10 January 2022
Trees of New Guinea
A new publication is unravelling the mysteries of trees on a paradise island.
With 13,634 plant species, the tropical island of New Guinea is the most floristically diverse island in the world.
Remarkably, 68% of New Guinea’s plant species are endemic, meaning they’re found nowhere else.
The ‘paradise island’ supports a mosaic of ecosystems, including large areas of intact mangroves, rainforest, montane forest and alpine grasslands.
This is partly driven by the wide variation in New Guinea’s landscapes, from its long coastline to the extensive highlands in the centre of the island.
New Guinea has an impressively rich tree flora with an estimated 5,000 species of tree occurring on the island.
Protecting and understanding New Guinea’s vast forests is incredibly important for retaining the carbon stored within these ecosystems and mitigating the effects of global climate change.
In the first publication of its kind, and following 11 years of work, we have put together a guide to all 693 tree genera in New Guinea, which covers approximately 40% of all genera on the island.
Here we take a look at some of our favourite trees of New Guinea.
The endemic klinki pine Araucaria hunsteinii is the tallest tree on New Guinea, standing above the canopy at an average height of 60 metres.
Some, however, can grow up to 90 metres, making them among the tallest trees in the world.
Unusually for such a tall tree, it is found in mid-montane forests above 500 metres.
It is a close relative of the monkey puzzle tree (A. araucana), and like that species, the seeds are edible.
World’s biggest banana
There are at least 10 native species of wild bananas in New Guinea and the island is a major centre of diversity with a 7,000-year history of cultivation.
While not actually a tree, Musa ingens is the largest species in the banana family and grows in the Arfak mountains reaching a height of 30 metres.
The leaves of this species can stretch to an impressive 5 metres and the species produces enormous fruits.
Some 100 species of nutmeg (Myristica) and 175 species of clove (Syzygium) relatives are found on New Guinea, providing flowers and fruits for animal pollinators and dispersers.
Nearly all the species of nutmeg in New Guinea are unique to the island, and some of them have a trait that is unique in the family: twigs with hollow swellings that are inhabited by ants.
Although the taxonomy of the nutmegs is fairly well understood, we know little about their ecological relationship with ants.
The cloves are a truly enormous genus with over 1,100 species worldwide that are currently being researched in collaborative projects with Kew.
About 175 species occur in the rainforests of New Guinea.
Tremendous tree ferns
New Guinea is a tree fern hotspot with 120 species from the Cyatheaceae and Dicksoniaceae families.
Over two thirds of these species are endemic to New Guinea and form distinct 'tree fern shrubberies’ in the montane and subalpine areas.
With their large arching fronds and stout trunks, often with numerous epiphytic orchids, the tree fern grasslands are one of the more enigmatic and evocative habitats of New Guinea.
Figs, in the genus Ficus, are very species rich and important ecological, providing fruits throughout the year for birds, bats and other wildlife.
On New Guinea, the figs, like the cloves, have 175 species with many of them arborescent.
Figs have developed a distinctive pollination system with tiny wasps unique to each species laying their eggs inside the fig, an example of coevolution.
170 native species of Rhododendron are found in New Guinea, with nearly all of them endemic, i.e. restricted, to New Guinea.
The rhododendrons of New Guinea are particularly conspicuous at higher elevations in the subalpine and alpine areas, with some reaching 4,200 metres (Rhododendron ultimum).
They vary from 15 metre tall tress (e.g. R. macgregoriae) to tiny epiphytes growing almost flat on the trunks of tree ferns (e.g. R. caespitosum).
New Guinea coffee
The coffee family, Rubiaceae, is one of the largest plant families, containing approximately 13,500 species, and there are nearly 800 species in the family in New Guinea.
The most species rich group is the genus Psychotria with over 150 endemic species on the island and one of the many plant groups on New Guinea in need of further research.