The World’s Rarest and Most Threatened Species

24 11 2009

The International Union for Conservation of Nature (IUCN) recently updated their “Red List” – the results of an ongoing survey to assess the threat to the world’s plant and animal species. In my newest article for Our Green Earth, I describe some of the most threatened species in the world and discuss the reasons for their plight. There are some pretty pictures too.

The World’s Rarest and Most Threatened Species.

[Edit 3rd December 2010: Sadly, Our Green Earth no longer exists but the owner has very kindly handed back copyright of my articles to me. Here, for your reading pleasure, is The World’s Rarest and Most Threatened Species…]

The World’s Rarest and Most Threatened Species

The International Union for Conservation of Nature (IUCN) is the world’s largest global environmental organisation and seeks to “provide pragmatic solutions to our most pressing environment and development challenges” (1). It supports and actively carries out work on climate change, energy, human livelihoods and greening of the world’s economy. Another of its major research efforts is the monitoring of the world’s animal and plant species in order to gain a deeper understanding of the biodiversity of our planet and the issues affecting them.

IUCN Red Lists

Every year, following extensive field surveys and data collection exercises, building on knowledge gleaned in previous years, the IUCN produces a “Red List” from its vast database of species from all over the world. The Red List – in reality much more than a simple list – provides a wealth of information about the animals and plants that are considered to be the most at risk. The latest update of the Red List, published in November 2009, describes a staggering 17,291 species (out of almost 50,000 species surveyed) that are threatened with extinction (1).

Red List classification

There are 6 classifications used by the IUCN to group the species that they study according to their level of threat.

  1. Extinct (EX) – when there is no reasonable doubt that the last individual of a species has died
  2. Extinct in the wild (EW) – when the species is known only to survive in captivity
  3. Critically endangered (CR) – when the species has dramatically reduced in population size and distribution according to IUCN criteria
  4. Endangered (EN) – when the species has significantly reduced in population size according to IUCN criteria
  5. Vulnerable (VU) – when the species has reduced somewhat in population size and distribution according to IUCN criteria
  6. Near threatened (NT) – where the species does not meet the threshold levels to be classified as CR, EN or VU, but shows signs that they will meet these criteria in the future (2)

According to the most recent Red List, there are 809 new EX species since the last List was produced, 66 EW, 3325 CR, 4891 EN, 9075 VU and 3650 NT species. Of these species, 72 are on our own British shores (3). Without a doubt, climate change, the destruction of habitats, excessive hunting and other human activities are largely to blame. For example, considering the presence of the highly biodiverse Amazon Rainforest across Brazil, a total of 6% of the species on the Red List are native to this country, hinting towards the negative impact of deforestation on species survival (4).

The most threatened species

There are too many animals and plants that have been classified as critically endangered in this year’s Red List, but presented here is a brief biography of 5 of the most threatened species in the world.

Gorgeted Puffleg (Eriocnemis isabellae) (Photo © Alex Cortes)

This critically endangered bird is native to southwestern Colombia where it inhabits a tiny area of “elfin” (dwarf) cloud forest in the Serraníadel Pinche. Although the species probably has a naturally limited spatial range, the Gorgeted Puffleg is only known to inhabit an area of less than 10km2. The world’s taste for cocaine and the riches to be gained from its export means that illegal coca plantations are replacing the bird’s preferred nesting sites and feeding grounds. In addition, a new road being built to connect mountain settlements is further removing elfin forest and has serious implications for the livelihood of many species, including the Puffleg (5).

Rabb’s Fringe-limbed Treefrog (Ecnomiohyla rabborum) (Photo © Brad Wilson)

The nocturnal Rabb’s Fringe-limbed treefrog lives high in the canopy of primary rainforest in Panama. Females lay their eggs in waterlogged holes in trees while the males were once heard croaking away at nighttime to attract mates. In the last 30 years however, this amphibian has declined in population numbers by over 80%. The reason is thought to be largely owing to a fungal infection of Batrachochytrium dendrobatidis, with the additional stress of habitat loss due to forest clearing to make way for luxury holiday homes. Conservationists have earmarked this species for captive breeding programs but so far these have proved somewhat unsuccessful, meaning that this poor frog could end up extinct in just a matter of time (6).

Giant Pangasius (Pangasius sanitwongsei) (Photo © Chavalit Vidthayanon)

Mercilessly pursued for food and the aquarium trade, the Giant Pangasius fish lives on the bottom and midwaters of the freshwater Mekong River that flows through Thailand, Cambodia, Laos and Vietnam, as well as China. Overzealous fishing, as well as the alteration of river flow to make way for irrigation dams and improved river transport has seen a decline in population numbers of this fish of over 99% in the last three decades. The government in the state of Yunnan, China, have classified this fish as a grade II protected species, however illegal poaching still occurs (7).

Smoky-winged Threadtail (Elattoneura leucostigma) (Photo © Matjaz Bedjanic)

Love them or hate them, insects play an important role in the food chain and the ecosystem as a whole. This critically endangered Sri Lankan dragonfly may in fact already be extinct as it has not been seen for approximately 60 years, but further research is needed to confirm this speculation. The threadtail’s freshwater habitat is mainly under pressure from water pollution, but deforestation, the planting of non-native tree species and water redirection have meant that its natural habitat is changing at great speed (8).

Polynesian Tree Snail (Samoana attenuata) (Photo © Trevor Coote)

Happily, this tiny tree-dwelling snail has come back from the dead. It was thought to be extinct until very small populations were found on the islands of Moorea and Tahiti. The species is still classified as critically endangered since its population size and distribution is extremely limited and threats that caused it to become extinct on the island of Bora Bora still remain. Of these, the most significant threat is that of the carnivorous snail Euglandina rosea. E. rosea was introduced by humans to several French Polynesian islands as a biological control agent to rid the islands of a pestilent species of crop-eating snail. Unexpectedly, E. rosea turned out to be equally as problematic as the species it was intended to keep in check since it has a voracious appetite for other, native, non-pestilent snails and slugs such as Samoana attenuata (9).

The future for threatened species

The alarming rate of the loss of biodiversity and the continued pressure on vulnerable species from human activity is a real cause for concern. Much-needed conservation work supported by the IUCN and other charitable organisations is ongoing but lacking in resources and funding. Breeding programs in zoos and safari parks and genetic research at scientific institutions around the world may help to alleviate part of the problem, but the real dilemma lies in the way we as humans treat our planet. With a few exceptions, species extinction today is largely the fault of our own activities and if we are to halt or reverse these downward trends then education and information is crucial.


  1. Press release, IUCN, November 2009:
  2. IUCN. (2001). IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, UK. ii + 30 pp.
  3. Platt, J, IUCN Red List update: 17,291 species are threatened with extinction, Scientific American, November 2009,
  4. Choppin, S., Red List 2009: Endangered species for every country in the world, The Guardian Data Blog, November 2009
  5. BirdLife International 2009. Eriocnemis isabellae. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2,
  6. Livingstone, S., Mendelson, J. & Angulo, A. 2009. Ecnomiohyla rabborum. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2,
  7. Jenkins, A., Kullander, F.F. & Tan, H.H. 2007. Pangasius sanitwongsei. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2,
  8. Bedjanič, M. 2007. Elattoneura leucostigma. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2,
  9. Coote, T. 2007. Samoana attenuata. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2,



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