The Best American Science and Nature Writing 2014 (35 page)

Meanwhile, the invincible creatures nearly doubled their range, and some scientists speculated that the insecticide was the cause. The poison often eliminated all the ant species where it was applied, giving
S. invicta
, which is thought to be a better colony founder, a chance to become the dominant type upon recolonization. The secrets of their survival are not entirely known, but Tschinkel thinks it has something to do with large colonies, large numbers of alates, large dispersal distances, and a long mating flight season.

The fire ant front line runs through the middle of Tennessee. I continued north on the ants' path and pulled off the highway in McMinnville, the heart of the state's nursery industry and just inside the line. Here, nursery growers have to douse plants' roots, where newly mated queens sometimes cling undetected, with chlorpyrifos, a toxic and expensive insecticide. Tommy Boyd, co-owner of Boyd & Boyd Nursery, told me his workers did the task while wearing gloves and respirators. He refused to touch the stuff himself because the insecticide gave him horrible headaches. “I don't want to die over some chemical,” Boyd told me.

I drove down a windy lane a short time later that brought me to Tennessee State University's Otis L. Floyd Nursery Research Center. Here I spoke with a gentle entomologist in a flannel shirt named Jason Oliver, who works on a less destructive and more natural ant eradication method: a project to introduce phorid flies, which prey on the ants back in Pantanal. In the late 1990s USDA researchers went to South America to capture different species of phorid flies, which they studied at an Animal and Plant Health Inspection Service (APHIS) lab in Gainesville, Florida, to determine the best one to introduce to various parts of the American South. Oliver's phorid flies are shipped from the lab to be released in Tennessee.

Phorids lay their eggs in the fire ant's thorax, and when the eggs hatch, the ant's head falls off.
⁷
Oliver showed me a video he had filmed in a petri dish, of a fly implanting eggs in an ant. A tiny dot buzzed about some ants; in the blink of an eye it brushed one of them, then continued flying. In that moment the fly had injected the eggs. It happened so quickly I asked Oliver to replay the video. It seemed like a perfect solution. But as impressive as the tiny fly was, it wasn't going to decapitate a whole colony, just make ants more scared to leave their nests. “We're always going to have fire ants,” Oliver told me. “There is no way to eliminate them.”

Weaving through rolling hills dotted with nurseries, I drove northwest from McMinnville, skirting the
S. invicta
front line: To the south, elementary schools, nursing homes, and greenhouses were being invaded, while to the north, the land was, supposedly, fire ant–free. The road took me through the area inundated in the catastrophic floods of May 2010. In Nashville, the Cumberland River rose 33 feet, flooding much of the city, including the Country Music Hall of Fame, the Grand Ole Opry House, and an untold number of fire ant mounds. Contrary to expectations, the ants didn't drown. Instead, they metastasized further.

The ants would have been well prepared, Louisiana State University entomologist Linda Hooper-Bui explained to me. In their homeland the Pantanal floods happen annually, so they learned to raft. As waters rise, ants evacuate lower tunnels and move higher in their mound, eventually gathering on top. Using hooks, called tarsi, on the tips of their legs, ants latch on to one another and create rafts. Late-stage larvae are covered in hooklike hairs that trap air, encasing them in bubbles. Worker ants stack these larvae three to five thick, forming pontoons that keep the rafts afloat. They place the queen in the middle with pupae and early-stage larvae, which don't have the crucial hairs to form the bubbles. Except for the clumps of eggs that workers carry in their jaws and a small amount of liquid food stored in their bodies that will last only a few days, the ants bring nothing aboard. Moreover, as the raft sets off, tipped into the water by the workers, they fling male alates overboard. If the raft is afloat longer than four days, the ants will begin to eat the brood—although not the ones used to make the raft. Rafts can hold together for as long as twenty-one days, surely long enough to survive the swollen Cumberland River.

Or at least this is what Steve Powell, an entomologist with the state of Tennessee, believes. In February of this year he received a call reporting fire ants in Cumberland City, a remote town about 80 miles north from Nashville and far above the front line. “There's no rhyme or reason why they should be there, so far from other fire ant infestations,” Powell said. “If I had to guess, I'd say it was the flood.”

Continuing my journey, I drove farther north into Cumberland City—a ramshackle collection of vine-ensnarled clapboard homes and shuttered storefronts on steep forested hills above the Cumberland River. On the edge of town sat a massive Tennessee Valley Authority coal plant with four 1,000-foot-tall smokestacks, some of the largest on earth. Beside the plant was a small restaurant with foggy windows, where farmers in overalls sat at low tables gobbling catfish and pork chops. I was looking for someone to speak with about the ants, expecting a thrilling validation of Powell's rafting theory. Instead I found an unsurprising surprise: Bailey Gafford, a weatherworn cattle farmer in mud-splattered boots, told me fire ants had been in Cumberland City since before the floods. He even suggested an innovative method of eradication I hadn't heard before: “Put snuff around the mound. They come out and you set 'em on fire.”

On my way out of Cumberland City I stopped at a Civil War cemetery, where wildflowers cloaked weather-beaten tombs, and atop a small hill stood a dozen crude cabins, campground for a long-forgotten battle. Our own battle against the ant was still in full swing, however, and it didn't look like we were winning. The war on
S. invicta
suddenly fit into a broader picture, that of the Insecticide-Military-Industrial Complex. It was around the time that President Obama announced, concerning the nation's ongoing war on terrorism, that we cannot remain on “a perpetual wartime footing.” The statement also seemed to apply to our war against the fire ants.

Besides, no matter how we perfect our tactics, these ultimate invaders seem to find new ways to advance. Somehow,
Solenopsis invicta
crossbred with
Solenopsis richteri
, another species that came from Pantanal by cargo ship to Mobile, in 1918.
⁸
Originally
S. invicta
drove out
S. richteri
, a less aggressive variety that prefers cooler weather and might have found the South too hot. But in the 1980s a hybrid of the two was discovered. No one knows exactly how the hybridization occurred—in certain parts of the Pantanal the two species' territories overlap, but they don't interbreed. Here they do, which is perhaps the most ominous sign. Purebred
S. invicta
don't survive more than three or four days in temperatures below freezing. Neither does
S. richteri.
But the hybrid survives freezing temperatures better than either pure species, according to a 2002 study in
Environmental Entomology.

Could a hybrid—or perhaps a hybrid of a hybrid—one day push that front line farther north, to Washington, DC, and Philadelphia? What about New York City, with its 8 million residents as clueless as I once was? Recently the ants were brought by ship from the United States to Australia and also Taiwan; from there they invaded China. According to a 2004 paper in
Biological Invasions
, fire ants could potentially infest France, Italy, Greece, Japan, South Korea, Mexico, Central America, and large parts of Africa and India. Is there a way for us to coexist with the creatures? I was still hopeful.

Upon returning to New Orleans I discovered that the fire ant mound in our backyard had quadrupled in size. It now towered above the grass blades like Kilimanjaro. As I stood dumbfounded, contemplating what to do, a potato bug ascended the northern flank, an agile alpinist indeed, somehow not inducing a swarm. I wanted to be like the potato bug and coexist with the mound, dance my fingers upon its slopes without getting stung, but I knew it was impossible. Even if Karen and I somehow avoided the nest, there were our animals to think of—the cats, the terrier, and Jazzy-B, who at that moment was watching me from inside with curious dog eyes. Last time he got off easy, but if he received hundreds of stings, the poison would surely overwhelm his little Chihuahua system. The choice was clear. I would have to eradicate the mound.

The abundance of killing choices was what puzzled me: Pit rival colonies against each other, grits, gasoline, a broom and gasoline, poison, and, if poison, which one? In the end I decided on a less ecologically invasive technique no one had mentioned except for Oliver—he muttered it under his breath toward the end of our conversation as if revealing a secret that embarrassed him: hot water. Ant Max and Spectracide Fire Ant Killer Mound Destroyer don't seem to want you to know about it.

With Jazzy-B and all the others safely inside, I emptied the cat litter box, dusted it with baby powder so the ants couldn't crawl up the sides, and shoveled the mound into it, quickly adding boiling water to fill it. A second pot of boiling water went into the open mound, to seep down into the interior tunnels and chambers, and then a third and a fourth, too, just to be sure I got the queen. There was an initial explosion of red, with numerous members of the brood being moved about, but the water cooked them instantly and, within the hour, the mound was dead.

I gathered my household armor and walked back toward the house, with far from a satisfying sense of achievement. I might have won this battle, but we were still losing the war. Inevitably, another mound would pop up. My “victory” was just a reprieve.

FROM
Conservation

 

E
ARLIER THIS YEAR
the Stanford human geographer Martin Lewis asked his students a simple question: How did they think U.S. family sizes compared with those in India? Between Indian and American women, who had the most children? It was, they replied, a no-brainer. Of course Indian women had more—they estimated twice as many. Lewis tried the question out on his academic colleagues. They thought much the same.

But it's not true. Indian women have more kids, it is true, but only marginally so: an average of 2.5 compared to 2.1. Within a generation, Indian women have halved the number of children they bear, and the numbers keep falling.

It's not that the population problem has gone away in India—yet. India has a lot of young women of childbearing age. Even if they have only two or three children each, that will still continue to push up the population, already over a billion, for a while yet. India will probably overtake China to become the world's most populous nation before 2030.

But India is defusing its population bomb. A fertility rate of 2.5 is only a smidgen above the long-term replacement level, which—allowing for girls who don't reach adulthood and some alarming rates of aborting female fetuses—is around 2.3. The end is in sight.

With most of the country still extremely poor, this is a triumph against all expectations. And it offers some intriguing clues to a question that has dogged demographers ever since Paul Ehrlich published his blockbuster book
The Population Bomb:
What can persuade poor people in developing countries to have fewer babies?

Taking time off from bemusing his students, Lewis decided to investigate. Being a geographer, he tackled the question with maps. He noted that within the overall rapid decline in Indian fertility, there continued to be great regional variations. So he mapped fertility in each Indian state and examined those patterns against the patterns for some of the demographers' favored drivers of lowered fertility. When he compared his maps, he found that variations in female education fit pretty well. So did economic wealth and the Human Development Index, which measures education, health, and income. The extent of urbanization looked like a pretty good match, too. But he also found that TV ownership tallied well with fertility across India. Not perfectly, he concluded, but as well as or better than the more standard indicators. A TV in the living room, in other words, might have the power to transform behavior in the bedroom.

 

Surprising? Maybe not. Lewis was following the lead of Robert Jensen and Emily Oster, development economists from the University of California, Los Angeles, and the University of Chicago, respectively. Four years ago, they reported compelling direct evidence from Indian villages that TV empowers women. They carried out detailed interviews in rural India as commercial cable and satellite TV were replacing the mostly dull and uninspired government programming.

The pair noted that the new diet of game shows, soap operas, and reality shows instantly became the villagers' main source of information about the outside world—especially about India's emerging urban ways of life. At the top of the ratings was
Kyunki Saas Bhi Kabhi Bahu Thi
(meaning “Because a mother-in-law was once also a daughter-in-law”). Based on life in the megacity of Mumbai, it was Asia's most watched TV show between 2000 and 2008 and was an eye opener for millions of rural Indian women. They saw their urban sisters working outside the home, running businesses, controlling money, and—crucially—achieving these things by having fewer children. Here was TV showing women a world of possibilities beyond bearing and raising children—a world in which small families are the key to a better life.

Soap operas give viewers time to develop strong emotional bonds with the characters, many of whom live as they do and experience the life traumas that they do. The impact of the new TV programming in rural India has been profound—and very positive, say Jensen and Oster. Their interviews revealed that when the new TV services arrived, women's autonomy increased while fertility and the acceptability of domestic violence toward women significantly decreased. Most of the changes occurred within a few months of the arrival of TV reception, when (as they put it) “interactions with the television are more intense.” In fact, the researchers found that TV's influence on gender attitudes, social advancement, and fertility rates was equivalent to the impact of an extra five years of female education. This was the social revolution that delivered the geographical variation in Lewis's maps.