A new study from the University of Utah has highlighted the potential threat posed by the balsam woolly adelgid (BWA) to northern Utah’s conifer forests. This invasive insect, originally from central Europe, was first detected in Utah in 2017 and has been spreading around the Wasatch Mountains, impacting popular recreation areas outside Salt Lake City. The research, conducted in collaboration with the U.S. Forest Service, has documented the current extent of BWA infestation and created a model to predict its severity in the Uinta-Wasatch-Cache National Forest. Lead author Mickey Campbell, a research assistant professor in the Department of Geography, emphasized the strong relationship between infestation severity and temperature.
The study’s findings indicate that climate change is likely to increase the exposure of conifer forests to damage from BWA. By analyzing climate projections for the years 2040, 2060, 2080, and 2100, the researchers were able to map current and future exposure to the insect based on temperature changes. As the climate warms, areas that were previously less suitable for the BWA may become more conducive to infestations, leading to greater damage to the forests. The study, published in the journal Forest Ecology and Management, aims to provide land managers with tools to predict and mitigate future damage as the BWA infestation spreads.
Unlike native bark beetles that have devastated conifer stands in other parts of the West, the BWA poses a different threat to Utah’s forests. Instead of burrowing through the phloem under the tree’s bark, the BWA sucks out the tree’s fluids and leaves behind toxic saliva, weakening the tree’s defenses and impeding nutrient flow. This can lead to the death of infested trees within three to five years. While white fir trees seem to withstand infestation well, other conifers like subalpine fir are more vulnerable to damage from the BWA. The research team surveyed plots in the Wasatch and Uinta mountains to assess the severity of infestations based on various indicators such as gouting, woolly deposits, crown deformities, and dead needles.
The study revealed that 41% of the study area’s subalpine fir biomass is currently exposed to some level of damage from the BWA. By 2100, under moderate climate projections, this exposure is expected to increase to 79%, with 37% predicted to suffer relatively high severity of infestation. Areas like Farmington Canyon north of Salt Lake City, where the BWA was first documented in Utah, are seeing widespread mortality of subalpine fir trees. The reasons for this susceptibility are still being investigated but could be related to the longevity of the infestation in that area or specific geographic factors that make it more favorable for the insect.
The interactive dashboard created by the research team illustrates how the BWA damage is projected to unfold in the Uinta-Wasatch-Cache National Forest. This tool will help land managers make informed decisions on how to address and mitigate the impact of the infestation as it spreads. The study emphasizes the importance of understanding the relationship between climate change, insect infestations, and forest health in order to protect the region’s valuable conifer forests. As temperatures continue to rise, proactive measures will be essential to safeguard these ecosystems from further damage.
