July 9, 2012
While in Sydney earlier this year, I stopped in at Australia Museum, the city’s equivalent of the Smithsonian Museum of Natural History, and learned a bit about the continent’s extinct megafauna. Australia didn’t have mammoths or saber-toothed tigers, but there were giant marsupials, such as the bear-like wombat Diprotodon and the thylacine (a.k.a. the Tasmanian tiger). On a tour of the museum, I came across a display that said that most of these mega-mammals had gone extinct tens of thousands of years before, the victims of either changes to the climate that led to drier conditions or human impacts, including hunting and landscape burning. The thylacine was the one exception to the megafauna story–it hung on until British colonization and then it was hunted to extinction.
But this story was incomplete it seems, though the museum holds no blame. A couple weeks after I returned to Washington, Science published a study addressing this very issue (for all the megafauna but the thylacine, but we’ll get to the tigers in a moment). Susan Rule of Australian National University and her colleagues analyzed pollen and charcoal in two sediment cores taken from a lake in northeast Australia to create a record of vegetation, fire and climate changes over the past 130,000 years. They also looked at spores of the fungus Sporormiella, which is found in dung and is most prevalent when there are large herbivores in the area.
With this record, Rule and her colleagues determined that there were two great climate upsets 120,000 and 75,000 years ago, but the megafauna had no problems surviving those times. However, between about 38,000 and 43,000 years ago, Sporormiella spores decreased in the record, likely reflecting the disappearance of large herbivores during that time, which correlates with the arrival of humans on the Australian continent. Following the megafauna disappearance, the cores displayed an increase in charcoal, an indicator of a greater frequency of wildfires. “The fire increase that followed megafaunal decline could have been anthropogenic, but [the record suggests] instead that relaxation of herbivory directly caused increased fire, presumably by allowing the accumulation of fine fuel,” the authors write. The lack of herbivores in the Australian ecosystem led to changes in the types of plants growing there–rainforests were replaced by sclerophyll vegetation that burns more readily.
So, the likely story is that humans came to Australia around 40,000 years ago, hunted mega-mammals to extinction, which spurred changes to the vegetation growing in the area and resulted in an increase in wildfires.
But what about the thylacine? Only one species, Thylacinus cynocephalus, survived to more recent times, though it disappeared from much of New Guinea and mainland Australia by about 2,000 years ago, likely due to competition with humans and, maybe, dingoes. A few pockets of the species were reported in New South Wales and South Australia in the 1830s but they were soon extirpated. The thylacine’s last holdout was the island of Tasmania, but locals quickly hunted them to extinction, certain the thylacines were responsible for killing sheep. The last known thylacine in the wild was killed in 1930, and the last one in captivity died in 1936. They were declared extinct in 1986.
Recent research has helped to flesh out the thylacine’s story: A study published last year in the Journal of Zoology found that the thylacine’s jaw was too weak to take down an animal as large as a sheep–the animals had been hunted to extinction for crimes they were biologically unable to commit. Though is appears that the hunting may have simply hastened the inevitable. Another study, published in April in PLoS ONE, found that the thylacine had low genetic diversity, which would have made the species more susceptible to disease and further declines, possible leading to extinction.
But is the thylacine really gone? Tasmanians occasionally claim to have seen a thylacine or found evidence of one in the area–in January, for example, two brothers found a skull they claimed came from a thylacine–but none of these sightings has ever panned out with real evidence, such as a clear photo or video. Zoologist Jeremy Austin of the University of Adelaide tested DNA in alleged thylacine droppings collected between 1910 and 2010 but none were actually from a thylacine.
Australian Museum scientists had planned to attempt cloning a thylacine, but those efforts were abandoned years ago. So, for now at least, all of Australia’s mega-mammals will stay extinct.
July 2, 2012
The Washington, DC area has seen its fair share of destructive storms–we get hurricanes, tornadoes and even the rare snowpocalypse. But on Friday night we got hit with another type of storm–one that I’d never heard of–called a derecho (pronounced ”deh-REY-cho”).
The storm swept through the area late Friday evening, bringing an incredible amount of thunder and lightning, winds up to 80 mph and sheets of rain. By morning, hundreds of trees had been blown down, millions were left without power and several people were dead. Netflix, Pinterest and Instagram had all been taken down by Amazon server outages caused by the storm. The Smithsonian Folklife Festival had to shut down for a day to clean up the mess. We were all left wondering, “what in the world had happened?”
The stifling heat wave that we’d been suffering through, which had stretched from the Midwest through the mid-Atlantic to the Southeastern United States and brought temperatures in excess of 100 degrees Fahrenheit, was to blame for the fast-moving band of thunderstorms. The Capitol Weather Gang explains:
As this stifling air bubbled northward, clashing with the weather front draped from near Chicago to just north of D.C., thunderstorms erupted. They grew in coverage and intensity as they raced southeast, powered by the roaring upper level winds and fueled by the record-setting heat and oppressive humidity in their path.
The coverage and availability of this heat energy was vast, sustaining the storms on their 600 mile northwest to southeast traverse. The storms continually ingested the hot, humid air and expelled it in violent downdrafts – crashing into the ground at high speeds and spreading out, sometimes accelerating further.
Though unfamiliar to those of us here on the East Coast, derechos occur more commonly in the Corn Belt, which runs from Mississippi into the Ohio Valley, but even there they are relatively infrequent. They can wreak their havoc at any time of the year but are most likely to occur during May, June and July. Derechos get their starts in curved bands of thunderstorms called “bow echoes,” which are perhaps better known for their ability to spawn tornadoes. But instead of rotating cells of winds, derechos blow and travel in straight lines.
Derechos have a long history here in the United States. The term “derecho” was coined by University of Iowa physics professor Gustavus Hinrichs in an 1888 paper in the American Meteorological Journal in which he illustrated the path of such a storm that had crossed over Iowa on July 31, 1877. The storm’s straight path across the state gave Hinrichs the inspiration for the storm’s name–”derecho” means “straight” in Spanish. But path alone isn’t quite enough for a storm to qualify as a derecho; wind speeds must also reach a minimum of 57 mph.
Given that derechos are associated with warmer weather, could they become more common as the United States heats up due to climate change? Tom Kines, senior meteorologist at AccuWeather.com, told the Guardian: “If indeed we are seeing global warming, then it will certainly increase the risk of something like this happening again.”
June 27, 2012
What’s more magical than a firefly light show on a warm summer night? Just remember that if you catch fireflies, you can keep them in a jar (with a lid punched to let in air and a moistened paper towel on the bottom) for only a day or two before you need to set them free.
(1) There are more than 2,000 species of fireflies, a type of beetle. Despite their name, only some species produce adults that glow. Fireflies in the western United States, for example, lack the ability to produce light.
(2) Males that do glow use their flash to attract females. Each species has its own pattern of light flashing.
(3) In some places at some times, fireflies synchronize their flashing.
(4) Firefly light can be yellow, green or orange.
(5) Firefly larvae may glow, even some that live underground or under water. They use the light to communicate to predators that they aren’t tasty (they produce unpalatable, defensive steroids for protection).
(7) A few firefly species are also carnivorous as adults. They don’t eat snails, though—they eat fireflies of other genera.
(8) Fireflies are among the many species that are bioluminescent, meaning that they can produce their own light.
(9) A chemical reaction within the firefly’s light organ produces the light—oxygen combines with calcium, adenosine triphosphate (ATP—the energy-carrying molecule of all cells) and a chemical called luciferin, when an enzyme called luciferase is present.
(10) The light is the most efficient light in the world. Nearly 100
One hundred percent of the energy in the chemical reaction is emitted as light.
(11) Luciferase has proven to be a useful chemical in scientific research, food safety testing and forensic tests. It can be used to detect levels of ATP in cells, for example.
(12) When luciferase was first discovered, the only way to obtain the chemical was from fireflies themselves. Today, synthetic luciferase is available, but some companies still harvest fireflies, which may be contributing to their decline.
(13) Other factors that may be contributing to firefly decline include light pollution and habitat destruction—if a field where fireflies live is paved over, the fireflies don’t migrate to another field, they just disappear forever.
(14) Observing fireflies in your backyard can help scientists learn more about these insects and why they’re disappearing.
June 25, 2012
If you could put a wild cheetah up against a greyhound in a race, the cheetah would win, no problem. After all, the cheetah’s top recorded speed is 65 mph, and the cats are thought to be capable of much more. Greyhounds top out around 40 mph, fast enough to provide a show for bettors at the racetrack, but no match for the cats.
But why should that be? Cheetahs and greyhounds are about the same size, and they’ve got similar body shapes. In a new study in the Journal of Experimental Biology, biologists from the University of London made a series of measurements of cheetahs from a zoo in England and a cheetah center in South Africa and greyhounds that had retired from their racing careers in England to figure out why the cats are faster. The animals were filmed with high-speed cameras as they raced along a 100-yard track chasing a mechanical lure. Some of them were also trained to run across a force plate.
The cats and dogs had several differences in how they ran–at any given speed, the cheetahs used longer strides and fewer of them than the greyhounds. The cats also supported their weight differently, putting more of it on their hindlimbs, which may enhance their grip and allow for better acceleration and maneuvering while leaving their forelimbs free to capture prey.
But the scientists can’t say definitively that they’ve found out why cheetahs are faster because these cheetahs weren’t. They topped out at 39.8 mph, never reaching anywhere close to 65 mph and not even running faster than the greyhounds in the study. “They have lived in a zoo for several generations and have never had to run to catch food. They have probably never learned to run particularly,” says Alan Wilson, one of the project scientists. The greyhounds, meanwhile, were trained for races, encouraged to develop to run at the fastest speeds possible.
Io9 called this a failed experiment, since the captive cheetahs were so slow. But I would argue otherwise–the researchers identified plenty of differences between the two animals that may explain the cheetah’s edge, which was the point of the study. That said, it would be nice if they could try this with with wild cheetahs, which Wilson says they will try. Though I suspect that wrangling one of those speedy cats will provide new challenges to the researchers.
June 20, 2012
Would you go on a mission to Mars? The Dutch startup company Mars One is planning to establish the first Mars colony in 2023, starting with four individuals and adding more people every two years, funded by turning the whole endeavor into a reality TV show.
It’s just the latest plan to colonize the Red Planet, but I’m doubtful it will happen. There’s the expense, for sure, and the trials of trying to convince anyone to go on a one-way journey with just a few other strangers (what if you don’t get along? It’s not like you can leave). And then there’s the radiation problem.
Out in space, there are gamma rays from black holes, high-energy protons from the Sun, and cosmic rays from exploding stars. Earth’s atmosphere largely protects us from these types of radiation, but that wouldn’t help anyone traveling to Mars. They would be exposed to dangers that include neurological problems, loss of fertility and an increased risk of cancer.
NASA scientists calculated in 2001 that a 1,000-day Mars mission would increase the risk of cancer somewhere between 1 and 19 percent. If the risk is on the lower end, then the outlook for Mars might be pretty good, but if it’s higher, then NASA, at least, wouldn’t send people (there’s no telling what a reality TV show might do). A 2005 study found even more to worry about—the radiation would be high enough to cause cancer in 10 percent of men and 17 percent of women aged 25 to 34 if they were to go to Mars and back.
The easy solution would seem to be to shield the vessel that carries the humans to Mars, but no one has figured out how to do that. When the thin aluminum currently used to build spacecraft is hit with cosmic rays, it generates secondary radiation that is even more deadly. Plastic might work—the shields on the International Space Station are made of plastic—but it’s not 100-percent effective. One scientist has suggested using asteroids to shield a vessel traveling between Earth and Mars. But somehow I don’t think Mars One is going to make that one work within a decade.
Or they could just send old people—a solution proposed a couple of years ago by Dirk Schulze-Makuch of Washington State University and Paul Davies of Arizona State University. “This is not a suicide mission. The astronauts would go to Mars with the intention of staying for the rest of their lives, as trailblazers of a permanent human Mars colony,” Schulze-Makuch and Davies wrote in the Journal of Cosmology. Loss of fertility wouldn’t be an issue for older astronauts and the radiation wouldn’t increase their lifetime cancer risk too much (since they’re already near the end of their lives).
That may be a solution more suited to NASA than Mars One, however, since television casting departments would probably want someone more like Snooki than Snooki’s grandma.
Editor’s note: In other Mars news, NASA is preparing for the August 5 landing of its massive unmanned science laboratory, Curiosity. The seven minutes between when the rover hits the top of the atmosphere and when it touches ground are the riskiest moments of the whole mission. The video below shows a few of the hundreds of things that need to go just right: