A researcher is investigating the impact of an invasive insect and the chemicals used to combat it on the ecosystem of old hemlock forests. Hemlock woolly adelgid (HWA) has been causing significant damage to forests in southwestern Nova Scotia for nearly ten years. Various entities, including Parks Canada, the province, local groups, and private landowners, have been employing insecticides like imidacloprid and dinotefuran to control the spread of this insect.
Mathilde Christjansen, a master’s student at Mount Allison University in Sackville, N.B., highlighted the lack of knowledge regarding the effects of woolly adelgid and the insecticides on other species. She emphasized that imidacloprid, designed to impact insect nervous systems, has also been detected in the brains of other animals such as fish and tadpoles.
Rather than studying every species in all hemlock forests individually, Christjansen’s team is using the eastern red-backed salamander as a bioindicator to assess the overall health of the ecosystem. These salamanders are sensitive to both environmental conditions and pollutants, making them ideal for monitoring ecosystem changes.
To conduct the study, scientists placed coverboards in forests last year to provide habitat for salamanders. They monitored these coverboards periodically to count and measure the salamanders living beneath them, tagging them for identification. Some forests under study are treated with either or both insecticides, while others remain untreated.
Additionally, the team conducted behavioral tests on the salamanders, including gentle poking to observe their reactions to predation and flipping them upside down to assess their agility. Christjansen explained that the salamanders’ health, population size, and size comparison between treated and untreated forests could offer insights into broader ecosystem impacts.
Chris Edge, a scientist with the Canadian Forest Service and one of the study’s supervisors, emphasized the importance of hemlock trees as ideal salamander habitats. Dying hemlocks can disrupt the unique forest microclimates that support salamander populations.
The study, a collaborative effort involving Mount Allison University, Canadian Forest Service, Acadia University, Environment and Climate Change Canada, and the University of Saskatchewan, forms part of a larger investigation into forest health in Eastern Canada. Christjansen plans to continue her study until next year, analyzing the data and videos collected during the summer fieldwork.
Sensitive to changes in moisture levels, salamanders may also be impacted by decreased forest foliage cover due to dying hemlocks, affecting their populations and behavior.