The Mississippi Basin is the third largest drainage basin in the world and is home to one of the ..... specialized and intensified than ever before from following a.
Land Use, Land Cover, and Climate Change Across the Mississippi Basin: Impacts on Selected Land and Water Resources Jonathan A. Foley, Christopher J. Kucharik, Tracy E. Twine, and Michael T Coe Center for Sustainability and the Global Environment (SAGE), Nelson Institute for Studies, University of Wisconsin, Madison, Wisconsin
Environmental
Simon D. Donner Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, Jersey
New
The Mississippi Basin is the third largest drainage basin in the world and is home to one of the most productive agricultural regions on Earth. Here we discuss how land use/land cover change and climatic variability may be affecting some key environ mental processes across the Mississippi and how these, in turn, affect the flow of selected ecosystem goods and services in the region. Specifically, w e consider the recent history of land use/land cover change, crop yields, basin river flow and hydrol ogy, and large-scale water quality in the Mississippi Basin. We find that agricultural activities may have had a profound influence on the basin and may have shifted the flow of many ecosystem goods and services into agricultural commodities, at the expense of altering many of the important biogeochemical linkages between atmos phere, land, and water.
so with only 20% of the world's corn acreage [USDA, 2003]. In addition, the Mississippi Basin is a major producer of soy beans (with over 40% of global soybean production), wheat, cotton, and other important agricultural commodities [USDA, 2003]. However, this impressive litany of agricultural pro duction statistics does not come without significant environ mental costs. Soil erosion, the destruction of native habitats, and a decline in biological diversity have all accompanied the transformation of the basin into a major agricultural region. Agricultural practices have also had a profound impact on the biogeochemical cycles of carbon, nitrogen, and phospho rus in the region. For example, agricultural land use has caused significant environmental losses of soil organic material [Mann, 1986; Darmody and Peck, 1997; Paustian et al, 1997; Kucharik et al, 2001], resulting in decreased soil "tilth," increased sediment loading in rivers, and the transfer of soil carbon to carbon dioxide in the atmosphere. Furthermore,
1. INTRODUCTION Covering roughly 3.2 million km , the Mississippi River drainage basin is the third largest basin in the world (Plate 1). Extending over more than 4 8 % of the continental United States, the Mississippi Basin is home to roughly 70 million people, plus a $100 billion per year agricultural economy [Goolsby et al, 1999]. The Mississippi Basin also contains some of the richest farmland found anywhere in the world. For example, the region produces approximately 40% of the world's corn and is responsible for about 70% of global corn exports, but does 2
Ecosystems and Land Use Change Geophysical Monograph Series 153 Copyright 2004 by the American Geophysical Union 10.1029/153GM19 249
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LAND USE IN THE MISSISSIPPI
FOLEY ET AL.
251
fertilizer use in the basin has led to increasing flows of excess
We will examine the results of several modeling studies
nitrogen and phosphorus to surface and groundwater systems,
that have been used to characterize the behavior of terrestrial
ultimately causing serious degradation of freshwater and
ecosystems and freshwater systems across the Mississippi
coastal ecosystems [Goolsby et aI., 1999; Donner et aI., 2002;
Basin, and how they respond to environmental and human
Donner and Kucharik, 2003].
drivers. In particular, we will focus our discussion on a few key
Altogether, land use and water management practices tied to agriculture have had a strong influence over much of the basin. But understanding how the environmental systems and
questions: 1.
sippi Basin changing?
natural resources of the Mississippi Basin may respond to agricultural land use and land cover change is difficult, because of the complex linkages between different components of the
2.
restrial ecosystems, and aquatic systems of the basin, and how they are affected by human activities (Figure 1). In this chapter, we will consider how the interactions among
How might land use/land cover change, combined with climate variability, affect the production of crops in
earth system operating in the region. It is therefore necessary to understand the interactions between the atmosphere, ter
How are the land use and land cover of the Missis
the region? 3.
How might land use/land cover change, combined with climate variability, affect the hydrology and water qual ity of the region?
the atmosphere, terrestrial ecosystems, and aquatic ecosys tem of the Mississippi Basin produce ecosystem goods and
2. HOW ARE LAND USE AND LAND COVER
services (e .g., "provisioning" services like food production,
CHANGING IN THE MISSISSIPPI?
plus "supporting" services such as providing clean water and the maintenance of regular water flows) that are of signifi
The Mississippi Basin covers a wide range of climatic and topographic regimes across the United States, ranging from
cant importance to humanity.
mesic temperate forests in the east to dry shrublands and irri gated agriculture in the west. If we consider the patterns of precipitation across the basin (Plate 1), we note that the 600 mm isoline of mean annual precipitation divides the eastern (semi-humid) part of the basin from the semi-arid western portion. Rain-fed corn and soybean cropping systems, grass
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climatic conditions
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