(CNN)When Europeans arrived in the Americas, they caused so much death and disease that it changed the global climate, a new study finds.
European settlers killed 56 million indigenous people over about 100 years in South, Central and North America, causing large swaths of farmland to be abandoned and reforested, researchers at University College London, or UCL, estimate. The increase in trees and vegetation across an area the size of France resulted in a massive decrease in carbon dioxide (CO2) in the atmosphere, according to the study.
Carbon levels changed enough to cool the Earth by 1610, researchers found. Columbus arrived in 1492,
"CO2 and climate had been relatively stable until this point," said UCL Geography Professor Mark Maslin, one of the study's co-authors. "So, this is the first major change we see in the Earth's greenhouse gases."
Before this study, some scientists had argued the temperature change in the 1600s, called the Little Ice Age, was caused only by natural forces.
But by combining archaeological evidence, historical data and analysis of carbon found in Antarctic ice, the UCL researchers showed how the reforestation -- directly caused by the Europeans' arrival -- was a key component of the global chill, they said.
"For once, we've been able to balance all the boxes and realize that the only way the Little Ice Age was so intense is ... because of the genocide of millions of people," Maslin told CNN.
Researchers analyzed Antarctic ice, which traps atmospheric gas and can reveal how much carbon dioxide was in the atmosphere centuries ago.
"The ice cores showed that there was a larger dip in CO2 (than usual) in 1610, which was caused by the land and not the oceans," said Alexander Koch, lead author of the study.
A small shift in temperatures -- about a 10th of a degree in the 17th century -- led to colder winters, frosty summers and failing harvests, Koch said.
The implications
The implications of the study go beyond climate science and also contribute to research in geography and history, Maslin said, noting that deaths of indigenous Americans directly contributed to the success of the European economy.
Natural resources and food shipped from the New World helped Europe's population to expand. It also allowed people to stop farming for sustenance and begin working in other industries for spare money.
"The really weird thing is, the depopulation of the Americas may have inadvertently allowed the Europeans to dominate the world," Maslin said. "It also allowed for the Industrial Revolution and for Europeans to continue that domination."
by John W. Kincheloe, III
Used with permission from Tar Heel Junior Historian 47: 1 (Fall 2007): 6-8, copyright North Carolina Museum of History.
European explorers came to the "New World" o
Archaeologists tell us that American Indians may have been on the North American continent for fifty thousand years. They were the first Americans, and they were great explorers, too. They didn't come to this continent all at once. It is thought that these ancient adventurers arrived at different times, over several thousands of years. They journeyed from Asia on foot or by boat. Their explorations took them through icy landscapes and along the coastlines. Eventually these earliest American explorers spread out over the entire continent.
Over time, their lives changed as they adapted to different environments. American Indians were creative. They found ways to live in deserts, in forests, along the oceans, and on the grassy prairies. Native peoples were great hunters and productive farmers. They built towns and traded over large distances with other tribes. These were the people the European explorers met when their ships landed in America.
As the English, French, and Spanish explorers came to North America, they brought tremendous changes to American Indian tribes. Europeans carried a hidden enemy to the Indians: new diseases. Native peoples of America had no immunity to the diseases that European explorers and colonists brought with them. Diseases such as smallpox, influenza, measles, and even chicken pox proved deadly to American Indians. Europeans were used to these diseases, but Indian people had no resistance to them. Sometimes the illnesses spread through direct contact with colonists. Other times, they were transmitted as Indians traded with one another. The result of this contact with European germs was horrible. Sometimes whole villages perished in a short time.
As early as 1585, English explorer Thomas Harriot observed how European visits to the small villages of coastal North Carolina Indians killed the Natives. He wrote:
Within a few days after our departure from every such [Indian] town, the people began to die very fast, and many in short space; in some towns about twenty, in some forty, in some sixty, & in one six score [6 x 20 = 120], which in truth was very many in respect of their numbers. . . . The disease was also so strange that they neither knew what it was nor how to cure it.
The introduction of European diseases to American Indians was an accident that no one expected. Neither the colonists nor the Indians had a good understanding of why this affected the Native people so badly.
The great impact of disease on the Native population of America is an important part of the story of European exploration. Experts believe that as much as 90 percent of the American Indian population may have died from illnesses introduced to America by Europeans. This means that only one in ten Natives survived this hidden enemy. Their descendants are the 2.5 million Indians who live in the United States today.
A third big change connected to this new trade was slavery. European settlers needed workers to help build houses and clear fields. They soon realized that they could offer trade goods like tools and weapons to certain American Indian tribes that would bring them other Indians captured in tribal wars. These captured Indians were enslaved and "purchased" by European settlers. You might think that Africans brought to America were the only enslaved people. It is surprising to learn that before 1700 in the Carolinas, one-fourth of all enslaved people were American Indian men, women, and children. Before 1700 the port city of Charleston shipped out many enslaved Native people to work in the Caribbean or to be sold in northern cities like Boston. Slavery led to warfare among tribes and to much hardship. Many tribes had to move to escape the slave trade, which destroyed some tribes completely. In time, the practice of enslaving Native peoples ended. However, it had greatly affected American Indians of the South and the Southwest.
Many big changes happened to the first Americans soon after Europeans met them. But Indian people survived diseases, huge shifts in their cultures, and even the destructive slave trade. North Carolina recognizes eight proud and enduring tribes today: the Eastern Band of Cherokee, Lumbee, Haliwa-Saponi, Sappony, Occaneechi Band of the Saponi Nation, Waccamaw-Siouan, Meherrin, and Coharie. They are now greatly outnumbered by the descendants of the European colonists, but their strong presence honors their distant ancestors—those earliest of American explorers.