Some roadkill scenes stay with you. For biologist Gabriel Falquetto, one of them was a buffy-headed marmoset lying on the ES-164 highway in Brazil’s Espírito Santo state, a species listed as critically endangered on the International Union for Conservation of Nature Red List, with an estimated 2,500 individuals left in the wild.

“It was extremely painful and discouraging,” Falquetto told Mongabay. “We travel through this region every day monitoring wildlife, and we celebrate every encounter with groups of buffy-headed marmosets in the forest.”

“Finding an individual in those conditions brings a feeling of sadness and helplessness. Beyond the loss of that animal, the incident reminds us of the impacts our activities have on biodiversity.”

About 2,900 kilometres away, on the road to Alta Floresta in northern Mato Grosso state, cases like that have not been recorded since 2024, when eight canopy bridges were installed to connect fragmented forest patches.

Camera trap footage showed that over 15 months, the aerial crossings enabled 15,000 safe crossings by arboreal animals, with no roadkill recorded.

The bridges are part of a program involving Projeto Reconecta and the municipal government, along with local organisations and business owners concerned by the growing number of wildlife-vehicle collisions.

Biologist Fernanda Abra, founder of Reconecta and an associate researcher at the Smithsonian National Zoo and Conservation Biology Institute in the United States, said she found two dead Schneider’s marmosets just hours before the first bridges were installed in Alta Floresta.

“A canopy bridge serves two purposes,” Abra said. “The first is to improve connectivity for wildlife, allowing animals to move from one side to the other in these fragmented forest areas. As a result, we also reduce roadkill.”

Each bridge has two camera traps, one aimed at the crossing and another at the forest, to record which animals use the structure and which reach it but do not cross.

In the first months of the program, cameras recorded black-faced black spider monkeys, Purus red howler monkeys, northern night monkeys, tufted capuchins, Schneider’s marmosets and the Alta Floresta titi monkey using the bridges.

Abra said the project is moving into a new phase.

“In August, we will install eight more bridges in the city’s urban area,” she said. “The only difference is that the electric utility will first need to lower the power lines and insulate them so that if animals jump from the bridge onto the wires, they won’t be electrocuted.”

Reconecta first installed canopy bridges in 2021, when the team worked with Waimiri-Atroari Indigenous people to put 32 crossings over BR-174, the highway that runs through their territory and the Amazon between Amazonas and Roraima states.

Over five years, cameras on those structures recorded about 1,250 primate crossings, including golden-handed tamarins.

“The outcomes of the BR-174 project have been incredible. We were able to test different bridge designs to find out which ones the animals prefer,” Abra said.

She said the current bridge uses a multilayer design for primates that move in different ways, including species that use prehensile tails, brachiating species such as spider monkeys, and species that walk across the ropes. Opossums, sloths and mouse opossums have also been recorded using the bridges.

Abra said results take time.

“Very often, our sense of urgency in conservation doesn’t take into account the timing of the impact,” she said.

In Alta Floresta, tufted capuchins took seven months to use one of the bridges for the first time.

Brazil has the greatest diversity of primates in the world and the fourth-largest road network.

“From our human perspective, roads mean connection and development. But for wildlife, they represent disconnection, barriers and a threat to survival,” Abra said.

A 2022 study found nearly 9 million mammals are killed on Brazil’s roads every year. A 2025 data compilation published in Nature also found the country ranks among those with the highest mortality rates of terrestrial vertebrates killed on roads.

“Habitat loss is one of the main drivers of population declines, especially among threatened species, but the impact of roadkill is still greatly underestimated,” primatologist Fabiano Rodrigues de Melo, a professor at the Federal University of Viçosa in Minas Gerais, told Mongabay.

Beyond direct deaths, roads isolate animal populations.

“When populations become isolated, they grow smaller and more vulnerable to threats,” said Amely Branquinho Martins, an environmental analyst at ICMBio and coordinator of the Brazilian Biodiversity Genomics project.

“Habitat loss and degradation can prevent an individual from one population from migrating to another, what we call gene flow,” Branquinho Martins said. “Without it, the species’ genetic diversity declines.”

Melo said the effects keep spreading because primates, especially fruit-eating species, help disperse seeds and contribute to pollination.

“A whole network of ecological interactions is ultimately lost with the disappearance of these species,” Melo said.

Abra is now expanding Reconecta to Suriname and Lucas do Rio Verde in Brazil, where 10 canopy bridges will be installed. She also wants to take the project to other biomes, including the Pantanal and the Atlantic Forest.

In June, she was named one of the recipients of the 2026 Wayfinder Award and joined the group of National Geographic Explorers, who receive funding from the organisation for their projects. She also received the Future For Nature Award in 2019 and the Whitley Award in 2024.

Brazil’s federal transport department has officially designated Reconecta’s rope bridge design as the recommended national standard for highways, as Congress considers a bill to create a national wildlife road safety plan that includes warning signs, speed reduction devices, and wildlife crossings.

“I envision a future with Reconecta Biomes. We already have Reconecta Amazon, and we’ll soon launch Reconecta Pantanal. I also see canopy bridges in the Atlantic Forest for the primates that live there, including muriquis and howler monkeys, which are both highly threatened,” she said.

“When everyone is involved, everyone values the initiative and works harder to make it succeed.”

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