- An NGO is working with local authorities in Indonesia’s North Sumatra province to build canopy bridges for primates to safely cross roads that fragment their forest habitats.
- Pakpak Bharat district has seen rapid growth of new roads to improve communities’ access to schools and hospitals, with the trade-off being that many of these roads disrupt wildlife connectivity.
- The bridges, designed to meet the needs of different species, have been used by various wildlife, though not yet the critically endangered orangutans that the designers had in mind, and are monitored regularly through camera traps and maintenance checks.
- Conservationists highlight the bridges’ role in preventing inbreeding among isolated populations and sustaining the ecosystem’s biodiversity, with hopes to expand the initiative across Sumatra.
JAKARTA — In Indonesia’s North Sumatra province, conservation groups and authorities have built canopy bridges that stitch back together primate habitat, including for orangutans, that were fragmented by roads over the years.
Road building has expanded throughout Pakpak Bharat district to connect communities living on the edges of the forest to schools, hospitals and other facilities. For the region’s wildlife, however, these roads have reduced connectivity between habitats, especially for tree-dwelling primates like the critically endangered Sumatran orangutan (Pongo abelii). Wildlife movements across habitats are essential to sustaining viable populations, according to ecological surveys by the Resilient Equatorial Forests Foundation (TaHuKah), an NGO based in Medan, the provincial capital, which started working in the area in 2022.
“This [canopy bridges] project was born from a shared vision with the local authorities, recognizing that alongside essential development like road infrastructure, we must safeguard the movement of wildlife,” Erwin Alamsyah Siregar, executive director of TaHuKah, told Mongabay in an email.
The foundation approached local public works authorities, forest management units, and communities to build artificial canopy bridges to stitch back together the landscapes fragmented by new and upgraded roads. TaHuKah also partnered with the conservation group Sumatran Orangutan Society (SOS), which helped identify the fragmented, smaller populations of the great apes and viable ways to reconnect them based on data from the last orangutan census, carried out in 2016. The foundation also worked with the organization Vertical Rescue Indonesia to install the bridges.
“If these fragmented populations can be protected and reconnected, the orangutans have the potential to thrive long into the future, fulfilling their vital role as ‘gardeners of the forest’ and keeping this precious rainforest ecosystem flourishing,” Helen Buckland, CEO of SOS, told Mongabay in an email.
Five canopy bridges have now been built along the newly surfaced Lagan-Pagindar road in Pakpak Bharat. Each took a team of 12 people three to four days to complete. Additional funding came from U.K.-based charity the Size of Wales, the Netherlands-based Dierenpark Amersfoort Wildlife Fund, and the Asian Species Action Partnership, a collective of conservation organizations.
The team constructed three types of canopy bridges — single rope, horizontal ladder, and a hybrid bridge — to cater to different species. The single ropes better suit more agile species, the horizontal ladders those needing stability, and the hybrid ones for a diverse range of animals. They also carried out safety tests and installed to monitor wildlife use of the bridges.
To date, the camera traps have snapped individuals from three species using the artificial canopy bridges: black Sumatran langurs (Presbytis sumatrana), long-tailed macaques (Macaca fascicularis) and black giant squirrels (Ratufa bicolor palliate). The cameras have not yet recorded orangutans using the bridges.
The Pakpak Bharat district government will install traffic signs ahead of wach canopy bridge to alert drivers to slow down. Every three months, bridge assessments and data collection from camera traps help monitor wear and tear, while TaHuKah conducts twice-a-year traffic surveys. In collaboration with a local forest management unit, TaHuKah also plans regular patrols to oversee the bridges and deter potential wildlife hunters.
“The fragmentation of forests in Pakpak Bharat is illustrative of one of the main issues faced by contemporary conservation — disrupted connectivity between wildlife populations related to socio-economic development,” Buckland said.
“Both the pace and pattern of habitat loss is leading to connectivity in the landscape being severed, trapping orangutans and other rare species in shrinking islands of forest too small to sustain them,” she added.
Canopy bridges offer a practical solution adaptable to regions where infrastructure disrupts wildlife corridors. In this part of Indonesia, they help balance human development needs with environmental conservation by enabling safe crossings for arboreal species and promoting harmony between human progress and ecosystems, Buckland said.
Conservation experts say isolated wildlife populations face a greater risk of inbreeding, which over time leads to a weaker gene pool that puts these species at risk of extinction. Buckland also said the loss of orangutans and other forest species could have cascading effects, impacting the entire ecosystem, including the natural resources that local communities rely on.
Orangutans spend more than 90% of their time in the forest canopy. They were once widespread across Southeast Asia, but now only survive on the islands of Sumatra and Borneo. Fewer than 14,000 Sumatran orangutans, 800 Tapanuli orangutans (Pongo tapanuliensis), and 104,700 Bornean orangutans (Pongo pygmaeus) are left in the wild, with the Tapanuli orangutan, restricted to a single patch of forest in North Sumatra, considered the world’s most endangered great ape.
TaHuKah’s Erwin said he hopes canopy bridges will become standard across other parts of Sumatra facing similar challenges in recognition of the need to protect Indonesia’s biodiversity.
“These bridges allow us to support isolated wildlife populations without compromising progress,” he said.
Basten Gokkon is a senior staff writer for Indonesia at Mongabay. Find him on 𝕏 @bgokkon.
See more from this reporter:
Report: Orangutans and their habitat in Indonesia need full protection now
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