Ice-age nettles may survive in dark Chinese caves

Walk into a cave in south-west China and you could be stepping back 30,000 years in time.

So says Alex Monro, a researcher in tropical plant diversity at the Natural History Museum, London, who thinks the caves could be a time capsule preserving rare nettles from the time of the last ice age.

Working with researchers from the Chinese Academy of Sciences, Monro has identified seven species of nettle that grow in isolated, dark corners of the karst landscapes of Guangxi and Yunnan provinces. Some species can survive in conditions in which just 0.02 per cent of sunlight penetrates the cave – that's less than reaches 100 metres deep into the oceans. "They grow at the backs of the main caverns in near-dark conditions," says Monro.

"Some of the specimens came from areas with very low light levels indeed, and one can easily interpret the site as being under full cave conditions," says Frank Howarth of the Hawaii Biological Survey in Honolulu, a speleologist who specialises in karst caves and their ecologies.

"There must be something quite special about their photosynthesis," says Monro, although the team has not yet investigated the photosynthetic mechanism. "They probably activate the photosynthetic process very quickly, which enables them to take advantage of very short bursts of light, and they might go for slightly different wavelengths," he says.

The nettle species seem to be unique to the remote caves and gorges, growing in isolated groups. One species, Elatostema retrorstrigulosum, is limited to only 10 adult plants, some growing in a grotto, hidden among stalagmites. The team have identified two of the species as "critically endangered" under the criteria of the International Union for Conservation of Nature; the rest are either "endangered" or "vulnerable".
Cold blast from the past

Nettles like these are not found in the surrounding tropical forest. To explain the discovery of these pockets of rare plants in an environment that is too tropical to support them, Monro suggests that the rare species could be "relicts of a vegetation from a previous cooler climate that resembled that of the caves".

Ancient cave paintings threatened by tourist plans

Prehistoric paintings in northern Spain could be irreparably damaged if plans to reopen the Altamira cave to tourists go ahead. Local officials want to reopen the cave to boost the local economy, but visitors could heat the caves and introduce microbes that destroy pigments.

The Altamira cave paintings were discovered in 1879 and are thought to be at least 14,000 years old. The paintings have attracted huge numbers of visitors – 175,000 in 1973, the busiest year on record. But the cave was closed to the public in 2002 after photosynthetic bacteria and fungi were found to be consuming pigments at alarming rates.

Plans to reopen the caves could restart the damaging processes. A team from the Spanish National Research Council in Madrid have modelled the effect of visitors over a number of years and say that tourists would increase the temperature, humidity and carbon-dioxide levels in the cave, creating conditions in which microbes would thrive.

In addition, visitors would bring with them organic matter in the form of skin flakes, clothing fibres and dust, which microbes can consume. Air turbulence created by moving people would spread bacterial and fungal spores to other, previously unaffected spaces.
Another Lascaux?

Although reopening the caves might boost the economy in the short term, says lead researcher Cesáreo Sáiz Jiménez, the damage would outweigh the benefit. "The paintings are a legacy from the past and their importance exceeds local culture."

The researchers say they want to prevent the scale of damage that occurred at the Lascaux cave in France, where mismanagement led to successive waves of pathogens attacking wall paintings there. For example, pesticides intended to destroy microorganisms became a source of nutrients for them instead.

Sáiz Jiménez and his colleagues conclude that only isolation from the outside world can prevent the same kind of damage at Altamira.

Why size matters in the plant world too

Over 60 years ago, evolutionary biologist Bernhard Rensch calculated that males are typically the larger sex in big-bodied species such as humans, whereas females outdo them in small-bodied species such as spiders. Now it turns out that many plants obey Rensch's rule too.

Most plants produce both male and female sex organs, but around 7 per cent are dioecious, meaning individuals are purely male or female. Kevin Burns and Patrick Kavanagh at Victoria University of Wellington in New Zealand measured the leaf and stem sizes of 297 plants from 38 dioecious plant species in herbarium collections of the National Museum of New Zealand and discovered that they follow the sex-size rule

Hot Zone—A Warming Planet's Rising Tide of Disaster

It was a hot, sticky day when patient zero arrived at a local hospital in Brownsville, Texas, in June 2005. Her body was racked with chills, she couldn’t stop vomiting, her blood pressure was perilously low, and she was passing blood in her urine. Clueless as to the cause, doctors pumped her up with fluids to treat dehydration, dosed her with antibiotics, and sent her home. But when blood tests and clinical evaluation were done with the help of the regional Texas Border Infectious Disease Surveillance project, a surprising culprit was unmasked: dengue hemorrhagic fever, a deadly viral disease usually regarded as a risk only in the tropics.

Long thought eradicated in the United States, dengue is roaring back. There had been prior cases of the disease’s milder cousin, classic dengue fever, in Brownsville, a bustling metropolis of about 140,000 people at the southernmost tip of Texas on the Gulf coast. But this was the first well-documented case of the more serious form of dengue infection, hemorrhagic fever, in a Texas resident infected in the continental United States. It is unlikely to be the last. From 1995 to 2005, some 10,000 cases were reported in the United States and the Texas-Mexico border region. The Centers for Disease Control and Prevention (CDC) believes that many cases are never counted, so these figures may be a vast underestimate.

A range of factors influence the spread of the dengue virus, but rising global temperatures may be the most important of all. Like many tropical diseases, dengue is spread by mosquito bites, and mosquitoes are exquisitely sensitive to climate. Frost kills both adults and larvae, which is why the disease hadn’t previously been able to get a foothold in the United States. With the advent of warmer winters, there is nothing holding the insects back. As a result, the two species of mosquito capable of transmitting dengue fever—Aedes aegypti and Aedes albopictus, also called the Asian tiger mosquito—have substantially expanded their habitat range since the middle of the 20th century

The Future History of the Arctic

Viewed through certain eyes, the diminishing ice cover at the top of the world is not a harbinger of destruction but an open door to commerce. The Northwest Passage is coming, at last. The Arctic is loaded with resources, and today as the ice recedes and open water stretches further, energy developers are licking their lips at the chance to get at all that hydrocarbon booty buried beneath frigid seas. The fight to come is: Who has the rights to what?

Writes Charles Emmerson: "If there is a scramble for the Arctic, it is a scramble in slow motion." That's because going after Arctic energy resources requires not just waiting for the waters to become passable, but also negotiating the fact that "different legal regimes apply to the land, the sea, and the seabed." It might be easiest to negotiate a new treaty to govern the newly open Arctic, but Emmerson doubts this will happen. If for no other reason, he writes, the pool of Arctic nations would be inviting other nations to join the deliberations if they did so. It looks like the future of the Arctic will be legal mess, but it will be a legal mess sorted out by Canada, the United States, Russia, Norway, and Denmark (owner of Greenland) while the rest of the world watches from the sidelines.

The Weather of the Future

Can the Big Apple, a city of islands (and DISCOVER's home), be spared from rising seas and fiercer storms? As we covered earlier this year, there's plenty to do to save New York from encroaching waters. Some architects see a circle of marshland around Manhattan to keep the waves at bay, bringing back mollusks to create natural reefs, or raising buildings off the ground to keep them from flooding. But none of this will be cheap. In Peter Ward's thought experiment that saw Miami's doom, "the fight for New York alone had necessitated cuts to national defense to the point that that United States had completely withdrawn from its foreign bases, defaulted on its Social Security obligations, and abandoned its short-lived national health care system."

In her book, Heidi Cullen explains that there are more mundane annoyances on the way. She quotes Columbia University energy expert Steve Hammer: "For New York, climate change means blackouts." Plain and simple, more extreme heat means more AC running non-stop, and the city's power system won't be able to keep up. The water supply will be stressed as less precipitation will fall as snow on the Catskills, meaning less meltwater to flow to the city's taps.

Climatopolis

We are an adaptive species. Unlike the birds and butterflies, Matthew Kahn writes, we humans can adapt to whatever new world comes our way. An optimist in a pessimistic group, he focuses the upside of a disaster. For one thing, the Rust Belt could receive an overdue makeover. Given the steady declines of Cleveland, Buffalo, and Detroit, it sounds like a joke today to imagine them vibrant again. However, Kahn points to the revitalizations of Boston and New York City after the dreadful 1970s. If global warming makes the Sun Belt too sunny and unlivable, perhaps what was old will become new again. Foresight, he says, will be the key. People who buy Detroit property today for next-to-nothing will look good if the city booms again. "Climate change will create big profit opportunities for insurance companies that are nimble enough to accurately price the real-time risk that policy owners (such as homeowners) face in different locations," he writes.

His oddly specific prediction: We're all going to eat dried fruit in the future. Kahn reasons that growers will want to hold inventory to deal with market fluctuations brought on by climate-related agricultural disasters, and dried fruit keeps.

How to Cool the Planet

Britain's Royal Society is celebrating its 350th anniversary this year, and even such an august scientific organization is no longer putting its stock in humanity's ability to curtail its CO2 emissions in time to prevent disaster. Last year the society complied a full report on plan B schemes--ways to tinker with the planet on a grand scale to save us from ourselves. Ideas to hack the Earth are now mainstream, as seen in the mass market books by Jeff Goodell and Eli Kintisch that hit the now-familiar plans: seeding the sea with iron to encourage the growth of carbon-sequestering plankton, seeding the clouds with aerosols to reflect away more sunlight, seeding space with giant mirrors to cut the amount of solar energy that reaches our little blue marble.

"The rising interest in geoengineering is driven less by mad scientists than by spineless politicians," Goodell writes. He, like the scientists at the Royal Society, would prefer that we address our carbon emissions proactively and many years down the road look back at the idea of sci-fi scale planet tampering as sheer madness. But, we probably won't. We, most likely, will wait until the last minute and then splurge to save ourselves. However, he writes, geoengineering isn't a quick fix. It buys us some time, but we'll still have to live with the world we've created.

Fracking Nation

Environmental ?concerns over a ?controversial mining method could put America's largest ?reservoirs of clean-burning natural ?gas beyond reach. Is there a better way ?to drill??

Tracy Bank was concerned. A geochemist, she makes her living studying how water interacts with rocks. And four years ago, when she arrived at the State University of New York at Buffalo, water was definitely interacting with rocks.

Buffalo is perched on the edge of the largest known reservoir of natural gas in America, a geologic formation known as the Marcellus Shale (pdf). The 95,000-square-mile slab, which lies under sizable portions of West Virginia, New York, Ohio, and Pennsylvania, could contain up to 500 trillion cubic feet of natural gas—enough to meet the nation’s natural gas needs for at least two years. Owing to this bounty, the areas above the shale are now in the grip of an unprecedented gas-drilling boom. The gas is extracted using a method called hydraulic fracturing, or fracking, a technique that involves pumping millions of gallons of water laced with ?chemicals deep underground to blast open the shale and release the gas trapped inside. The blasting is what got Bank worried.

Fracking has already drawn considerable scrutiny from environmental groups, unhappy homeowners, and teams of lawyers who blame the drilling method for polluting pristine rivers, turning bucolic farmlands into noisy industrial zones, and leaking enough methane to make ordinary tap water as flammable as lighter fluid. Bank is now bringing attention to yet another problem: radiation. Her research shows that high-pressure fluids striking the shale could dislodge naturally occurring radioactive compounds such as uranium and strontium, putting groundwater at risk of contamination.

Climate Science Wins a Round, But the Campaign Goes Poorly

In 2010 climate researchers struggled to move past the controversy that had rocked their community the year before. The accusation was incendiary: that scientists had grossly exaggerated the case for global warming by manipulating their data. The evidence was murky: more than 1,000 e-mails and documents exchanged by leading climate scientists, which had been hacked from their computers. But the verdict, as delivered by five separate investigations, was clear: The accused scientists were exonerated of any misconduct.

Three British investigations focused on the Climate Research Unit at the University of East Anglia, site of the stolen e-mails and a leading center for studying global warming. Meanwhile, two American panels examined the integrity of Michael Mann, a prominent climate researcher at Pennsylvania State University. All five groups concluded that none of the scientists had violated academic standards. “We find that their rigor and honesty as scientists are not in doubt,” declared a report headed by Sir Muir Russell, chair of one of the British investigations.

Lisa Graumlich, a University of Washington paleoecologist who served on another British group, led by Lord Ronald Oxburgh, looked into a broader charge: whether there was something “fundamentally broken” about the integrity of the Climate Research Unit. Such charges, she determined, were baseless. On the contrary, as the Ox­burgh panel’s final report (pdf) put it, the attacks leveled against the scientists “showed a rather selective and uncharitable approach to information made available by the CRU.” Michael Mann was more blunt. In an e-mail to me, he asserted that the people who attacked his work “don’t have the science on their side, and they surely know this. So smears and disinformation are all they have left.”