A researcher is investigating the impact of an invasive insect and the chemicals used to combat it on the wildlife in aged hemlock forests. Over the past ten years, the hemlock woolly adelgid (HWA) has been causing significant damage to forests in southwestern Nova Scotia. To mitigate its spread, various entities, including Parks Canada, the province, local groups, 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., highlighted the lack of knowledge regarding the effects of woolly adelgid and the insecticides on other species. Christjansen expressed concerns about the potential impact of imidacloprid on various animals’ nervous systems, as it has been detected in the brains of creatures like fish and tadpoles.
Rather than individually examining all species across hemlock forests, Christjansen’s team is focusing on a single small amphibian as an indicator of the overall ecosystem health. The eastern red-backed salamander was chosen due to its sensitivity to environmental conditions and pollutants, making it a reliable bioindicator species.
For their study, scientists placed coverboards in forests last year to provide habitat for salamanders. They monitored the boards periodically to count and measure salamanders living beneath them. Some forests under study are treated with either or both insecticides, while others remain untreated.
In addition to population surveys, the team conducted behavioral tests on the salamanders, including gentle prodding to observe their reactions to predation and flipping them upside down to assess their recovery speed. Christjansen emphasized that the salamanders’ condition, population size, and health in treated and untreated forests could offer insights into broader ecosystem impacts.
Julia Riley, an associate professor at Mount Allison University and one of the study supervisors, praised salamanders as effective indicators of forest health due to their abundance in Eastern Canada woodlands. She highlighted the substantial biomass contribution of salamanders to forest ecosystems compared to deer populations.
The study also examines how dying hemlock trees affect salamanders. Chris Edge, a supervisor and scientist at the Canadian Forest Service, explained that the demise of hemlocks disrupts the unique habitat conditions they provide, such as cool and moist microclimates due to their dense canopies. The loss of these ecosystems could have long-lasting repercussions.
With collaboration from Mount Allison University, Canadian Forest Service, Acadia University, Environment and Climate Change Canada, and the University of Saskatchewan, the project forms part of a broader investigation into forest health in Eastern Canada. Christjansen plans to continue her study until the following year, analyzing the data and videos collected during the summer fieldwork.
The research team’s efforts shed light on the intricate interplay between invasive species, insecticides, and forest ecosystems, emphasizing the importance of understanding and preserving delicate ecological balances.