Statewide mapping and assessment of vernal pools: a New Jersey case study

In 2001, the New Jersey Department of Environmental Protection (NJDEP) adopted rules specifically protecting vernal pool habitat for the first time. Vernal pools are small isolated temporary bodies of water that provide critical breeding habitat for a number of amphibian species. To implement these rules and ultimately afford vernal pools protection, the NJDEP first needed to assemble a statewide database of vernal pool locations. In response, the Rutgers University Center for Remote Sensing and Spatial Analysis (CRSSA) was funded to develop a cost effective technique to map vernal pool locations statewide. The objective of CRSSA's mapping effort was to develop a complete potential vernal pool database to be able to identify individual isolated vernal pools as well as areas of high local density, or 'hotspots'. CRSSA used visual interpretation of leaf-off color infrared digital orthophotography in a computerized GIS environment to identify and map over 13,000 potential vernal pools. Using the 1m scale imagery, we determined the minimum detectable pool size to be on the order of 0.02 ha in size. Subsequent field checking has revealed a 12% error of commission that was due to our inclination towards erring on the side of inclusion in mapping many water features as potential vernal pools. For a vernal pool to receive regulated protection, it must be 'certified' that it serves as habitat for obligate or facultative vernal pool amphibian species. To aid in these efforts, CRSSA developed an interactive internet mapping site to assist NJDEP and its citizen volunteer corps in locating and navigating to their survey areas and to facilitate the on-line submittal of survey observations.