Environmental group World Wildlife Fund discovered 1,060 new species on the island at the rate of two a week between 1998 and 2008.
Among the finds are 12 mammals including a snub-fin dolphin – the first new dolphin to be discovered for 30 years.
Discoveries also included the greater monkey-faced bat and Sir David’s long beaked echidna, an anteater named after Sir David Attenborough.
Some 71 new fish including a 2.5metre-long river shark, 218 new kinds of plants, two birds, 580 invertebrates, 134 amphibians and 43 reptiles were also uncovered on the island, which is divided between Papua New Guinea and Indonesia.
New Guinea contains the third largest tract of rainforest in the world, after the Amazon and the Congo, and shelters 6 to 8 per cent of Earth’s species, although its landmass is just 0.5 per cent of the world’s surface.
But WWF warns that, while the island’s forests and rivers are among the richest in the world for wildlife, many of the creatures and plants found in the space of a decade are under threat from human activities.
Natural habitats are vanishing at ‘an alarming rate’, according to Dr Susanne Schmitt, New Guinea programme manager at WWF-UK.
‘The island’s forests are facing serious threats including logging, mining, wildlife trade and conversion to agriculture, particularly oil palm,’ she said.
‘As a region with high rates of poverty, it is absolutely essential that New Guinea’s precious reefs, rainforests, and wetlands are not plundered but managed sustainably for future generations.’
However, the charity warned that many are at risk from human activity.
It said studies showed that in Papua New Guinea between 1972 and 2002, almost a quarter of rainforests were cleared or damaged by logging or subsistence agriculture, while demand for palm is an increasing threat today.
Dr Neil Stronach, WWF Western Melanesia’s programme director, said: ‘This report shows that New Guinea’s forests and rivers are among the richest in the world.
‘But it also shows us that unchecked human demand can push even the wealthiest environments to bankruptcy.’