- The Torricelli Mountain range in northern Papua New Guinea holds a staggering amount of biodiversity in a tiny area.
- A recent analysis suggests that the threat of extinction to species living in the Torricellis if the land were cleared of its forests would be among the highest on Earth.
- A community conservation group called the Tenkile Conservation Alliance has worked to end the hunting of critically endangered tree kangaroos in the Torricellis and has proposed a 1,250-square-kilometer (483-square-mile) protected area to further protect the mountains’ forests and species.
- But the government of Papua New Guinea has stopped short of officially recognizing the conservation area as the threat from industrial logging companies in the region remains.
Millions of years ago, as the Indo-Australian plate pushed into the Pacific plate, a volcanic arc of islands began to emerge near the modern-day island of New Guinea that would one day form the Torricelli Mountains. And in this ancient, slow-motion reordering of Earth’s crust, life inevitably layered on top of the substrata to form one of the most species-rich spots on the planet.
“You’ve got to remember that there was the Sepik River pumping vegetation from the mainland off into the ocean, some of which was clearly reaching this island arc system,” Australian zoologist Tim Flannery of the Australian Museum in Sydney told Mongabay.
Along with that botanical foundation came a number of animals: amphibians, to be sure, which seem particularly adept at rafting on plant life from one piece of land to another, according to Flannery, along with a predecessor of the northern glider (Petaurus abidi), a marsupial species with bewitchingly bulbous eyes found only in the Torricellis.
“We’re still working out exactly what species came across at that phase,” he said, but it’s clear “there was a rich source of colonists.”
Later, the emergence of a mountain range connected this island arc to the Doberai Peninsula of western New Guinea, which is also known as the Bird’s Head, or Vogelkop in Dutch and Indonesian, for its namesake shape. As a result of this “amazing orogeny” in the early Pliocene Epoch and another linkage with New Guinea’s Central Highlands, a number of species that had previously been confined elsewhere were able to expand their range into what would become the Torricellis, according to Flannery.
This swirl of life radiating in “has led to that relatively tiny mountain range having probably the highest endemism, for mammals at least, in all of Papua New Guinea,” Flannery said. “And I wouldn’t be surprised it was true for other groups as well.” To Western scientists, nearly all of that remained a mystery until very recently — a hair’s breadth, in fact, in geologic time.
“In the early ’80s, it seemed just like any other outlier mountain range, where you’d expect less endemism and less diversity than you would from the center,” Flannery said. “It was only that slow development of understanding of the geological history of [the Torricelli Mountains] that we started to make sense of this exceptional richness that we were discovering up there.”
That was around the time Flannery was surveying his way through the area and the island of New Guinea, eventually describing four species of tree kangaroo himself. (The Torricelli Mountains are the only place on Earth where three of them coexist side by side.)
For the Torricellis, the overall biodiversity numbers are staggering — and likely to be even more so if zoologists and botanists continue to find species amid the range’s forests. Papua New Guinea’s roughly half of the island is thought by scientists to hold 6-8% of all Earth’s species, said Jim Thomas, CEO of the Tenkile Conservation Alliance (TCA).
Thomas’s back-of-the envelope calculations, based on estimates that the Torricellis are home to at least half of PNG’s mammals and birds and likely a greater proportion of the country’s reptiles and amphibians, suggest that the mountains could hold some 4% of the world’s biodiversity, he said. “I mean, for 0.003% of the world’s land area — it’s a ‘wow’ factor for me,” Thomas said. “I’m so lucky to be working here.”
Thomas and his wife Jean left their jobs as zookeepers in Australia to start the TCA in 2003. Before the TCA, the region’s wildlife and two of its three species of tree kangaroo, the tenkile (Dendrolagus scottae) and the weimang (D. pulcherrimus), faced an uphill survival battle. Both had been hunted to near extinction, and Flannery has said he felt at the time as if he were witnessing the twilight of the tenkile’s time on Earth.
In the ensuing decades, however, the Torricellis have experienced a community-led renaissance for the range’s biodiversity, engineered in large part by the TCA and the belief that people and wildlife can flourish side by side. World-renowned conservationists like Flannery and Jane Goodall credit the TCA for bringing education, health care and economic opportunity to the people of the Torricellis, while halting the hunting that was winnowing away the numbers of tree kangaroos and other mammals in the range.
Meanwhile, populations of both the tenkile and weimang are growing, according to surveys supported by the TCA, though both are still considered critically endangered by the IUCN, the global conservation authority. Flannery also said that data suggest the weimang is returning to territory it’s been absent from for perhaps a century.
More recently, though, satellite data and imagery show the threat of logging has surged, while at the same time, the TCA’s effort to protect the range with a conservation area supported by 43 communities in the Torricellis has stagnated. In a 2022 podcast, Thomas told Mongabay that he thinks the lack of government action since 2008 — when the TCA first put forth a proposal for the Torricelli Mountain Range Conservation Area — stems from the sway that industrial logging interests hold over Papua New Guinea’s politics. (Papua New Guinea’s environment ministry, which the TCA has been working with for official recognition of the conservation area, didn’t respond to multiple requests from Mongabay for comment.)
Now, a new scientific metric helps cement the importance of the biodiversity that the region contains. But logging companies have pushed to make inroads and degrade the forest as other data reveal.
The work of Flannery and other researchers have shown that the Torricellis are a repository of immense biodiversity, but science is only just beginning to sort out just how deep that fount of species goes. And that, backers of the protected area say, is a critical reason for the government to solidify protections for the area as soon as it can.
Measures of ‘LIFE’
Today, the Torricellis occupy a unique niche in the broader landscape of New Guinea. Even on a wildly biodiverse island, the mountains stand out as exceptional. Flying over the range gives the impression of unbroken forest undulating to the horizon, infrequently broken by a tributary of the looping Sepik River or a steep escarpment here or there, carved by periodic deluges that add up to the Torricellis’ 1,700 millimeters (67 inches) of annual rainfall. Signs of human settlement do appear sporadically, often as pinprick clearings surrounded by rotating swaths of gardens at varying stages of recovery, until, moving farther from the center, the high canopy takes over once again.
Likely more worrisome for the forest’s wildlife are the roads that cut through the bushy green like splayed herringbones, spines of red earth with ribs flayed out, tracing the links to the forests these arteries provide. Indeed, for years, TCA staff have fought — so far successfully — to keep the construction of a logging road that would bisect the larger lobe of the proposed 1,250-square-kilometer (483-square-mile) conservation area.
TCA project officer Fidelis Nick, who lives close to where the road would pass through the mountains on the way to the coast, has continued to petition those in his community and nearby against its construction. He says it would provide the access to timber that logging companies desire, ultimately threatening the gains that he and the rest of the team have made since the early 2000s for tree kangaroos and many other species dependent on standing forest.
For now, progress on that road has stalled, according to satellite data and imagery visualized on the platform Global Forest Watch (GFW). But overall, GFW data show Torricelli Mountain Range Conservation Area lost 2% of its primary forest cover between 2012 and 2023 — and the data suggest that trend is accelerating. Recent data from 2024 show a new surge in logging road expansion in and near another portion of the proposed conservation area.
Alongside that data, another metric demonstrates the importance of the Torricellis’ forests to biodiversity — and the gravity of threats to the survival of those species.
Satellite imagery from Planet Labs visualized on the platform Global Forest Watch (GFW) show roads proliferated between and within the two main portions of the proposed Torricelli Mountain Range Conservation Area in 2024. Image by Morgan Erickson-Davis/Mongabay.
In January 2025, University of Cambridge postdoctoral research associate Alison Eyres and her colleagues published a study detailing a new global method for understanding the risk of extinction for species living in a given area, called “LIFE” (Land-cover change Impacts on Future Extinctions). The tool integrates data from the IUCN on species’ ranges, with maps of land cover, to come up with a “LIFE” score that assesses what the loss of a given area would mean.
At Mongabay’s request, the team analyzed the area of the proposed Torricelli Mountain Range Protected Area, as it’s now known. The total LIFE score they generated ranked in the top 1% of all areas for the number of extinctions it would produce over the next 100 years if all of the forests were razed.
Eyres called the relative importance of the region “quite striking.”
“I knew that that area was important, but I didn’t really realize how important,” she said in an interview.
Among the animals that contribute most to that score are the tenkile, the northern glider, and a handful of frog species, several of which are new to science since 2000.
The question posed by the study, about how many extinctions might occur if such a biodiverse bank of habitat were loss, is in part academic because it’s unlikely that all of the Torricelli’s forests would be wiped out completely. But it also brings to the fore species that live in a given area and are particularly susceptible to extinction. Often, that’s because a species has a naturally narrow range, especially in a place like New Guinea, where diversity has proliferated in unique but diminutive ecological niches. It could also be that they’ve lost habitat elsewhere. Or it could be some combination of these and other factors.
Eyres noted that a focus of future work would be to incorporate deeper understanding of how less dramatic waves of degradation, or threats such as hunting, could tip the scales toward extinction. But these would be more difficult to map than out-and-out destruction, especially on a global scale.
She also said it’s important to ground-truth the IUCN data to make sure that species’ ranges are accurate. Particularly with species that are newer to science and narrowly distributed, she added, “It does mean that you should then want to go and look at more local knowledge of whether they’re actually in that site.”
Herpetologist Fred Kraus of the University of Michigan described several of the amphibians that contributed substantially to the Torricellis’ LIFE score and confirmed that they’re found in the Torricellis.
“Every one of them occurs in high-elevation parts of the range,” Kraus told Mongabay.
‘Data deficient’
Several of the species high on the list for the Torricellis are classified as “data deficient” by the IUCN. But just because there isn’t reliable information to determine their conservation status doesn’t mean that those species should be ignored, Eyres said.
“Often data deficient species are ones which are really in trouble so [it’s] really good to be able to include them in analyses like this,” she said in an email to Mongabay.
Plus, the way the LIFE analysis is structured allows the team to update the model as new and better data become available, Eyres added.
The pursuit of reliable information about the species of the Torricelli Mountains is yet another way that the TCA has contributed, in Flannery’s view. He said the conservation effort spearheaded by the TCA has given scientists a good handle on the health of the populations of tree kangaroos and larger mammals, difficult as they are to study in the field.
Now the challenge is to focus on smaller and more elusive animals, Flannery said, “some of which have only ever been collected once.”
“Because they’re data-deficient, we don’t know whether they’re just naturally rare. Are they declining to extinction because of some threat? Are they adequately conserved within the bounds of the [hunting] moratorium area?” he added. “They’re all questions that we can’t really answer until we get better data, so that data deficiency is a big red flag for me and kind of a signpost as to where we should be concentrating our effort.”
The species that contributes most to the Torricellis’ LIFE score, the Ziegler’s water rat (Hydromys ziegleri), is listed as data deficient. Still, even species that scientists know more about, like the northern glider, bring up questions for scientists. Thomas said the last-known sighting of the glider was in 2007, so there are concerns that it may no longer reside in the range.
If gliders do still exist in the Torricellis, it’s surprising that the TCA team hasn’t recorded its presence, Thomas said, especially because they’ve expanded their efforts to survey the region’s wildlife. In 2024, Jean Thomas started the rokrok meri project, equipping 86 women from Torricelli communities with mobile phones and tasking them with snapping photos of frogs (“rokrok” in Pidgin) and anything else they come across.
The project has turned up at least 100 known frog species by Jim Thomas’s reckoning and “many” more that have yet to be described by scientists.
“There’s just heaps,” Thomas said, all representing the dazzling diversity of amphibians inhabiting the cloud forests of the Torricellis.
The TCA is also working with a botanist who says he’s identified a couple of dozen new species of plants. And Thomas said one of the country’s longest lizards, the crocodile monitor (Varanus salvadorii), routinely turns up in staff surveys.
Flannery said it’s hard to overstate the value of the on-the-ground data from TCA staff, which has included camera trapping.
“Those forests are very difficult to research in. The slopes are steep,” he said. “It’s physically exhausting, doing anything from radio tracking to just spotlighting at night.”
Now, furnishing people with camera phones has been a game changer, he added.
“It’s brilliant,” Flannery said. “It’s really helping us.”
In the future, he said he hopes new tools like eDNA analysis will illuminate the biodiversity landscape in the Torricellis even further. Elsewhere, across the Torres Strait, a team of scientists in northern Australia has had success keeping tabs on a tree kangaroo species that lives there with thermal drones.
The full suite of data will open the region’s secrets in new and exciting ways, including one that Flannery is hesitant to talk about right now, but could potentially send shockwaves through the zoological community.
“It’s an ongoing quest to try to understand that diversity,” he said.
Insidious threats
And it could unlock other mysteries — ones for which even protection of the sort provided by the TCA communities can’t contend with.
“There are real signs that some species are really suffering for reasons we don’t understand,” Flannery said, adding that the northern glider might fall into that category.
“I really fear for its continued existence,” he said, which would mark the first modern extinction of a mammal on the island of New Guinea.
“That’s a real landmark,” Flannery added. “I wouldn’t call it gone yet, but I just think there’s a warning flag being raised with the data deficiency.”
The TCA’s work has effectively eliminated hunting in the proposed protected area since the Thomases began working with communities to agree on a hunting moratorium in the early 2000s, he said. Now, it’s the formal recognition of the conservation area and the bulwark against logging it would provide that’s become an overarching goal. It’s far from a foregone outcome, though the 2024 passage of a new protected areas law in PNG has sparked hope. But other threats loom on the horizon — like climate change.
Of the Torricellis, Flannery said, “It’s a low mountain range with high endemism at high elevation. How that will play out in future, we don’t know, but it’s likely not to be good news.
“It’s likely that some stuff will be pushed off the top of the mountains,” he added.
Still, if anything, the specter of a warmer world has galvanized those intent on protecting PNG’s wildlife and the habitat that sustains it as soon as possible so they’re best equipped to face any surmountable challenges.
The researchers who work there agree that the country sits in a unique position, having sidestepped, at least comparatively, the loss of forest to timber extraction, to oil palm and other agriculture, and to mega-scale mining projects experienced in nearby Southeast Asia and throughout the world’s tropical forests. But those threats remain at PNG’s doorstep, as logging does in the Torricellis; in parts of the country, they’re already leaving their scars.
Proponents of industry say that mining, logging and agriculture companies bring jobs, services and infrastructure development. But conservationists and community rights advocates say those benefits are often theoretical and that government elites typically siphon off more of the economic rewards, leaving little to actually reach people on the ground. They contend that the urgent focus should be to protect the country’s vast natural wealth.
As Kraus put it, “Now is when you want to act, because you can actually get something done.”
Banner image: A grizzled tree kangaroo (Dendrolagus inustus), pictured here at the TCA base in Lumi. The animal is found in the Torricellis and other mountain ranges in northern New Guinea. Image by John Cannon/Mongabay.
Additional reporting by Morgan Erickson-Davis.
John Cannon is a staff features writer with Mongabay. Find him on Bluesky and LinkedIn.
Logging threats loom over tree kangaroo refuge in Papua New Guinea
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