1493: Uncovering the New World Columbus Created (7 page)

Historians call the freeze the Little Ice Age. Enduring from about 1550 to about 1750 in the Northern Hemisphere, this global thermal anomaly is difficult to pin down; its onset and duration differed from one region to the next. Because few people then kept written records of weather conditions, paleoclimatologists (researchers of ancient climate) must study it with imperfect measures like the thickness of tree rings and the chemical composition of tiny bubbles of gas in polar ice. Based on such indirect evidence, some researchers proposed that the Little Ice Age was attributable to a decline in the number of sunspots known as the Maunder Minimum. Because sunspots are correlated with the sun’s energy output, fewer sunspots implies less-intense solar irradiation—enough, these researchers argued, to cool the earth. Other scientists theorized that the temperature drop was due to big volcanic eruptions, which blast sulfur dioxide into the upper atmosphere. High above the clouds, the sulfur dioxide mixes with water vapor to form minute droplets of sulfuric acid—shiny motes in the sky—that reflect some of the sun’s light into space. This phenomenon existed in 1642; a massive eruption in the southern Philippines the year before is now thought to have cooled the earth for as long as three years. Both hypotheses have drawn sharp criticism, though. Many scientists believe that the impact of the Maunder Minimum was too small to account for the Little Ice Age. Others argue that a series of individual volcanic eruptions could not have caused a steady temperature drop.

In 2003, William F. Ruddiman, a paleoclimatologist at the University of Virginia, suggested a different cause for the Little Ice Age—an idea that initially seemed outlandish, but that is increasingly treated seriously.

As human communities grow, Ruddiman pointed out, they open more land for farms and cut down more trees for fuel and shelter. In Europe and Asia, forests were cut with the ax. In the Americas before Colón, the primary tool was fire—vast stretches of it. For weeks on end, smoke from Indian bonfires shrouded Florida, California, and the Great Plains. Today, many researchers believe that without regular burning, much of the midwestern prairie would have been engulfed by an invading tide of trees. The same was true for the grasslands of the Argentine pampas, the hills of Mexico, the Florida dunes, and the high plains of the Andes.

American forests, too, were shaped by flame. Indians’ “frequent fiering of the woods,” remarked English colonist Edward Johnson in 1654, made the forests east of the Mississippi so open and “thin of Timber” that they were “like our Parkes in England.” Annual fire seasons removed scratchy undergrowth, burned out noxious insects, and cleared land for farms. Scientists have conducted fewer studies of burning in the tropics, but two California paleoecologists (scientists who study past ecosystems) surveyed the fire history of thirty-one sites in Central and South America in 2008 and found that in every one the amount of charcoal in the soil—an indicator of fire—had increased substantially for more than two thousand years.

Enter now the Columbian Exchange. Eurasian bacteria, viruses, and parasites sweep through the Americas, killing huge numbers of people—and unraveling the millennia-old network of human intervention. Flames subside to embers across the Western Hemisphere as Indian torches are stilled. In the forests, fire-hating trees like oak and hickory muscle aside fire-loving species like loblolly, longleaf, and slash pine, which are so dependent on regular burning that their cones will only open and release seed when exposed to flame. Animals that Indians had hunted, keeping their numbers down, suddenly flourish in great numbers. And so on.

Indigenous pyromania had long pumped carbon dioxide into the air. At the beginning of the Homogenocene the pump suddenly grows feeble. Formerly open grasslands fill with forest—a frenzy of photosynthesis. In 1634, fourteen years after the Pilgrims land in Plymouth, colonist William Wood complains that the once-open forests are now so choked with underbrush as to be “unuseful and troublesome to travel through.” Forests regenerate across swathes of North America, Mesoamerica, the Andes, and Amazonia.

Ruddiman’s idea was simple: the destruction of Indian societies by European epidemics both decreased native burning and increased tree growth. Each subtracted carbon dioxide from the air. In 2010 a research team led by Robert A. Dull of the University of Texas estimated that reforesting former farmland in American tropical regions alone could have been responsible for as much as a quarter of the temperature drop—an analysis, the researchers noted, that did not include the cutback in accidental fires, the return to forest of unfarmed but cleared areas, and the entire temperate zone. In the form of lethal bacteria and viruses, in other words, the Columbian Exchange (to quote Dull’s team) “significantly influenced Earth’s carbon budget.” It was today’s climate change in reverse, with human action removing greenhouse gases from the atmosphere rather than adding them—a stunning meteorological overture to the Homogenocene.

Flying the plane back across the Atlantic, the effects of the Little Ice Age are obvious in the Americas, too. Clearly visible from the air is the filling in of Indian lands by forest—and by snow. Ice is solid enough that people ride carriages on Boston harbor; it freezes over most of Chesapeake Bay, and nearly wipes out the two score French colonists who this year have founded Montreal. Introduced cattle and horses die in snowdrifts in Maine, Connecticut, and Virginia. Other impacts are harder to see. The forests are filling in former Indian lands with cold-loving species like hemlock, spruce, and beech. Vernal pools take longer to evaporate in the canopy they provide in these cool summers. Mosquitoes that breed in those pools thus have an increased chance for survival.

Using fire, indigenous people in the Americas cleared big areas for agriculture and hunting, as shown in this map of North America’s eastern seaboard.
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European diseases caused a population crash across the hemisphere—and an extraordinary ecological rebound as forests filled in abandoned fields and settlements. The end of native burning and the massive reforestation drew so much carbon dioxide from the air that an increasing number of researchers believes it was a main driver of the three-century cold snap known as the Little Ice Age.
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Among these paradoxically cold-loving mosquitoes is
Anopheles quadrimaculatus,
the overall name for a complex of five near-indistinguishable sibling species. Like other
Anopheles
mosquitoes,
A. quadrimaculatus
hosts the parasite that causes malaria—the insect’s common name is the North American malaria mosquito. Southeast England at this time is rampant with malaria. Precise documentation will never become available, but there is good reason to suspect that by 1642 malaria has already traveled in immigrant bodies from England to the Americas. A single bite into an infected person is enough to introduce the parasite to its mosquito host, which spreads the parasite far and wide. Virginia and points south have already proven so unhealthy for Europeans that plantation overseers are finding it difficult to persuade laborers to come from overseas to work in the tobacco fields.

Some landowners already have resolved this problem by purchasing workers from Africa. Partly driven by the introduction of malaria, a slave market is beginning to quicken into existence, a profitable exchange that will entwine itself over time with the silver market. As ever, the ships from Africa will form a kind of ecological corridor, through which travel passengers not on any official manifest. Crops like yams, millet, sorghum, watermelon, black-eyed peas, and African rice will follow the slave ships to the Americas. So will yellow fever.

Beyond Chesapeake Bay the airplane flies west, heading toward Mexico. Beneath its wings unfurl the Great Plains. From their southern edge come herds of Spanish horses, scores at a time, brought by silver galleons on the return trip across the Atlantic. Apache and Ute race hundreds of miles south to meet the horses, followed by Arapaho, Blackfoot, and Cheyenne. As European villagers learned from Mongol horsemen, peasant farmers, tied to their land, are sitting ducks for cavalry assault. The rush by Indian nations to acquire horses is thus a kind of arms race. All over the North American West and Southwest, native farmers are abandoning their fields and leaping onto the backs of animals from Spain. Long-sedentary societies are becoming wanderers; the “ancient tradition” of the nomadic Plains Indian is coming into existence, a rapid adaptation to the Columbian Exchange.

As natives acquire horses, they come into conflict with each other and the labor force on Spain’s expanding ranches. The ranch workers are Indians, African slaves, and people of mixed ancestry. In a kind of cultural panic, the colonial government has created a baroque racial lexicon—mestizo, mulatto, coyote,
morisco, chino, lobo, zambaigo, albarazado
—to label particular genetic backgrounds. All of these people and more meet in Mexico City, the capital of New Spain, the richest piece of Spain’s American empire. Wealthier and more populous than any city in Spain, it is an extraordinary jumble of cultures and languages, with no one group forming the majority. Neighborhoods are divided by ethnicity—one entire barrio is occupied by Tlaxcalans from the east. As the back-and-forth continues, engineers struggle to prevent the city from physical collapse. Mexico City has flooded six times in the last four decades, once remaining inundated for five years. A troubled, teeming, polyglot metropolis with an opulent center and seething ethnic neighborhoods at its periphery that is struggling to fend off ecological disaster—from today’s perspective, the Mexico City of 1642 seems strikingly familiar. It is the world’s first twenty-first-century city.

The airplane flies west, to Acapulco, on Mexico’s Pacific coast, the eastern terminus of the galleon trade. Ringed by protective mountains, untroubled by sandbars or shoals, the harbor is a majestic setting for one of the more listless settlements in the Americas: several hundred huts scattered like lost clothes at the edge of the water. Most of Acapulco’s few permanent inhabitants are African slaves, Indian laborers, and Asian sailors who jumped ship (the galleons are mainly crewed by Filipinos, Chinese, and other Asians). When the galleons arrive, Spaniards show up, some of them coming from as far as Peru. A market and fair springs into existence; millions of pesos change hands. Then the town empties again as the ships are beached and readied for the next trip across the Pacific.

Follow the silver to its destination in China. The Little Ice Age has taken hold in East Asia, too, though here the impact is typically less a matter of snow and ice than of crashing, copious rain alternating with bouts of cold drought. The five worst years of drought in five centuries occurred between 1637 and 1641. This year, rain is drowning the crops. All the impacts have been exacerbated by a series of volcano eruptions in Indonesia, Japan, New Guinea, and the Philippines. Millions have died. Cold, wet weather and mass deaths ensure that more than two-thirds of China’s farmland is no longer being tilled, adding to the famine. Cannibalism is rumored to be frequent. The Ming court—paralyzed by infighting, preoccupied with wars to the north—does little to help the afflicted. It simply doesn’t have the funds. Like the Spanish king, the Ming emperor backs his military ventures with Spanish silver, which his subjects must use to pay their taxes. When the value of silver falls, the government runs out of money.

The Ming have long believed their duty is to protect China from malign foreign influence. They have failed. American crops like tobacco, maize, and sweet potato are spreading over hillsides. American silver is dominating the economy. Although the emperors don’t know it, American trees are helping to bring the rains. All of these are working against the Ming. Popular discontent is already at such levels that mobs of peasant rebels are tearing violently through half a dozen provinces. Unhappy, unpaid soldiers are mutinying. Flood and famine simply exacerbate the anger. In two years Beijing will fall to a rebellious ex-soldier. Weeks later, the soldier will be overthrown by the Manchus, who establish a new dynasty: the Qing (pronounced, roughly speaking, “ching”).