The world’s largest jungle-covered island is New Guinea, located in the southwestern Pacific Ocean just north of Australia. At 821,400 square kilometers (317,150 square miles), it is the second largest island on Earth after Greenland, but unlike Greenland’s ice-covered landscape, New Guinea is blanketed in tropical rainforest. Its jungle is considered the third largest rainforest on the planet, after the Amazon and the Congo, spanning more than 730,000 square kilometers across the island.
Why New Guinea, Not Borneo?
Borneo is sometimes confused with New Guinea for this title, and it’s a fair question. Borneo is also densely forested and ranks as the third largest island in the world at 748,168 square kilometers. But New Guinea edges it out in both total land area and remaining forest cover. About 30 million hectares of intact tropical forest remain on New Guinea alone, representing roughly half of all the large, intact forest blocks left across the tropics. Borneo has lost significantly more of its original forest to logging and palm oil plantations over the past several decades.
A Layered Landscape of Forest Types
New Guinea’s jungle isn’t a single uniform carpet of trees. The island rises from sea level to peaks above 4,800 meters, creating distinct forest bands at different elevations. Lowland rainforest dominates up to about 1,500 meters, with tall canopy trees reaching 30 meters or more. Unlike the rainforests of Southeast Asia, where a single tree family tends to dominate the upper canopy, New Guinea’s lowland forests are a patchwork of many different species, making the canopy more varied from one ridge to the next.
Below the lowland forests, coastal areas host mangrove swamps and seasonal wetlands where fire-tolerant paperbark trees grow on waterlogged plains. Higher up, montane forests take over with shorter, denser canopies shrouded in cloud and moss. Some of the wettest spots on the island, along the Fly-Digul shelf and surrounding highlands, receive more than 7,600 millimeters (300 inches) of rain per year, making them among the wettest places on Earth.
The Most Plant-Diverse Island on Earth
A comprehensive survey led by the Royal Botanic Gardens at Kew identified 13,634 plant species on New Guinea, drawn from 1,742 genera and 264 families. That makes it the most floristically diverse island in the world. Even more striking, 68 percent of those plants (9,301 species) are endemic, meaning they grow nowhere else. More than two-thirds of every plant you’d encounter in New Guinea’s jungle simply doesn’t exist on any other landmass.
This extraordinary plant diversity supports equally rich animal life. The island is home to birds of paradise, tree kangaroos, and an enormous range of reptiles and amphibians. Conservation scientists have estimated that adequately protecting all of New Guinea’s vertebrate species within reserves would require designating at least two-thirds of the island for conservation.
Hundreds of Cultures in One Forest
New Guinea’s dense jungle and rugged terrain have kept human communities isolated from one another for thousands of years, producing one of the most linguistically diverse places on the planet. Roughly 800 distinct languages have been identified on the island, and only 350 to 450 of those are even related to each other. The rest evolved independently. Several thousand separate communities live across the island, most numbering just a few hundred people. This cultural fragmentation is a direct product of the jungle itself: mountain ridges, swampy lowlands, and unbroken forest made travel between valleys difficult for millennia.
The Island Is Split Between Two Nations
Politically, New Guinea is divided roughly in half. The eastern portion is the independent nation of Papua New Guinea, while the western half (known as Papua and West Papua) belongs to Indonesia. This split matters for conservation because the two sides face different pressures and operate under different environmental policies.
On the Papua New Guinea side, Global Forest Watch data shows the country lost about 74,000 hectares of natural forest in 2024 alone. Between 2002 and 2024, it lost 990,000 hectares of humid primary forest, accounting for about half of all tree cover loss during that period. Overall, Papua New Guinea lost roughly 2 million hectares of tree cover from 2001 to 2024, a 5 percent reduction from its forest area at the start of the century. The Indonesian side faces its own deforestation challenges, driven largely by logging and agricultural expansion.
Climate That Sustains the Jungle
New Guinea sits squarely in the tropics, and its climate is what keeps the forest so thick. Monthly average temperatures stay above 18°C year-round with minimal seasonal variation. Annual rainfall across most of the island exceeds 200 centimeters, and there is either no dry season at all or only a brief one lasting fewer than four months. In any given month, rainfall rarely drops below 60 millimeters. This constant warmth and moisture is what allows the forest to grow so densely and support such a wide range of life, from the lowland swamps to the cloud forests near the peaks.