Identifying Vulnerability of Eastern Hemlock in Canada to Spread of Hemlock Woolly Adelgid Using GIS Analysis in Various Climate Change Scenarios
Hemlock Wooly Adelgid (Adelges Tsugae) is a destructive invasive insect pest currently affecting Eastern Hemlock (Tsuga Canadensis) along Eastern North America. Eastern Hemlock is a keystone species in many ecosystems and Hemlock Woolly Adelgid has been known to cause up to 100% mortality in Eastern Hemlock stands. Hemlock Woolly Adelgid has recently been introduced to Nova Scotia and is also found in multiple counties along the United States/Ontario Border. Due to this, a GIS-based Multi-Criteria Evaluation (MCE) that predicts future spread of Hemlock Woolly Adelgid could be useful in establishing a framework to quickly identify areas of likely infestation and show the possible future extent of Hemlock Woolly Adelgid. MCE criteria used to predict the spread of Hemlock Woolly Adelgid were: Mean winter temperature/minimum winter temperature, Eastern Hemlock density, distance from current Hemlock Woolly Adelgid infestation and road type/ distance from roads. Using these criteria, maps showing the probability and possible extent of infestation in Canada were developed for climate change scenarios RCP4.5 and RCP8.5. Results of the MCE models show that areas of high Eastern Hemlock density and along road ways are the most vulnerable to spread and changing climate will extend the area Hemlock Woolly Adelgid is able to spread. Additional refinements could be made to our analysis if an accurate Eastern Hemlock inventory for Canada could be developed, and so our analysis does not identify specific vulnerable Eastern Hemlock stands but instead focuses on areas of most risk. Wind direction and bird migration patterns represent additional Hemlock Woolly Adelgid vectors that could be included in future analysis.