When world governments or ecological organizations such as Greenpeace and the World Wildlife Fund want to find out about the status of a species, they turn to the IUCN (International Union for Conservation of Nature and Natural Resources, now known simply as the World Conservation Union). Every four years, this organization publishes its Red List, outlining what scientists know about the states of the various species of plants and animals that cover our planet.
The IUCN has three categories for what it calls "threatened" species:
- Vulnerable species are at a high risk of becoming extinct in the wild. Polar bears and the common hippopotamus are categorized as vulnerable species.
- Endangered species are at a very high risk of becoming extinct in the wild. The golden-rumped sengi, a cat-sized elephant shrew that is restricted to the coastal forests of Kenya, and the tiger chameleon, which lives on only three islands in the Seychelles, are both endangered species.
- Critically Endangered species are at an extremely high risk of extinction in the wild. A number of species of Sri Lankan dragonflies are critically endangered, as are Aran Rock lizards, a Spanish mountain lizard that is confined to a mere 10 square miles of the Pyrenees.
The IUCN notes that species extinction is a natural phenomenon. They estimate that the natural rate of extinction (including both plants and animals) is one to five species per year. Unfortunately, they also estimate that, these days, dozens of species go extinct every day.
What poses the greatest threat to the most fragile species of our planet? Mankind.