Agricultural intensification in the Mississippi River Basin: Spatial heterogeneity, drivers and consequences

Background/Question/Methods

The Mississippi River Basin (MRB) produces 78% of the world's exported feed grains and exemplifies a highly productive social-ecological system which has multiple ecological and social consequences. Several lines of evidence indicate that the process of agricultural intensification in the basin accelerated significantly beginning in 1960 and continued through the 1980's to the present time despite the well-documented negative environmental consequences and associated increased health risks for people living in the region.  Although agricultural production is the dominant land use, the environmental and social context in which agricultural systems are situated varies within the basin and the degree of intensification also varies within the MRB.  We used this spatial heterogeneity to analyze social-biophysical interactions and linkages using differentially defined units of analysis: watershed, county and farm-scale. The central question addressed in this presentation is “How does the biophysical setting interact with signals from the social system to determine the trajectory and distribution of agricultural intensification in the MRB?” We expected ecosystem state factors to interact with agricultural policies and programs to determine the locally variable trajectories of agricultural intensification.

Results/Conclusions

Field-scale N mass balances are highly variable across working farms and N management practices that are most effective in reducing nitrate leaching losses from farm fields are generally rare in the MRB. Yield-oriented national agricultural policy drives intensification; however there is divergence of ecological and economic characteristics at the county level which is driven mainly by soil fertility and productive capacity. Counties with fertile soils are dominated by corn-soybean, have high rates of N loss and contribute disproportionately to hypoxia. Farms are larger, more profitable and receive the bulk of direct government payments which are directed to support crop production. Communities located in these counties have reduced poverty and unemployment. In contrast, counties with less fertile soils are more agriculturally diverse with greater acreage in perennial crops and reduced N losses. Farms are less economically viable and receive a much smaller proportion of direct payments, mainly those that are promoting conservation. Alternative farming systems that promote multiple ecosystem services are also more common in these counties compared to those with the most fertile soils. Thus, conservation payments are directed at farming areas with the lowest environmental impacts. In these less fertile counties the communities are more economically stressed. Our analysis suggests that regions in the basin are diverging with intensification continuing in those areas with the greatest productive capacity.