Crossings: How Road Ecology Is Shaping the Future of Our Planet

by Ben Goldfarb

The vast majority of travel within national forests occurs on just 20 percent of their roads; some units’ networks are so tortuous, redundant, and laced with dead-end “cherry-stem” roads that the Forest Service could demolish most of its mileage without diminishing access in the slightest. Using the right roads has never precluded destroying the wrong ones.

More than 80 percent of the United States lies within a kilometer of a road, a distance at which cars project twenty decibels and trucks and motorcycles around forty, the equivalent of a humming fridge.

In Australia male tree frogs croak at higher frequencies near freeways (at risk to their romantic prospects, since females may associate squeakier ribbits with less studly mates).

no individual monarch experiences the species’ entire life cycle. The butterfly I saw dancing through traffic in Minnesota was likely third generation: her grandparents had gone to Mexico and her offspring would as well, but she would never lay her compound eyes on monarch Valhalla herself.

Today America’s road crews apply more than twenty million tons of salt annually, and Minnesota is among the heaviest users. Each winter the state spreads thirty-six tons for every mile of four-lane highway.

Slater envisions a sort of eagle-credit system, whereby wind farms whose turbines kill raptors expiate their sins by hiring workers to lug dead ungulates out of the danger zone. “We could increase survivorship of overwintering eagles by making this plentiful food source safe to them,” Slater said.

The migration pathway that exists today may shift northward tomorrow; the wetland across the highway may become a refuge from megafires the day after that. Wildlife passages would be valuable on any planet, but on one that’s heating up, they’re indispensable.

Conservationists and construction companies made for axiomatic enemies. Yet the imperative of climate adaptation had forced environmentalists into an unfamiliar position—advocates of building things, not just of stopping them from being built.

The Salmon SuperHighway was a manifestation of that trend: a climate-sensitive conservation plan that embraced infrastructure rather than fighting it, a stimulus for people and planet.

Some scientists have compared roads to motion-activated trail cameras, perpetually documenting whatever crosses their path.

It isn’t outlandish to suggest that AVs will become the most ingenious road-ecology tools ever devised, a roving squadron of automated scientists perpetually uploading terabytes of real-time data about the animals, dead and alive, whose paths they cross. As ecologists speculated in Nature, their sensors could “monitor pond-breeding amphibians during migrations, reptiles thermoregulating on warm asphalt, butterflies and birds flying over the road, and small mammals crossing roads or moving in surrounding areas.”

Autonomy’s masters could program their creations to drive slower at dusk, when animals are active, or avoid hotspots.