Understanding the ecology of a region is an important part of historic and prehistoric archaeology. What animal and plant resources were available to the past inhabitants of the sites we investigate makes up a large component of our research. How close a site is to a permanent water source, what kinds of foods were available in the neighborhood, and what arable land was nearby are just a few of the questions the archaeologist must ask.
One reason background research is so critical to archaeological studies is the fact that massive environmental changes may have occurred in the past that are not readily apparent today. Although the climate of the midwest and plains has been fairly stable since the end of the Altithermal 6000 years ago, the effects of human settlement can be so massive as to have become an invisible presence on the landscape.
From Fen to Farmland
Driving along the Interstate highways in the North American midwest during the height of summer, one is struck by the immense fertility of the region. For miles and miles, maize or soybeans march in tidy monocultural rows, the area producing hundreds of millions of bushels of crops each year, feeding much of the world and its animals.
But it was not always thus. In a recent article in the Journal of Historical Geography, geographer Michael A. Urban discusses the immense changes wrought by 19th century agricultural practices, including the introduction of drainage tile below the surface of the land.
At the time of the American colonization, the landscape in central Illinois and other parts of the midwest could be characterized as tall grass prairie with many sloughs and wet prairie potholes. Although the original inhabitants were well aware of the economic resources of the prairies, the new Euroamerican settlers were not. These large stretches of wetlands were seen as inherently unhealthy; they were certainly the causes of mosquito infestations and malaria outbreaks throughout the 19th century. Malaria was the number one killer of people living in central Illinois until the 1850s.
A Boom in Population
The change came with a boom in population during the 1840s and 1850s. The people came via the Illinois Central Railroad, and the railroad held a vested interest in increasing the number of settlers in the region. The ICRR began a campaign to construct ditches, running a contest for the best ditching machine design. The mole plow, a tool which excavated drainage tunnels, was brought to the American midwest in 1856. But it wasn't until 1870s that drainage tile, the use of ceramic crockery tubes placed in rows beneath the surface of the land, became feasible. And farmers soon discovered that efficient drainage tiles were only as good as the adjacent streams, and so stream and river channels were widened, straightened, and deepened.
The upshot of all of this activity was the complete change of the landscape from marshy unoccupied wetlands to straight lines of agriculture stretching on for miles and miles; and the completely disarranged ecological foundations of the area.
Archaeology and Drain Tile
Archaeological studies of this period of time have included investigations of brick and tile factories. The disturbance of agricultural fields by the placement of drainage tile has been noted on archaeological sites throughout the midwest; one occasionally finds the odd site that has been bisected by a ceramic tube. But the massive changes wrought to the American wet prairielands is something not readily visible to the casual passerby--or the archaeologist in her field investigations. This is a perfect example of why previous research is so important to the archaeologist: the current environmental conditions may not be what they were in the past.
Sources
Imlay SJ, and Carter ED. 2012. Drainage on the Grand Prairie: the birth of a hydraulic society on the Midwestern frontier. Journal of Historical Geography 38(2):109-122.
Urban MA. 2005. An uninhabited waste: transforming the Grand Prairie in nineteenth century Illinois, USA. Journal of Historical Geography 31:647-665.
