- Located at the edge of the western Pacific Ocean, New Guinea is a vast island where the biota of Asia and Australasia meet, making it a melting pot of unique plants and animals that occur nowhere else on the planet.
- Development pressure is ramping up across the island, however, opening up landscapes to new roads, industrial logging and agricultural conglomerates pushing biofuel agendas.
- New Guinea’s low-elevation forests, which represent some of the world’s last vestiges of ancient lowland tropical rainforest, are particularly imperiled, according to a new study.
- To avert tragedy, the authors urge policymakers to improve land-use planning systems, focus on retaining intact forest landscapes, and strengthen the rights of the people who live among them.
The island of New Guinea is famed for its eye-popping diversity of plants, animals and human cultures. Estimated to host one-tenth of Earth’s species, it’s the world’s second-largest island and has the third-largest intact expanse of tropical forest in the world, after the Amazon and the Congo. It’s where birds-of-paradise perform their effervescent courtship displays, tree kangaroos shimmy up trees to dizzying heights, and the world’s largest butterfly flits between foliage in the forest canopy.
This extraordinary biodiversity is partly the result of centuries of evolutionary isolation at the edge of the western Pacific, where the biota of Asia and Australasia meet. It also comes from powerful tectonic activity that shaped a rugged and mountainous landscape, making many areas difficult for humans to access and develop.
Today, roughly 80% of New Guinea’s forest cover remains intact, sharply contrasting with nearby islands like Borneo, Java and Sumatra, which have seen extensive development and deforestation.
However, experts are increasingly concerned that developers are shifting their focus to New Guinea, which is split roughly in half between Indonesia, which controls the island’s west, and Papua New Guinea, in the east. Major road schemes, industrial logging and agricultural conglomerates pushing biofuel agendas are carving into the island’s ancient landscapes, especially on the Indonesian side.
A new study that models deforestation risk across the island predicts that its low-elevation forests are likely to be especially vulnerable. This is worrisome, the authors note, since these ecosystems are among the tallest, most biologically rich and carbon-dense ecosystems on Earth, representing some of the world’s last vestiges of old-growth primary tropical rainforest. In short, they’re irreplaceable.
“Lowland rainforests are being decimated across the tropics, becoming very rare in most regions,” William Laurance, study co-author and a distinguished research professor at James Cook University in Australia, told Mongabay in an email. “In New Guinea, lowland forests are extremely biologically rich, with some of the highest diversity seen on Earth. [They] also store massive amounts of carbon that could otherwise worsen global warming” if released.
The research team calculated that forest destruction in New Guinea could spew up to 2 billion metric tons of carbon emissions into the atmosphere by the year 2040. This is a “frightening” number, Laurance said, which could derail the climate commitments of the Indonesian and PNG governments.
Both governments have made zero-emissions climate commitments as well as adopted ambitious goals on protecting and preserving biodiversity in recent years.
The Manokwari Declaration, signed in the Indonesian city of that name in the island’s western tip in 2018, calls for protecting 70% of the forest cover in Indonesian New Guinea. It also includes commitments to enhance Indigenous rights, improve protected area management, and revoke permits from noncompliant plantations. In PNG, meanwhile, a new Protected Areas Act was passed in 2024 with provisions to safeguard 30% of the territory there by 2030.
With development pressure rising and such conservation commitments on the table, the researchers say there’s a “critical opportunity” to use evidence-based approaches to guide conservation efforts to where they’ll have the greatest benefits for both biodiversity and communities.
Megadiverse lowland forests at risk
To conduct the study, the researchers from Australia, Indonesia and Germany combined machine-learning models with a technique called cellular automata that allowed them to visualize future deforestation patterns at high resolution based on a range of development scenarios.
Unsurprisingly, the areas the models identified as most at risk of deforestation were located in accessible lowland areas near previously cleared land and human settlements, with road construction, logging and agricultural expansion, especially for oil palm plantations, among the greatest drivers of forest loss.
In the Indonesian half of the island, known as the Papua region, the models indicated forests at elevations lower than 380 meters (1,250 feet) are likely to be lost first. This is a worrying prospect, the authors say, given protected areas cover just 10% of land lower than 500 m (1,640 ft) in Papua. In PNG, where protected areas cover just 3.7% of all land, the models showed the frontier of deforestation will likely creep into higher ground, to elevations of up to 750 m (2,460 ft).
The differing patterns may partly be due to different drivers of deforestation in the two halves of the island, according to Christoph Parsch, a spatial ecologist at Georg-August University Göttingen in Germany and lead author of the study. In PNG, deforestation is mainly caused by logging rather than plantations, he said. As a result, deforestation hotspots in PNG are influenced more by how accessible the forest is, rather than how suitable the land is for growing crops.
The spread of deforestation into mid-elevation areas in PNG would present severe conservation challenges, Parsch noted, since these are often zones where lowland and montane species meet, generating high levels of species richness and endemicity.
Although New Guinea’s steep highlands might be spared the initial brunt of development pressure because they’re hard to reach, Parsch said many unregulated “ghost roads” are appearing in these areas, making them more accessible to developers. Prior research in Southeast Asia has found sharp spikes in deforestation soon after such illegal and unmapped roads are built into forest-rich lands.
Maliwan Namkhan, a conservation biologist at King Mongkut’s University of Technology in Thailand, who wasn’t involved in the recent study, said much is at stake if New Guinea follows a similar path of forest degradation as seen elsewhere in the region. Species that are yet to be studied or even discovered could be lost, she said, and trying to reverse the harm of forest destruction is notoriously challenging.
“In other parts of Southeast Asia, widespread habitat loss has already led to the extinction or local extinction of numerous species,” Maliwan said. “Even when species survive in small, isolated areas, reintroducing them to other parts of their original range is extremely difficult, costly, and time-consuming.”
Maliwan welcomed the new study as an example of how modeling can be used to forecast development-related risks and target conservation efforts. “In the case of New Guinea — where large tracts of lowland forest still remain — such research can help prioritize protection efforts before it’s too late,” she said.
Priority locations for conservation
To provide more insight into where conservation efforts might have the most impact, Parsch used the deforestation-risk findings in a follow-up study that pinpoints biodiverse areas most at risk of deforestation.
Using vertebrate species as a proxy for overall biodiversity, he and his colleagues identified important areas for conservation prioritization in the Wamena and Central Mountain ranges and the lowlands around Mamberamo Foja Wildlife Reserve in Indonesian Papua. In PNG, priority locations included the Torricelli Mountain range, the Western Highlands and the Huon Peninsula. They also located “irreplaceable” hotspots of at-risk biodiversity on offshore islands like Raja Ampat and Biak, on the Indonesian side, and Bougainville in PNG.
The sheer number of vertebrate species included in the study illustrates the scale of New Guinea’s biodiversity, amounting to 1,896 species, including 501 amphibians, 837 birds, 303 mammals and 255 reptiles. Nearly 10% of these are considered at risk of extinction by the IUCN, the global wildlife conservation authority, and a whopping 64%, or 1,216 species, are endemic to the island.
Pinpointing the locations most at risk of deforestation is particularly useful in a region like New Guinea, where tiny areas can harbor staggering amounts of biodiversity found nowhere else on the planet. Recent analyses have shown, for instance, that losing forests in PNG’s Torricelli Mountain range could trigger some of the world’s highest rates of species extinctions.
“There are a lot of evolutionarily distinct species in New Guinea, which, if you lose them, you don’t just lose the species, you lose entire blocks of the tree of life,” Parsch said.
The study concludes that over the short term, limited conservation funds and resources should be directed toward saving irreplaceable species facing imminent development pressure, while working to preserve extensive tracts of intact forest.
To make progress, the researchers call on both governments to adopt more proactive and inclusive conservation policies, such as effective land-use planning, strengthening anticorruption measures, and promoting cross-border collaboration to protect species that range across national boundaries.
Empowering Indigenous communities, who are widely acknowledged as among the world’s most effective at preventing deforestation and conserving ecosystems, is essential, Parsch said. He emphasized the importance of supporting community development programs like social forestry and strengthening customary land rights.
George Gale, an associate professor of conservation ecology at King Mongkut’s University, who also wasn’t involved in either study, said the findings give a solid overview of where conservation action is needed across the region. It’s now up to conservationists and civil society organizations on both sides of the border to push for measures that protect vital habitats before it’s too late, he said.
“It’s going to take a major effort to protect some of these forests,” Gale said. “Developers and loggers work very quickly if there’s money to be made. It’s definitely a race against time.”
Banner image: A magnificent bird-of-paradise (Cicinnurus magnificus). Image courtesy of Christoph Parsch.
Editor’s note (May 22, 2025): An image caption that incorrectly identified the masked bowerbird has been updated.
Carolyn Cowan is a staff writer for Mongabay.
Citations:
Parsch, C., Wagner, B., Engert, J. E., Panjaitan, R., Laurance, W. F., Nitschke, C. R., & Kreft, H. (2025). Forecasting deforestation and carbon loss across New Guinea using machine learning and cellular automata. Science of The Total Environment, 970, 178864. doi:10.1016/j.scitotenv.2025.178864
Engert, J., Campbell, M. J., Cinner, J. E., Ishida, Y., Sloan, S., Supriatna, J., … Laurance, W. F. (2024). Ghost roads and the destruction of Asia-Pacific tropical forests. Nature. doi:10.1038/s41586-024-07303-5
Parsch, C., Denelle, P., Bless, A., & Kreft, H. (2025). Diverging conservation priorities across New Guinea: Conflicts and opportunities. Global Ecology and Conservation, 60, e03549. doi:10.1016/j.gecco.2025.e03549
See related story:
PNG’s Torricelli Mountains teem with life — and the risk of extinction
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