Wildlife

This Technical Summary pertains to the LRRB-produced Report 2011-19, “Performance Assessment of Oversized Culverts to Accommodate Fish Passage,” published August 2011.

Wetlands are known for their susceptibility to invasive plants. During the past few decades, diversity and complexity of native plant communities in southern Minnesota wetlands have become threatened by reed canarygrass, a perennial, cool-season grass that outcompetes native vegetation. This invasion is often associated with disturbances such as ditch building and stream channeling sedimentation, and with intentional planting for forage and erosion control.

This Technical Summary pertains to the LRRB-produced Report 2009-20, “Cost Analysis of Alternative Culvert Installation Practices in Minnesota,” published June 2009.

This Technical Summary pertains to report 2021-29, Assessing Culverts in Minnesota: Fish Passage and Storm Vulnerability.

This Technical Summary pertains to Report 2022-30, Cost-Effective Roadside Revegetation Methods to Support Insect Pollinators.

Roadsides contain promising habitat for insect pollinators, yet roadside restorations can be expensive and are rarely evaluated for effectiveness. Where do we establish pollinator-friendly revegetation to maximize benefits? How effective are current revegetation practices at providing habitat for pollinators? We address these questions with two studies. Chapter 2 examines the impact of roadside-adjacent habitat that has been identified as pollinator-friendly for bumble bees. We use pollinator habitat maps to examine associations between the amount of nearby pollinator-friendly habitat and bumble bees (abundance and richness). We also regroup land covers to more specifically align with bumble bee habitat needs and compare the ability of both land cover categorizations to predict bumble bee metrics. This study can help refine predictors in mapping efforts to prioritize locations for pollinator habitat enhancements. Chapters 3 and 4 combine detailed insect and floral surveys of sites with known revegetation history to test efficacy of current revegetation methods for providing habitat for insect pollinators. We show which plants establish after seeding and how communities change as they age. We find that native flowering plants are more likely to establish in roadsides when they are planted, but native and non-native seeded sites converge in the plant community through time. Bumble bee and butterfly abundance and diversity is tied to flowering plant abundance and diversity, regardless of their status as native plants. This work identifies where pollinator-friendly restorations should be implemented and how current seeding practices could be modified to improve benefits to pollinators while reducing costs.

This Technical Summary pertains to report 2022-19, Reduce Vehicle-Animal Collisions with Installation of Small Animal Exclusion Fencing.

The presence of small animals on Minnesota’s roadways presents a public safety concern and negatively impacts wildlife populations. For the past four years, the Minnesota Zoo has partnered with the Minnesota Department of Transportation to test and evaluate the effectiveness of standard plans for small animal exclusion fencing, with the goal of redirecting turtles and small wildlife away from roadways and to existing through-road infrastructure where practicable. Wildlife can pose a significant threat on roadways, and driver avoidance of or direct collisions with small animals can result in substantial damage or injury, particularly for motorcyclists and bicyclists and those who stop to assist wildlife across roadways. Turtles are the focus of this research as their unique life histories and slow population growth rates make them particularly vulnerable to impacts from road mortality. To address this, we implemented a before-after-control-impact study at 11 sites around the greater Twin Cities region during the 2018–2021 period. Our results showed that standard chain-link fencing (including trenching and wrap-around end treatments) can effectively reduce mortality of adult turtles. However, this design did not result in decreases in mortality of juvenile and hatchling turtles. After retrofitting fences with ½-inch wire mesh, we documented a substantial reduction in the mortality of all age classes (up to 91% over pre-treatment) of turtles, thereby demonstrating its utility as an effective mitigation strategy. The development and adoption of a vetted standard plan will increase efficiency, reduce costs, improve public safety, and reduce mortality of turtles and other wildlife on Minnesota roads.

This report documents existing reports on culvert design for aquatic organism passage in Minnesota and nationally. The review is designed to build upon the work of Hansen et al. 2009 and 2011 to: 1) summarize current aquatic organism passage practices, 2) summarize aquatic organism passage needs for Minnesota species, 3) discuss the importance of roughness or streambed sediment within a culvert in different systems (high, medium, or low slope) in single and multiple barrel systems, and 4) summarize physical experiments of sediment transport and geomorphic processes through culverts.

Culverts at road-stream crossings can create barriers to movement within a stream network that can have dramatic consequences for fish populations by fragmenting habitat. Culverts can become barriers when flow conditions exceed fish swimming ability, e.g., for drop at the outlet and insufficient depth or excess flow velocity. In this project, we use a simple modelling framework to assess 50 culverts throughout Minnesota to: a) determine what fraction of these culverts currently present a fish passage barrier for both high flows (velocity barrier) and low flows (depth barrier) and b) to summarize design parameters that most affect passibility (e.g., culvert width). The estimated high and low flows are fed into the HY-8 culvert hydraulics model, and the resulting velocity and depths are compared to published fish swimming capabilities. We also assess future (2061-2080) high-and low-flow fish passage conditions for five culvert sites using global climate model outputs, Hydrologic Simulation Program Fortran (HSPF) runoff models, and the fish passibility modelling framework. Both low-and high-flow conditions in streams are very responsive to future climate, with either positive or negative future changes, depending on which global climate model is used. This study concludes that maintaining a low-flow channel or embedded culvert barrel will make culverts more passable during changes in low flows and ensuring culvert widths equal to or greater than the bankfull channel width in combination with embedded sediment will help mitigate increases in high fish-passage flows and high peak flows.