Field Notes From a Catastrophe: Man, Nature, and Climate Change (10 page)

After a while, we went down the hall to Webb’s office. On his computer he called up a program named Pollen Viewer 3.2, and a map of North America circa 19000 B.C. appeared on the screen. Around that time, the ice sheets of the last glaciation reached their maximum extent; the map showed the Laurentide ice sheet covering all of Canada as well as most of New England and the upper Midwest. Because so much water was tied up in the ice, sea levels were some three hundred feet lower than they are now. On the map, Florida appeared as a stubby protuberance, nearly twice as wide as it is today. Webb clicked on “Play.” Time began to move forward in thousand-year increments. The ice sheet shrank. A huge lake, known as Lake Agassiz, formed in central Canada and, a few thousand years later, drained. The Great Lakes emerged, and then widened. Around eight thousand years ago, open water finally appeared in Hudson Bay. The bay began to contract as the land around it rebounded from the weight of the ice sheet.

Webb clicked on a pull-down menu that listed the Latin names of dozens of trees and shrubs. He chose
Pinus
(pine) and again hit “Play.” Dark-green splotches began to move around the continent. Twenty-one thousand years ago, the program showed, pine forests covered the entire Eastern Seaboard south of the ice sheet. Ten thousand years later, pines were concentrated around the Great Lakes, and today pine predominates in the southeastern United States and in western Canada. Webb clicked on
Quercus
(oak), and a similar process began, only
Quercus
moved in a very different pattern from
Pinus
. More clicks for
Fagus
(beech),
Betula
(birch), and
Picea
(spruce). As the earth warmed and the continent emerged from the ice age, each of the tree species migrated, but no two moved in exactly the same way.

“The trick you’ve got to remember is that climate is multivariate,” Webb explained. “The plant species are having to respond both to temperature changes and to moisture changes and to changes in seasonality. It makes a big difference if you have a drier winter versus a drier summer, because some species are more attuned to spring and others to fall. Any current community has a certain mixture. If you start changing the climate, you’re changing the temperature, but you’re also changing moisture or the timing of the moisture or the amount of snow and, bingo, species are not going to move together. They can’t.”

Webb pointed out that the warming predicted for the next century is on the same scale as the temperature difference between the last glaciation and today. “You know that’s going to give us a very different landscape,” he said. I asked what he thought this landscape would look like. He said he didn’t know—his central finding, from more than thirty years of research, is that, as the climate changes, species often move in surprising ways. In the short term, which is to say in the remainder of his own life, Webb said that he expected mostly to see disruption.

“We have this strange sense of the evolutionary hierarchy, that the microorganisms, because they came first, are the most primitive,” he told me. “And yet you could argue that this will just give a lot of advantage to the microorganisms of the world, because of their ability to evolve more quickly. To the extent the climate is putting organisms as well as ecosystems under stress, it’s opening the opportunities for invasive species on the one hand and disease on the other. I guess I start thinking: Think death.”

Any species that is around today, including our own, has already survived catastrophic climate change. The fact that a species has survived such a change, or even many such changes, is no guarantee, however, that it will survive the next one. Consider, for example, the outsized megafauna—seven-hundred-and-fifty-pound saber-toothed cats, elephantine sloths, and fifteen-foot-tall mastodons—that once dominated the North American landscape. These megafauna lived through several glacial cycles, but then something changed, and they nearly all died out at the same time, at the beginning of the Holocene.

Over the past two million years, even as the temperature of the earth has swung wildly, it has always remained within certain limits: The planet has often been colder than today, but rarely warmer, and then only slightly. If the earth continues to warm at the current rate, then by the end of this century temperatures will push beyond the “envelope” of natural climate variability.

Meanwhile, thanks to us, the world today is a very different—and in many ways diminished—place. International trade has introduced exotic pests and competitors; ozone depletion has increased exposure to ultraviolet radiation; and many specie shave already been very nearly wiped out, or wiped out altogether, by overhunting and overharvesting. Perhaps most significantly, human activity, in the form of farm sand cities and subdivisions and mines and logging operations and parking lots, has steadily reduced the amount of available habitat. G. Russell Coope is a visiting professor in the geography department at the University of London and one of the world’s leading authorities on ancient beetles. He has shown that, under the pressure of climate change, insects have migrated tremendous distances; for example,
Tachinus caelatus
, a small, dullish-brown beetle common in England during the cold periods of the Pleistocene, today can be found only some five thousand miles away, in the mountains west of Ulan Bator, in Mongolia. But Coope questions whether such long-distance migrations are practical in a fragmented landscape like today’s. Many organisms now live in the functional equivalent of “oceanic islands or remote mountain tops,” he has written. “Certainly, our knowledge of their past response may be of little value in predicting any future reactions to climate change, since we have imposed totally new restrictions on their mobility; we have inconveniently moved the goal posts and set up a ball game with totally new rules.”

A few years ago, nineteen biologists from around the world set out to give, in their words, a “first pass” estimate of the extinction risk posed by global warming. They assembled data on eleven hundred species of plants and animals from sample regions covering roughly a fifth of the earth’s surface. Then they established the species’ current ranges, based on climate variables such as temperature and rainfall. Finally, they calculated how much of the species’ “climate envelope” would be left under different warming scenarios. The results of this effort were published in
Nature
in 2004. Using a midrange projection of temperature rise, the biologists concluded that, if the species in the sample regions could be assumed to be highly mobile, then fully 15 percent of them would be “committed to extinction” by the middle of this century, and, if they proved to be basically stationary, an extraordinary 37 per cent of them would be.

The Mountain Ringlet (
Erebia epiphron
) is a dun-colored butterfly with orange and black spots that curl along the edges of its rounded wings. Mountain Ringlets feed on a coarse, tufted grass known as matgrass, overwinter as larvae, and as adults have an extremely brief lifespan—perhaps as short as one or two days. A montane, or mountain species, it is found only at elevations above a thousand feet in the Scottish Highlands, and farther south, in Britain’s Lake District, only above fifteen hundred feet.

Together with a colleague from the University of York, Chris Thomas has for the last few years been monitoring the Mountain Ringlet, along with three other species of butterfly—the Scotch Argus (
Erebia aethiops
), the Large Heath (
Coenonympha tullia
) and the Northern Brown Argus (
Aricia artaxerxes
)—whose ranges are similarly confined to a few locations in northern England and Scotland. In the summer of 2004, researchers for the project visited nearly six hundred sites where these “specialist” species had been spotted in the past, and the following summer they repeated the process. Documenting a species’ contraction is more difficult than documenting its expansion—is it really gone, or did someone just miss it?—but preliminary evidence suggests that the butterflies are already disappearing from lower elevation, and therefore warmer, sites. When I went to visit Thomas, he was getting ready to take his family to Scotland on vacation, and was planning to recheck some of the sites. “It’s a bit of a busman’s holiday,” he confessed.

As we were wandering around his yard in search of Commas, I asked Thomas, who was the lead author of the extinction study, how he felt about the changes he was seeing. He told me that he found the opportunities for study presented by climate change to be exciting.

“Ecology for a very long time has been trying to explain why species have the distribution that they do, why a species can survive here and not over there, why some species have small distributions and others have broad ones,” he said. “And the problem that we have always had is that distributions have been rather static. We couldn’t actually see the process of range boundaries changing taking place, or see what was driving those changes. Once everything starts moving, we can begin to understand: is it a climatic determinant, or is it mainly other things, like interactions with other species? And, of course, if you think of the history of the last million years, we now have the opportunity to try and understand how things might have responded in the past. It’s extremely interesting, the prospect of everything changing its distribution, and new mixtures of species from around the world starting to form and produce new biological communities—extremely interesting from a purely academic point of view.

“On the other hand, given our conclusions about possible extinctions, it is, to me personally, a serious concern,” he went on. “If we are in the situation where a quarter of the terrestrial species might be at risk of extinction from climate change—people often use the phrase ‘being like canaries’—if we’ve changed our biological system to such an extent, then we do have to get worried about whether the services that are provided by natural ecosystems are going to continue. Ultimately, all of the crops we grow are biological species; all the diseases we have are biological species; all the disease vectors are biological species. If there is this overwhelming evidence that species are changing their distributions, we’re going to have to expect exactly the same for crops and pests and diseases. Part of it simply is we’ve got one planet, and we are heading it in a direction that, quite fundamentally, we don’t know what the consequences are going to be.”

Part II

Man

Chapter 5

The Curse of Akkad

The world’s first empire was established forty-three hundred years ago, between the Tigris and Euphrates Rivers. The details of its founding, by Sargonof Akkad, have come down to us in a form somewhere between history and myth. Sargon—Sharru-kin, in the Akkadian language—means “true king”; almost certainly, though, he was a usurper. As a baby, Sargon was said to have been discovered, Moses-like, floating in a basket. Later, he became cupbearer to the ruler of Kish, one of ancient Babylonia’s most powerful cities. Sargon dreamed that his master, Ur-Zababa, was about to be drowned by the goddess Inanna in a river of blood. Hearing about the dream, Ur-Zababa decided to have Sargon eliminated. How this plan failed is unknown; no text relating the end of the story has ever been found.

Until Sargon’s reign, Babylonian cities like Kish, and also Ur and Uruk and Umma, functioned as independent city-states. Sometimes they formed brief alliances—cuneiform tablets attest to strategic marriages celebrated and diplomatic gifts exchanged—but mostly they seem to have been at war with one another. Sargon first subdued Babylonia’s fractious cities, then went on to conquer, or at least sack, lands like Elam, in present-day Iran. He presided over his empire from the city of Akkad, the ruins of which are believed to lie south of Baghdad. It was written that “daily five thousand four hundred men ate at his presence,” meaning, presumably, that he maintained a huge standing army. Eventually, Akkadian hegemony extended as far as the Khabur plains, in northeastern Syria, an area prized for its grain production. Sargon came to be known as “king of the world”; later, one of his descendants enlarged this title to “king of the four corners of the universe.”

Akkadian rule was highly centralized, and in this way anticipated the administrative logic of empires to come. The Akkadians levied taxes, then used the proceeds to support a vast network of local bureaucrats. They introduced standardized weights and measures—the
gur
equalled roughly three hundred liters—and imposed a uniform dating system, under which each year was assigned the name of a major event that had recently occurred: for instance, “the year that Sargon destroyed the city of Mari.” Such was the level of systematization that even the shape and the layout of accounting tablets were imperially prescribed. Akkad’s wealth was reflected in, among other things, its artwork, the refinement and naturalism of which were unprecedented.

Sargon ruled, supposedly, for fifty-six years. He was succeeded by his two sons, who reigned for a total of twenty-four years, and then by a grandson, Naram-sin, who declared himself a god. Naram-sin was, in turn, succeeded by his son. Then, suddenly, Akkad collapsed. During one three-year period, four men each, briefly, claimed the throne. “Who was king? Who was not king?” the register known as the Sumerian King List asks, in what may be the first recorded instance of political irony.

The lamentation “The Curse of Akkad” was written within a century of the empire’s fall. It attributes Akkad’s demise to an outrage against the gods. Angered by a pair of inauspicious oracles, Naram-sin plunders the temple of Enlil, the god of wind and storms, who, in retaliation, decides to destroy both him and his people:

For the first time since cities were built and founded,
The great agricultural tracts produced no grain,
The inundated tracts produced no fish,
The irrigated orchards produced neither syrup nor wine,
The gathered clouds did not rain, the
masgurum
did not grow.
At that time, one shekel’s worth of oil was only one-half quart,
One shekel’s worth of grain was only one-half quart…
These sold at such prices in the markets of all the cities!
He who slept on the roof, died on the roof,
He who slept in the house, had no burial,
People were flailing at themselves from hunger.