The ecological effects of storm surges on Arctic bird and vegetation communities in the outer Mackenzie Delta, Northwest Territories

Coastlines in the Western Canadian Arctic are predicted to experience increases in the frequency and intensity of storm surges as rapid climate change continues to alter weather and biophysical factors of this land-sea connection. Although storm surges have the potential to cause widespread and persistent vegetation loss, little information is available about the influence of decreasing disturbance intervals (between storms), expected timelines of recovery for vegetation, and how this dramatic vegetation change alters habitat availability and/or quality for local wildlife populations. In my MSc research, I investigated how Arctic bird diversity is affected by heterogeneous vegetation recovery post-storm and characterized ecological recovery of vegetation from repeated disturbance. In the first part of my thesis (Chapter 2), I used a combination of Landsat & Sentinel satellite imagery (1984-2019) and measured post-storm soil & vegetation attributes to characterize vegetation loss and recovery in areas of the outer Mackenzie Delta (NWT) affected by storm surges in 1999 and 2016. My observations of areas affected by the 1999 storm indicate that sites farther from the river channel lacked vegetation re-establishment and had higher soil salinity. Furthermore, our analyses suggest that sites affected by the 1999 storm that were re- inundated by the 2016 storm differed in response depending on whether sites had previously revegetated or not; more vegetation re-established at the previously unvegetated sites, whereas there were decreases in the diversity of the plant community re-establishing at the previously revegetated sites. In the second part of my thesis (Chapter 3), I employed field survey protocols from the Program for Regional and International Shorebird Monitoring (PRISM) to investigate how avian community assemblage is affected by heterogeneous re-vegetation 20 years following the 1999 storm. Comparisons of my bird survey data with vegetation and habitat factors showed that the drier, post-storm vegetation barrens were preferred by ground-nesters or species that use open habitats such as lapland longspur and semipalmated plover; whereas the wetter, mostly ponded, revegetated habitats were frequented by species of ducks, red-necked phalarope, and savannah sparrow. Taken together, my research shows that areas that have revegetated after the 1999 storm can be considered as functionally recovered in comparison to our Reference (i.e., unaffected) sites in terms of vegetation and bird communities, but that areas still exist ~20 years post-storm that do not show any characteristics of recovery.

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