Bees, butterflies and other insects are important plant pollinators in natural ecosystems and agricultural settings. However, pollinator populations have been decreasing in recent decades. Researchers say one factor contributing to the decline is the degradation and loss of their habitat. Northern Arizona University ecologist and conservation biologist Clare Aslan says utility companies, like Salt River Project (SRP), have an opportunity to improve the habitat for pollinators in their rights-of-way (ROWs) created through the landscape for power lines.
Aslan, associate professor and co-director of the Center for Adaptable Western Landscapes in NAU’s College of the Environment, Forestry, and Natural Sciences, is the principal investigator of a research project, “The Contribution of Electric Utility Transmission Line Rights-of-Way to Pollinator Biodiversity in Arizona.” She believes findings from her research will help power companies develop strategies to increase native plant and pollinator abundance and diversity, reverse habitat degradation and promote ecosystem health across multiple plant communities.
Supporting Aslan’s project is the Electric Power Research Institute (EPRI), a nonprofit organization that funds scientific research to help utility companies make sustainable decisions. EPRI has awarded Aslan and colleagues a $379,177 grant to study pollinators through various ecosystems and elevations across a total of about 15 linear miles of right-of-way. The four-year study involves research plots in the Coconino, Apache-Sitgreaves and Tonto National Forests in the ponderosa pine, pinyon/juniper and Sonoran Desert.
“Pollinators seem to act like a canary in a coal mine,” Aslan said. “They respond to environmental changes caused by pollution, excess pesticide, a loss of habitat, invasive species, climate change—all the drivers. Changes seem to be happening in every ecosystem and we’re seeing lower pollinator diversity where there’s high environmental disturbance. Reduced numbers of pollinators impact plant populations. They transfer genes from one plant to another. If we lose that, we can have isolated plant populations, secondary extinctions or extinction cascades—ripples from reductions to losses of other species.”
Aslan and her team, including NAU undergraduate students, will apply Integrated Vegetation Management (IVM) treatments in replicated study blocks in the ponderosa pine plant community. Study blocks will receive five treatments: current condition (two or three years since the area has been mowed); herbicide use; mechanical removal of vegetation through mowing or cutting; a combination of both mechanical removal of plants and herbicide use; and off ROW (no treatment).
Researchers will monitor and collect pollinators that visit the sites and the plants that attract them. The goal of the project is to evaluate how different combinations of IVM treatments affect plant and pollinator abundance and composition on ROWs in Arizona. The research also will compare pollinator abundance in the ROWs with the habitat adjacent to ROWs across all ecoregions.
“Using IVM, ROWs are capable of supporting pollinator populations because harmful non-native invasive plants can be suppressed while low-growing native grasses, forbs and flowering plants attractive to pollinators can be encouraged,” Aslan said. “ROWs may provide the only habitat in intensively managed regions and can serve as corridors to connect patches of habitat.”
Seth Munson, a U.S. Geological Survey (USGS) botanist and co-principal investigator on the project, will be managing the plant surveys along with USGS field researchers also supporting the effort. Permits to create plots on public land will be obtained from the Forest Service.
Aslan says the region in the study area has a high diversity of native bees, large native bumble and carpenter bees, charismatic species like non-native honeybees and tiny solitary bees that look more like flying ants. She expects to see all of these plus moths, butterflies, hummingbirds and flies—especially at the higher elevations—as pollinators.
“We are going to need electric power delivery and we do have human-made structures cutting across our landscape, but I believe there are ways to manage this that can be multi-beneficial,” she said. “How pollinators respond will affect plants on all levels. If we can generate recommendations that will create and maintain habitat to benefit a maximum diversity of species, we can achieve more sustainable plant and pollinator communities and gain conservation benefits.”
The field work is expected to begin in the lower elevations this spring and in the higher elevations this summer. Project results and recommendations will be shared with SRP, which manages the ROWs.
Bonnie Stevens | Office of the Vice President for Research