A new study by Baylor University geology（地质学） researchers shows that Native Americans' land use nearly a century ago produced a widespread impact on the eastern North American landscape and floodplain（泛滥平原） development several hundred years prior to the arrival of major European settlements. The study appears on-line in the journal Geology.

Researchers attribute early colonial land-use practices, such as deforestation, plowing¹（耕作） and damming with influencing present-day hydrological（水文学的） systems across eastern North America. Previous studies suggest that Native Americans' land use in eastern North America initially² caused the change in hydrological systems, however, little direct evidence has been provided until now.

The Baylor study found that pre-European so-called "natural" floodplains have a history of prehistoric³ indigenous⁴（本土的，国产的） land use, and thus colonial-era Europeans were not the first people to have an impact on the hydrologic systems of eastern North America. The study also found that prehistoric small-scale agricultural societies caused widespread ecological⁵ change and increased sedimentation⁶（沉淀） in hydrologic systems during the Medieval Climate Anomaly–Little Ice Age, which occurred about 700 to 1,000 years ago.

"These are two very important findings," said Gary Stinchcomb, a Baylor doctoral candidate who conducted the study. "The findings conclusively⁸ demonstrate that Native Americans in eastern North America impacted their environment well before the arrival of Europeans. Through their agricultural practices, Native Americans increased soil erosion and sediment⁷ yields to the Delaware River basin."

The Baylor researchers found that prehistoric people decreased forest cover to reorient（使适应） their settlements and intensify⁹ corn production. They also contributed to increased sedimentation in valley bottoms about 700 to 1,000 years ago, much earlier than previously¹⁰ thought. The findings suggest that prehistoric land use was the initial cause of increased sedimentation in the valley bottoms, and sedimentation was later amplified¹¹ by wetter and stormier conditions.

To conduct the study, the Baylor researchers took samples from several different spots along the Delaware River Valley. Landforms were mapped based on relative elevations¹² to Delaware River base flow and archaeological（考古学的） excavations¹³ assessed the presence of human habitation. The Baylor researchers then used a site-specific geoarchaeological approach and a regional synthesis of previous research to test the hypothesis that the indigenous population had a widespread impact on terrestrial sedimentation in eastern North America.

"This study provides some of the most significant evidence yet that Native Americans impacted the land to a much greater degree than previously thought," said Dr. Steve Driese, professor and chair of Baylor's department of geology, College of Arts and Sciences, who co-authored the study. "It confirms that Native American populations had widespread effects on sedimentation."