New Guinea has the most plant species of any island

  • New Guinea is the planet’s most speciose island when it comes to plants, reports a comprehensive assessment of vascular plant species published in the journal Nature.
  • The research concludes New Guinea has 13,634 species of plants from 1742 genera and 264 families. That gives New Guinea, the world’s second largest island, the highest plant diversity of any island on Earth, surpassing Madagascar (11,832 species), Borneo (11,165 species), and Sumatra (8,391 species).
  • New Guinea’s flora is also highly unique. The study finds that more than two-thirds of its plants are endemic, meaning they are only found on the island.
  • But time may be running short for New Guinea’s biodiversity, since 2002 the island lost 1.15 million hectares of primary forest and nearly 2 million hectares of total tree cover. New Guinea’s high degree of endemism makes its flora particularly vulnerable.
NASA Landsat image of the island of New Guinea. The western half of the island in controlled by Indonesia, while the eastern half is the independent country of Papua New Guinea.

New Guinea is the planet’s most floristically diverse island, reports a comprehensive assessment of vascular plant species published in the journal Nature.

The species list, which was compiled by 99 botanists from 56 institutions across 19 countries, verified the identity of over 23,000 plant names from over 704,000 specimens collected from New Guinea since the 1750s.

The research concludes New Guinea has 13,634 species of plants from 1742 genera and 264 families. That gives New Guinea, the world’s second largest island, the highest plant diversity of any island on Earth, surpassing Madagascar (11,832 species), Borneo (11,165 species), and Sumatra (8,391 species). New Guinea’s diversity of plants is greater than that of the entire archipelago of the Philippines (9,432 species).

Just five families account for more than a third of plant species on the island. Orchids, with 2,856 species or 21% of the island’s species, are the most diverse.

There are 3,962 species of trees in New Guinea or about four times the number found across all of North America.

Fraction of species that are trees (pink), herbs (dark blue), epiphytes (orange), shrubs (green), climbers (light blue), non-climbing palms (yellow) and tree ferns (mid blue). Courtesy of NATURE.
Fraction of species that are trees (pink), herbs (dark blue), epiphytes (orange), shrubs (green), climbers (light blue), non-climbing palms (yellow) and tree ferns (mid blue). Courtesy of NATURE.

New Guinea’s flora is also highly unique. The study finds that more than two-thirds of its plants are endemic, meaning they are only found on the island. New Guinea’s high degree of endemism is “unmatched in tropical Asia” according to the researchers.

“New Guinea is extraordinary: it is a paradise island teeming with life,” said the paper’s lead author, Rodrigo Cámara-Leret of the University of Zurich, in a statement. “As the second largest island in the world after Greenland and the world’s largest tropical island, it supports a mosaic of ecosystems and is globally recognized as a centre of biological diversity.”

“However, despite this, knowledge on New Guinea’s flora has remained scattered for years, limiting research in this megadiverse area. Our paper set out to address this.”

Rainforest in the Tamrau Mountains, West Papua, Indonesia. Photo RBG Kew
Rainforest in the Tamrau Mountains, West Papua, Indonesia. Photo Royal Botanic Gardens, Kew
The genus Freycinetia, with 140 species, is a group of forest climbers in the Pandanaceae family, one of the 20 most diverse groups in New Guinea. Credit RBG Kew.
The genus Freycinetia, with 140 species, is a group of forest climbers in the Pandanaceae family, one of the 20 most diverse groups in New Guinea. Credit Royal Botanic Gardens, Kew.

Prior to this paper’s publication, the estimates of the number of species on New Guinea ranged from 9,000 to 25,000. The Global Biodiversity Information Facility, an international research initiative backed by governments and organizations, lists more than 14,000 species for Papua New Guinea (correction) alone, significantly exceeding the 10,793 species verified by the new study. Improving the accuracy of the number of plant species is critical for efforts to conserve the island’s flora, say the researchers.

“It is clear, in the context of the biodiversity crisis, that this paper represents a milestone in our understanding of the New Guinea flora and provides a vital platform to accelerate scientific research and conservation,” said study co-author Peter Wilkie of the Royal Botanic Garden Edinburgh. “Research at its best is collaborative and this demonstrates what can be achieved when scientists from around the world work together and share expertise and data.”

Scientists' campsite in a tree fern savanna in the Cromwell Mountains of Papua New Guinea. Photo RBG Kew.
Scientists’ campsite in a tree fern savanna in the Cromwell Mountains of Papua New Guinea. Photo RBG Kew.
This joint expedition of the Papua New Guinea Forest Research Institute & Kew was supported by the residents of Indagen Village, according to Kew. Credit RBG Kew.
This joint expedition of the Papua New Guinea Forest Research Institute & Kew was supported by the residents of Indagen Village, according to Kew. Credit Royal Botanic Gardens, Kew.

The data is the product of more than 15,000 collections gathered from the wilds of New Guinea over the past 260 years. The island’s complex topography — including dramatic mountain ranges, deep valleys, alpine grasslands, and dense lowland rainforests — have made collecting expeditions more perilous than almost any place on Earth. Accordingly, botanists are still discovering new species at a rapid pace: more than 2,800 species have ben described in the past 50 years.

“Species discovery shows no sign of leveling off,” the authors write, noting they expect another 4,000 species to be described in “The Last Unknown” in the next half century.

But time may be running short for New Guinea’s biodiversity, since 2002 the island lost 1.15 million hectares of primary forest and nearly 2 million hectares of total tree cover. Papua New Guinea accounted for 53% of tree cover loss during that period. Logging, conversion of forests for plantations and small-scale agriculture, and fire are threats to the island’s native biota.

New Guinea’s high degree of endemism makes its flora particularly vulnerable, according to the paper. Deforestation of a single mountainside or valley could result in the extinction of species limited to that specific place.

“Such high richness of endemic species means that both countries have a unique responsibility for the survival of this irreplaceable biodiversity,” the authors write. “Given the general trend of plant endemism to increase with elevation, the conservation of ecosystems along altitudinal gradients is particularly critical.”

Residents from Indagen village helping the expedition team to field camp in the Cromwell Mountains of Papua New Guinea. Credit RBG Kew
Residents from Indagen village helping the expedition team to field camp in the Cromwell Mountains of Papua New Guinea. Credit Royal Botanic Gardens, Kew

But the researchers believe their work will provide much more than just an inventory of what’s being lost in New Guinea.

“Our work allows us to understand what exists, and with that knowledge we are better equipped to conduct more informed science and applied conservation planning,” the University of Zurich’s Cámara-Leret told Mongabay via email. “Having a list verified by the leading New Guinea botanists will be essential for many branches of science. For example, having accurate names is essential for conservation planning as for understanding the potential impacts of climate change on biodiversity. Usually, modelers integrate lists of species and geographic occurrences with climate data. But if species’ names or geographic distributions are wrong, then the results can be very misleading.”

Marie Briggs (RBG Kew) and Victor Simbiak (Universitas Negeri Papua, Indonesia) preparing plant specimens in Tamrau Mountains, West Papua. Credit RBG Kew.
Marie Briggs (RBG Kew) and Victor Simbiak (Universitas Negeri Papua, Indonesia) preparing plant specimens in Tamrau Mountains, West Papua. Credit Royal Botanic Gardens, Kew.

Cámara-Leret said that several of the study’s authors are working closely with the local government of Indonesia’s West Papua province to help identify priority areas for conservation.

“This is part of a grand vision by the local governor to conserve 70% of the forests of West Papua, as explained in the Manokwari Declaration,” he said. “As part of our research, we have been looking into the potential impacts of climate change on biological, but also cultural heritage.”

This rich cultural and biological diversity is what makes New Guinea so unique. Study co-author Tim Utteridge at the Royal Botanic Gardens, Kew, says that helping protect it should be of prime concern.

“I have been working in Indonesia for over 20 years and have always been fascinated by the beautiful and bountiful biodiversity of New Guinea,” Utteridge said in a statement. “We all now have a unique responsibility for the survival of this irreplaceable biodiversity.”

Table: Countries with over 10,000 species of vascular plants

Country Vascular plant species
Brazil  > 34,000
China  > 31,000
Colombia  > 24,000
Mexico  > 23,000
South Africa  > 21,000
Peru  > 19,000
Australia  > 19,000
Indonesia  > 19,000
Ecuador  > 18,000
Myanmar  > 16,000
United States  > 15,000
Venezuela  > 15,000
India  > 15,000
Bolivia  > 14,000
Malaysia  > 14,000
Argentina  > 13,000
Chile  > 13,000
Russia  > 12,000
Madagascar  > 11,000
Costa Rica  > 11,000
Papua New Guinea  > 11,000
Panama  > 10,000
Philippines  > 10,000
Tanzania  > 10,000
Turkey  > 10,000

 

CITATION: Rodrigo Cámara-Leret et al. New Guinea has the world’s richest island flora. Nature August 5, 2020. DOI: 10.1038/s41586-020-2549-5


CORRECTION (6-Aug-2020): This original version of this story contained the following line: “The Global Biodiversity Information Facility, an international research initiative backed by governments and organizations, lists nearly 30,000 species for Papua New Guinea alone, far exceeding the 10,793 species verified by the new study”. This was based on this line in the paper: “Our species total for Papua New Guinea differs markedly from the 29,756 species that were presented in an unverified list of the Global Biodiversity Information Facility”. On August 6, 2020, a representative from GBIF brought it to our attention that GBIF only includes 14,428 species for PNG.

This story first appeared on Mongabay

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