The final output from the MCE model used is two maps showing the vulnerability of Eastern Hemlock to the potential spread of Hemlock Woolly Adelgid under climate scenarios RCP 4.5 and 8.5 in Eastern Canada. Three main trends were clearly observed for both climate scenarios. First, when the vulnerability of Hemlocks is compared to the density of Hemlocks in the same area, it is shown that the highest vulnerability occurs along areas of high density due to HWA's ease of spread between trees located in close proximity. The next observed trend is the high vulnerability occurring along road vectors as a result of transport through human vectors from the United States of America into Canada. Finally, although there are outliers to this trend, generally vulnerability is higher in the South and decreases towards the North, because of increasing distance from current HWA populations as well as decreasing temperatures. Interestingly, it was found that Hemlock Woolly Adelgid was very unlikely to spread to the farthest south regions of Ontario (Sarnia to Windsor areas) despite the close proximity to current HWA. This is likely due to the very low densities of Eastern Hemlock, but additionally, possibly due to more severe and unpredictable winters as a result of climate change. The hot spot analysis conducted for both climate scenarios confirmed these trends and identified clusters of high vulnerability in Ontario, Quebec, New Brunswick, and Nova Scotia. These results indicate that highly dense Hemlock groves which are nearby roads will be at most risk to the potential spread of HWA, whereas remote areas of low density will be less vulnerable and will require less monitoring. The combination of the hemlock vulnerability and hot spot results can aid in the management and monitoring of Eastern Hemlock in Canada as efforts to prevent the spread of HWA in Canada continue. This would be done through identifying areas showing the highest vulnerability to potential spread from the maps and focusing management resources on these locations.
In addition, two climate scenarios were used to evaluate the potential of spread under different future temperatures. The first scenario, RCP 4.5, represents lower future emissions and was identified as the best case scenario. RCP 8.5 represents higher future emissions and was used for the worst case scenario. Both RCP 4.5 and RCP 8.5 indicated predicted temperatures from 2020 to 2040. It was hypothesized that there would be a large difference in susceptibility to spread between the two climate scenarios, with spread under RCP 8.5 extending much farther north. However, the model's output did not show a big difference in the spread between the two. As predicted, HWA spread under RCP 8.5 did extend north of the spread under the best case scenario RCP 4.5, but this was only by a small margin, and no changes in spread was found in the south.
The protection and preservation of the keystone species Eastern Hemlock in Canada are essential and will become more challenging with the increasing risk of Hemlock Woolly Adelgid spreading into Canada. The use of a multi-criteria evaluation model to analyze the vulnerability of Eastern Hemlock to the future possible spread of Hemlock Woolly Adelgid into Canada has provided results which could potentially assist Canadian environmental agencies in monitoring and managing Eastern Hemlock groves and preventing the spread of this destructive invasive species.