(This is the third in a series of posts about the environmental context of human ecosystems and archaeological sites in eastern North America, ca. AD 800-1700).
Last summer I wrote about ancient forest clearing practices of American Indians in the Eastern Woodlands region, particularly in reference to the Mohawk and Hudson valleys of New York State. I focused especially on sites of archaeological and geological data recovery in New York’s Capital District, such as the Goldkrest site in East Greenbush and Collins Lake near Schenectady. To conclude the second of two essays on human ecosystems of the Medieval Warm Period and Little Ice Age, I said:
“Recent research by Pederson et al (2005) has observed significant evidence of the Medieval Warm Period in the lower Hudson region. Some of this evidence is a substantial influx of wood charcoal into stream sediments at that time, as revealed in soil cores taken from Piermont Marsh. While the current assumption is that the charcoal indicates increased natural burning during extended droughts (which are also indicated by other, complementary evidence), it may well be time to entertain the possibility that increased evidence of fire ca AD 800-1300 may partially, or perhaps mainly, indicate human activity, such as controlled burns designed to enhance hunting, and the gradual but progressive expansion of humanly created settlement space, meadows, agricultural fields, and forest edges.”
Now it is possible to comment further, in this case concerning recent research in the Delaware valley. A study published this spring by a team from Baylor University, led by Gary Stinchcomb and including Temple University archaeologist Michael Stewart, has taken a different perspective than Pederson et al (2005) regarding causality in the depositional data. The incorporation of evidence from archaeological surveys in the Delaware Valley study area seems to have been a critical element of research design that has allowed a different perspective on evidence of increased soil deposition in low-lying areas. The research project combined soil sampling, landform mapping, and the results of archaeological excavation. The basic idea is that the expansion of agricultural fields for increased maize production was a significant factor leading to increased soil erosion and the re-deposition of sediment in the Delaware floodplain.
The article in the journal Geology titled “Pre-colonial (A.D. 1100-1600) Sedimentation Related to Prehistoric Maize Agriculture and Climate Change in Eastern North America” makes several key points or observations. Foremost among these is that increasing floodplain sedimentation at this time was an anthropogenic event that has been “documented throughout eastern North America.” Moreover, the authors believe that the data demonstrate the combined effects of prehistoric land use intensification and climate change. They see human forest clearing and increased agriculture as largely responsible for the initial increase in floodplain sedimentation, with a climatic shift to wetter and stormier conditions contributing later on. Following the general pattern of this sequence, the initial anthropogenic effect appears to have occurred during the so-called Medieval Climatic Anomaly, which is demonstrated as a significant, prolonged warm period by other Mid-Atlantic to Northeast regional data (cf. Pederson et al 2005).
Science Daily reported the story in March of this year, providing individual perspectives from some of the researchers. Co-author Steve Driese was quoted in Science Daily as saying “This study provides some of the most significant evidence yet” of the effect of ancient Native Americans in transforming their environment. Lead author Gary Stinchcomb was quoted as saying that “The findings conclusively demonstrate that Native Americans in eastern North America impacted their environment well before the arrival of Europeans.” Increased agriculture apparently led to increased erosion, leading to increased “sediment yields to the Delaware River basin.” And then the sedimentation process was augmented by wetter and stormier conditions (also see White and Rodbell n.d. regarding stormier conditions in the Mohawk River basin ca. A.D. 1180-1600).
This exciting perspective of multiple causes of environmental change in the Delaware basin steers thinking away from an unfortunate either-or proposition, that the effect has to be either anthropogenic or due to climate change. Coming to this refreshing conclusion leaves open the possibility of learning more about the role of human agency, of perhaps learning that land use intensification was a response to climate change experienced palpably on the relatively short time scale of human perception.
2011 Baylor Univeristy (2011, March 22). Native Americans Modified American Landscape Years prior to Arrival of Europeans. ScienceDaily. Accessed March 26, 2011
Curtin Archaeological Consulting Inc.
2010 Did Climate Change Affect the Hudson Valley, AD 800-1300?
Pederson, Dee Cabaniss, Dorothy M. Peteet, Dorothy Kurdyla, and Tom Guilderson
2005 Medieval Warming, Little Ice Age, and European Impact on the Environment
during the Last Millennium in the Lower Hudson Valley, New York, USA. Quaternary Research 63(2):238-249.
Stinchcomb, G. E., T. C. Messner, S. G. Driese, L.C. Nordt, and R. M. Stewart
2011 Pre-colonial (A.D. 1100-1600) Sedimentation Related to Prehistoric Maize Agriculture and Climate Change in Eastern North America. Geology, Accessed March 26, 2011
White, Ian Robert and Donald T. Rodbell
n.d. A ~ 1000 Year Record of Sedimentation in Collins Lake as Evidence of Local Storminess and Flooding on the Mohawk River (New York). Accessed on April 14, 2010.