HUMAN-INDUCED LAND TRANSFORMATIONS

Leonard Gaydos, William Acevedo, Cindy Bell

As populations increase worldwide, humans are transforming landscapes with important consequences. Some of the most profound, yet little studied, changes are occuring around the world's great cities. With support from the U.S. Geological Survey, Ames scientists are documenting past land use changes, building models of the urbanization process, and making data, visualizations, and maps available to other scientists, policy makers, and the public for a variety of applications.

Human-Induced Land Transformations has as its goal mapping patterns and rates of major land use changes at the regional scale for the last 200 years, and making predictions for the next 200 years. The San Francisco Bay Area has served as an initial test site.

Using historic topographic maps, land use maps, and Landsat data, a geodynamic mapping data base is being completed to document land use change since the Gold Rush. Seven historic eras have been mapped and used to construct an animation that shows the extent and pace of urbanization in the region. Starting with initial settlement in the core cities of San Francisco, Sacramento, Oakland, and San Jose the animation shows how the area grew deliberately in the early years and then explosively after World War II. Current work is on refining the data for publication on CD-ROM and adding information on transportation development.

A computer model of urbanization, developed by collaborators at Hunter College, New York City, is being calibrated with the historic data. This computer model employs the techniques of cellular automata to determine whether grid cells become urbanized each iteration based on a set of parameters related to existing states and neighborhood properties. Once calibrated, it will be used to predict several scenarios of future growth.

Several applications of the work are being pursued. U.S. Geological Survey hydrologists have seen correlations between urbanization trends and increased heavy metal concentrations in San Francisco Bay. U.S. Forest Service scientists are interested in impacts of further urbanization on forestlands in the Sierrra Nevada. Urban planners and conservationists have used the data to focus attention on alternatives to urban sprawl.

Figure Caption

The magnitude of human-induced land transformations is illustrated in this sequence of maps showing change in urban land use for San Francisco (black patches on the maps).

Ames-Moffett contact: Dr. Leonard Gaydos

lgaydos@gaia.arc.nasa.gov

or tel: (415) 604-6368

Program office: USGS Reimbursable