Hemlock Wooly Adelgid Risk Assessment at Marsh-Billings-Rockefeller National Historical Park

Ben E. Machin, Daniel P. Ruddell, Dale R. Bergdahl, Christina Marts

Redstart Forestry, Inc. (1,2), University of Vermont Rubenstein School for the Environment and Natural Resources (3) and Marsh-Billings-Rockefeller National Historical Park (4)

Non-native invasive species (NNIS) represent an increasing challenge to management and stewardship of natural and cultural resources that extends across traditional political and ownership boundaries. A GIS-based risk assessment model was developed in Vermont as part of a coordinated effort to reduce the spread and impacts of hemlock woolly adelgid (HWA), a non-native invasive insect  that has heavily impacted hemlock ecosystems in the eastern United States. A primary aim has been to translate research into practical application, and the model was refined through application at Marsh-Billings-Rockefeller National Historical Park. The approach offers an example of cooperative development of systems that integrate spatial data to assist land managers in evaluating the threats of NNIS and developing response strategies.

The model incorporated a literature search, interviews, and historical documentation in identifying:  1) factors associated with the risk of HWA introduction and establishment (“susceptibility”); and   2) potential impact of HWA infestations (“vulnerability/ resistance”). Modeled “susceptibility” factors included: a) climate interaction (cold hardiness zones revised to account for effects of latitude and elevation); b) dispersal potential (distance to documented sources of HWA introduction); and c) host range (FIA hemlock distribution coverages). Modeled “vulnerability” factors were based on HWA research that indicated soil moisture, site productivity, and aspect as key factors affecting varying impacts of HWA across the landscape. GIS layers to address these factors were developed from attributes in the Vermont soils database and a USGS Digital Elevation Model.

Information from the GIS database assisted efforts to address an accidental introduction of HWA in 2005 and integrated information from subsequent eradication efforts. It has also been used to augment qualitative risk assessment based on USDA APHIS guidelines and has potential to inform quantitative risk assessments. Current efforts are expanding information layers to include data applicable to a number of other pests of high concern.

corresponding author:

Ben E. Machin
Redstart Forestry, Inc.
211 Joe Lord Road
Corinth, VT 05039
redstart@sover.net