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Spanning over 4,000 kilometers (2,500 miles) and being built over the course of decades, the Trans-Papua Highway cuts across the entire length of Indonesian New Guinea's two provinces, including 7 key protected areas.

While the project is nearly complete, experts warn it will cost billions annually to maintain, and threaten to open up untouched rainforest to palm oil expansion contributing an additional 4.5 million hectares of deforestation by 2036.

For this episode, we interviewed David Gaveau, founder of The TreeMap and Bill Laurance, distinguished professor, and director of the Center for Tropical, Environmental, and Sustainability Science at James Cook University in Australia.

Both experts explained the environmental, financial, and social costs of the project, which runs through Indonesia's Lorentz National Park, a UNESCO World Heritage Site.

If you missed the first three episodes of Mongabay Explores New Guinea you can find it via the podcast provider of your choice or find all the episodes of the Mongabay Explores podcast on our podcast homepage here.

Episode Artwork: Tearing up trees to expand the road for the Trans West Papua highway. Daniel Beltrá/Greenpeace

Editor's Note: Bill Laurance, is a Distinguished Research Professor at James Cook University in Cairns, Australia as well as the founder and director of ALERT (Alliance of Leading Environmental Researchers & Thinkers) and a member of Mongabay's advisory board.

Sounds heard during the intro and outro include the following: rusty mouse-warbler, growling riflebird, raggiana/lesser bird-of-paradise, superb fruit-dove, long-billed honeyeater, little shrike-thrush, brown cuckoo-dove, black-capped lory. Special thanks to Tim Boucher and Bruce Beehler for identifying them.

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