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https://www.nationalacademies.org/trb/events

Evaluating Mowing Practices for Pollinator Habitat Enhancement: Highway Vegetation Management and Its Impact on Endangered Polinator

ORS 634.045 requires several state agencies, including Oregon Department of Transportation (ODOT), to maintain and revise a bee pollinator safety plan to educate the public and increase pollinator habitat. It is not clear to ODOT how to document habitat on their properties, if current mowing practices enhance or reduce pollinator habitat, and how to prioritize areas for compliance of conservation practices. The US DOT has guidelines for vegetation management for right-of-ways (ROWs), but there have been contrasting results for key practices, such as mowing and efforts at establishing pollinator-attractive plants have not resulted in long lasting habitat and may result in costly landscaping. Finally, there are concerns that the habitats near roadway locations with vehicles and environmental pollutants may result low mortality rates to pollinators. Consequently, it is unclear how ODOT routine mowing practices, which covers an estimated 20,000 acres annually, enhances the vegetation that is important to threatened or endangered pollinators. This research seeks to identify mowing practices that encourage these plants and to help meet protection targets without increased costs. The research will study pollinator activity in three geographic regions and develop “high benefit” pollinator vegetation management practices with a neutral (or lessened) cost to ODOT. The research will be conducted over three seasons and have three parts: (1) In-field vegetation documentation using new app and method analysis; (2) Cost-Benefit Analysis; and (3) Feasibility analysis. The in-field tasks include selecting 27 site locations on ODOT secondary or tertiary roads, with appropriate ROWs, across three ODOT regions (i.e., 9 per region). The study will have three levels of mowing intensity: high (at least once per year), medium (once every other year) and low (less than once every two years). Each location will be monitored for plant diversity and density and bee pollinator activity during the appropriate seasons – with particular measurement directly before and after mowing. The research will determine if mowing intensity and date of mowing influences the density of plants of highest value to pollinators by: (1) relating plants found to Melittflora records filtered for the region; and (2) calculating the richness of bee species found at each site. The research will also use historic estimates of average seasonal traffic volume at each site as a covariate to investigate the impact of traffic on the diversity of the bee community for a given plant community. Site characteristics will also be documented (e.g. distance from the roadway). The cost-benefit analysis will focus on detailing normal vs pollinator staff/resource costs, timing for mowing, and comparing to outcomes of high pollinator activity. The feasibility analysis will compare normal maintenance resource availability and use compared to recommended optimal mowing for pollinator benefits. Finally, the project would result in a regional pocket guide of the most important plants for pollinators that vegetation management crews will encounter, as well as new continuing education trainings for vegetation management staff. This information could be used in future construction (or Maintenance) locations to identify plant species that are both of high value to pollinators and known to persist under ROW conditions that could help inform how to modify seed blends following road construction.