New Guinea's "lost world" of extraordinary plants and animals is naturally protected by rugged and inhospitable terrain but that may not last, says a New Zealand biologist.
One of the biggest threats was farming, said Dr Michael Heads, a biologist who studied the island's plants and animals for six years.
"The biggest threat is from cultivating sweet potato. As the population grows, intensively cultivated farms will push right up into the mountains," he said. "Forestry is a bit of a threat but the mountains are so steep it's impossible to get the logs out."
A survey by a team of international scientists, revealed this week, showed the island's mist-shrouded Foja Mountains to be one of the most biologically diverse areas on Earth.
The region of 300,000ha on the upper slopes of the mountains is one of the least explored areas in western New Guinea, a part of Indonesia previously known as Irian Jaya.
In the tropical rainforest, scientists found the rare Berlepsch's six-wired bird of paradise, 40 species of mammals, including the golden-mantled tree kangaroo, and 20 species of frogs previously unknown to science.
Many animals were partly tame because they had never had contact with humans.
Dr Bruce Beehler, of US-based Conservation International, and his team of Indonesian and Australian scientists reached the remotest parts of the Foja Mountains by helicopter.
The expedition was 20 years in the planning and carried out last December.
Dr Heads, an expert on birds of paradise, was sceptical of claims that a host of new species had been found, saying more work would have to be done to establish whether they had never been seen before.
