It was dusk and mildly chilly in Rome when I stepped out of Roma Termini, the city’s busy central train station, and heard relentless screeching noises from above. I looked up to see thousands of birds covering the treetops like bees on a honeycomb. A cloud of them sprang from one tree only to quickly dissolve into another. Bigger clouds of black specks curled and twisted even higher, over rooftops and looming cranes.
Starlings. Thousands of them, and just a small portion of the 1 to 5 million that overwinter in Italy’s capital.
To nature lovers, starling swarms – called “murmurations” – are fascinating and beautiful. Stunning videos of murmurations have captured the admiration of the Internet. They’re also a favorite example of swarming science, each individual bird following cues on speed and direction from its neighbors to form a massive, swirling shape in the sky.
Life is scarce here in the heart of the Atacama Desert. Nothing grows. Rain calls twice a century, and never leaves a message. This is one of the world’s most desiccated landscapes, a 600-mile strip along Chile’s western coast that stretches from the Pacific Ocean to the Andes Mountains. And, oh yeah: It’s been this way for about 150 million years.
If you were an early colonizer of the Americas, making your way down from the Bering Land Strait during the Last Ice Age, the Atacama would have loomed before you as a stretch of pure wasteland. No food, no shade, no water: this would be the place to avoid. You’d be better off traveling down the coast, or even braving the highlands of the cooler Altiplano to the east. That’s why, when archaeologists go out looking for early human settlements, they tend to write off this barren deathtrap. Harsh and inhospitable, they say, the Atacama was a barrier to life.
But was it? Read the rest of this entry »
Once upon a time in Borneo, everybody was dying of malaria, so they sprayed a lot of the insecticide DDT (dichlorodiphenyltrichloroethane), which killed the mosquitoes that transmitted the disease. Cases dropped, but inexplicably, peoples’ roofs started caving in. DDT had also killed wasps that kept the caterpillar population in check, so the caterpillars ate the roof thatch. Geckos ate the wasps, and cats ate the geckos. Cats started dropping dead, and the rat population flourished, which lead to an outbreak of the plague. So, to solve the problem, health officials parachuted cats into Borneo.
Or, at least that’s how the story goes.
I first heard of this ecological fable — nicknamed “Operation Cat Drop” — from a friend who liked to break it out at dinner parties. Frankly, it sounded a bit ridiculous. So, ridiculous in fact, that somebody could very well have made it up, and some have argued that the tale is just that: fiction. The cat story started popping up in print in the 1960s, making appearances in The New York Times, Time, and Natural History magazine. In the late 1960s and early 70s, biomagnification and the ecological impacts on avian species took center stage in the public debate over the safety of DDT. But, I’ve always wondered whether there was any truth to the cat story, which did come up in congressional hearings on DDT use. Turns out, there’s more than you’d think. Patrick O’Shaughnessy, an environmental engineer at the University of Iowa, did some digging and found kernels of truth from which the cat drop myth probably grew. His work was published in the American Journal of Public Health. Here’s what we know…
In the 1950s, the World Health Organization (WHO) launched a global effort to eradicate malaria, following successful campaigns in the United States, Europe, and Venezuela. Resistance to the insecticide had popped up in some mosquitoes, but they were very optimistic. Perhaps a little too optimistic. From 1952-55, in the Sarawak region of Borneo, malaria control teams sprayed DDT, benzene hexachloride, and briefly dieldrin twice a year inside local long houses with thatch roofs. At first, the program enjoyed some success. From 1953 to 1955, the fraction of local mosquitoes carrying the disease fell from 35.6% to 1.6%.
As my devoted readers no doubt realize by now, I’m on a bit of a Rachel Carson kick. I wrote a blog post and produced a radio show about her last fall, and I’m working on an article about her for Johns Hopkins magazine (Carson got her master’s degree at Hopkins). Why this slight Carson obsession? It started with the 50th anniversary of Silent Spring, which got me wondering, as a science writer, how someone armed only with scientific knowledge and words could have such influence. I believe we science writers sometimes sell ourselves short in terms of what we can accomplish, especially in this age of disposable Web writing. Carson can remind us of the potential of writing for impact, not just for mouse clicks.
In 1953, Rachel Carson spoke at a symposium at the American Association for the Advancement of Science’s annual meeting. The topic was the sea frontier. Unlike the other eight panel members with whom she shared a stage, Carson was not a research scientist; she had until recently worked as a staff writer for the US Fish and Wildlife Service. (She was also the only woman on the panel).
At the conference she talked about the book she was writing, The Edge of the Sea, which would be based mainly on her observations, and less on the work of other scientists, as her previous books had been. Carson had scientific training, but it was her writing that earned her the speaking slot: her 1951 book The Sea Around Us had made her the nation’s most famous writer about the oceans and perhaps about all of science.
Although Rachel Carson spent almost her entire career writing about the sea, she is remembered today for her one book about things that happen on land. That book, Silent Spring, awoke the American public to the dangers of many common pesticides, and launched the environmental movement. But while the birth of environmentalism would not have happened exactly when it did and how it did without Carson’s advocacy, it would have happened: Americans would not have tolerated smoggy cities, burning rivers, and toxic chemical clouds for much longer. “I suspect that the audience [of Silent Spring] was close to an environmental awakening,” said Jane Lubchenco, a marine biologist and past head of the US National Oceanic and Atmospheric Administration, at a symposium dedicated to Carson at this year’s AAAS meeting. “No doubt [Carson] catalyzed it, but the ground was fertile.”
If you’re a writer looking for a good symbol, consider the tree. The author of Genesis did, twice: he placed the tree of life and the tree of knowledge front and center in the Garden of Eden. Homer did, too: When his hero Odysseus returned home after twenty years of war and travel, needing to prove his identity to his skeptical wife, Penelope, he used a tree. “Move our bed into the hallway,” Penelope told her servant, laying a trap. (I’m paraphrasing here.) “It can’t be done,” Odysseus protested. “I carved a post of that bed from a living olive tree.” Only then did Penelope believe the strange man was really her husband, as steady as that post.
Trees have long impressed us with their steadfastness; in fact, some trees from Biblical times are still with us today. But a new story I read recently casts trees in a different role. I first came across a version of this story in a paper published in the journal BioScience in 2007. The authors looked at where trees live using a tool known as a “climate envelope,” which is a line drawn on a map around the entire range where a given species is able to survive. The scientists compared climate envelopes for 130 trees under 2007 conditions to those predicted for the end of the century, using the same computer models that the UN’s Intergovernmental Panel on Climate Change bases its forecasts on. On average, they found that trees’ envelopes moved 700 kilometers north, nearly the distance from Memphis to Chicago.
So does that mean our trees will be moving north as things get warmer? Traveling trees can make great stories: Shakespeare’s Macbeth was vanquished when Birnam Wood moved a few miles to his fortress at Dunsinane Hill. And it would be dramatic indeed if future northern woodsmen and women hunt deer among sprawling live oaks and big-leaf magnolias instead of spruce and pine trees. But the scientists who wrote the BioScience paper noted that actual trees are unlikely to track their climate envelopes’ northward migration in the coming years, at least if unassisted by humans. Trees can “move” up to a few miles in a generation, by setting their seeds aloft in the wind or encasing them in a shell so they can survive a trip in the gut of an animal. But tree generations are long, and most seeds land close to home. Sugar maples, for example, lead a chaste adolescence, and don’t start making seeds until the age of 22 or so. They then send out seeds attached to little helicopters, which spin and float at most the length of a football field before touching down. Scientists estimate trees’ maximum migration rate to be around 50 kilometers per century, with many traveling far slower—a tortoise’s pace in this race.
The rainforests of Madagascar highlight, with great clarity, the power the physical environment exerts on evolution. As a study abroad student in the fall of 2006, I was researching the sleep habits of the brown mouse lemur in Ranomafana National Park, a protected tract of land in the high rain-forested mountains of Madagascar’s east coast.
During the day, I bushwhacked through this dense rainforest, attempting to locate two or three of these nocturnal mouse lemurs, who had been fixed with tracking collars, as they slept. In the evening, I waited for the lemurs to wake up so that I could record the size and consistency of their sleeping groups.
One day, as the sun was setting on the bamboo, ferns, and mossy trees of the forest, I watched as multiple lemurs suddenly emerged and attempted to rouse the female lemur I was tracking from her sleep. These lemurs, all male, were attempting to mate with my study subject.
Female brown mouse lemurs, and indeed many species of female lemurs in Madagascar, are only receptive to mating for a very short period of time each year. To make the most of this short mating season, the male lemurs, deathly focused on a single goal, spend the winter months growing testicles that end up being a quarter of their entire body mass. It is no question, given the males’ months of stored hormonal energy, that there would be a significant interest in my study subject that day. Read the rest of this entry »
An Ecologist’s Battle
Invasive plants are the ones that don’t play well with others. They steal their neighbors’ food and water, and they refuse to share. And you’ll see them all around the Baltimore area: vines smothering stream banks and blanketing entire trees; the brambles tangling and choking the understory; the annuals carpeting the forest floor. They’re the botanical version of an alien invasion.
Or, they can make nice additions to our gardens. Vanessa Beauchamp, an invasive plant ecologist, tells me about a hiker who came upon her research team in a park outside Baltimore. “She asked us what we’re doing, and we explained we’re studying this invasive grass that we think is a really big problem, and we’re trying to understand more about its ecology. And she says, ‘Oh my gosh that stuff is so pretty, I dug up a bunch and planted it in my yard.’”
The plant was wavyleaf basketgrass, a native of Europe and Asia. It sounds innocent enough, like a prairie grass that might rustle softly in a summer breeze. And it’s pretty enough, too, with intensely green leaves that unfurl on either side of a central shoot, and a head of spiky seeds that sticks up a foot or so above the ground. The seeds are the problem, though—they hitch rides on pant legs, animals, basically anything that comes by—and disperse to new locations that way. The plant can grow just fine even in the deep shade of a mature forest. In Patapsco Valley State Park, where it was discovered in the mid-1990s, it now carpets acres of forest floor. The Maryland Department of Natural Resources launched a war on it but lost, due to lack of funding. Now the plant has spread to other parks in the area, and experts like Beauchamp fear there may be no containing it.
But if it’s green and pretty, what’s the worry? Beauchamp says it’s all about the community of life in the forest. Exotic plants like basketgrass are newcomers to this community, so nothing has evolved to eat them—a lesson Beauchamp has learned firsthand. “When we worked on wavyleaf basketgrass, we literally spent the summer crawling around on the forest floor. I figured we would just be tick city,” she says. Instead, of the half dozen people on her crew, “We got one tick between all of us. I mean, that’s insane.”
Few of us would be sad to see the ticks disappear. But without the thousands of insects, worms, mites, and spiders that make their living in the forest understory, the woods would be a vastly different—and less lively—place. “Nobody’s looked at how insects are able to use this grass…We see very little insect damage on the grass at all. We see no deer damage,” says Beauchamp. “If there’s no insects eating them, there’s no birds eating those insects, and up and up and up.”
A wavyleaf basketgrass army
Beauchamp moved to Towson University in Baltimore from Arizona five years ago. For an invasive species expert, the move meant more than packing and unpacking boxes—it meant abandoning one biome and learning a new one. Luckily for Beauchamp, Maryland has no shortage of invasive plants, and it didn’t take her long to find one she could claim as her own. “I came across this wavyleaf basketgrass that nobody knew anything about, and I said ‘All right. That’s mine.’”
One of the questions Beauchamp is asking is how aggressive the grass actually is. Many writers on the Web claim it crowds out other plant species, but Beauchamp wonders whether it might just take advantage of openings on the forest floor, especially those created by Maryland’s massive plant-munching deer population. To test how competitive wavyleaf basketgrass is, her research team is growing the grass in a greenhouse alongside other native and invasive grasses, and seeing which puts on the most weight. They hope to have results soon.
Beauchamp is also trying to figure out how the seeds disperse. And she thinks she’s found a suspect: pet dogs. When hikers let their dogs run through a basketgrass patch, they “come out looking like a chia pet,” says Beauchamp. Fore more precision, she had her students count the number of seeds sticking to a dog. “We found that a single dog going through this grass for 30 seconds can get over 2000 seeds on it,” she says.
Dogs may not be the only culprit, though; Beauchamp also has her eye on deer. She and her team tested this hypothesis in a rather macabre way: they got severed deer legs from a meat processor, and “walked” the legs through a basketgrass patch. Again, the legs came out covered in seeds.
But Beauchamp admits she can’t answer the most important questions: how much wavyleaf basketgrass is there, and where? “I have absolutely no number to tell you in terms of how many acres this grass covers in Maryland,” she say. “None.” Unfortunately, when she wrote a grant to fund a project that would get at such a number, she got caught in a chicken-and-egg situation: the review panel rejected the proposal, saying Beauchamp and colleagues hadn’t demonstrated how much of a threat the grass poses. “But if I don’t have any money to study it, how can I demonstrate that?” she asks.
So like any good scientist, she’s gotten creative. She mustered a “wavyleaf basketgrass army” of undergraduates and high school teachers to go out and count plants in different locations. She’s also teaming with a Catonsville Community College professor who’s developing a smartphone app that will allow anybody to report a basketgrass sighting, along with GPS coordinates. Beauchamp is hoping the data her team and concerned citizens collect will convince funders and policymakers that the grass is worth studying on a larger scale.
Beauchamp vs. basketgrass
Beauchamp versus basketgrass is the latest chapter in a long saga of human battles against invasive plants. And so far the invaders have scored most of the victories. Here in Maryland, English ivy, Japanese stilt-grass, mile-a-minute weed (an Asian species known as “kudzu of the north”), and other exotics have become far more familiar sights in our parks and forests than most of our native plants. Will wavyleaf basketgrass join this list of dubious characters, or could this be the time we outsmart the weed?
(All photos courtesy of Vanessa Beauchamp)