Interesting article looking at the increase in the number of "at risk" species. There are problems with such calculations given we do not know how many species we actally have on the planet.
From an economics perspective it becomes more interesting when we try to value each species. Is a whale worth more than a monkey? Why do insects fair so badly? Fish stocks are declining and people appear to care less about species that they rarely see (or are on the ugly side in the cuteness stakes).
Life on earth[Economist]
MORE species are under threat than ever before according to the World Conservation Union. Its “Red List”, published on Wednesday September 12th, gives warning that 16,306 species are under threat of extinction (of 41,415 described), nearly 200 more than in 2005. This number has risen steadily since the first report in 1996. Corals have been added to the endangered list alongside the usual apes and dolphins. There is cause for concern but biodiversity scientists are less confident accountants than the list might suggest. Nobody knows how many species occupy the planet. Most experts think 10m is roughly correct, though they have only formally noted 1.4m. The most reliable data describe creatures that humans find easy to count: colourful, land-based and big enough to hunt.
Currently in Athens at ETSG 2007. There are two Environmental Economics (trade and the environment) sessions this year. Google ETSG 2007 to see the papers and our own humble offering. Greek is not my strongest language hence hyperlinking is a little tricky.