A researcher is investigating the impact of an invasive bug and the chemicals used to combat it on the species inhabiting ancient hemlock forests. Hemlock woolly adelgid (HWA) has been causing significant damage to forests in southwestern Nova Scotia for nearly ten years. Various entities such as Parks Canada, the province, local groups, and private landowners have been employing insecticides like imidacloprid and dinotefuran to control its spread.
However, 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. Christjansen emphasized that imidacloprid, designed to impact insect nervous systems, could also affect other animals’ nervous systems, as evidenced by its presence in the brains of creatures like fish and tadpoles.
Rather than studying all species in every hemlock forest individually, the team is using the eastern red-backed salamander as a bioindicator species to gain insight into the whole ecosystem’s health. This species is sensitive to environmental conditions and pollutants, making it an ideal indicator of forest well-being.
To conduct the study, scientists placed coverboards in forests last year to serve as habitat for salamanders. They periodically checked under these coverboards to count the salamanders, measuring and tagging them during the process. Some forests under study are treated with either or both insecticides, while others remain untreated.
The researchers also conducted behavioral tests on the salamanders found, such as lightly poking them to observe their reaction to predation and flipping them upside down to assess their recovery speed. Christjansen noted that the salamanders’ population size, health status, and size comparison with those in non-treated or treated forests could indicate broader ecosystem effects.
Julia Riley, an associate professor at Mount Allison University and a Canada Research Chair in integrative wildlife ecology, explained that salamanders, due to their reactivity to environmental changes and their substantial numbers, are excellent indicators of forest health.
The study also examines the impact of dying hemlocks on salamanders. Chris Edge, a scientist with the Canadian Forest Service, underlined how the demise of hemlock trees, caused by HWA, disrupts the unique habitat that these forests provide. This disruption can affect salamander populations and behavior, given their sensitive skin’s high moisture requirements.
The project is a collaboration among Mount Allison University, Canadian Forest Service, Acadia University, Environment and Climate Change Canada, and the University of Saskatchewan. It is part of a broader initiative focusing on forest health in Eastern Canada.
Christjansen plans to continue her study until next year, analyzing the data and field videos gathered over the summer months. The research team aims to deepen understanding of the complex interactions between invasive species, insecticides, and forest ecosystems, particularly their impact on sensitive species like the eastern red-backed salamander.