Health in Papua New Guinea - Geography - Ecology

Ecology

Papua New Guinea is part of the Australasia ecozone, which also includes Australia, New Zealand, eastern Indonesia, and several Pacific island groups, including the Solomon Islands and Vanuatu.

Geologically, the island of New Guinea is a northern extension of the Indo-Australian tectonic plate, forming part of a single land mass which is Australia-New Guinea (also called Sahul or Meganesia). It is connected to the Australian segment by a shallow continental shelf across the Torres Strait, which in former ages had lain exposed as a land bridge, particularly during ice ages when sea levels were lower than at present.

Consequently, many species of birds and mammals found on New Guinea have close genetic links with corresponding species found in Australia. One notable feature in common for the two landmasses is the existence of several species of marsupial mammals, including some kangaroos and possums, which are not found elsewhere.

Many of the other islands within PNG territory, including New Britain, New Ireland, Bougainville, the Admiralty Islands, the Trobriand Islands, and the Louisiade Archipelago, were never linked to New Guinea by land bridges. As a consequence, they have their own flora and fauna; in particular, they lack many of the land mammals and flightless birds that are common to New Guinea and Australia.

Australia and New Guinea are portions of the ancient supercontinent of Gondwana, which started to break into smaller continents in the Cretaceous era, 65-130 million years ago. Australia finally broke free from Antarctica about 45 million years ago. All the Australasian lands are home to the Antarctic flora, descended from the flora of southern Gondwana, including the coniferous podocarps and Araucaria pines, and the broadleafed southern beech (Nothofagus). These plant families are still present in Papua New Guinea.

As the Indo-Australian Plate (which includes landmasses of India, Australia, and the Indian Ocean floor in between) drifts north, it collides with the Eurasian Plate. The collision of the two plates pushed up the Himalayas, the Indonesian islands, and New Guinea's Central Range. The Central Range is much younger and higher than the mountains of Australia, so high that it is home to rare equatorial glaciers. New Guinea is part of the humid tropics, and many Indomalayan rainforest plants spread across the narrow straits from Asia, mixing together with the old Australian and Antarctic floras.

PNG includes a number of terrestrial ecoregions:

• Admiralty Islands lowland rain forests – forested islands to the north of the mainland, home to a distinct flora.
• Central Range montane rain forests
• Huon Peninsula montane rain forests
• Louisiade Archipelago rain forests
• New Britain-New Ireland lowland rain forests
• New Britain-New Ireland montane rain forests
• New Guinea mangroves
• Northern New Guinea lowland rain and freshwater swamp forests
• Northern New Guinea montane rain forests
• Solomon Islands rain forests (includes Bougainville Island and Buka)
• Southeastern Papuan rain forests
• Southern New Guinea freshwater swamp forests
• Southern New Guinea lowland rain forests
• Trobriand Islands rain forests
• Trans Fly savanna and grasslands
• Central Range sub-alpine grasslands

At current rates of deforestation, more than half of the country's forests could be lost or seriously degraded by 2021, according to a new satellite study of the region. Nearly one quarter of Papua New Guinea's rainforests were damaged or destroyed between 1972 and 2002.