Tennessee Makes Way for the Monarchs

NASHVILLE — A few years ago I started noticing wildflowers blooming beside the highway: ironweed and goldenrod and snakeroot and black-eyed Susan. The first time it happened the sun was in my eyes as I drove west toward Memphis, and a late summer drought was filling the air with dust motes. For a moment I thought I was imagining flowers where flowers had never been before. A daydream on a lonesome stretch of highway as twilight came on.

There was nothing unusual about the flowers themselves — they’re the plants that commonly bloom along Nashville’s greenways during late summer — but these flowers weren’t in a park or a nature preserve. They were growing right on the interstate median and on the side of the road. I figured the state’s Department of Transportation simply hadn’t gotten around to mowing yet.

Then I started to see the flowers in springtime, too, and all summer. The decision not to mow, it turns out, was deliberate. The Tennessee Department of Transportation — like many other state transportation departments across the country — now practices swath mowing, a strategy that allows wildflowers to bloom unmolested in rural areas till after the first frost. Instead of clearing the entire space between the road and the right-of-way fence, mowers clear only a 16-foot-wide area next to the road.

The mowed swath preserves clear sightlines for drivers while allowing wildflowers to grow in the deep margins between the mowed area and the fence. After the wildflowers have gone to seed, and the seeds have had time to ripen and drop, mowers clear the entire area again to keep trees from becoming established too close to the road. In Tennessee, this plan began as an experimental program in 2013 and now encompasses all rural highways managed by the state. That’s 13,807 miles of blooming flowers across Tennessee.

The flowers are beautiful, of course, and there’s a practical benefit to the plan, too: Reducing the frequency of mowing saves money. But neither beauty nor cost-cutting is the primary motive for swath mowing. The real reason behind the change is a concern for the health of the state’s pollinators — butterflies, honeybees, native bees, beetles and other insects.

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CreditWilliam DeShazer for The New York Times
CreditWilliam DeShazer for The New York Times

“We pay attention,” said Shawn Bible, the transportation manager of the department’s Highway Beautification Office. “We knew there was a problem with pollinators, and we saw an opportunity to help, so we jumped in to do it.”

Wildflowers once grew in profusion on roadsides everywhere. The shoulder of a highway, from blacktop to tree line, is the perfect setting for flowers that require full sun; it’s a ribbon of meadow that unfolds before the eye for as long as the road goes on. During my childhood in Alabama, every highway and back road was alight with butterfly weed, which belongs to the family of milkweeds. In summer it formed a bright corridor of orange flowers so covered with orange monarch butterflies that from a distance it looked as though the flowers themselves were taking flight and floating on the breeze.

But the monarch butterfly population has fallen precipitously since then. There are many reasons for the drop in their numbers, including climate change and deforestation in their Mexican wintering grounds. In this country the butterfly’s greatest threat is habitat destruction along their migration routes — the loss of both nectar flowers for food and milkweed plants for reproduction — primarily through the widespread use of herbicides like Roundup.

In 1996, the year before Roundup-resistant crops were first planted in the United States, the eastern population of the migratory monarch butterfly was around 700 million. Since then their numbers have dropped by more than 80 percent, according to the Xerces Society for Invertebrate Conservation, which works to preserve pollinator populations, and the tally is far worse for the migratory population west of the Rockies. Down by more than 99 percent, it’s now on the brink of extinction.

But it’s not just monarchs. As Ms. Bible noted, other crucial pollinators are in steep decline worldwide, with about 40 percent of insect pollinators now facing extinction, according to the Food and Agriculture Organization of the United Nations.

The transformation of American roadsides from narrow flowering meadows to close-cropped lawns isn’t the chief danger to troubled pollinators, but it hasn’t helped. And unlike the question of how farmers can limit the use of herbicides and still make money, the question of how to restore roadside meadows so that blooming plants can feed and sustain pollinators isn’t controversial.

Over the years, we’ve come to expect unvaried green space to unfold beside us as we drive on interstate highways, but that expectation is changing. The Tennessee Transportation Department was an early adopter of pollinator-friendly practices, but it’s far from alone. The Transportation FAST Act, which President Barack Obama signed into law in December 2015, urged state transportation departments to use land-management practices that promote pollinators.

CreditWilliam DeShazer for The New York Times

“Roadsides can offer feeding, breeding and nesting opportunities for pollinators, and also can aid pollinator migration by linking fragmented habitats and forming habitat corridors,” wrote Deirdre Remley and Allison Redmon in “Public Roads,” a publication of the Federal Highway Administration. “Roadsides extend through all types of landscapes and can be particularly important sources of habitat in highly altered landscapes such as intensely managed agricultural lands or urban areas.”

Coming home from Alabama this month, I stopped at the Tennessee welcome center in Ardmore, stepped out of my car, and was astonished to discover a newly planted pollinator meadow just down the hill from the welcome center. Up close, the acre-size plot was blooming with asters and liatris and ironweed and two different kinds of goldenrod. The plot was so loud with insects that the roar of highway traffic, only yards away up the little hill, was faint by comparison. While I stood there, dumbfounded, a monarch butterfly floated past. I was too stunned to take its picture.

The Ardmore rest area is the first meadow that the Transportation Department has specifically planted for pollinators, but others are in the works, among other pollinator-friendly partnerships and initiatives. This summer, the department announced a new partnership with the Tennessee Department of Environment and Conservation and the Tennessee Department of Agriculture to promote pollinators in state parks by planting wildflower meadows within park borders.

In Ardmore, just behind the fence beyond the pollinator meadow, is more state property. It is not planted or managed, and yet it, too, is blooming with ironweed and goldenrod and snakeroot. Last week I asked Ms. Bible about it. “That’s one of those wonderful opportunities” to let nature set the agenda, she said. “Those plantings are just natural.”

Margaret Renkl is a contributing opinion writer who covers flora, fauna, politics and culture in the American South. She is the author of the book “Late Migrations: A Natural History of Love and Loss.”

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