Who decides they are extinct?

This question might pop up in your mind. If not there is no harm in thinking for once. Who in the whole world decides that a certain species is endangered or extinct? It vexed me.

After some research and it was evident that there are many local agencies authorized by the local governing bodies to conduct research and surveys to find the population density and frequency of sightings and so on of species in a particular location.


But there exists an International body whose responsibility is to keep a track of the conservation status of species and subspecies including plants and animals. This is known as International Union for the Conservation of Nature and Natural Resources (IUCN). As one of the oldest and also the largest environment network, IUCN has over 1000 professionals, 11,000 volunteer scientists, 60 offices and numerous partners across the world. Like many other record keeping organizations and keepers of numbers, metrics and NGOs, IUCN is located near Geneva, Switzerland.

IUCN has a list called 'IUCN Red List'. This list is a comprehensive inventory of the status of plants and animal species globally. This list is a sort of a reference guide and supposedly very accurate picture of the status of the species and sub-species. The list is updated every 5 or 10 years with the help of contributions from numerous assigned local bodies. The list is updated using a 'peer-review' method of collating and substantiating data. For the interested, you can get more info on the red list and its assessment technique here.

The List has the following categories:

• Extinct (EX)
• Extinct in the Wild (EW)
• Critically Endangered (CR)
• Endangered (EN)
• Vulnerable (VU)
• Near Threatened (NT)
• Least Concern (LC)
• Data Deficient (DD)
• Not Evaluated (NE)
  

Finally the onus is on the local bodies and area specialists who are actively involved in gathering and collating data. What beats me is how the local bodies must be working on this?

Do they sit and watch birds, animals and plants in an area all day, 365 days a year? What decides if they are endangered or not? What if the bird or animal is an 'elusive or shy' type and does not allow itself to be seen? How many sightings over a period of time is it required to classify a bird or animal into a particular category? What if the local authority kept missing the sightings due to body odor or noises that scared the species away?Anyone out there has some answers?

Also take a look at a form (PDF) for enlisting a species as endangered.