settlers burn the rain forest to clear the land. The land is used to grow crops and raise livestock or for new towns. Satellite photos show how the forest continues to shrink.
The government of Brazil has pledged time and again to slow down the clearing of land. However, they have not done enough to stop illegal burning and logging. But it's not just Brazil's problem. The Amazon is a treasure for all of humanity. Other countries, including the United States, must do more to help Brazil preserve the Amazon.
In order to protect the area, the Central Amazon Conservation Complex in Brazil was added to the UNESCO World Heritage List in 2000. The heritage site makes up the largest protected area in the Amazon Basin (over 6 million hectares). The rain forest is over 55 million years old. There are still many parts of the Amazon that no one has ever been to, and many species that no one has ever seen.
Fact File
The Amazon
You can’t drive there! The main form of transportation in the Amazon is by boat. The only way to get around the rain forest is through the Amazon River system. The river system has 20 percent of all the Earth’s fresh water. Each year during the rainy season, the rivers flood over nine meters deep.
The Amazon is famous for these flooded forests. Tourists will spend days boating through the flooded areas, watching tropical birds flying in the humid air, and fish swimming through the water.
1. What is the main threat to the Amazon rain forest?| A．Air and water pollution | B．Floods in the rainy season |
| C．Natural disasters near the forest | D．Burning the rain forest for the land |
| A．To tell that there are many different animals in the Amazon rain forest. |
| B．To explain through some figures that the size of the Amazon rain forest is quite large. |
| C．To indicate what will disappear in the Amazon rain forest if nations don’t take any action. |
| D．To emphasize that the Amazon rain forest is important and unique. |
| A．Getting larger | B．Getting smaller | C．Being protected | D．Being cleared |
| A．Farmers and builders are clearing the land |
| B．The destruction of the land is steady |
| C．The local people refuse to protect the rain forest. |
| D．The rain forest in the Amazon is facing great danger |
| A．The government of Brazil should take full responsibility. |
| B．Laws should be established to stop farmers from cutting and burning the forest. |
| C．Brazil and other countries should work together to protect the Amazon. |
| D．Brazil cannot make any more efforts to stop illegal burning and logging. |
| A．Life in the Amazon Rain Forest | B．The World’s Natural Treasures |
| C．Travel Around the Amazon | D．Protect the Amazon Together |
