【自然科学-环境】
New rules to limit numbers on Everest are delayed
（427字 精读 必做篇）
Like beads on a slender string, a long queue of mountaineers clings to a single safety rope. They are waiting to ascend to the icy peak of the world’s tallest mountain: Everest. The climbers and their guides have braved sheer rock, avalanches and wild winds. But the crowds that await interludes of good weather to rush for the summit can be just as deadly. Climbers jostle and bicker; long delays deplete supplies of oxygen. Last year four of the 11 deaths on the mountain during the spring climbing season were blamed on overcrowding.
“It is quite a commotion up there,” says Jeremy Tong of jtrace, a trekking firm, who had to queue to reach the summit last year. The Nepalese government had promised new rules to thin out the mob. (Because of coronavirus the Chinese government has called off all ascents this year on the northern face of the mountain, which is in its territory.) It came up with a series of new requirements to obtain a permit to make an attempt on the peak. Applicants should have successfully climbed another Nepalese mountain of at least 6,500 metres (Everest is 8,848 metres). They should provide documentation certifying their physical fitness for the challenge and employ experienced guides. The authorities are also considering raising the cost of a permit from $11,000 to $35,000. Yet this week they announced that they would not put these changes into effect this year, since there had not been sufficient consultation on them within the government.
Mountaineers are far less likely to die on Everest than they were just a few decades ago. Rescue teams and helicopters stand ready to help those in need, which is not always the case with other Himalayan peaks. But there are many more climbers than there used to be (see chart).
[attach]249681[/attach]
The Nepalese authorities handed out 381 permits to teams of mountaineers last year, generating a welcome dollop of cash. They are presumably keen to ensure that stricter rules do not shrink revenues. Even if the government comes out ahead, with extra income from higher fees offsetting any decrease in the number of permits issued, an entire industry depends on Everest. Nepal is among Asia’s poorest places: about half of its 30m people subsist on less than $3.20 a day, according to the World Bank. Guides risk their lives because they can earn perhaps $5,000 a season working at the highest altitudes, more than seven times the average annual wage. With last year’s bad publicity and the impending tightening of the rules, their earnings may have peaked.
Source: The Economist
【自然科学-生物】
A Humble Fish with a Colorful Edge
（399字 2分51秒 精听 必做篇）
先做精听再核对原文哦~
[attach]249682[/attach]Hundreds of millions of years ago a humble fish swam in the lakes and rivers of the supercontinent Gondwana. Eventually Gondwana broke apart, becoming the continents we know today. And the descendants of that fish, now called cichlids, continue to swim the fresh waters of both Africa and South America.
Cichlids have some of the most incredible visual systems known. Humans have genes that code for three different types of visual pigments, called opsins. Cichlids have seven.
"But what is interesting within cichlids, which is this group of very diverse fishes, is that they can express different sets of these seven genes. So they only express three typically, but different species express different groups of these seven genes." Biologist Daniel Escobar-Camacho, from the University of Maryland in College Park. "So for example, we have opsin genes that code for the blue, green, and red opsin…whereas cichlids have genes that are sensitive to UV, to violet, to blue, to blue-green, to green, light green, and red."
But selection pressure has kept only some of those genes intact.
African cichlids, whose visual systems are well studied, evolved in fairly clear, calm, blue lakes with plenty of sunlight. And it was known that they’ve maintained the genes for seeing short wavelength light, at the blue end of the spectrum. But their South American counterparts live in the murky waters of the Amazon River basin, bathed mostly in reds and oranges.
Escobar-Camacho analyzed DNA from three different Amazonian cichlids: the freshwater Angelfish, the Discus, and the Oscar, all of which are also popular in home aquariums. He discovered that each species has completely lost at least one of the seven opsin genes, and some have even lost two. But they've each lost different genes.
“What is interesting is that they are expressing genes in the retina that allow them to be long wavelength-sensitive. And this is in concordance with the light environment in Amazon waters, because Amazon waters transmit long wavelengths best.”
In other words, Amazonian cichlids were most sensitive to red and orange light, which makes sense because Amazonian rivers filter out most of the blues and greens. The results are in the journal Molecular Ecology.
The finding is consistent with an idea called the "sensitivity hypothesis," which holds that a color visual system evolves by adapting to the dominant wavelengths of light in the environment. In other words, what you get is what you see.
Source: Scientific American
【自然科学-环境】
Brazil has the power to save Earth’s greatest forest—or destroy it
（1048字 精读 选做篇）
Although its cradle is the sparsely wooded savannah, humankind has long looked to forests for food, fuel, timber and sublime inspiration. Still a livelihood for 1.5bn people, forests maintain local and regional ecosystems and, for the other 6.2bn, provide a—fragile and creaking—buffer against climate change. Now droughts, wildfires and other human-induced changes are compounding the damage from chainsaws. In the tropics, which contain half of the world’s forest biomass, tree-cover loss has accelerated by two-thirds since 2015; if it were a country, the shrinkage would make the tropical rainforest the world’s third-biggest carbon-dioxide emitter, after China and America.
Nowhere are the stakes higher than in the Amazon basin—and not just because it contains 40% of Earth’s rainforests and harbours 10-15% of the world’s terrestrial species. South America’s natural wonder may be perilously close to the tipping-point beyond which its gradual transformation into something closer to steppe cannot be stopped or reversed, even if people lay down their axes. Brazil’s president, Jair Bolsonaro, is hastening the process—in the name, he claims, of development. The ecological collapse his policies may precipitate would be felt most acutely within his country’s borders, which encircle 80% of the basin—but would go far beyond them, too. It must be averted.
Humans have been chipping away at the Amazon rainforest since they settled there well over ten millennia ago. Since the 1970s they have done so on an industrial scale. In the past 50 years Brazil has relinquished 17% of the forest’s original extent, more than the area of France, to road- and dam-building, logging, mining, soyabean farming and cattle ranching. After a seven-year government effort to slow the destruction, it picked up in 2013 because of weakened enforcement and an amnesty for past deforestation. Recession and political crisis further pared back the government’s ability to enforce the rules. Now Mr Bolsonaro has gleefully taken a buzz saw to them. Although congress and the courts have blocked some of his efforts to strip parts of the Amazon of their protected status, he has made it clear that rule-breakers have nothing to fear, despite the fact that he was elected to restore law and order. Because 70-80% of logging in the Amazon is illegal, the destruction has soared to record levels. Since he took office in January, trees have been disappearing at a rate of over two Manhattans a week.
The Amazon is unusual in that it recycles much of its own water. As the forest shrivels, less recycling takes place. At a certain threshold, that causes more of the forest to wither so that, over a matter of decades, the process feeds on itself. Climate change is bringing the threshold closer every year as the forest heats up. Mr Bolsonaro is pushing it towards the edge. Pessimists fear that the cycle of runaway degradation may kick in when another 3-8% of the forest vanishes—which, under Mr Bolsonaro, could happen soon. There are hints the pessimists may be correct. In the past 15 years the Amazon has suffered three severe droughts. Fires are on the rise.
Brazil’s president dismisses such findings, as he does science more broadly. He accuses outsiders of hypocrisy—did rich countries not fell their own forests?—and, sometimes, of using environmental dogma as a pretext to keep Brazil poor. “The Amazon is ours,” the president thundered recently. What happens in the Brazilian Amazon, he thinks, is Brazil’s business.
Except it isn’t. A “dieback” would directly hurt the seven other countries with which Brazil shares the river basin. It would reduce the moisture channelled along the Andes as far south as Buenos Aires. If Brazil were damming a real river, not choking off an aerial one, downstream nations could consider it an act of war. As the vast Amazonian store of carbon burned and rotted, the world could heat up by as much as 0.1°C by 2100—not a lot, you may think, but the preferred target of the Paris climate agreement allows further warming of only 0.5°C or so.
Mr Bolsonaro’s other arguments are also flawed. Yes, the rich world has razed its forests. Brazil should not copy its mistakes, but learn from them instead as, say, France has, by reforesting while it still can. Paranoia about Western scheming is just that. The knowledge economy values the genetic information sequestered in the forest more highly than land or dead trees. Even if it did not, deforestation is not a necessary price of development. Brazil’s output of soyabeans and beef rose between 2004 and 2012, when forest-clearing slowed by 80%. In fact, aside from the Amazon itself, Brazilian agriculture may be deforestation’s biggest victim. The drought of 2015 caused maize farmers in the central Brazilian state of Mato Grosso to lose a third of their harvest.
For all these reasons, the world ought to make clear to Mr Bolsonaro that it will not tolerate his vandalism. Food companies, pressed by consumers, should spurn soyabeans and beef produced on illegally logged Amazonian land, as they did in the mid-2000s. Brazil’s trading partners should make deals contingent on its good behaviour. The agreement reached in June by the eu and Mercosur, a South American trading bloc of which Brazil is the biggest member, already includes provisions to protect the rainforest. It is overwhelmingly in the parties’ interest to enforce them. So too for China, which is anxious about global warming and needs Brazilian agriculture to feed its livestock. Rich signatories of the Paris agreement, who pledged to pay developing ones to plant carbon-consuming trees, ought to do so. Deforestation accounts for 8% of global greenhouse-gas emissions but attracts only 3% of the aid earmarked for combating climate change.
If there is a green shoot in Mr Bolsonaro’s scorched-earth tactics towards the rainforest, it is that they have made the Amazon’s plight harder to ignore—and not just for outsiders. Brazil’s agriculture minister urged Mr Bolsonaro to stay in the Paris agreement. Unchecked deforestation could end up hurting Brazilian farmers if it leads to foreign boycotts of Brazilian farm goods. Ordinary Brazilians should press their president to reverse course. They have been blessed with a unique planetary patrimony, whose value is intrinsic and life-sustaining as much as it is commercial. Letting it perish would be a needless catastrophe.
Source: The Economist
【笔记格式要求】
精读笔记格式要求：
1.总结文章中心大意
2.总结分论点或每段段落大意
3.摘抄印象深刻或者觉得优美的句子
4.总结文章中的生词
5.记录阅读时间、总结时间、总时间
精听笔记格式要求：
1.逐句听写整篇文章
2.对照原文修改听写稿，标记出错原因
3.总结文章中心大意
4.总结精听过程中的生词
5.记录听写时间、总结时间、总时间
这里也给大家两点学习小建议哦~
精读：如遇到读不懂的复杂句，建议找出句子主干，分析句子成分，也可以尝试翻译句子来帮助理解~
精听：建议每句不要反复纠结听，如果听 5 遍都没听出来，那就跳过，等完成后再回听总结原因，时间宝贵，不要过于执着哦~
