Monarch butterflies once coursed through North America in clouds so dense they darkened the sky. Now their migrations have dwindled to an uncertain trickle. The species could become the 21st century's passenger pigeon, a once-omnipresent species driven to extinction. But there's hope: In a literally last-ditch effort, ecologists hope to save the black-and-orange beauties by creating habitat along Interstate 35, which runs from Texas to Minnesota and tracks a major monarch migration route. The country's forgettable roadsides could seed the monarchs' salvation.

It may seem improbable, at least at first. But the I-35 restoration is part of a quiet revolution occurring in some of America's most unappreciated spaces. Roadsides and utility corridors, biologists say, are potentially vital sources of life. They can become grasslands and shrublands, rich habitats that once formed after fire and other natural disturbance, but have become rare in human-dominated landscapes.

Even the most intensively developed regions, from the agricultural heartland to the heart of New York, contain millions of acres of potential habitat. People just need to wrap their heads around that idea. "People think that everything has to look like their front lawn. If you don't mow roadsides, people complain," says Chip Taylor, a University of Kansas ecologist and founder of conservation group Monarch Watch. "But if you like birds, if you like butterflies, you should want to restore roadside habitats. There is so much land that can be restored."

The notion goes back several decades, most notably to landscape ecologist Richard Forman, who estimated total US roadside habitat at 10 million acres, an area the size of Maryland. Taylor thinks there's much more. Whatever the figure, it's been largely ignored. In a few places, like Iowa, roadsides are partially managed with consideration for wildlife, but that's rare. Most places reflect a reflexive cultural preference for domestic landscapes as tidy as they are ecologically impoverished.

That worm is finally turning. Last summer the White House pledged to help pollinators—not just commercial honeybees, but also wild pollinators, the thousands of species of native bees and butterflies threatened by pesticides, disease and habitat loss. Modern landscapes simply don't offer sufficient food and shelter to the creatures who literally make it bloom.

While the White House pollinator strategy didn't contain a lot of specifics or funding, Taylor says, it's been a powerful catalyst, pulling together government agencies, conservationists, farmers and private companies to discuss what must be done. The planned I-35 monarch corridor, which in February received a $3.2 million boost from the U.S. Fish and Wildlife Service, emerged from these talks. And it wouldn't only be monarchs that benefit, notes naturalist David Mizejewski of the National Wildlife Federation, but other pollinators and invertebrates, small mammals, migratory and ground-nesting birds: the entire community of life that thrives where monarchs do.

The project is in its infancy. That means partners must be enlisted, seed sources and funding sought, and best-practices developed to balance road visibility with ecosystem vibrancy. Most of all, both along the I-35 corridor and elsewhere, the people who manage these spaces need to be educated. "I ask, 'Why do you mow there?'" said Rick Johnstone, founder of Integrated Vegetation Management Partners, of highway managers whose cuts extend hundreds of feet beyond the tarmac. "They say, 'We always have.' I say, 'I know you have—but why do you do it?' It's a mindset."

While Johnstone works along roads, his specialty is utility corridors: the company-managed rights-of-way that extend along high-tension power lines and gas pipelines. In the continental US these cover some 20 million acres, roughly equivalent to the size of Maine, and like roadsides traditionally have been subject to routine mowing and landscape-scale herbicide dosing.

In a few places in the northeast, though, where rocky terrain made mowing difficult and public safety concerns mitigated herbicide use, utility companies have experimented with other management techniques. They eliminate tall and fast-growing trees that could interfere with their equipment, but otherwise allow smaller vegetation to grow unfettered. The result is dense shrubland, an early-stage forest habitat that, like grassland, teems with life and is desperately needed.

"Conservation organizations could not afford to manage the amount of shrubland that power companies manage in the process of protecting their high-tension lines," says ecologist Robert Askins of Connecticut College, who has studied flourishing bird populations along power lines. Other researchers have studied their value for pollinators, and the White House pollinator strategy tasked federal agencies to work with utility companies in promoting corridor habitat.

As with roadsides, Johnstone says, there's much work to be done in designing locale-specific strategies and convincing managers to change their habits. Conscientious stewardship requires expertise and extra commitment, especially at first: It's much simpler, after all, to just cut everything down. But eventually, Johnstone says, the shrublands become largely self-perpetuating. They cost less and less to maintain. In the long run, then, being nature-friendly doesn't just make for richer landscapes. It saves money, too.