Spatial Models On the Ecology and the Human System of An Urbanized Watershed (presentation)

BOUMANS, R., Costanza, R., Farley, J., Maxwell, T., Villa, F., Voinov, A., Voinov, H., Grove, J.M., Dalton, S. E., Ostrom, L.

Institute of Ecological Economics, University of Maryland System, P.O. Box 38, Solomons MD, 20688, Phone: (410) 326-7281. Email:

USDA Forest Service, Northeastern Research Station, 705 Spear Street, South Burlington, Vermont 05403.

Research Associate, University of Maryland, Baltimore County. Baltimore Ecosystem Study, Rm. 134 TRC Bldg., University of Maryland at Baltimore County, 5200 Westland Blvd., Baltimore, Md. 21227

Center for the Study of Institutions, Population and Environmental Change (CIPEC), Indiana University, 513 North Park Street, Bloomington, Indiana 47408.


Modern humans view themselves as apart from nature. When natural resources and waste absorption capacity of the environment were vast relative to the size of human populations, both ecology and social sciences could advance within this paradigm. In the modern world, however, just as social scientists must recognize that ecological limits are a major constraint on continued human progress, life scientists must accept that humans are an integral part of virtually every ecosystem. This mutual interdependence is the main structuring factor in urban ecosystems. Shifting the paradigm of humans as outside agents impacting a system to one of humans as integral parts of the system opens up scarcely exploited scientific territories that stand between the social and life sciences. This new paradigm promises hybrid vigor in the development of theory, methodology and policy with practical implications for policy makers.

We currently lack a well-developed framework for joining socioeconomic and ecological data. The IEE seeks to develop an appropriate framework by integrating more detailed socioeconomic data and models into existing spatial watershed landscape models. These computer models will allow us to simulate the human ecosystem to examine the human and ecological impacts of alternative development strategies. Processes addressed by the model include the human-modified spatial fluxes of water, carbon, and nutrients over time. Just as different physical properties of soil, patterns of rainfall, etc. influence these spatial fluxes, different socioeconomic characteristics of human communities influence the type and degree of human modifications to them. These modifications in turn have an impact on the ecosystem's ability to generate and sustain wealth, which can alter spatial socioeconomic patterns and generate feedback processes whose effects are hard to predict intuitively.

In our model, four basic stocks of capital represent wealth:

1. Built capital, the physical infrastructure represented by houses, roads and other long-lasting commodities.
2. Human Capital, the societal investment in knowledge and its upkeep,
3. Social capital, the intensity and direction of the many kinds of relationships between individual humans,
4. Natural capital, the natural environment and the ecosystem goods and services derived from it.

Traditional economic models focus on built capital and to a lesser extent on human capital. Sociology and political science tend to focus on aspects of social capital and human capital. Life sciences often restrict themselves to natural capital. In reality, these capital stocks are highly interdependent.

Progress to date:

Based upon an ecosystem model calibrated for the Patuxent watershed (MD), we developed a spatial model of the ecosystem processes within the Gwynn's Falls watershed in Baltimore. The simulated output underlines the importance of the storm drain system built in response to large impermeable areas, typical of urbanized watersheds. Storm drains cause rapid transport of rainwater to streams and prevent the water from percolating into the soil. New design criteria (a result of societal investment in human capital), smaller impermeable areas (decreased investment in built capital), and community involvement in beautifying neighborhoods (investment in social capital) are required to allow rain water to again percolate into the soil to restore Natural capital. Increased percolation restores ecosystem services such as replenishment of aquifers with purified drinking water, retention of water in the soil for flood prevention, increasing soil moisture to stimulate primary production, and the creation of temporary anaerobic conditions that stimulate de-nitrification. This is just one example of how our model can simulate the impacts of different development scenarios on each of these types of capital stock and thereby suggest effective development policies.

We have also made progress on the modeling of social, human and built capital. We are calibrating and refining these models for the inhabitants of the Gwynn's Falls watershed. When fully developed, we will integrate these models into the ecosystem model using our Spatial Modeling Environment software, the result of seven years of previous IEE research.

The greatest promise of the LTER Baltimore Environment Study is the potential for cooperative, integrated research required to develop a new paradigm. For example, a credible Gwynn's Falls Landscape Model will require enormous amounts of data from a large geographic area and a broad range of disciplines, which is beyond the reach of any one research group alone. However, if we familiarize ourselves with the work and language of other research teams, we can integrate their results into our own, and tailor our output to meet their needs as well. This may occasionally require some modification of methodologies to facilitate data sharing, and a minor shifting of focus. In compensation, the end result should be a holistic understanding of the Baltimore ecosystem, useful to scientists as well as policy makers, rather than a more traditional reductionist explanation favored by so much academic research.