Ecological Boundary Delineation
Scott Ferson
Supported by the Electric Power Research Institute
Project Description
This project will collect the diversity of methods that are currently being used to draw ecological boundaries in a single friendly software package. These methods are used to find the borders around wetlands, fragile habitats, to locate vegetation structures sensitive to environmental change, and to plan human activities with the least environmental impact. The methods must contend with complex multivariate data which is often noisy, but which may not have been sampled thoroughly on a grid, but only at a few single points, or possibly across transects. By offering these disparate analytical methods in one enviroment, researchers will be better able to compare there properties and better choose among the alternative methods.
Despite the importance of ecological boundaries in a variety of scientific questions and a multiplicity of management strategies, very little research has been focused on delineating ecological boundaries. Virtually all maps of biological resources produced before 1970 were drawn by eye, without the benefit of any formal algorithm for determining the positions of boundaries. Cornell systematist William L. Brown (of character displacement fame) humorously offered Brown's Rule which states that the boundary between two species will be drawn where the fewest samples have been taken. Over the last two decades, algorithmic approaches have been employed, but they have used poorly documented, often ad hoc methods whose properties were not well or widely understood.
Mapping of ecological boundaries has lately become a common activity among environmental engineers and managers, ecologists, land use planners, and biological reserve designers. Many applications arise in diverse areas such as critical habitat mapping, home range demarcation, land use partitioning, wetland delineation, vegetation mapping, ecotone identification, patch boundary localization. But each of these applications harks to the same problem of where to draw the line to separate regions. Each of these applications has one or more methods which were usually designed from scratch for its particular purpose. Surprisingly little systematic attention has been paid to how these boundary delineation methods behave, or to the similarities or discrepancies among them, or to whether one might be much better than another.
Drawing boundaries on maps is largely controlled by pragmatic considerations. Legal and political realities force managers to draw lines somewhere (even when the empirical information is sketchy) and these lines sometimes then take on a life of their own which is often unjustified by the underlying ecological reality. Once the position of the boundary has been decided, it is sometimes difficult to return to an ecologically meaningful description even if the situation changes or the original determination was flawed. Since the justification for the boundary was ad hoc in the first place, it is often even more difficult for a researcher to be effective in arguing that the line should be moved or reconsidered. Thus, it can be doubly difficult to overcome the troublesome (but natural) legalistic inertia that seems to accompany drawing a line.
While the simple boundary delineation methods currently available in software packages such as GIS and image analysis systems may be adequate for incidental use in research and planning, in cases where the drawing of boundaries is central or even crucial to the question or goal, much more sophisticated methods must be employed. We propose to develop a microcomputer software shell (tentatively named EcoBound) containing a comprehensive variety of these methods for delineating ecological boundaries that can be applied to sparse points, transects, or grids of possibly multivariate environmental data. The shell will be modular in design so as to accommodate inclusion of future methods. By collecting the diverse methods into one shell with a convenient interface for communication with GIS, image analysis and general statistical packages, this research will facilitate consistent and rational usage of the various methods available. By using objective methods with known statistical properties, researchers will be better equipped to defend the conclusions they finally draw. Likewise, when the determination method is well understood and conveniently accessible in software, others can check the conclusions with new data, alternate methods, or different assumptions, and thereby improve the quality of the review process.
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