- Massive infrastructure projects currently underway on the Southeast Asian islands of Borneo and Sumatra are set to severely erode forest connectivity across key habitats of the Sunda clouded leopard.
- Two major highway networks and the relocation of Indonesia’s capital city to Borneo will further fragment the domain of the arboreal predator that has already experienced steep population declines in recent decades due to the expansion of oil palm and poaching.
- Experts say the findings will help to target conservation actions, but they add that road design standards and development planning processes remain woefully inadequate in the region.
- The authors call for improved development strategies that seriously consider sustainability and include data-based environmental assessments and mitigation measures, such as wildlife crossings and avoidance of sensitive ecosystems.
Sunda clouded leopards spend most of their lives in the leafy shade of the forest canopy. Equipped with exquisite camouflage, superb climbing skills and outsize canines, they’re formidable arboreal predators. But amid a development boom, the big cats’ uncompromising dependence on forest cover could prove a fatal weakness.
A new study indicates that a slew of major infrastructure projects underway on the Sunda clouded leopard’s (Neofelis diardi) sole range islands of Borneo and Sumatra will severely erode forest connectivity in its core habitats and movement corridors, even inside protected areas.
The study, published in Science of the Total Environment, modeled the impacts of three megaprojects — the Pan Borneo Highway, the Trans-Sumatra Highway and the relocation of the Indonesian capital city to Borneo — on the species’ key strongholds as a proxy for wider changes in forest connectivity.
As forest-dependent top predators, clouded leopards are reliable barometers of overall ecosystem health, study lead author Żaneta Kaszta, from the University of Oxford’s Wildlife Conservation Research Unit, told Mongabay. “Clouded leopards serve as a useful model species with which to develop predictions of connectivity to measure the impacts of infrastructure developments.” If the arboreal felines are thriving at the top of the food chain, the web of life beneath them is also likely in good shape, she said.
The link between large-scale infrastructure and tropical biodiversity loss is well-studied. Prior research has found, for instance, that more than one-fifth of Southeast Asia’s terrestrial mammal species are threatened by road networks. By opening up forests to mining, illegal logging, poaching, and forest clearance for agriculture, roads gradually carve habitats into isolated fragments, dividing wildlife populations and restricting animals’ movement to find mates and food.
For top predators like Sunda clouded leopards that require vast home ranges, live at low density and have slow reproductive rates, the effects of massive development projects can be devastating. Both of the world’s two species of clouded leopard are categorized as vulnerable on the IUCN Red List due to steep population declines over the past two decades triggered by the loss of roughly one-third of their core forest habitat.
Forest connectivity loss
To examine how the three megaprojects will impact forest habitat connectivity across Borneo and Sumatra, Kaszta and her colleagues from Australia, Canada, Indonesia, the U.K. and the U.S. overlaid habitat suitability models and clouded leopard distribution data from prior camera-trapping studies on plans for each project to calculate where habitat connectivity is most at risk.
Their models indicated that of the three developments, the development of Indonesia’s new capital city, known as Nusantara, in East Kalimantan province will result in the greatest reduction of forest connectivity, particularly in South and East Kalimantan provinces, in such core clouded leopard strongholds as the richly forested Meratus Mountains.
Echoing the concerns of many critics of the project, Kaszta said the impacts of the new capital city will be felt across the entire island of Borneo, and reverberate far into the future. “The new capital will have cascading effects on wildlife and its habitats, some of them very hard to predict,” she said. “Since large cities need large resources, [there will be] huge demand for further infrastructure development and energy, as well as agriculture expansion. All of this inevitably [equates to] more forest loss.”
Stanislav Lhota, a wildlife biologist at the Czech University of Life Sciences, who was not involved in the study, said that besides predators like clouded leopards, a plethora of other local species will find themselves living in increasingly smaller fragments of habitat with limited food sources as the new capital is built. Competition, he said, will be fierce. “There are now 10 species of non-human primates in Nusantara. However, some of them (such as white-fronted and silvered langurs) are very likely to be outcompeted by closely related species if they are restricted to small patches of forest.”
Heartlands and strongholds at risk
The clouded leopard models also identified grave threats associated with the two major highway projects. They found that the Pan Borneo Highway — a scheme that aims to link up Malaysian Borneo, Brunei and Indonesian Borneo (known as Kalimantan) via a series of road upgrades and new carriageways — will proportionally take the highest toll on protected area connectivity. Some 5% of the total connectivity loss due to the road scheme occurred on protected land.
Environmental and community rights groups have long raised concerns over the toll of the road project on protected areas. The section of the route that traverses Indonesian Borneo (where it’s known as the Trans-Kalimantan Highway) alone will traverse 25 protected areas, according to prior research.
By far the most extensive and important of the 28 clouded leopard core habitats the team identified in Borneo spans the island’s iconic Heart of Borneo primary forest landscape. Other important areas for the big cats typically radiate around this mountainous central core forest, linked to it by a series of forested corridors, although several satellite core habitats are already completely cut off.
The authors raise particular concerns over the proposed route of the northern segment of the Trans-Kalimantan Highway, which cleaves right through the Heart of Borneo landscape, risking a “huge negative effect on clouded leopard and forest connectivity,” Kaszta said. She called on decision-makers to reconsider the alignment of this road section while they still have the chance to do so. “Results like this should alarm decision-makers,” she said.
Crucially, much of the central Heart of Borneo landscape currently receives no legal protection, according to the study. “Without legal protection the large central core area in the heart of Borneo might soon become dismembered and its fragments isolated,” the authors write in the study. “We advocate prioritizing protection of the central part of the main core area, which we predict supports a high density of Sunda clouded leopard movement.”
Further north, in Malaysian Borneo’s Sabah state, the highway will drive a hard divide between the state’s largest core primary forest area and smaller forest patches that nonetheless retain significant wildlife populations, increasing the likelihood of genetic isolation and inevitable local extinctions.
Benoit Goossens, director of the Danau Girang Field Centre, a scientific research and training facility in Sabah, who was not involved in the study, said that while many roads already crisscross the biodiverse state, plans to widen and upgrade so many carriageways will come as a shock to many wildlife populations living in sensitive areas, such as the Maliau Basin, Kalabakan Forest Reserve and Tawai Forest Reserve.
“[When the road] is a two-way highway, you still have elephants, banteng, clouded leopards and sun bears crossing it,” Goossens told Mongabay. “But when they upgrade it to four lanes — that’s going to be difficult for wildlife to cross, unless they build underpasses and overpasses.”
Goossens was part of a team that in 2019 found that all planned infrastructure in Sabah, including the Pan Borneo Highway, could reduce the connectivity of Sunda clouded leopard habitat by 23% and the species’ population size by up to 63%, with significant impacts on its genetic diversity.
In Sumatra, the Trans-Sumatra Highway, although largely already under construction, will also further disrupt the connectivity of remaining tracts of forest. The authors identified “relatively large” clouded leopard strongholds in the Leuser Ecosystem and Kerinci Seblat National Park, and seven smaller, more isolated core habitat areas across the island, typically linked only by thin and poorly protected forest corridors.
With a route charting 2,700 kilometers (about 1,700 miles) down Sumatra’s spine, the major highway scheme poses a particular threat to the narrow, but vital, movement corridors that connect these scattered core areas across the island. The authors also flag sections of the scheme that have degraded the integrity of the clouded leopard’s only two remaining larger core habitats, such as recent upgrades of highway section running adjacent to Gunung Leuser National Park, which risks isolating the clouded leopard populations between the eastern and western halves of this biodiversity hotspot, according to the study.
Road design standards woeful
Wai-Ming Wong, the director of small cat conservation science at the wildcat NGO Panthera, said the stark findings from Borneo and Sumatra highlight an “urgent” need for more conservation action for clouded leopards to avert the “deleterious effects of inbreeding and genetic isolation” that can follow habitat fragmentation.
“The findings underscore the vulnerability of Sunda clouded leopard habitats and the importance of protecting core areas establishing connectivity corridors,” Wong said, adding that maintaining large tracts of connected habitat that big cats and many other forest-dwelling species need to survive amid the sea of development is key.
Other sources said that beyond conservation work, biodiversity considerations must be embedded deeper within the planning process in the species-rich region to ensure development doesn’t come at the expense of natural heritage.
First, road design standards need to improve, Goossens said. Wildlife crossings, such as underpasses or bridges that enable animals to transit beneath or over highways, should be fully budgeted, crucial considerations during the design phase of developments, rather than merely an afterthought. “I’m still hopeful we can push for underpasses and overpasses to help with connectivity [of the Pan Borneo Highway in Sabah],” he said. “Overpasses would be really good for primates, even for orangutans.”
Further, the study authors call for overarching improvements in national development planning frameworks around environmental impact assessments. “If development strategies are planned in a forward-looking and sustainable manner, guided by scientific analyses and data-based assessments, there is potential for the management of Sumatra and Borneo to be a paradigm for building balanced human-wildlife coexistence,” they write in the study.
While the construction of Indonesia’s new capital city will have inevitable impacts, it could also present opportunities to strengthen conservation efforts, the authors note. According to Nusantara’s new biodiversity master plan, the ultimate goal is to ensure 65% of the area of the new capital is tropical rainforest, by designating protected areas and rehabilitating degraded lands and forests.
It will now be up to policymakers, planners and conservation groups to translate the vision on paper into reality. But for Lhota, the emphasis on restoring forests that have been destroyed in the past, such as coal mine pits, seems misplaced. He said he’d rather see a focus on protecting existing forests.
“In the end, we could easily end up with coal mines planted with tree plantations of no environmental value, while the natural forests that survived into the early 2020s would have been largely destroyed by the new development,” Lhota said. “Forests are not instant noodles, they take time to grow back … The first priority should be to protect what’s left of the natural habitat.”
Carolyn Cowan is a staff writer for Mongabay. Follow her on 𝕏, @CarolynCowan11.
Banner image: The Sunda clouded leopard (Neofelis diardi) has a slightly darker coat than the mainland clouded leopard (Neofelis nebulosa). Image by Spencer Wright via Wikimedia Commons (CC BY 2.0)
Citations:
Kaszta, Ż., Cushman, S. A., Hearn, A., Sloan, S., Laurance, W. F., Haidir, I. A., & Macdonald, D. W. (2023). Projected development in Borneo and Sumatra will greatly reduce connectivity for an apex carnivore. Science of The Total Environment, 918, 170256. doi:10.1016/j.scitotenv.2024.170256
Clements, G. R., Lynam, A. J., Gaveau, D., Yap, W. L., Lhota, S., Goosem, M., … Laurance, W. F. (2014). Where and how are roads endangering mammals in Southeast Asia’s forests? PLOS ONE, 9(12), e115376. doi: 10.1371/journal.pone.0115376
Alamgir, M., Campbell, M. J., Sloan, S., Suhardiman, A., Supriatna, J., & Laurance, W. F. (2019). High-risk infrastructure projects pose imminent threats to forests in Indonesian Borneo. Scientific Reports, 9(1). doi:10.1038/s41598-018-36594-8
Kaszta, Ż., Cushman, S. A., Hearn, A. J., Burnham, D., Macdonald, E. A., Goossens, B., … Macdonald, D. W. (2019). Integrating Sunda clouded Leopard (Neofelis diardi) conservation into development and restoration planning in Sabah (Borneo). Biological Conservation, 235, 63-76. doi:10.1016/j.biocon.2019.04.001
See related story:
Unseen and unregulated: ‘Ghost’ roads carve up Asia-Pacific tropical forests
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