Climate change must have presented challenges as well as opportunities for ancient cultures , but can episodes of changing climate contribute to the rise and fall of civilizations?

Climate change must have presented challenges as well as opportunities for ancient cultures , but can episodes of changing climate contribute to the rise and fall of civilizations?

In a forthcoming issue of the Journal of Archaeological Science, Cornell University archaeologist Sturt Manning and an international team of scientists show how tree rings in ancient Egyptian wooden artifacts have opened a window into how the climate influenced cultural developments in the ancient Near East.

Tree rings provide a wonderful record of changing weather patterns over the life of a tree. The thickness of individual tree rings indicates how much water was available to the tree during each growing season.

The tree rings in the ancient Egyptian wood revealed that around 2200 B.C., there was a relatively brief but intense episode of drought, which Manning and his team say could have caused disruptions in the civilizations of Egypt and Mesopotamia.

In a Cornell University news release, Manning said, "This record shows that climate change doesn't have to be as catastrophic as an Ice Age to wreak havoc."

Ohio doesn't have a comprehensive record of ancient tree rings to tell us how the climate has changed over time, but there are other ways of getting at that information.

Every spring, for example, pollen fills the air. Some of it settles to the bottom of ponds, where it can accumulate in layers of muck. These layers are like pages in a book, recording the plants growing near the pond from one year to the next.

Ohio University archaeologist Elliot Abrams and his colleagues studied pollen from Patton Bog in Athens County. Their results, published in the current issue of Midcontinental Journal of Archaeology, indicate a change around 1000 B.C. from layers dominated by tree pollen to layers with grass pollen.

This change would have been a big problem for the ancient hunters and gatherers of southern Ohio who relied on nuts for much of their diet. Fewer trees mean fewer nuts.

Abrams and his team say that farming began in southern Ohio partly as a result of this climate change. A drier climate reduced the availability of nuts, and people adapted by shifting their attention to a variety of seed-bearing plants, such as sunflower and goosefoot.

At first, they just gathered the seeds. Later, they began to plant their favorite varieties and weed out others. Within a few centuries, they had become part-time farmers. By A.D. 1, they were deliberately setting fires to clear the land for more-extensive gardens. Charcoal from these fires shows up in layers dating to this period.

The Patton Bog pollen record documents Ohio's changing climate along with how the American Indians living here adapted to those changes. The choices they made would have far-reaching consequences.

Climate change is going to be a big factor in our future. Learning the lessons of the past might help us respond appropriately to the challenges and opportunities we will face in the coming decades. And archaeology has an important contribution to make in recovering those unwritten lessons.

Bradley T. Lepper is curator of archaeology at the Ohio Historical Society.

blepper@ohiohistory.org