Why the most floristically biodiverse island on Earth is not a Biodiversity Hotspot (it’s good news!)

23rd September 2020

This piece has been written by Thom Starnes, Key Biodiversity Areas Programme Officer with the IUCN Freshwater Biodiversity Unit 

Latest research confirms that New Guinea is the most floristically diverse island on Earth (Cámara-Leret et al., 2020), overtaking Madagascar in the sheer number of native plant species. To anyone familiar with the island’s rich natural heritage, this probably does not come as a great surprise. With an area of 786,000 km2, New Guinea is the world’s second largest island after Greenland, and the largest tropical island, split between the independent country of Papua New Guinea and the Indonesian provinces of Papua and West Papua. Home to the world’s third largest rainforest after the Amazon and the Congo, the island of New Guinea contains eight of the world’s 233 Centres of Plant Diversity and Endemism (CPD) (Davis et al., 1994). Situated on the equator and with a vast mountain range – the New Guinea Highlands – traversing its length, the island’s topography gives rise to an exceptionally wide range of habitats and ecological niches. Coupled with its situation at the meeting point of Malesia, Australia and the Pacific and its complex tectonic history, this has contributed to its unique evolutionary history, giving rise to a highly endemic flora and fauna. If you have heard the term ‘Biodiversity Hotspot,’ you might be forgiven for assuming that New Guinea is one, but it isn’t.

Image: Map of New Guinea

The term ‘Biodiversity Hotspot’ was coined by Norman Myers in the late 1980s (Myers, 1990, 1988) and the Hotspots themselves were mapped out and published in 2000 in seminal paper in Nature (Myers et al., 2000) which has been cited over 27,000 times. The purpose of defining Biodiversity Hotspots was to prioritise conservation action and funding by identifying areas that had the highest number of endemic species (species occurring nowhere else) and were under the greatest threat. With limited resources at the disposal of conservationists, the Hotspots were designed to deliver the biggest ‘bang for buck’ in terms of conserving overall diversity and preventing extinctions.

To qualify as a Biodiversity Hotspot, a region had to contain at least 1,500 endemic plant species and have lost 70 percent or more of its primary vegetation (Myers et al., 2000). At the time of Myers’ paper, the natural fauna and flora of New Guinea remained relatively intact. In fact, New Guinea is specifically mentioned as one of the ‘good news’ areas or ‘major wilderness areas’ with more than 75% of original pristine vegetation remaining and a human population density below 5 people per km2.

Despite its remarkable overall species richness and high levels of endemism, New Guinea has not been a conservation priority because it simply hasn’t been threatened enough. However, that is starting to change and some have argued that New Guinea should now be included in the list of Biodiversity Hotspots. A report by WWF in 2015 projected that the New Guinea region could lose up to 7 million ha of forest by 2030, citing the island as one of 11 global ‘deforestation fronts’ (WWF, 2015). New Guinea may not meet the original Biodiversity Hotspot criteria, but the writing is on the wall.

Neighbouring Borneo offers alarming clues as to the impending fate of New Guinea. Since the 1950s, Borneo has experienced a rate of industrial deforestation virtually unprecedented in history, losing half of its total forest cover (McAlpine et al., 2018). Other islands in the archipelago have suffered a similar fate. Between 1990 and 2010, the island of Sumatra lost 40 percent of its old-growth forest (Margono et al., 2012). Deforestation on Borneo has been slowing down in part because it is becoming increasingly difficult to exploit natural resources from the less accessible interior and also because of increasing public attention and pressure from environmental groups (Gaveau et al., 2019). However, attention is turning now toward the comparatively unexploited forests of New Guinea and work to open up the interior is already well underway. New Guinea is already home to the world’s largest copper and gold mine and a WWF/IUCN study identified the ecoregions in New Guinea as some of the world’s most threatened by mining. During the current period 2018 – 2022 Papua New Guinea aims to nearly double its national road network, which would open up large areas to deforestation (Alamgir et al., 2019).

New Guinea has been romantically described as the ‘last of the wild’ (Sanderson et al., 2002), but more recent analysis shows that New Guinea is now succumbing to greater human pressure (Allan etal., 2017). Tragically, until 70% of its primary forest is lost, however, New Guinea will not qualify as a Biodiversity Hotspot, by which time for many species and ecosystems, it will be too late.

Through its Tropical Important Plant Areas (TIPAs) programme, researchers at Kew are already working to identify the most important plant areas of New Guinea and protect socio-economically important plant species. Together with protected area expansion and the identification of Key Biodiversity Areas for plants and other taxonomic groups, this Nature Based Solutions approach will be key to protecting this crown jewel of botanical diversity and ensuring that New Guinea does not succumb to the same fate as its neighbours. The time for action is now, before it’s too late.

Image: Vanda lissochiloides, one of the 2,856 species of orchid native to New Guinea. Orchidaceae account for 20% and 17% of the flora of Papua New Guinea and Indonesian New Guinea, respectively.

Author bio: 

I am Key Biodiversity Areas Programme Officer with the IUCN Freshwater Biodiversity Unit in Cambridge. In this capacity I take Red List assessments of freshwater fishes, molluscs, decapods (crabs and shrimps), odonates (dragonflies and damselflies) and plants and then use these data to map out the most important sites for the persistence of global freshwater biodiversity. It was during a year working at the Royal Botanic Gardens, Kew that I first became interested in the use of maps in ecology and conservation, and I’ve since gone one to work with Amphibian and Reptile Conservation and with the RSPB as a Senior GIS Analyst before coming to IUCN. My current role is about ensuring that the most important sites for global freshwater biodiversity are mapped and recognised as Key Biodiversity Areas.


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