New Guinea, in the South Pacific, has been found to contain the highest plant diversity of any island in the world, according to research involving scientists from Scotland’s leading botanic garden.

Botanists from the Royal Botanic Garden Edinburgh (RBGE), together with colleagues at Kew and other leading research institutes, compiled the first list of all of the plants in the world’s largest tropical island.

The research, published in the journal Nature, recorded 13,634 species of plants from 1,742 genera and 264 families, positioning New Guinea as the most floristically diverse island in the world.

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The results mean New Guinea has 16 per cent more plant diversity than well-known biodiversity hotspot Madagascar, which has 11,488 species recorded.

The experts warn that further botanical exploration is urgently needed, however, so species that remain unknown can be collected before they disappear.

RBGE tropical botanist Dr Mark Hughes, who was part of the research organisation’s most recent expedition to New Guinea, said today/yesterday [WED]: “The diversity on New Guinea is absolutely astounding -- and breathtakingly beautiful.

“RBGE has been working there since the 1960s, and we have an ongoing expedition programme, but much of the information about the island has been held in herbaria, botanic gardens, in separate papers and inside experts’ heads, scattered around the world.

“This international collaboration meant all this expertise was brought together and put in one place.

“There is much to be revealed. We are working on a project at the moment looking at the begonias of Papua New Guinea, where I believe only around 25% of the species have names -- that’s a massive chunk of diversity that’s not yet been recognised or protected.”

“Yet even with this snapshot of diversity, New Guinea is still the most diverse island on the planet. It’s so important that everything on that island is recognised and we don’t let things disappear without a trace. It needs to be preserved as a global heritage site for sure.”

New Guinea has fascinated naturalists for centuries. It is home to some of the best-preserved ecosystems on the planet -- from mangroves to huge expanses of lowland rainforest to alpine grasslands unmatched elsewhere in the Asia-Pacific region.

Botanists have been identifying and naming plants collected in New Guinea since the 17th century, storing the samples in plant collections in herbaria in Papua New Guinea, Indonesia, the Netherlands, and the UK.

However, despite notable advances in resolving the taxonomy of many New Guinea plants, publications remain scattered, as botanists have mostly worked independently from each other. As a result, New Guinea remained “one of the last unknowns for science”.

The new data was compiled by 99 botanists from 56 institutions across 19 countries, including the Natural History Museum and the Papua New Guinea University of Technology.

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The authors found 68% (9301) of the plants in New Guinea are endemic to the island, meaning more than two-thirds of its plants cannot be found anywhere else. This makes

New Guinea the only island in the South East Asian archipelago with more endemic than non-endemic species and is unmatched in tropical Asia.

This uniqueness, scientists believe, could be explained by its greater land surface area and habitat diversity, its location marking the junction between South East Asia, Australia and the Pacific, and by having one of the world’s most complex tectonic histories.

Dr Peter Wilkie, head of sapotaceae research at the RBGE said: “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.

“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.

“This checklist is a great starting point but there are still many species awaiting scientific description.”

To solve the great uncertainty around the number of plants known to science on the island, which ranged from 9,000 to 25,000, the botanists verified the identity of more than 23,000 plant names from over 704,000 specimens in a large-scale collaborative effort.

They found New Guinea contains almost three times the vascular plant species of Java (4,598) and 1.4 times the vascular plant species of the Philippines (9,432), the only two large South East Asian island regions with published Floras.

Orchids accounted for 20% of the flora in Papua New Guinea and 17% of Indonesian New Guinea, comparable to that in megadiverse countries such as Ecuador (23%) and Colombia (15%) and tree species accounted for 29% of all the flora. By comparison, the Amazon had 2.6 times more trees, but in an area 6.4 times larger.

Dr Rodrigo Camara-Leret, lead author and post-doc researcher at the University of Zurich and formerly at the Royal Botanic Gardens, Kew, added: “New Guinea is extraordinary: it is a paradise island teeming with life.“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 recognised 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.”