Fall Colloquium lecture notes pre-industrial climate change

10/08/08 - Way before Americans were driving SUVs, agricultural practices of Indian tribes in North and South America were causing global climate change, such as the Medieval Warming period and the Little Ice Age.Charles Mann, author and journalist who has written for the New York Times Magazine, the Washington Post, and the Law and Order television series, explained habits of pre-industrial cultures and their effects on the climate in the Fall 2008 Honors Colloquium last night.

Mann started his lecture with a painting of American Indians on horses, with feather head dresses from his high school history textbook, which he said was inaccurate because Europeans brought over horses and American Indians didn't wear head dresses.

Another common misconception, Mann said, was that Indians had more impact on their land in North America than European settlers did.

"[European settlers] hadn't been there as long," Mann said after the speech. "In 1650 we have these small groups of settlers, but the main story is this decline" of tribes.

American Indians in Massachusetts had deforestation practices to grow corn. In the Cahokia city, outside present-day St. Louis, Mo., natives cut down trees, which reduced the land's ability to retain water, causing floods.

They also dug a canal, which would fill with water and float tree logs right to the city. But that canal also channeled floodwaters into the city.

"If you're going to make the land more flood prone, the last thing you want to do is cut a channel that takes those floods right to your front door," Mann said.

When native tribes in both Americas burned trees, the Earth lost some of its ability to absorb carbon dioxide, which contributed to the Medieval Warming period.

When trees grew back and European methods called for less deforestation, Mann said the Earth absorbed a lot of carbon dioxide, which contributed to the Little Ice Age, lasting from the 1500s until about 1700.

By the time European settlement became widespread, in about 1650, Mann said corn farms were all over New England.

"Europeans who came in 1650 came into a landscape that was pretty much empty," Mann said.

Adding charcoal to the soil, which retains 85 percent of its carbon, Mann said, compensated for South American deforestation practices and this allows for re-growth of vegetation.

But despite their efforts to revive the soil quality, almost all of South America was affected by human presence according to a chart Mann showed. The same chart showed that about half of the continental United States was also affected.

And though Europeans had a low environmental impact, they brought almost 16 diseases to the Americas, while the Americas sent only one back to Europe, Syphilis. Malaria, Yellow Fever and Small Pox were just some of the diseases brought to the Americas by Europeans.

The cause of this, Mann said, is that Europeans lived with living domesticated animals, while Native Americans did not. A slide showed a painting of a house of a Powhatan tribe, a sub-tribe of the Algonquin Indians, which had lots of pelts stacked against the wall.

"The one thing you notice is there's plenty of animals there, but they're all dead," Mann told a laughing audience.

He also dedicated his lecture to dispelling common misconceptions about American Indians, mainly the idea that they were in sparse tribes and were in harmony with the environment. He began by examining Tenochtitlan, an ancient city in Mexico, constructed on a lake, and Mann called it "one of the most heavily urbanized places on the Earth in the 16th century."

Matt Horn, a URI graduate student, called the evening "entertaining and intriguing."

He said it looked at global climate change in a historical perspective, and said it helps suggest the truth behind today's science.

"If this is saying a whole bunch of primitive cultures can alternate the environment, hell yeah, we can, too," Horn said, adding that it looks at climate change from a new and broader perspective.

"I think there's a lot of approaches to climate change," he said. "It's a hot topic, so a lot of people are going to want to get their foot in the door.