The Implications of the Emerald Ash Borer (Agrilus planipennis) on Riparian Canopy Cover in Three Halifax Regional Municipality Parks

Abstract

Invasive species are posing an increasingly large threat to Canada’s urban forest. The Emerald Ash Borer (EAB) is an invasive pest with the potential to eliminate entire ash stands. The EAB was discovered in Nova Scotia in 2018. In this study I aimed to address the research question “what are the implications of the EAB on short-term riparian zone canopy cover in three Halifax Regional Municipality (HRM) parks?”. Both census and cruise-transect-sampling methods were exercised to determine ash proportions and distribution in each park. For the census method, all trees within the park were measured (diameter at breast height (DBH), crown condition, crown position) and digitally geo-positioned to determine distribution. Using an equation derived from existing ash data, ash crown projections were then calculated for each ash tree based on DBH. The cruise method was conducted using plots dispersed along a transect line stretching the length of the stream. It was found in the park undergoing census method (Fish Hatchery Park) that ash accounted for approximately 30% of total canopy cover within the assessed park. Analysis of plot data demonstrated ash presence in 41% of all plots sampled, only five of which were projected to fall below Nova Scotia’s riparian-zone regulatory basal area as a result of ash removal. In Moirs Mill Park, ash accounted for 20% of all trees measured, and were present in eight of the 11 plots. In Sir Sandford Fleming Park, ash accounted for 5.5% of all trees measured and were present in eight of the 20 plots. Overall, the arrival of EAB will have a modest impact on riparian canopy cover in the HRM parks sampled. The visual distribution and locationspecific data along the riparian zone will help forest managers and planners understand areas of highest risk.