Understanding Linkages Among Human and Biogeochemical Processes in Agricultural Landscapes

Humans have profoundly altered global cycling processes at multiple scales. Current estimates suggest human activities have doubled the amount of biologically active nitrogen on a global basis, with agriculture accounting for 75 percent of the human-derived nitrogen. A complex set of environmental and socio-economic factors influence agricultural fertilizer management practices. Linkages among socioeconomic and ecological subsystems are recognized as crucial in efforts to pursue sustainable ecosystem management and improve nitrogen-use efficiency. Disconnections between human and natural subsystems must be addressed as well as disconnections within the component subsystems. Within the human realm, those who pollute do not pay the costs associated with resource degradation. Likewise, the biophysical system that has evolved as a result of high, input industrial agriculture is fraught with ecological disconnections. For example, uncoupling of carbon and nitrogen cycles is a defining trait of agricultural systems and is the root cause of the leakiness of these systems. On average, 45 percent to 55 percent of fertilizer nitrogen applied is lost to the environment. The goal of this research project is to understand how interactions among social and biophysical subsystems impact on carbon and nitrogen cycles in intensively managed agricultural landscapes at multiple scales. Specific objectives of the project are (1) to investigate how the human subsystem responds to the environmental consequences of carbon nitrogen uncoupling, (2) to evaluate the relationships between nitrogen leakiness, institutional capacity, and proximity to degraded aquatic resources, (3) to determine which policy changes are likely to be most effective in promoting more efficient nitrogen fertilizer-management practices, and (4) to model and simulate multi-scale interactions among policies, farm managers, and institutions as well as nitrogen losses across space and time. To understand how institutions respond to degradation of aquatic ecosystems, the investigators will compare the institutions and management approaches used in the Chesapeake Bay, where the negative impacts of excess nitrogen inputs are experienced more locally and by the farmers themselves, to those in the Midwest, where the negative impacts are much more remote. Research methods include field research, isotopic tracer studies, construction of mass balances at multiple scales, face-to-face interviews and surveys with stakeholders, geographical information systems, remote sensing, global positioning systems, statistical tools, systems modeling, and simulation. This project has implications for coupled human-natural systems theory and methodology, social systems theory, and environmental policy. The theory of how the human and biophysical subsystems of managed landscapes is not well developed, particularly in the case of intensively managed, high-input agricultural systems. This research will enhance fundamental understanding of how social and ecosystem emergent properties mediate interactions among human and natural systems. In addition to using a synthetic interdisciplinary approach, the investigators will depart from a microeconomic model of social dynamics in which the aggregated behavior of individual actors is taken to represent social processes. They will focus primarily at the institutional level, where the social emergent properties govern the interactions between and social and natural subsystems. The project also will have practical outcomes of relevance to the development of agricultural and resource-management policy. This project is supported by an award resulting from the FY 2005 special competition in Biocomplexity in the Environment focusing on the Dynamics of Coupled Natural and Human Systems.

Lead Investigator: 
Emergent Properties
isotopic tracers, mass balance, GIS, systems model
Chesapeake Bay, US Midwest
Temporal Scope: 
Spatial Scope: 
Natural System: 
temperate carbon, nitrogen cycling
Human System: 
agriculture, fertilizer