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A "bathtub ring" is left around Lake Mead, a Colorado River reservoir, as water levels fall (courtesy of flickr user loop_oh)

First, check out my story on the Colorado River in the October issue of Smithsonian:

From its source high in the Rocky Mountains, the Colorado River channels water south nearly 1,500 miles, over falls, through deserts and canyons, to the lush wetlands of a vast delta in Mexico and into the Gulf of California.

That is, it did so for six million years….

The river has become a perfect symbol of what happens when we ask too much of a limited resource: it disappears. In fact, the Colorado no longer regularly reaches the sea.

But the Colorado River isn’t the only waterway that humans have manipulated to such a great—and devastating—degree. A new study published in today’s Nature reports that nearly 80 percent of the world’s population is facing threats to freshwater security because of damage to riverways caused by stressors like pollution, dams, agriculture and invasive species.

The list of regions most under threat is long and includes: much of the United States, Europe and central Asia; the Middle East, the Indian subcontinent and the eastern half of China; and desert belts in both the northern and southern hemispheres. “A strikingly small fraction of the world’s rivers remain unaffected by humans,” the scientists wrote. Those areas tend to be remote and unsettled.

The threat goes beyond the issue of freshwater availability. The researchers found that what humans are doing to river ecosystems has put thousands of species at risk and endangered the biodiversity of 65 percent of the habitats associated with the world’s rivers.

I sometimes feel like a broken record here. Yesterday, it was the message that a fifth of plant species are threatened with extinction. Earlier, a prediction that one in five lizard species could be extinct by 2080. Scientists keep showing us how we are messing up the world around us and how that is harming us. In the most recent study, they’re even kind enough to give us suggestions on how to prevent the worst from happening—better land use mangement and irrigation are a couple of examples—and explain that this would save money in the long term. But can we change our fate? I don’t know.

The snowdrop (Galanthus nivalis) is listed by the IUCN as Near Threatened (image credit: RBG Kew)

One in five plants are threatened with extinction, according to a new study. And we’re to blame.

Scientists from the International Union for the Conservation of Nature (IUCN), London’s Natural History Museum and the Royal Botanic Gardens, Kew evaluated 7,000 plant species (out of a known 380,000 species) and assessed their conservation status and the reasons why threatened species are in danger. Twenty-two percent of the species for which they could carry out an assessment were classified as threatened with extinction, and habitat loss was the main reason for species’ declines, most often from conversion into farmland.

“This study confirms what we already suspected,” says Stephen Hopper, Kew’s director, “that plants are under threat and the main cause is human-induced habitat loss.”

Gymnosperms, non-flowering plants that include conifers and ginkgo trees, were the most threatened group in the study. And tropical rain forests were the most threatened habitat; most threatened plant species grow in the tropics.

Reading evaluations of threatened species sometimes feels like deja vu. So many species are threatened (plants aren’t quite the worst off—greater percentages of amphibians and corals are in danger), especially in the tropics, and habitat loss is often a major factor. But the decline of plants should be a wake-up call. Humans cannot survive if the plant species that feed, clothe and fuel us disappear.

“We cannot sit back and watch plant species disappear—plants are the basis of all life on earth, providing clean air, water, food and fuel,” Hopper says. “All animal and bird life depends on them and so do we.”

Is this your view of a scientist? (via wikimedia commons)

The scientists we feature in Smithsonian magazine are sometimes perplexed about why we’ve included details about their personal lives. It’s the science that matters, they say, so why would anyone care about their art collection or television-director father? Bob Hazen, the mineralogist at the heart of our October story on the origins of life, had a similar reaction when he found out that the writer, Helen Fields, had included details about his weekend home and collecting habits. The answer to his “why” is found in the issue’s editor’s note:

Fields says the stories she most likes to report are about how science actually gets done—“how it works and the people who do it. I think science often seems like these grand ideas are handed down from on high,” she says. “But they come from people with dogs and kids and interests.”

That isn’t a surprise to anyone who has a scientist for a friend or relative. If all there was to a person was their research, lunch conversations would get boring and repetitive pretty fast. But if you don’t know a scientist personally, it might be easy to buy into the stereotype of the man in the white lab coat holding a brightly colored, bubbling test tube or flask (which is nothing more than dry ice in colored water, but it makes for a nice TV image) spouting research findings in dry, jargon-filled language.

It doesn’t take much, though, to show that stereotype is just a stereotype. (Sure, some scientists wear lab coats, but those bubbly, bright liquids are a rare find in the real world of science.) For example, after a group of seventh graders visited Fermilab, their drawings of scientists changed from being mostly white men in lab coats and glasses to a diverse group of men and women wearing regular clothes. And the PBS science show NOVA has been running a web series, “The Secret Life of Scientists & Engineers,” in which you can learn about scientists’ hidden passions, like rock music and Native American dance.

Science can be so interesting/perplexing/thrilling/(insert your own adjective) that the people doing the research sometimes become nothing more than background noise in a complex world. But the researchers behind the science are important and interesting parts of the story, too. And learning more about them can help to demystify science and get more people interested in it. That’s something we all should want.

Hannibal, a male clouded leopard at Smithsonian's National Zoo's Conservation & Research Center (photo courtesy of the National Zoo)

Members of the cat family (Felidae) are nearly all lone creatures and use meows and roars to communicate to potential mates over long distances. (Lions are the exceptions; they’re the only social kitty species.) Scientists have wondered why some calls are high pitched—like your housecat’s meow—or deeper, like a cheetah’s. Size would be the obvious answer, and research until now has shown that larger cats tend to have lower pitched calls. But a new study in the Biological Journal of the Linnean Society says that it’s habitat that matters more.

Gustav Peters and Marcell Peters, of the Zoological Research Museum in Bonn, Germany, examined the relationship between call frequency, a cat’s habitat and its place in the evolution of cats. The researchers found that cats that lived in open habitats like the African plains tended to communicate with deep-sounding calls. Kitties that lived in forested habitats, such as clouded leopards, produced high-pitched calls.

Their finding was unexpected because “most studies of sound transmission of animal acoustic signals found that lower frequencies prevail in dense habitats,” Peters told the BBC. High-frequency sounds can more easily become disrupted by the vegetation found in forests while low-frequency sounds travel less well in open spaces where they can be disrupted by air turbulence. Why cat calls seem to have evolved in such a contrary way will have to be the subject of further study.

(And if you’ve ever wondered why only lions, tigers, jaguars and leopards can roar, here’s why: Only those four species have an elastic ligament connecting bones that support the larynx in the throat. That ligament is necessary to produce a roar.)

A three-week-old Florida panther kitten (image copyright Science/AAAS)

Call them panthers, mountain lions, cougars or pumas, the Americas’ largest cat species has been dwindling in eastern North America for hundreds of years. They were extirpated from everywhere but some shrinking habitat in Florida between Naples and Miami. And even there, the panthers were not doing well. By the mid-1990s, the population consisted of just a couple dozen adult cats, and they were suffering from the problems of inbreeding: low reproduction rates, sperm quality and testosterone levels; heart defects; kinked tails; and high loads of parasites and pathogens. It wasn’t looking good for the Florida kitties.

A male Florida panther looks down from a tree (Image courtesy of Larry W. Richardson)

In 1995, conservationists tried to bolster the Florida population by introducing eight female panthers from Texas. The two subspecies used to intermingle, so transferring a few females would restore some of the natural gene flow. Fifteen years later, scientists are declaring the program a success. The addition of just a few new kitties to the gene pool resulted in a more diverse population that no longer suffered from the problems of inbreeding. And the population tripled in size. (The study appears in today’s issue of Science.)

Florida’s panthers, like so many cat species, still face serious challenges to their survival, including habitat loss and disease. But it’s heartening to see that relatively simple solutions—transferring a handful of cats combined with efforts to preserve habitat and reduce deaths from car accidents—can have such a positive effect on a population.

Earlier this week, the BBC announced the discovery of tigers in Bhutan living high above the treeline, far from where anyone had expected the cats could survive. Scientists hope to create a corridor connecting small, scattered tiger populations, such as this one in Bhutan, with others across much of Asia. The idea being that, like the Florida panthers, Asia’s tiger populations would get stronger from increased genetic diversity.

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