PARENT SESSION
Symposium 3: Complex Interactions Between Human Population and the Environment: Integrating Demographic, Socioeconomic, and Ecological Perspectives .
Organized by: Jianguo(Jack) Liu and RL Clark
Monday, August 2, 8:00 AM to 11:30 AM, Oregon Ballroom 204.
Human population and environment in the U.S. Great Plains.
Gutmann, Myron*,1, Parton, William2, Ojima, Denis2, Williams, Stephen2, Easter, Mark2, 1 University of Michigan, Ann Arbor, MI2 Colorado State University, Fort Collins, CO
ABSTRACT- The Great Plains of the United States is an important region for understanding the accumulated impact of more than a century of agricultural development and the slowly growing impact of urban and suburban populations on a grassland ecosystem. The objective of this paper presentation is to use historical data about population change and agricultural and land use changes, along with the CENTURY Soil Organic Matter model to estimate the long-term impact of these changes. The main data come from historical censuses of population and agriculture, combined with historical information about precipitation and temperature. The paper focuses on the experiences of counties in the Great Plains, making use of eight sample counties in Colorado, Texas, Kansas, Nebraska, and North Dakota. While most of the analysis focuses on areas where the population is small and most land is used for agriculture, the sample counties include regions where the population has been urbanized and growing rapidly over the past fifty years. The results are generally expressed as changes in Carbon and N mineralization, along with other trace gas results. The primary findings show that the development of agriculture in the Great Plains has generally reduced soil carbon and nitrogen, but that the process of decline eventually stabilizes, and developments in agriculture since the 1950s (irrigation and other soil inputs) can in some cases raise levels of C and N. The striking exception to this is the case of irrigated cotton production in Texas, where high temperatures have a dramatic impact. Another important finding is that the direct result of population through the conversion of farmland to land used for residential, commercial, and other uses may be less important than previously anticipated.
Key words: population, agriculture, landuse, carbon