At around seven in the morning, with fog still settled over the hills of Espírito Santo state, biologist Gabriel Falquetto found a buffy-headed marmoset lying dead on the ES-164 highway. The species, native only to Brazil's Atlantic Forest, is listed as critically endangered, with roughly 2,500 individuals thought to remain in the wild. Falquetto monitors wildlife along this road daily as part of his work at the Kaetés private reserve, and he said the sight of a crushed marmoset undid the pleasure of every earlier sighting of the species moving safely through the canopy. Nearly 1,800 miles north, near the Amazon town of Alta Floresta in Mato Grosso state, a different outcome has been recorded.

In 2024, eight rope canopy bridges were strung between patches of forest that had been split apart by roads. Camera traps have since documented 15,000 crossings by tree-dwelling animals over fifteen months, and in that entire period, not one roadkill has been logged. The bridges were installed by Projeto Reconecta, working with the local government, business owners and conservation groups who had grown alarmed at the rising toll of wildlife struck by vehicles. Fernanda Abra, the biologist who founded Reconecta and now works with the Smithsonian's National Zoo in the United States, said the idea took shape after she discovered two dead Schneider's marmosets, another threatened Amazonian species, hours before the first bridge went up.

For her, the structures do more than save individual animals: they restore a kind of movement that roads had quietly erased, letting fragmented populations mix, breed and survive across barriers humans built without a second thought. The contrast between the two sites raises an uncomfortable question for a country that holds a disproportionate share of the planet's primate diversity.