A scholar is investigating the impact of an invasive insect and the chemicals employed to combat it on the biodiversity of mature hemlock forests. Hemlock woolly adelgid (HWA) has been causing significant damage to forests in the southwestern region of Nova Scotia for nearly ten years. To combat its spread, insecticides like imidacloprid and dinotefuran have been utilized by Parks Canada, the province, local organizations, and private landowners.
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 pointed out that imidacloprid, designed to impact insect nervous systems, has been detected in the brains of other creatures such as fish and tadpoles.
Rather than examining all species in every hemlock forest individually, Christjansen’s team is using the eastern red-backed salamander as a bioindicator species to gain insights into the overall ecosystem. This species is sensitive to both environmental conditions and pollutants, making it a valuable indicator of forest health.
Scientists deployed coverboards in forests last year as part of the study. These coverboards serve as habitats for salamanders, allowing researchers to periodically survey and monitor the salamander populations underneath. Some forests under study are treated with either or both insecticides, while others remain untreated.
Behavioral tests were conducted on the salamanders found, including gentle prodding to observe their response to predation and flipping them upside down to assess their recovery speed. Christjansen explained that the salamanders’ condition and size in treated and untreated forests could provide insights into broader ecosystem impacts.
Julia Riley, an associate professor at Mount Allison University and a Canada Research Chair in integrative wildlife ecology, emphasized the salamanders’ importance as indicators of forest health due to their abundance in woodland ecosystems.
The study also evaluates how the decline of hemlock trees affects salamanders. Chris Edge, a supervisor and scientist with the Canadian Forest Service, highlighted the unique habitat provided by hemlocks, emphasizing the potential consequences of losing these ecosystems.
Due to salamanders’ sensitive skin, a reduction in forest moisture resulting from decreased foliage coverage could further impact their populations and behaviors. The project involves collaboration between Mount Allison University, Canadian Forest Service, Acadia University, Environment and Climate Change Canada, and the University of Saskatchewan, forming 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 footage collected during the summer. The research aims to shed light on the complex interactions between invasive species, insecticides, and forest ecosystems.