CARLOS Tiger without Time

Food for hungry mouths, feed for animals headed to the slaughterhouse, fiber for clothing and even, in some cases, fuel for vehicles—all derive from global agriculture. As a result, in the world’s temperate climes human agriculture has supplanted 70 percent of grasslands, 50 percent of savannas and 45 percent of temperate forests. Farming is also the leading cause of deforestation in the tropics and one of thelargest sources of greenhouse gas emissions, a major contributor to the ongoing maul of species known as the “sixth extinction,” and a perennial source of nonrenewable groundwater mining and water pollution.

To restrain the environmental impact of agriculture as well as produce more wholesome foods, some farmers have turned to so-called organic techniques. This type of farming is meant to minimize environmental and human health impacts by avoiding the use of synthetic fertilizers, chemical pesticides and hormones or antibiotic treatments for livestock, among other tactics. But the use of industrial technologies, particularly synthetic nitrogen fertilizer, has fed the swelling human population during the last century. Can organic agriculture feed a world of nine billion people?

In a bid to bring clarity to what has too often been an emotional debate, environmental scientists at McGill University in Montreal and the University of Minnesota performed an analysis of 66 studies comparing conventional and organicmethods across 34 different crop species. “We found that, overall, organic yields are considerably lower than conventional yields,” explains McGill’s Verena Seufert, lead author of the study to be published in Nature on April 26. (Scientific American is part of Nature Publishing Group.) “But, this yield difference varies across different conditions. When farmers apply best management practices, organic systems, for example, perform relatively better.”

In particular, organic agriculture delivers just 5 percent less yield in rain-watered legume crops, such as alfalfa or beans, and in perennial crops, such as fruit trees. But when it comes to major cereal crops, such as corn or wheat, and vegetables, such as broccoli, conventional methods delivered more than 25 percent more yield.

The key limit to further yield increases via organic methods appears to be nitrogen—large doses of synthetic fertilizer can keep up with high demand from crops during the growing season better than the slow release from compost, manure or nitrogen-fixing cover crops. Of course, the cost of using 171 million metric tons of synthetic nitrogen fertilizer is paid in dead zones at the mouths of many of the world’s rivers. These anoxic zones result from nitrogen-rich runoff promoting algal blooms that then die and, in decomposing, suck all the oxygen out of surrounding waters. “To address the problem of [nitrogen] limitation and to produce high yields, organic farmers should use best management practices, supply more organic fertilizers or grow legumes or perennial crops,” Seufert says.

In fact, more knowledge would be key to any effort to boost organic farming or its yields. Conventional farming requires knowledge of how to manage what farmers know as inputs—synthetic fertilizer, chemical pesticides and the like—as well as fields laid out precisely via global-positioning systems. Organic farmers, on the other hand, must learn to manage an entire ecosystem geared to producing food—controlling pests through biological means, using the waste from animals to fertilize fields and even growing one crop amidst another. “Organic farming is a very knowledge-intensive farming system,” Seufert notes. An organic farmer “needs to create a fertile soil that provides sufficient nutrients at the right time when the crops need them. The same is true for pest management.”

But the end result is a healthier soil, which may prove vital in efforts to make it more resilient in the face of climate change as well as conserve it. Organic soils, for example, retain water better than those farms that employ conventional methods. “You use a lot more water [in irrigation] because the soil doesn’t have the capacity to retrain the water you use,” noted farmer Fred Kirschenmann, president of Stone Barns Center for Food and Agriculture at the “Feeding the World While the Earth Cooks” event at the New America Foundation in Washington, D.C., on April 12.

At the same time, a still-growing human population requires more food, which has led some to propose further intensifying conventional methods of applying fertilizer and pesticides to specially bred crops, enabling either a second Green Revolution or improved yields from farmlands currently under cultivation. Crops genetically modified to endure drought may also play a role as well as efforts to develop perennial versions of annual staple crops, such as wheat, which could help reduce environmental impacts and improve soil. “Increasing salt, drought or heat tolerance of our existing crops can move them a little but not a lot,” said biologist Nina Fedoroff of Pennsylvania State University at the New America event. “That won’t be enough.”

And breeding new perennial versions of staple crops would require compressing millennia of crop improvements that resulted in the high-yielding wheat varieties of today, such as the dwarf wheat created by breeder Norman Borlaug and his colleagues in the 1950s, into a span of years while changing the fundamental character of wheat from an annual crop to a perennial one. Then there is the profit motive. “The private sector is not likely to embrace an idea like perennial crop seeds, which do not require the continued purchase of seeds and thus do not provide a very good source of profit,” Seufert notes.

Regardless, the world already produces 22 trillion calories annually via agriculture, enough to provide more than 3,000 calories to every person on the planet. The food problem is one of distribution and waste—whether the latter is food spoilage during harvest, in storage or even after purchase. According to the Grocery Manufacturers Association, in the U.S. alone, 215 meals per person go to waste annually.

“Since the world already produces more than enough food to feed everyone well, there are other important considerations” besides yield, argues ecologist Catherine Badgley of the University of Michigan, who also compared yields from organic and conventional methods in a 2006 study (pdf) that found similar results. Those range from environmental impacts of various practices to the number of people employed in farming. As it stands, conventional agriculture relies on cheap energy, cheap labor and other unsustainable practices. “Anyone who thinks we will be using Roundup [a herbicide] in eight [thousand] to 10,000 years is foolish,” argued organic evangelist Jeff Moyer, farm director the Rodale Institute, at the New America Foundation event.

But there is unlikely to be a simple solution. Instead the best farming practices will vary from crop to crop and place to place. Building healthier soils, however, will be key everywhere. “Current conventional agriculture is one of the major threats to the environment and degrades the very natural resources it depends on. We thus need to change the way we produce our food,” Seufert argues. “Given the current precarious situation of agriculture, we should assess many alternative management systems, including conventional, organic, other agro-ecological and possibly hybrid systems to identify the best options to improve the way we produce our food.”

By David Biello  | S.A. / April 25, 2012

He was on Ecuador‘s bank notes and stamps, an evolutionary remnant, a money-spinning tourist attraction and an icon of internationalconservation. No one knew if he was gay, impotent, bored or just very shy. But he is thought to have been about 100 years old and in his primewhen he died on Sunday at the Charles Darwin research centre in theGalápagos Islands, although the giant tortoise known as Lonesome George and commonly called the “rarest animal on Earth” may in fact have been far older – or much younger.

In the 40 years he spent in a field on Santa Cruz Island, having been relocated from Pinta Island in 1972, the 200lb, 5ft-long animal showed little interest in either man or other tortoises. He mostly ignored thefemale company provided to encourage him to breed, kept his 3ft scraggy neck down in the long grass, and only responded to his keeper, Fausto Llerena, who runs a tortoise breeding centre.

“The park ranger in charge of looking after the tortoises found Lonesome George, his body was motionless,” said Edwin Naula, head of the Galápagos National Park. “His lifecycle came to an end.”

George was found near a water hole, but no one knows how or why he died, and evolutionary scientists are still baffled by his life in the volcanic Pacific islands 1,000km off Ecuador that inspired Darwin’s theories on evolution and which are now a global laboratory for conservation.

The last known representative of the giant Galápagos tortoise subspecies Chelonoidis nigra abingdoni had every reason to shun humanity, however. His relatives were exterminated for food or oil by whalers and seal hunters in the 19th century, and his habitat on Pinta was devastated by escaped goats. George possibly has relations on neighbouring Isabela Island, but it is more likely his whole subspecies is now extinct – the end of what is probably a 10m-year-old line.

On Monday, scientists who had spent time with George recalled his peculiar ways. “George was the last of his kind. He had a unique personality. His natural tendency was to avoid people. He was very evasive. He had his favourites and his routines, but he really only came close to his keeper Llerena. He represents what we wanted to preserve for ever. When he looked at you, you saw time in the eyes,” said Joe Flanagan, the head vet of the Houston zoo, who knew George for more than 20 years.

Scientists’ attempts to get George to mate with other giant tortoises from the Galápagos Islands and to eventually repopulate Pinta all failed and were often comical. Artificial insemination did not work, nor did a $10,000 reward offered by the Ecuadorean government for a suitable mate. In the 1990s, Sveva Grigioni, a Swiss zoology graduate student, smeared herself with female tortoise hormones and, in the cause of science, spent four months trying to manually stimulate him – to no avail.

In 2008 and 2009 George unexpectedly mated with one of his two companions, but although two clutches of eggs were collected and incubated, all failed to hatch.

Henry Nicholls, author of Lonesome George: The Life and Loves of the World’s Most Famous Tortoise, reported that George was irresistibly attracted to the late Lord Devon’s wartime helmet, presumably because it resembled the shell of a young tortoise. Even after being put on a diet, the celibate tortoise with the scraggy neck, who could have been expected to live until he was well over 200, remained obstinately alone.

Conservation scientists on Monday said George was important because he symbolised both the rapid loss of biodiversity now taking place around the world, and provided the inspiration to begin restoring it in places like the Galápagos Islands. “Because of George’s fame, Galápagos tortoises which were down to just a few animals on some islands have recovered their populations. He opened the door to finding new genetic techniques to help them breed and showed the way to restore habitats,” said Richard Knab of the Galápagos Conservancy, which is running giant tortoise breeding programmes with the Ecuadorean government.

In 1960, 11 of the Galápagos Islands’ original 14 populations of tortoises remained, and most were on the point of extinction. Today, around 20,000 giant tortoises of different subspecies inhabit the islands and most of the feral goats have been eradicated.

But George will be sorely missed for financial reasons, too. As the star of the islands and an icon of global wildlife, he helped attract 180,000 money-spinning visitors a year to the archipelago. He is likely to become a conservation relic and will probably be embalmed and displayed – alone still.

* By John Vidal, environment editor, Guardian, 25 June 2012

Saudi Arabia will let its female athletes compete in the Olympics for the first time, its embassy in London said. Until now, Saudi Arabia was one of three countries that did not allow women to participate in the games.  The other two — Qatar and Brunei — also reversed course this year and said they will send female athletes to the London games, which begin July 27.

“The Kingdom of Saudi Arabia wishes to reaffirm its support for the sublime meanings reflected by Olympic Games and the cherished values of excellence, friendship and respect that they represent,” the Saudi Embassy in London said in a statement announcing the decision.

The International Olympic Committee had been pressing Saudi Arabia to allow women to compete and act as officials, and said in March that talks were going well.

“IOC is confident that Saudi Arabia is working to include women athletes and officials at the Olympic Games in London in accordance with the International Federations’ rules,” the committee said March 19.

The decision is a rare concession for a kingdom where women are banned from driving.

They also cannot vote or hold public office, though that will change in 2015.

Women in Saudi Arabia also cannot marry, leave the country, go to school or open bank accounts without permission from a male guardian, who usually is the father or husband. Much of public life is segregated by gender.

When it came to sports, female athletes were barred from the Olympic Games because they would be participating in front of a mixed-gender crowd.

The Saudi Embassy did not say what prompted the kingdom to change its mind. Officials in Saudi Arabia could not immediately be reached for comment.

The embassy statement added that women who qualify for the games will be allowed to participate, raising questions how many female athletes will be ready at such short notice.

Dalma Rushdi Malhas, who became the first Saudi woman to compete in the youth Olympics, praised the decision, calling it “a dream come true.”

“This just opens so many doors for women,” Malhas, an equestrian, told CNN International.

Malhas said she won’t be competing in the London games this summer, “but I look forward to giving my best and I’m determined to keep on trying for the next games, hopefully.”

Earlier this year, Human Rights Watch issued a report in which it said the Saudi government’s policy of banning women’s participation in national competitive sports reflects the “predominant conservative view that opening sports to women and girls will lead to immorality: ‘steps of the devil,’ as one prominent religious scholar put it.”

In 2009 and 2010, the country closed private gyms for women, and its schools’ curriculum does not include physical education classes for women, the rights group said.

And while the Saudi National Olympic Committee selects athletes to represent it in competition, the committee does not have a women’s section.

Saudi Arabia’s 153 official sports club are also closed to women, Human Rights Watch said. The only exception is the female basketball section of Jeddah United, a private sports company that is not among the official sports clubs, the group said.

For its part, Qatar will send three women to London this year: a shooter, a swimmer and a runner.

Brunei will send a woman who will compete in hurdling.

* CNN, June 25, 2012

An adviser was essential to starting a research career, but no one else at his university worked on amphibians. He was bereft. For a field biologist studying behavior, the animals that are the subjects of study may turn out to be lifelong companions. The young biologist had already given up on tortoises, his first love, because there were none nearby. Now amphibians were out. What was he to do?

A friend and fellow biology student reminded him that his real interest was in studying behavior, not a specific animal, and told him about a cave with large numbers of a relatively unstudied order of arachnids (spiders, ticks, mites and other creatures that people commonly call insects, but are not), easily observed, with a wide range of behaviors. The creatures in question were harvestmen; the most familiar North American member is the daddy longlegs.

As Dr. Machado, now head of the Laboratory of Arthropod Behavior and Evolution at the University of São Paulo, recalled recently, he had never heard of this group, but he was intrigued enough to go to the cave, where he encountered one small problem. “I am a little arachnophobic,” he said, “a little bit.” And “there were huge spiders inside the cave.”

For a moment he hesitated, but the harvestmen drew his gaze, some of them gathered in tangled groups of spindly legs and small bodies, others guarding nests of eggs. “They were amazing,” he said. In three months he had enough information to persuade an ant specialist at the university to advise him, and to publish his first scientific paper; he had found his life’s work.

“It was,” he said, “completely accidental.”

Now, a decade and a half later, Dr. Machado is one of the foremost experts on the creatures he first saw in the cave. He was at the annual meeting of the Animal Behavior Society here this month to describe the extraordinary amount of care that males in some varieties of harvestmen take of nests and eggs, and how he and his colleagues had experimentally demonstrated the reason. Within those groups, the nest-guarding males attracted more females and had more opportunities to copulate.

He was an editor of the definitive work on the creatures, and the research he and colleagues in his lab have done is drawing the attention of other scientists to a once obscure group.

This kind of career is often recounted by field biologists, an accidental start leading to a lifelong passion for an animal others might ignore. Although the framework of science may seem hyper-rational, some decisions are more like choosing a spouse than designing an experiment, with room for serendipity and accident.

The childhood of the biologist Edward O. Wilson offers one of the best-known tales of turning an accident to good use. Dr. Wilson, among his many other achievements, is a world authority on ants. He is an author, with Berth Holldobler of “The Ants,” the definitive tome on this subject, which won a Pulitzer Prize in 1991, a rare achievement for a book of serious science.

But birds were his first love. He lost the sight in one eye in a childhood accident, and with it the depth perception needed to pick birds out in the forest leaves. He turned instead to close observation of the forest floor, and ants. He wrote in his autobiography, “Naturalist,” that “most children go through a bug phase. I just never grew out of it.”

Some passions are easily understood. Jane Goodall loves chimpanzees, which she described as, “next to Homo sapiens, the most fascinating and complex in the world today.” Elephants, lions, wolves and ravens have caused scientists to fall in love with them as well as study them.

Other loves are more difficult for people outside of the field to grasp. Mark Siddall at the American Museum of Natural History is a great fan of the animals he studies — leeches. He told The New York Times in an article a few years ago that as a child, he hated leeches. They would attach themselves to him while he was swimming. Now he collects them all over the world.

It may be that field scientists, in their professional lives, learn to love the one they’re with, so to speak, or the one that will interest an adviser, and get a grant. Certainly, scientists are not trained to pick the animal that they love to study. And there is no rule that they have to stick with one animal, even if that often happens.

I asked Marlene Zuk, a professor in the department of ecology, evolution and behavior at the University of Minnesota, who wrote a book about insects, “Sex on Six Legs,” whether she had stayed with insects, or one variety of insect.

She said that she had studied several animals, including red jungle fowl, the ancestor of chickens, and had a strong interest in birds as well as insects, but that crickets had been her main focus for many years. She said that graduate students in animal behavior are encouraged to think of what question they want to ask, not what animal they want to study. If a romance ensues, well, scientists are human.

And when passionate connections are formed, they can be contagious. She said in an e-mail that because of the work of Dr. Machado and his lab, “I have developed a huge love of harvestmen.”

Dr. Zuk said that insects have a strong appeal to her partly because they are so different from people that it is hard to anthropomorphize them. She has stuck with crickets, she says, because “I keep finding out interesting things with them, some of them serendipitously. Also, I wanted an animal that had a sexual signal that was easy to analyze, and one that got parasites.”

“But,” she added, “I do really like them, also.”

Arguing against immigration policies that force foreign-born innovators to leave the United States, a new study to be released on Tuesday shows that foreign nationals played a role in more than three out of four patents at the nation’s top research universities.

Conducted by the Partnership for a New American Economy, a nonprofit group co-founded by Mayor Michael Bloomberg of New York, the study notes that nearly all the patents were in science, technology, engineering and math, the so-called STEM fields that are a crucial driver of job growth.

The report points out that while many of the world’s top foreign-born innovators are trained at United States universities, after graduation they face “daunting or insurmountable immigration hurdles that force them to leave and bring their talents elsewhere.”

The Partnership for a New American Economy released a paper in May saying that other nations were aggressively courting highly skilled citizens who had settled in the United States, urging them to return to their home countries. The partnership supports legislation that would make it easier for foreign-born STEM graduates and entrepreneurs to stay in the United States.

“Now that we know immigrants are behind more than three of every four patents from leading universities, the federal laws that send so many of them back to their home countries look even more patently wrong,” Mayor Bloomberg said in a statement.

But some worry that the partnership’s ideas for immigration reform would undermine similarly skilled American workers while failing to address broader problems with immigration policy.

“No one is asking what is in their best interest, the American worker,” said Eric Ruark, director of research for the Federal for American Immigration Reform, an advocacy group that is pushing for reduced immigration. “It’s what is best for the employers. What is best for the foreign workers. It’s not as if the foreign workers aren’t skilled. What’s being ignored is we already have a domestic work force that has the same skills.”

The most recent study seeks to quantify the potential costs of immigration policies by reviewing 1,469 patents from the 10 universities and university systems that had obtained the most in 2011. The schools include the University of California system, Stanford and the Massachusetts Institute of Technology.

Patents, the study maintains, are a gauge for a nation’s level of innovation and an important way for the United States to maintain an edge in STEM fields.

In one illustration of the issue, the study notes that nine out of 10 patents at the University of Illinois system in 2011 had at least one foreign-born inventor. Of those, 64 percent had a foreign inventor who was not yet a professor but rather a student, researcher or postdoctoral fellow, a group more likely to face immigration problems.

Some of the patents that were reviewed for the report have become business ventures. Wenyuan Shi, a professor at the University of California, Los Angeles, earned a patent for an ingredient in a lollipop he developed that works as a dental treatment for children. A native of China, Mr. Shi has created a company to commercialize his inventions.

But current immigration laws can make it difficult for foreign-born students to remain in the United States after graduation. And employers may be wary of hiring them because green cards, allowing for permanent residency status, are limited and the process of obtaining one is cumbersome and expensive.

Under the current system, foreign-born students are allowed to stay in the United States for 12 to 29 months after graduation, provided they find a job or internship in their field.

After that, more permanent visas are difficult to obtain, restricted by factors like country quotas. The study notes that China is entitled to the same number of visas as Iceland.

Dr. Ashlesh Murthy came to the United States from India in 2001 to pursue a master’s degree in molecular biology at the University of Texas at San Antonio. Working with his professors there, he developed a vaccine for the sexually transmitted disease chlamydia, which obtained patents in 2011 and 2012.

Nonetheless, Dr. Murthy had to negotiate a bureaucratic maze to remain in the United States, and at one point was stuck in India for an extra month because American officials in India doubted a previously approved visa.

Noting that university officials petitioned a congressman to intervene on his behalf, Dr. Murthy, said, “If I was not in a position where they really wanted me, I seriously doubt I would have gotten back.”

As Kim Jong-un, the young leader of North Korea, consolidates his grip on power, China is showing signs of increasing frustration at the bellicose behavior of its longtime ally.

Since succeeding his father, Kim Jong-il, six months ago, Mr. Kim has quickly alienated the Obama administration and put North Korea on track to develop a nuclear warhead that could hit the United States within a few years, Chinese and Western analysts say.

Most surprising, though, is how Mr. Kim has thumbed his nose at China, whose economic largess keeps the government afloat. For example, shortly after Mr. Kim took over, a Chinese vice minister of foreign affairs, Fu Ying, visited Pyongyang, North Korea’s capital, and sternly warned him not to proceed with a ballistic missile test. The new leader went ahead anyway.

Now, the Obama administration and the Chinese government, who warily consult each other on North Korea, are waiting to see if Mr. Kim will follow in his father’s footsteps and carry out a nuclear test, which would be North Korea’s third. The previous tests were in 2006 and 2009.

This month, the North Korean news agency said there were no plans for a third test “at present,” a statement analysts said suggested Mr. Kim was just waiting for a moment that better suited him.

“We have made this absolutely clear to them; we are against any provocation,” Cui Tiankai, another Chinese vice minister of foreign affairs, said in a recent interview when asked about a possible third nuclear test by North Korea. “We have told them in a very direct way, time and again, we are against it.”

Asked why China did not punish North Korea for its actions, Mr. Cui replied: “It’s not a question of punishment. They are a sovereign state.”

China backed sanctions against North Korea at the United Nations Security Council after the first two nuclear tests, he said. “If they refuse to listen to us,” he added, “we can’t force them.”

Mr. Kim’s erratic behavior unfolded early on. In late February, his government signed an agreement with the United States to freeze its nuclear weapons and ballistic missile programs, giving hope that he would turn out to be more open to change than his father. But six weeks later, Mr. Kim ripped up the accord and, without informing China, ordered the missile test that Washington viewed as a test run for launching a nuclear weapon.

The missile test, in April, was a failure, but that did little to alleviate concerns within the Obama administration that Mr. Kim was intent on pushing ahead with its nuclear weapons program. “The North is on track to build a warhead that could in a few years hit any regional target and eventually the United States,” said Evans J. R. Revere, a former United States principal deputy assistant secretary of state for East Asian and Pacific affairs.

Since the failed missile test, Mr. Kim has formalized North Korea as a “nuclear armed state” in the Constitution, another signal that the government has no intention of giving up its nuclear program, Mr. Revere said. With virtually no contact between the United States and North Korea, Mr. Revere argued, it is time for Washington to toughen its approach.

In a series of quick maneuvers, Mr. Kim, whose exact age is not known (he is believed to be 28 or 29), assumed the mantle of power immediately after his father’s death and cast aside early assumptions that his tenure would be a regency largely run by his elderly relatives.

The China News Service, a state-run agency, headlined an article last week: “Smooth transfer of power six months after Kim Jong-il’s death. North Korea enters era of Kim Jong-un.” The top North Korean Army generals, some of them in their 80s, have joined ranks around Mr. Kim, presenting a unified command, said Daniel A. Pinkston of the International Crisis Group in Seoul, who has written a forthcoming report by the group on North Korea.

At a congress of the ruling Communist Party in April, members of the Kim family were appointed to senior positions in the Politburo. The new appointees included Kim Kyong-hui, a younger sister of Mr. Kim’s father. Her husband, Chang Song-taek, also won a spot on the Politburo.

“There are no indications of any opposition to the transfer of power in the party, state or military,” Mr. Pinkston said. “Although many North Koreans are dissatisfied with the government, the barriers to collective action make it very risky and nearly impossible to organize any resistance.”

To recover from the embarrassment of the failed missile test, Mr. Kim unleashed a bellicose warning to South Korea in late April, threatening that a “special operations action” team would “reduce to ashes the rat-like” leadership of President Lee Myung-bak.

In contrast to his taciturn father, Mr. Kim has been seen more in public, particularly with students and children, a propaganda campaign intended to present a more benign image to an impoverished and embittered population.

On the basis of his years at a Swiss boarding school, Mr. Kim was thought by some analysts to be a potential economic reformer. These assumptions have turned out to be misplaced, and the new leader has shown no interest in following the advice of China to open up the economy, even in a modest way.

Despite Mr. Kim’s obstinacy, China keeps the economy from collapsing. Right after Mr. Kim assumed power, for example, China gave North Korea 500,000 tons of food and 250,000 tons of crude oil, according to the International Crisis Group report. That helped overcome what a German aid official, Wolfgang Jamann, said in Beijing on Friday was the worst drought in 60 years. His organization, Global Food Aid, has run a food program in North Korea since 1997.

“If it continues not to rain, it would be a problem,” said Mr. Jamann, who just returned from a trip to North Korea.

So far, though, the aid seems to have prevented disaster. According to South Korea’s Foreign Ministry, food shortages, while still grim in many rural areas, do not seem as serious as might be expected, given the drought.

China’s generosity has not bought it immunity against North Korean rancor. More than two dozen Chinese fishermen were held captive for two weeks by North Korea in May. After their release, one of the fishermen described how his boat was boarded by North Korean Navy men brandishing guns.

After “13 days in hell,” the fishermen were released, according to interviews in the Chinese news media. But not before the boats and men were stripped, the men to their underpants, the fisherman said.

Such behavior ignited protests on Chinese Web sites, and normally calm Chinese analysts who follow North Korea said they were infuriated by the indignities. “I was disappointed in our government’s soft line during the incident with the seized boats,” said a Chinese analyst who spoke on the condition of anonymity for fear of angering his superiors.

Nonetheless, senior Chinese officials “dare not use China’s economic leverage” against North Korea, said Shi Yinhong, a professor of international relations at Renmin University in Beijing. That is because a collapse of the North Korean government could result in a united Korea allied with the United States, which would be a nightmare scenario for China, Mr. Shi said.

Indeed, as China becomes more concerned about what it sees as the United States’ stepped-up containment efforts against China — including the positioning of more warships in the Pacific — the less inclined it is to help the United States on North Korea, said Yun Sun, a China analyst in Washington.

“China will not help the U.S. and South Korea solve the North Korea problem or speed up a China-unfriendly resolution, since China sees itself as ‘next-on-the-list,’ ” she wrote in an article last week for the Center for Strategic and International Studies in Hawaii, where Pacific Command, the arm of the American military overseeing the increased United States naval presence in the Pacific, is located.

And over all, there are unyielding historical reasons for China’s protectiveness toward North Korea, said an experienced American diplomat and expert on China.

“Beijing disapproves of every aspect of North Korean policy,” J. Stapleton Roy, a former United States ambassador to China and now vice chairman of Kissinger Associates, wrote in an article this month, also for the Center for Strategic and International Studies.

But with long memories of both the Korean War and how Japan used the peninsula to launch its invasion and occupation of much of China from 1937 to 1945, “Beijing has an overriding security interest,” Mr. Roy wrote, “in maintaining influence in Pyongyang and in not permitting other powers to gain the upper hand there.”