How are species classed as extinct? (BBC)

[eppur_se_muova]

David Attenborough's long-beaked echidna has been found to be alive and well, despite fears it had become extinct. So how are species classified as dying out?

When extinct species are rediscovered they are, aptly, called Lazarus species. They include the New Zealand storm petrel and a freshwater fish from Madagascar called the rheocles sikorae, in recent years.

The long-beaked echidna, named after the famous naturalist, is not among them because its status was the category below, newly entitled "possibly extinct".
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The 844 {extinctions} figure is a gross underestimate, he says, because we are only aware of about 10% of the planet's life, so many species are dying out that we're not aware of.

Furthermore, out of the 1.8 million species we are aware of, only 41,000 have so far been classified in conservation terms, says Mr Hilton-Taylor.
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more: http://news.bbc.co.uk/2/hi/uk_news/magazine/6901056.stm

[XemaSab]

1. It really, really emphasizes the need to preserve the last undeveloped places

The difference between critically endangered and extinct is 2.