New Britain-New Ireland lowland rain forests

The Admiralty Islands lowland rain forests cover the volcanic Admiralty Islands of Papua New Guinea, which make up Manus Province in the country's Islands Region, an isolated archipelago lying roughly 280 kilometers off the northern coast of New Guinea. Lowland tropical rainforest dominates the larger islands, with characteristic canopy trees including Calophyllum, Barringtonia, and Terminalia, fringed by coastal shrub zones of Sararanga and Pandanus. The climate is warm and wet year-round, with daytime highs near 30 to 32 degrees Celsius, cooler nights, and about 3,400 millimeters of annual rainfall that peaks during the June-to-August wet season. Long isolation from any landmass has produced notable endemism, including several endemic birds such as the superb pitta and Manus fantail, the Admiralty flying-fox, and the emerald green snail, the first land snail listed as vulnerable by the IUCN. Commercial logging and forest conversion now place heavy pressure on the remaining forests, especially in the interior of Manus Island.

The Banda Sea Islands moist deciduous forests cover a scattered archipelago in southeastern Indonesia, spanning the Tanimbar Islands, the Kai Islands, and the Barat Daya Islands (except Wetar) within Wallacea, the transition zone lying between the Asian and Australian faunal realms. Its forests form a mosaic of evergreen and semi-evergreen rain forest, moist deciduous forest, and dry deciduous forest, with characteristic Australo-Melanesian trees such as Dillenia, Pometia, Manilkara, Inocarpus, Heritiera, Diospyros, Garcinia, and Myristica. The climate is a tropical monsoon regime of two seasons: a wetter, more humid west monsoon running from mid-December to June, followed by a drier east monsoon. Despite the small size of these islands, the ecoregion supports an exceptional 21 endemic bird species alongside 22 mammal species, with endemic birds such as the Tanimbar cockatoo and blue-streaked lory threatened by introduced rats and cats. Among its native plants, Myristica includes the nutmeg tree (Myristica fragrans), long valued for the spices nutmeg and mace.

The Biak-Numfoor rain forests cover a cluster of Indonesian islands in Papua Province, chiefly Biak, Supiori, and Numfoor along with smaller islands of the Padaido group, lying within Cenderawasih Bay north of Yapen and the New Guinea mainland. Original vegetation is lowland tropical wet evergreen forest, divided between alluvial forests on flatlands and river valleys and hill forests on the slopes, with multi-tiered canopies whose dominant emergents include Pometia pinnata and species of Ficus, Alstonia, and Terminalia. The climate is tropical, humid, and consistently wet, with temperatures varying little through the day or year. These islands hold the highest concentration of endemic birds of any single area in New Guinea, and the brilliantly patterned Biak emerald monitor lizard serves as the ecoregion's flagship species; large coastal stands of Calophyllum occur in northern Biak, and the lowland forests shelter an endemic palm, Manjekia maturbongsii. For gardeners, native ornamentals here include Calophyllum, Diospyros, Garcinia, and Myristica.

The Buru rain forests cover Buru Island, the third-largest of Indonesia's Maluku (Moluccas) Islands, set between the Banda and Seram Seas, where two mountain ranges rise to about 2,700 meters. Dense tropical evergreen and semi-evergreen forest blankets much of the island, dominated by tall, straight dipterocarp trees in the genera Hopea, Shorea, and Vatica, with cool, rainy montane forest taking over above roughly 800 to 900 meters and fire-resistant paper-bark (Melaleuca cajuputi) holding the drier ground. The climate is equatorial and monsoonal, with a rainy season running from October to April and the heaviest rain falling in the mountains. The ecoregion is rich in endemic wildlife found nowhere else, including the curve-tusked Buru babirusa, ten Buru-endemic birds such as the Buru racket-tail, and the flagship Buru opalescent birdwing butterfly, though selective logging and swidden farming continue to degrade the forest. Gardeners may recognize native genera with ornamental kin here, including insectivorous Nepenthes pitcher plants on the southwest limestone karst and the aromatic paper-bark Melaleuca.

The Central Range Papuan montane rain forests cloak the mountain spine of New Guinea, running along the Central Cordillera from Indonesia in the west into Papua New Guinea in the east, generally between about 1,000 and 3,000 meters elevation. Vegetation shifts with altitude: lower montane forests hold oaks of the beech family such as Castanopsis acuminatissima and Lithocarpus alongside laurels, Elaeocarpus, and tall stands of Araucaria, while upper slopes are dominated by moss-draped evergreen southern beech (Nothofagus) and the highest forests turn to ancient conifers like Podocarpus, Dacrycarpus, and Papuacedrus mixed with myrtle-family trees. The climate is humid, tropical, and ever-wet, with rainfall exceeding 2,500 mm annually across most of the highlands and surpassing 7,000 mm in the wettest catchments, and temperatures averaging around 18 degrees Celsius and cooling with elevation. These highlands are a global hotspot for birds-of-paradise and carry exceptionally high endemism in mammals, birds, and vascular plants, though only roughly 14 percent lies in protected areas such as Lorentz National Park. For gardeners, the region is the native home of ornamental conifers including Araucaria and Podocarpus.

The Halmahera rain forests cover Halmahera and its neighboring islands, including Bacan, Morotai, the Obi Islands, Ternate, Tidore, and Gebe, in the North Maluku province of eastern Indonesia. These mountainous, partly volcanic islands belong to Wallacea, a group that sits in the Australasian realm but was never joined to either Australia or Asia, so its plants and animals mix elements of both worlds and include many species found nowhere else. Tropical lowland and montane forest dominates, ranging from evergreen to semi-evergreen rainforest, with drier stands in southern rain shadows; characteristic trees include dipterocarps such as Shorea assamica and Vatica rassak. The climate is a tropical rainforest climate. The ecoregion is rich in endemic birds and is the home of the standardwing bird-of-paradise as well as Wallace's giant bee, the world's largest bee. For gardeners, this is the native range of two famous spice trees, clove (Syzygium aromaticum) and nutmeg (Myristica fragrans).