A researcher is investigating the impact of an invasive insect and the chemicals used to combat it on the species residing in ancient hemlock forests. Hemlock woolly adelgid (HWA) has been causing significant damage to forests in southwestern Nova Scotia for almost ten years. To control its spread, various entities including Parks Canada, the province, local organizations, and private landowners have been employing insecticides such as imidacloprid and dinotefuran.
However, Mathilde Christjansen, a master’s student at Mount Allison University in Sackville, N.B., pointed out the limited knowledge about how woolly adelgid and the insecticides are affecting other species. She emphasized the potential impact of imidacloprid on various animals beyond insects due to its neurotoxic properties found in the brains of fish and tadpoles.
Instead of examining all species in every hemlock forest individually, Christjansen’s team is focusing on the eastern red-backed salamander as a bioindicator species to provide insights into the overall ecosystem health. The salamander’s sensitivity to environmental conditions and pollutants makes it a valuable indicator of forest well-being.
The research involved placing coverboards in forests last year to create salamander habitats. Scientists monitored these coverboards periodically to count and study the salamanders living below them. Some forests received treatment for HWA using either or both insecticides, while others remained untreated.
Behavioral tests were conducted on the salamanders, including observing their reactions to simulated predation and assessing their ability to recover when placed upside down. Christjansen explained that the salamanders’ population size, health status, and size comparison between treated and untreated forests could shed light on broader ecosystem impacts.
Julia Riley, an associate professor at Mount Allison University and a Canada Research Chair in integrative wildlife ecology, highlighted the salamanders’ significance as indicators of forest health due to their abundance and biomass in Eastern Canada woodlands, surpassing even deer populations.
The study also examines the influence of dying hemlocks on salamanders as these trees provide essential habitat features like cool and moist microclimates that support the species. The project, conducted in collaboration with various institutions, forms part of a larger initiative investigating forest health in Eastern Canada.
Christjansen plans to analyze the data and field videos collected over the summer to continue her study until the following year. The study’s findings could offer valuable insights into the broader implications of HWA and insecticide use on forest ecosystems.