Classifying Habitat for Delmarva Fox Squirrel from LiDAR
US Fish & Wildlife Service Chesapeake Bay Field Office

The Chesapeake Bay Field Office of the US Fish & Wildlife Service (USFWS) is responsible for the recovery of the Delmarva fox squirrel (DFS), an endangered species found in tall, mature stands of mixed pines and hardwoods on the Delmarva Peninsula. Critical to the conservation effort is the ability to map and understand the distribution and abundance of mature forest stands used as habitat. Most vegetation maps delineate stands by dominant species, regardless of forest maturity, thus the Service needed a way to identify tall, mature stands. LiDAR first return and bare earth data can be used to classify canopy height and canopy closure, and is available for all of Maryland from an orthophoto project conducted in 2003-2005. The USFWS approached Sewall for assistance. Sewall developed a set of routines to derive the needed GIS layers, with Dorchester County as the test case. The final result was a set of interpretive grids and polygons for eight Delmarva Peninsula counties containing data on tree height, canopy density, and DFS habitat.

The USFWS chose Sewall for several reasons: (1) Sewall has foresters with strong GIS analysis skills and specific experience in LiDAR processing, (2) the USFWS enjoys a long-standing productive relationship with Sewall, and (3) Sewall recently assisted the USFWS with National Vegetation Classification (NVC) mapping of the Blackwater National Wildlife Refuge where the Maryland LiDAR data had been used.

To implement the project, Sewall used LiDAR data and bare earth elevation data, producing a grid of canopy heights and canopy closure, transforming this data to polygons of different height and closure classes, and distinguishing interpretive polygons of potential Delmarva fox squirrel habitat. In a unique add-on to this process, Sewall integrated ancillary data on land use and wetlands to enhance discriminations, such as delineating agricultural land from forest land in early regeneration stages. A key challenge was the processing of the huge volume of LiDAR data: all processes were built to be run in batch mode.

The USFWS is now using this information to determine the distribution, abundance and connectivity of mature forest Delmarva fox squirrel habitat and to assess the quantity of younger forest stands that will mature into habitat in the future. Comparison of the LiDAR defined height classes with known-age stands also enables a coarse assessment of timber harvest