Field Notes From a Catastrophe: Man, Nature, and Climate Change (8 page)

The symposium in Reykjavík lasted for four days. One morning, when the presentations on the agenda included “Char as a Model for Assessing Climate Change Impacts on Arctic Fishery Resources,” I decided to rent a car and take a drive. In recent years, Reykjavík has been expanding almost on a daily basis, and the old port city is now surrounded by rings of identical, European-looking suburbs. Ten minutes from the car-rental place, these began to give out, and I found myself in a desolate landscape in which there were no trees or bushes or really even soil. The ground—fields of lava from some defunct, or perhaps just dormant, volcanoes—resembled macadam that had recently been bulldozed. I stopped to get a cup of coffee in the town of Hveragerdi, where roses are raised in greenhouses heated with steam that pours directly out of the earth. Farther on, I crossed into farm country; the landscape was still treeless, but now there was grass, and sheep eating it. Finally, I reached the sign for Sólheimajökull, the glacier whose retreat Oddur Sigurdsson had described to me. I turned off onto a dirt road. It ran alongside a brown river, between two crazily shaped ridges. After a few miles, the road ended, and the only option was to continue on foot.

By the time I got to the lookout over Sólheimajökull, it was raining. In the gloomy light, the glacier appeared less sublime than merely forlorn. Much of it was gray—covered in a film of dark grit. In its retreat, it had left behind ridged piles of silt. These were jet-black and barren—not even the tough local grasses had had a chance to take root on them. I looked around for the enormous boulder I had seen in the photos in Sigurdsson’s office. It was such along way from the edge of the glacier that for a moment I wondered if perhaps it had been carried along by the current. A raw wind came up, and I started to head down. Then I thought about what Sigurdsson had told me. If I returned in another decade, the glacier would probably no longer even be visible from the ridge where I was standing. So I climbed back up to take a second look.

Chapter 4

The Butterfly and the Toad

Polygonia c-album
, generally known as the Comma butterfly, spends most of its life pretending to be something that it is not. In its larval, or caterpillar, stage, it has a chalky stripe down its back, which makes it look, uncannily, like a bird dropping. As an adult, with wings folded, it is practically indistinguishable from a dead leaf. The Comma gets its name from a tiny white mark on its underside shaped like the letter “C.” Even this is thought to be part of its camouflage—an ersatz tear of the sort leaves get when they are particularly old and tatty.

The Comma is a European butterfly—its American cousins are the Eastern Comma and the Question Mark—and it can be found in France, where it is known as
le Robert-le-Diable
; Germany, where it is called
der C-Falter
, and the Netherlands, where it is
Gehakkelde Aurelia
. The Comma reaches the northern edge of distribution in England. This is unremarkable—many European butterflies come to the end of their range in Britain—but from a scientific standpoint fortunate.

The English have been watching and collecting butterflies for centuries—some of the specimens in the British Natural History Museum date back to the 1700s—and in the Victorian era, passion for the hobby was such that every city, and many a small town, supported its own entomological society. In the 1970s, Britain’s Biological Records Centre decided to marshal this enthusiasm for a project called the Lepidoptera Distribution Maps Scheme, whose aim was to chart precisely where each of the country’s fifty-nine native species could—and could not—be found. More than two thousand amateur lepidopterists participated, and in 1984, the results were collated into a hundred-and-fifty-eight-page atlas. Every species got its own map with different colored dots showing the number of times it had been sighted in any given ten square kilometers. In the map for
Polygonia c-album
, the Comma’s range was shown to extend from the south coast of England northward to Liverpool in the west and Norfolk in the east. Almost immediately, this map became out of date; in the years that followed, hobbyists kept finding the Comma in new areas. By the late 1990s, the butterfly was frequently being sighted in the north of England, near Durham. By now it is well established in southern Scotland, and has been sighted as far north as the Scottish Highlands. The rate of the Comma’s expansion—some fifty miles per decade—was described by the authors of the most recent butterfly atlas as “remarkable.”

Chris Thomas is a biologist at the University of York who studies lepidoptera. He is tall and rangy, with an Ethan Hawke-style goatee and an amiably harried manner. The day I met him, he had just returned from looking for butterflies in Wales, and the first thing he said to me when I got into his car was please not to mind the smell of wet socks. A few years ago, Thomas, together with his wife, their two sets of twins, an Irish wolfhound, a pony, some rabbits, a cat, and several chickens moved into an old farmhouse in the town of Wistow, in the vale of York. The University of York has an array of thermostatic chambers where Commas are raised under temperature-controlled conditions, fed carefully monitored diets, and measured on a near-constant basis, but in the spirit of British amateurism, Thomas decided to turn his own backyard into a field lab. He scattered wildflower seeds he had collected from nearby meadows and ditches, planted nearly seven hundred trees, and waited for the butterflies to show up. When I visited the place in mid-summer, the wildflowers were in bloom and the grass was so high that many of the tiny trees looked lost, like kids in search of their parents. The vale of York is almost completely flat—during the last ice age, it formed the bottom of a giant lake—and from the yard Thomas pointed out the spires of Selby Abbey, built nearly a thousand years ago, and also the cooling towers of the Drax power plant, Britain’s largest, some fifteen miles away. It was cloudy, and since butterflies don’t fly when it’s gray, we went inside.

Butterflies, Thomas explained after putting the kettle on for tea, can be divided into two groups. First, there are the “specialists,” who require specific—winsome cases, unique—conditions. These include the Chalkhill Blue (
Polyommatus coridon
), a large, turquoise butterfly that feeds exclusively on horseshoe vetch, and the Purple Emperor (
Apatura iris
), which flies in the treetops of well-wooded areas in southern England. Then there are the “generalists,” who are less picky. Among Britain’s generalists, there are, in addition to the Comma, ten species that are widespread in the southern part of the country and reach the edge of their range somewhere in the nation’s midsection. “Every single one has moved northward since 1982,” Thomas told me. A few years ago, together with lepidopterists from, among other places, the United States, Sweden, France, and Estonia, Thomas conducted a survey of all the studies that had been done on generalists that reach the upper limits of their ranges in Europe. The survey looked at thirty-five species in all. Of these, the scientists found, twenty-two had shifted their range northward in recent decades, while only one had shifted south.

After a while, the sun emerged, and we went back outside. Thomas’s wolfhound, Rex, a dog the size of a small horse, trailed behind us, panting heavily. Within about five minutes, Thomas had identified a Meadow Brown (
Maniola jurtina
), a Small Tortoiseshell (
Aglais urticae
), and a Green-veined White (
Pieris napi
), all species that have been flitting around Yorkshire since butterfly record-keeping began. Thomas also spotted a Gatekeeper (
Pyronia tithonus
) and a Small Skipper (
Thymelicus sylvestris
), which until recently had been confined to a region well south of where we were standing. “So far, two out of the five species of butterflies that we’ve seen are northward invaders,” he told me. “Sometime within the last thirty years they have spread into this area.” A few minutes later, he pointed out another invader sunning itself in the grass—a
Polygonia c-album
. With its wings closed, the Comma was a dull, dead-leaf brown, but with them open, it was a brilliant orange.

That life on earth changes with the climate has been assumed to be the case for a long time, indeed for very nearly as long as the climate has been known to be capable of changing. Louis Agassiz published
Études sur les glaciers
, the work in which he laid out his theory of the ice ages, in 1840. By 1859, Charles Darwin had incorporated Agassiz’s theory into his own theory of evolution. Toward the end of
On the Origin of Species
, in a chapter titled “Geographical Distribution,” Darwin describes the vast migrations that he supposes the advance and retreat of the glaciers must have necessitated:

As the cold came on, and as each more southern zone became fitted for arctic beings and ill-fitted for their former more temperate inhabitants, the latter would be supplanted and arctic productions would take their places. The inhabitants of the more temperate regions would at the same time travel southward … As the warmth returned, the arctic forms would retreat northward, closely followed up in their retreat by the productions of the more temperate regions. And as the snow melted from the bases of the mountains, the arctic forms would seize on the cleared and thawed ground, always ascending higher and higher as the warmth increased, whilst their brethren were pursuing their northern journey.

For Darwin and his contemporaries such a narrative was necessarily speculative. Much as the existence of ice ages had had to be inferred from the signs they left behind—erratics, moraines, and striated bedrock—so, too, the succession and redistribution of species on Earth could only be reconstructed from fragmentary traces: scattered bones, fossilized insect casings, ancient pollen deposits. Even as paleontologists and paleobotanists found more and more evidence of how species had responded to climate change in the past, it was taken for granted that the process was not something that could be observed in real time, an assumption that has now been proven false.

Almost anywhere you go in the world today, except perhaps for the urban areas where most of us live, it is possible to observe biological changes comparable to the northern expansion of the Comma. A recent study of common frogs living near Ithaca, New York, for example, found that four out of six species were calling—which is to say, mating—at least ten days earlier than they used to, while at the Arnold Arboretum, in Boston, the date of peak blooming for spring-flowering shrubs has advanced, on average, by eight days. In Costa Rica, birds like the keel-billed toucan (
Ramphastos sulfuratus
), once confined to the lowlands, have started to nest on mountain slopes; in the Alps, plants like purple saxifrage (
Saxifraga oppositifolia
) and Austrian draba (
Draba fladnizensis
) have been creeping up toward the summits; and in the Sierra Nevada of California, the average Edith’s Checkerspot butterfly (
Euphydryas editha
) can now be found at an elevation three hundred feet higher than it was a hundred years ago. Any one of these changes could, potentially, be a response to purely local conditions—shifts, say, in regional weather patterns or in patterns of land use. The only explanation that anyone has proposed that makes sense of them all, though, is global warming.

The Bradshaw-Holzapfel Lab occupies a corner on the third floor of Pacific Hall, a peculiarly unlovely building on the campus of the University of Oregon in Eugene. At one end of the lab is a large room stacked with glassware and at the other, a pair of offices. In between are several workrooms that look, from the outside, like walk-in refrigerators. Taped to the door of one of them is a handwritten sign: “Warning—if you enter this room mosquitoes will suck your blood out through your eyes!”

William Bradshaw and Christina Holzapfel, who run the lab and share one of the offices, are evolutionary biologists. They were introduced as graduate students at the University of Michigan, and have been married for thirty-five years. Bradshaw is a tall man with thinning gray hair and a gravelly voice. His desk is covered in a mess of papers, books, and journals, and when visitors come to the lab, he likes to show them his collection of curiosities, which includes a desiccated octopus. Holzapfel is short, with blond hair and bright blue eyes. Her desk is perfectly neat.

Bradshaw and Holzapfel have shared an interest in mosquitoes for as long as they have been interested in each other. In the early years of their lab, which they set up in 1971, they raised several species, some of which, in order to reproduce, required what is delicately referred to as a “blood meal.” This, in turn, demanded a live animal able to provide such a meal. For a time, this requirement was met by rats sedated with phenobarbital, but, as rules about experimenting with animals grew more stringent, Bradshaw and Holzapfel found themselves forced to decide whether it was more humane to keep sedating the same rat over and over again, or to use a new rat and let the old one wake up to find itself covered with bites. Eventually, they grew weary of such questions and decided to stick to a single species,
Wyeomyia smithii
, which needs no blood in order to reproduce. At any given moment the Bradshaw-Holzapfel Lab houses upwards of a hundred thousand
Wyeomyia smithii
in various stages of development.

Wyeomyia smithii
is a small and rather ineffectual bug. (“Wimpy” is how Bradshaw characterizes it.) Its eggs are practically indistinguishable from specks of dust; its larvae appear as minuscule white worms. As an adult, it is about a quarter of an inch long and in flight looks like a tiny black blur. It is only when you examine a
Wyeomyia smithii
very closely, under a magnifying glass, that you can see that its abdomen is actually silver, and that its two hind legs are bent gracefully above its head, like a trapeze artist’s.