Environmental management practices are trending away from simple, local-scale assessments toward complex, multiple-stressor regional assessments. Landscape ecology provides the theory behind these assessments while geographic information systems (GIS) supply the tools to implement them. A common application of GIS is the generation of landscape metrics, which are quantitative measurements of the environmental condition or vulnerability of an area (e.g., ecological region or watershed). The generation of these metrics can be a complex, lengthy undertaking, requiring substantial GIS expertise.
The Landscape Ecology Branch in cooperation with U.S. EPA Region 4 and TVA are developing a user friendly interface to facilitate this process. ATtILA is an easy to use ArcView extension that calculates many commonly used landscape metrics. By providing an intuitive interface, the extension provides the ability to generate landscape metrics to a wide audience, regardless of their GIS knowledge level. ATtILA is a robust, flexible program. It accepts data from a broad range of sources and is equally suitable across all landscapes, from deserts to rain forests to urban areas.
Four families of metrics are included in the extension, and each group has a dialog to accept user input on which metrics to calculate and what input data to use:
- landscape characteristics: related to land cover proportions and patch metrics (e.g. percent forest cover or number and size of forest patches)
- riparian characteristics: describe land cover adjacent to and near streams (e.g. percent of crop land within 30 meters of streams)
- human stressors: concern population, roads, and land use practices (e.g. population change or road/stream crossings)
- physical characteristics: provide statistical summaries of such attributes as elevation and slope
Once metrics have been calculated, the extension has three types of output display available.
- displays areas ranked by individual metric values
- ranks areas by a weighted index made up of two or more metrics
- displays a bar chart of selected areas and metrics
Because of the size of landscape data sets and the complexity of the calculations to generate some metrics, we recommend a minimum of a Pentium II 266 MHz (or equivalent) with 32 MB of memory. A preferred system would be a Pentium II 400MHz (or equivalent) with 64MB of memory and a fast (<8 ms) hard drive or better.
To use the ATtILA, you will need version 3.1 or later of ArcView and the Spatial Analyst version 1.1 extension. Both UNIX and Windows (95, 98 and NT) environments are supported.
For further information contact: LEBProjects@epa.gov