Emerging Hot Spot Analysis and Forests: A Case Study on the Hemlock Woolly Adelgid’s Invasion into Nova Scotia using Fine Spatial Resolution Satellite Imagery.

Abstract

Adelges tsugae (hemlock woolly adelgid) is an invasive forest insect first identified in Nova Scotia in 2017. This insect poses a threat to the Acadian Forests, as Tsuga canadensis (eastern hemlock) is a keystone species in this ecosystem. The loss of such a critical species has been shown to cause significant ecological changes in area previously infested by A. tsugae forests in the northeast United States. Remote sensing techniques have been used to model the spread of invasive forest insects across the globe, including A. tsugae in the northeastern United States. In this project, the relatively new method of emerging hot spot analysis - a combination of the Getis-Ord Gi* spatial statistics and the Mann-Kendall trend test for evaluating correlation in temporal data – was used to identify various types of hot spots of the normalized difference vegetation index, derived from PlanetScope satellite imagery, in two study areas in southwest Nova Scotia which correspond to the loss of forest canopy due to A. tsugae. While emerging hot spot analysis was not able identify forest loss specifically due to A. tsugae, it did provide a novel method for examining forest change when utilizing high spatial resolution sensors at a small (1.5-2km2) spatial extent.