ASLA in Nashville: Planting Design and Transportation PPN Meeting Recap

by the Transportation PPN leadership team

At the Transportation and Planting Design PPNs’ joint session, the conversation focused on best practices to incorporate pollinator habitats along transportation corridors and approaches to fight back against invasive species. If you’re interested in learning more about this topic, check out the reading & resources list prepared by Planting Design and Transportation PPN leaders. / image: Alexandra Hay

For the 2021 ASLA Conference on Landscape Architecture, the Transportation Professional Practice Network (PPN) teamed up with the Planting Design PPN to engage in a lively campfire discussion about planting design for pollinators.

Pollinator planting has been and remains a hot topic (see the December 9, 2021 Field post by Liia Koiv-Haus, ASLA, “Making Space for Pollinators,” and “Roadside Realm” from the March 2021 issue of Landscape Architecture Magazine). Both PPNs agreed that preserving pollinator habitat is important, but the methods and resources used to create habitat differed. This is due, in part, to the landscape scales in which each PPNs’ members typically practice. Other differences included maintenance abilities and strategies, budgets, and “owner” motivation. Planting design practitioners are often hired by property owners intent on creating habitat; transportation practitioners are usually required to justify spending public dollars on habitat creation and not on other, more easily justifiable, competing interests (such as roadway improvements and accessibility).

Transportation PPN leaders started the discussion by outlining federal and state resources that departments of transportation (DOTs) use to inform policy and practice decisions about pollinators. The U.S. Department of Transportation Federal Highway Administration’s Pollinators and Roadsides: Best Management Practices for Managers and Decision Makers is the primary reference for state transportation agencies. The document elaborates on a variety of techniques used by state DOTs, four of which also appeared in Liia Koiv-Haus, ASLA’s “Making Space for Pollinators”—altered mowing practices, reduced herbicide use, protection of existing stands of native vegetation, and re-seeding efforts post construction.

Altering mowing practices—simply change the time and frequency of mowing to favor plants preferred by pollinators—appears to be an easy solution to managing roadsides for native plants and pollinator habitat. It saves money in resources and staff time, reduces greenhouse gases, and is ecologically beneficial to more than pollinators. However, the complexities of implementing this technique—beyond gaining public buy-in—were not thoroughly inventoried. There are competing vegetation management goals that can be met with strategic mowing. Mowing for invasive species control typically occurs prior to seed setting. Mowing for pollinator habitat allows seeds to develop and, ideally, disperses seed. And for states with robust “snow and ice” seasons, late season mowing competes with staff time more frequently used to prepare for the upcoming winter months.

image: Nancy Buley, Hon. ASLA

Establishing and maintaining native wildflower stands require extensive maintenance resources most state DOTs lack. Of course, this differs geographically. In the northeast, maintaining the open fields necessary to develop pollinator habitat requires routine maintenance to keep woody persistents from re-establishing. If left fallow, natural succession leads to forests, not meadows. Rights-of-way (ROW) land dedicated to habitat must be rotationally mowed at least once every two years to keep the trees and shrubs from overtaking the herbaceous flowering plants. Returning to the same location multiple times in one growing season to mow small areas for different outcomes is not feasible. Spot herbicide treatment is another tactic, but that method comes with other problems and critics. Many states are scaling back on herbicide use, and some are even banning herbicide use on public lands (New York recently banned glyphosate use on public lands).

The timing of the mowing is critical, but the real trick is establishment. The literature on meadow establishment suggests that successful wildflower meadows take at least three years to establish. Federal funds don’t cover long-term maintenance, so most wildflower meadows must be created in capital projects. This leaves the task up to contractors hired to construct and build roads and highways. And to make matters worse, most capital contracts last only one year—not enough time to prevent weeds from overtaking target species according to most wildflower meadow scholars and practitioners.

Planting Design PPN leader Abigail Leonard, Associate ASLA (left), and Transportation PPN leader Jean Senechal Biggs, ASLA (right) / image: Nancy Buley, Hon. ASLA

The consensus amongst most of the PPN members at the session was that pollinator habitat is tricky. Some report the persistence of “edge to edge,” or back of pavement to ROW fence, mowing practices. The remedy: a public relations campaign teaching the benefits of reduced mowing along with the creation of “wow moments” using colorful displays and seasonal interests to elicit public ‘buy-in’ of unmowed ROWs.

Others pointed to the need for more scientific and pragmatic approaches. “No-mow” seed mixes that look like established lawns but require little to no maintenance were recommended, especially for steep slopes, but it is unclear if these plantings are suitable as pollinator habitat.

Federal incentives for creating wildflower habitat were also discussed. The Monarch Candidate Conservation Agreement with Assurances (CCAA) is an agreement that takes a landscape-scale conservation vision for the preservation of habitat for the monarch butterfly. In December 2020, the United States Fish and Wildlife Service (USFWS) determined that listing the monarch under the Endangered Species Act was warranted but precluded by higher priority listing actions. This means that the monarch is endangered but the USFWS lacks sufficient staff to process the action. The warranted but precluded decision has stalled the official listing and, for the purposes of the Monarch CCAA, means that the monarch is still considered a “candidate” species. Before the monarch is officially listed, departments of transportation and utility companies can join the CCAA to offset the impending regulatory requirements the listing will have on their actions.

Candidate Conservation Agreements with Assurances, or CCAAs, are voluntary conservation agreements between the USFWS and non-federal property owners. Property owners commit to implementing mutually agreed upon conservation measures for the candidate species. In return the USFWS assures that additional conservation measures above and beyond those contained in the agreement will not be required and that additional land, water, or resource limitations will not be imposed when the species becomes listed (Monarch CCAA, 2020). The agreement is administered by the University of Chicago at Illinois.

The Monarch CCAA outlines the criteria for joining. For transportation agencies, this means quantifying the total amount of land owned, determining how much of that land will be enrolled in the program, and using the formula in the CCAA to calculate the acreage adoption rates. Adopted acres are the percent of enrolled lands to which conservation measures are applied to enhance, restore, and maintain monarch habitat.

The program offers flexibility—land can be taken in and out of adoption; the only caveat is that the total amount of acreage being adopted must remain constant. With a few technical exceptions, actions on enrolled lands are not required to undergo expensive and time-consuming agency reviews or necessitate mitigation measures, saving staff time and resources. Incidental takes of monarch habitat would be authorized by the USFWS once the species is officially listed. The CCAA describes covered actions as those reasonably certain to cause a take of the monarch butterfly by removing or disturbing milkweed or flowering nectar resources on areas suitable for monarch habitat. Actions include general operations, routine maintenance, and the modernization of infrastructure on enrolled land. Areas suitable for monarch habitat include low-growing, early successional vegetation with milkweed or flowering plants used by monarchs for nectar. Actions on enrolled lands performed in compliance with the agreement and all applicable federal, state, and local statutes and regulations that may result in a take of monarch butterflies are authorized under the permit.

image: Alexandra Hay

Conservation measures outlined in the CCAA are designed to meet the benefit standard for lands managed by the energy and transportation sectors. Lands are to be maintained as grassland, meadows, prairies, or shrub-scrub habitat; active management activities will prevent the growth of trees and woody vegetation. Adopted lands are managed to address key threats (loss of habitat resulting from either mowing or herbicide use) to habitat loss. Conservation measures include:

  • Seeding and Planting,
  • Controlled Grazing,
  • Brush Removal,
  • Prescribed Burning,
  • Suitable Habitat Idle Lands or Set-Asides,
  • Conservation Mowing, and
  • Targeted Herbicide Treatment.

Conservation targets for both the Western and Eastern US include the maintenance and enhancement of flowering nectar plants and avoiding the removal of flowering nectar plants and shrubs. The Western US has additional conservation measures such as reporting all Western Monarch observations, including breeding.

PPN members were aware of the Monarch CCAA and some state DOT landscape architects indicated that their state was considering or had joined. Others reported resistance by upper management and a direction to wait and see when the monarch listing will become effective. The administrative costs to join the Monarch CCAA are significant but minor when compared to the staff time and resources needed to comply with impending regulations. And many believe that the benefits—both ecologically and for the monarch—justify the expenditure.

For highlights from all the PPN events at the 2021 ASLA Conference on Landscape Architecture in Nashville, see this previous post. For landscape architects and allied professionals interested in participating as speakers at the conference this year, the Call for Presentations for the 2022 ASLA Conference on Landscape Architecture in San Francisco is open now through February 22, 2022.

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