The World's 100 most threatened species is a compilation of the most threatened animals, plants, and fungi in the world. It was the result of a collaboration between over 8,000 scientists from the International Union for Conservation of Nature Species Survival Commission (IUCN SSC), along with the Zoological Society of London. The report was published by the Zoological Society of London in 2012 as the book, Priceless or Worthless?

While all the species on the list are threatened with extinction, the scientists who chose them had another criterion: all the species have no obvious benefit for humans and therefore humans have no vested interests trying to save them. Iconic and charismatic species, such as tigers and pandas—along with economically important species—have many defenders, while these apparently "worthless" species had none. The title of the report, "Priceless or Worthless?", is based on that shared quality of the species. The report's co-author, Ellen Butcher, stated one of the guiding principles of the list, "If we take immediate action we can give them a fighting chance for survival. But this requires society to support the moral and ethical position that all species have an inherent right to exist."Kew Magazine stated that, "A strong and consistent moral and ethical stance needs to be taken, they (the authors of The List) argue, that all species have a right to exist."

The report was released in Jeju, South Korea, on September 11, 2012, at the quadrennial meeting of IUCN, the World Conservation Congress. At the Congress, it was reported that scientists are finding it more and more common to have to justify funding for protection of species by showing what the human benefits would be. Jonathan Baillie, of the Zoological Society of London and co-author of the report, stated that, "The donor community and conservation movement are increasingly leaning towards a 'what can nature do for us?' approach, where species and wild habitats are valued and prioritised according to these services they provided for people. This has made it increasingly difficult for conservationists to protect the most threatened species on the planet."

Some of the threatened species are down to only a handful of surviving members. Santa Catarina's guinea pig, native to a single island in Brazil, is down to its last 40–60 individuals, reduced by hunting and habitat disturbance. The great Indian bustard is threatened by habitat loss resulting from agriculture and human development, and is down to the last 50–249 individuals. Elaeocarpus bojeri, a flowering plant found only on the island of Mauritius, has fewer than 10 surviving individuals, because of loss of habitat. The Baishan fir (Abies beshanzuensis), native to China, is down to five surviving mature individuals. "Priceless or Worthless?" describes the threats that each species is facing, along with measures that would aid their survival.

Species list

+ The world's 100 most threatened species Species Common name Type Image Location(s) Estimated population Threats Abies beshanzuensis Baishan fir Plant (Tree) Baishanzu Mountain, Zhejiang, China Three mature individuals agriculture fire Actinote zikani Insect (butterfly) Near São Paulo, Atlantic forest, Brazil Unknown habitat loss from human expansion Aipysurus foliosquama Leaf scaled sea-snake Reptile Ashmore Reef and Hibernia Reef, Timor Sea Unknown unknown—probably degradation of coral reef habitat Amanipodagrion gilliesi Amani flatwing Insect (damselfly) Amani-Sigi Forest, Usamabara Mountains, Tanzania < 500 individuals population pressure and water pollution Antisolabis seychellensis Insect Morne Blanc, Mahé island, Seychelles Unknown invasive species climate change Antilophia bokermanni Araripe manakin Bird Chapado do Araripe, South Ceará, Brazil 779 individuals recreational facilities water diversion Aphanius transgrediens Aci Göl toothcarp Fish south-eastern shore of former Lake Aci, Turkey few hundred pairs competition and predation by Gambusia road construction Aproteles bulmerae Bulmer's fruit bat Mammal Luplupwintern Cave, Western Province, Papua New Guinea 150 hunting cave disturbance Ardea insignis White bellied heron Bird Bhutan, North East India and Myanmar 70–400 individuals hydropower development Ardeotis nigriceps Great Indian bustard Bird Rajasthan, Gujarat, Maharashtra, Andhra Pradesh, Karnataka and Madhya, India 50–249 mature individuals agricultural development energy transmission lines Astrochelys yniphora Ploughshare tortoise Reptile Baly Bay region, northwestern Madagascar 440–770 illegal collection for international pet trade Atelopus balios Rio Pescado stubfoot toad Amphibian Azuay, Cañar and Guyas provinces, south-western Ecuador Unknown Chytridiomycosis logging agricultural expansion Aythya innotata Madagascar pochard Bird volcanic lakes north of Bealanana, Madagascar 80 mature individuals agriculture hunting and fishing introduced fish Azurina eupalama Galapagos damsel fish Fish Unknown Unknown climate change oceanographic changes related to the 1982/1983 El Nino Bahaba taipingensis Giant yellow croaker Fish Chinese coast from Yangtze River, China to Hong Kong Unknown over-fishing due to value of swim-bladder in traditional medicine Batagur baska Common batagur Reptile (turtle) Bangladesh, Cambodia, India, Indonesia and Malaysia Unknown illegal export to China Bazzania bhutanica Plant Budini and Lafeti Khola, Bhutan 2 sub-populations forest clearance overgrazing development Beatragus hunteri Hirola Mammal (antelope) South-east Kenya and possibly south-west Somalia < 1,000 individuals habitat loss competition with livestock poaching Bombus franklini Franklin's bumblebee Insect (bee) Oregon and California Unknown disease from commercial bees habitat destruction and degradation Brachyteles hypoxanthus Northern muriquiWoolly spider monkey Mammal (primate) Atlantic forest, south-eastern Brazil < 1,000 large-scale deforestation and logging Bradypus pygmaeus Pygmy three-toed sloth Mammal Isla Escudo de Veraguas, Panama < 500 illegal logging of mangrove forests for firewood and construction hunting Callitriche pulchra Plant (freshwater) pool on Gavdos, Greece Unknown habitat exploitation by livestock modification of the pool by locals Calumma tarzan Tarzan's chameleon Reptile Anosibe An'Ala region, eastern Madagascar < 100 agriculture Cavia intermedia Santa Catarina's guinea pig Mammal (rodent) Moleques do Sul Island, Santa Catarina, Brazil 40–60 habitat disturbance possible hunting result of having such a small population Cercopithecus roloway Roloway guenon Mammal (primate) Côte d'Ivoire Unknown hunting habitat loss Coleura seychellensis Seychelles sheath-tailed bat Mammal (bat) Two small caves on Silhouette and Mahé, Seychelles < 100 habitat degradation predation by invasive species Cryptomyces maximus Willow blister Fungi Pembrokeshire, United Kingdom Unknown limited habitat Cryptotis nelsoni Nelson's small-eared shrew Mammal (shrew) Volcán San Martín Tuxtla, Veracruz, Mexico Unknown logging cattle grazing fire agriculture Cyclura collei Jamaican iguanaJamaican rock iguana Reptile Hellshire Hills, Jamaica Unknown habitat destruction predation by introduced species Daubentonia madagascariensis Aye-aye Mammal (primate) Deciduous forest, East Madagascar Unknown poaching limited habitat Dendrophylax fawcettii Cayman Islands ghost orchid Plant (orchid) Ironwood Forest, George Town, Grand Cayman Unknown infrastructure development Dicerorhinus sumatrensis Sumatran rhino Mammal (rhino) Sabah, Sarawak and Peninsular Malaysia, Kalimantan and Sumatra, Indonesia < 100 hunting (horn is used in traditional medicine) Diomedea amsterdamensis Amsterdam albatross Bird Breeds on Plateuau des Tourbières, Amsterdam Island, Indian Ocean. 100 mature individuals disease incidental by-catch in long-line fishing Dioscorea strydomiana Wild yam Plant Oshoek area, Mpumalanga, South Africa 200 collection for medicinal use Diospyros katendei Plant (tree) Kasyoha-Kitomi Forest Reserve, Uganda 20 individuals in a single population agricultural activity illegal tree felling alluvial gold digging small population Dipterocarpus lamellatus Plant (tree) Siangau Forest Reserve, Sabah, Malaysia 12 individuals logging of lowland forest creation of industrial plantations Discoglossus nigriventer Hula painted frog Amphibian Hula Valley, Israel Unknown predation by birds range restriction due to habitat destruction Dombeya mauritiana Plant Mauritius Unknown encroachment by invasive plant species habitat loss due to cannabis cultivation Elaeocarpus bojeri Bois Dentelle Plant (tree) Grand Bassin, Mauritius < 10 individuals habitat degradation Eleutherodactylus glandulifer La Hotte glanded frog Amphibian Massif de la Hotte, Haiti Unknown charcoal production slash-and-burn agriculture Eleutherodactylus thorectes Macaya breast-spot frog Amphibian Formon and Macaya peaks, Masif de la Hotte, Haiti Unknown charcoal production slash-and-burn agriculture Eriosyce chilensis Chilenito (cactus) Plant Pta Molles and Pichidungui, Chile < 500 individuals collection of flowering plants Erythrina schliebenii Coral tree Plant Namatimbili-Ngarama Forest, Tanzania < 50 individuals limited habitat and small population size increase vulnerability Euphorbia tanaensis Plant (tree) Witu Forest Reserve, Kenya 4 mature individuals illegal logging agricultural expansion infrastructure development Eurynorhyncus pygmeus Spoon-billed sandpiper Bird Breeds in Russia, migrates along the East Asian-Australasian Flyway to wintering grounds in India, Bangladesh and Myanmar 100 breeding pairs trapping land reclamation Ficus katendei Plant Kasyoha-Kitomi Forest Reserve, Ishasha River, Uganda < 50 mature individuals agriculture illegal tree felling alluvial gold digging Geronticus eremita Northern bald ibis Bird Breeds in Morocco, Turkey and Syria. Syrian population winters in central Ethiopia. about 3000 individuals habitat degradation and destruction hunting Gigasiphon macrosiphon Plant (flower) Kaya Muhaka, Gongoni and Mrima Forest Reserves, Kenya, Amani Nature Reserve, West Kilombero Scarp Forest Reserve, and Kihansi Gorge, Tanzania 33 timber extraction agriculture encroachment and development predation by wild pigs Gocea ohridana Mollusc Lake Ohrid, Macedonia Unknown increasing pollution levels off-take of water sedimentation events Heleophryne rosei Table mountain ghost frog Amphibian Table Mountain, Western Cape Province, South Africa Unknown invasive plants water abstraction Hemicycla paeteliana Mollusc (land snail) Jandia peninsula, Fuerteventura, Canary Islands Unknown overgrazing trampling by goats and tourists Heteromirafa sidamoensis Liben lark Bird Liben Plains, southern Ethiopia 90–256 agricultural expansion overgrazing fire suppression Hibiscadelphus woodii Plant (tree) Kalalau Valley, Hawaii Unknown habitat degradation due to feral ungulates competition with invasive plant species Hucho perryi Sakhalin taimen Fish Russian and Japanese rivers, Pacific Ocean between Russia and Japan Unknown overfishing damming agriculture other land use Johora singaporensis Singapore freshwater crab Crustacean Bukit Timah Nature Reserve and streamlet near Bukit Batok, Singapore Unknown habitat degradation due to reduction in water quality and quantity Lathyrus belinensis Belin vetchling Plant Outskirts of Belin village, Antalya, Turkey < 1,000 urbanisation over-grazing conifer planting road widening Leiopelma archeyi Archey's frog Amphibian Coromandel peninsula and Whareorino Forest, New Zealand Unknown Chytridiomycosis predation by invasive species Lithobates sevosus Dusky gopher frog Amphibian Harrison County, Mississippi, USA 60–100 fungal disease climate change land-use changes Lophura edwardsi Edwards's pheasant Bird Quang Binh, Quang Tri and Thua Thien-Hue, Viet Nam Unknown habitat loss hunting Magnolia wolfii Plant (tree) Risaralda, Colombia 3 isolation of species