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Development Threat Analysis shows where unprotected open space lands are most likely to be developed over a specific time frame. Considering this analysis in conjunction with data on lands with high ecological or cultural value can help governments and conservation organizations in determining conservation priorities.
Development threat analyses typically involve the collection and processing of a variety of socio-economic background data. Data selection, collection and processing techniques can be complex and challenging. Extensive research is frequently required by the modeler to investigate prior successful modeling techniques and approaches. Knowledge of the age, scale, format and precision of available data is then used in conjunction with the modeling technique options to make final decisions about what data can be used and how to best compile and process it to achieve meaningful analysis. Some of the modeling techniques used in development threat analyses in the Mid-Atlantic region are briefly characterized at the end of this description.
The end result of the development threat analysis process is frequently a Geographic Information System product that enable users to overlay a base map of the project area with maps depicting areas where development pressure is projected to be the greatest and maps showing the area’s natural resource priority areas. The natural and manmade resources found in the area can be shown on separate overlays that can be easily added to, and taken off of the base map so the affect to different resources can be clearly seen. Examples of data that can be shown on map overlays are the location of various habitat types, current and future land use, proposed infrastructure, land cover, floodplains, drinking water supplies, current and projected population densities and cultural resources such as historic landmarks and archaeological sites.
The results of development threat analyses have a wide variety of applications. They allow end users to prioritize conservation work by focusing land purchase and other preservation efforts to areas that are both ecologically valuable and highly vulnerable to development. Threat analyses can allow both conservation groups and governments to be proactive, instead of reactive to development pressures. By showing how development is likely to affect natural, agricultural and other resources, analyses can guide county and municipal governments on the development of their comprehensive plans and land development ordinances as well as their investments in public infrastructure.
Large-scale threat analysis, or the combination of analyses from neighboring areas, allow regional and interstate conservation efforts to be more strategically planned. Additionally, a development threat analyses can provide important planning tools in creating and maintaining sustainable resource-based industries, such as timber and wood product industries.
No single “standard” development threat analysis technique has been accepted or adopted for completing development threat analyses. A variety of approaches have been developed in recent years, each customized to match the data available for the region being studied.
The use of Geographic Information System (GIS) mapping is advised, as it will allow data from multiple sources to be combined and manipulated. GIS allows for complex analyses to be done on the interaction of multiple factors affecting an ecosystem, and a GIS can be used to create maps where multiple data sets can easily be overlaid. Depending on the software used, people other than those conducting the analysis may be able to download free, simple to use software that will allow them to view the results of the analysis.
The scale and age of the data inputs to the process are critical to the accuracy and detail of the analysis. Regional-scale datasets will almost always be less accurate then local data, because regional data inputs have to be consistent across large areas. This invariably leads to the need to use the lowest common denominator for data available -- in terms of scale, age and precision. The larger the project area, the less precise the data inputs and resultant outputs are. Local data and analysis will frequently be more reliable than landscape and regional scale analyses because on-the-ground local knowledge is more accurate. However, local analysis is frequently infeasible due to lack of available data in a usable GIS format, and due to the relatively high costs of developing models for smaller areas. Economies of scale force most development threat analysis to be completed at the landscape or regional scale.
A short synopsis is provided to give the reader an overview of each project; for detailed information, please follow the links provided:
The Chesapeake Bay Program, Resource Land Assessment developed six analytical approaches for assessing the value of forests, farms and wetlands within the Chesapeake watershed using GIS models to manipulate and combine data from a variety of sources. The resulting assessment models can be utilized individually or in combination. The composite data sets can be reclassified and applied at different geographic scales based on the needs of the user.
One of the analyses is the vulnerability model. The vulnerability layer evaluates the relative potential risk of future land conversion to urban uses. Vulnerability is defined as a function of suitability for development and proximity to growth “hot spots.” The vulnerability layer is useful as a stand-alone layer to evaluate development trends, but can also be combined with the other resource land assessment layers to prioritize land conservation efforts.
For more information, visit http://www.chesapeakebay.net/about/programs/rla
The Development Threat Assessment for SmartConservation, which analyzed the 5-county area surrounding Philadelphia, was compiled by the Delaware Valley Regional Planning Commission for the Natural Lands Trust between 2002 and 2003. The data used was already partially or completely available, allowing the completion of an analysis that would have otherwise been too costly and time-consuming. Five subcomponents of data were used:
The Development Threat Assessment for the Schuylkill Priority Lands Strategy was also conducted by the Delaware Valley Regional Planning Commission (DVRPC) for the Schuylkill Watershed in 2006-7. The assessment was based on a model acquired from California (UPLAN Model) and was calibrated for use in the DVRPC region. On a county level, the model spatially assigns population and employment forecasts to acres consumed based on attractors (transportation access, public sewer and water, proximity to existing development), discouragements (congestion) and masks (developed land, protected land, wetlands).
For more information, visit http://www.schuylkillprioritylands.org
Patty Elkis, PP, AICP, Associate Director, Planning Division, Delaware Valley Regional Planning Commission was the original author for this document; Peter Claggett, USGS reviewed it.
Copyright © is held by the Pennsylvania Land Trust Association
Text may be excerpted and reproduced with acknowledgement of ConservationTools.org and the Pennsylvania Land Trust Association.