There's a really good article in today's Guardian about the importance of biodiversity -
http://www.guardian.co.uk/environment/2010/aug/16/nature-economic-security
The UN chief has come out with guns blazing, saying that countries are being incredibly short-sighted if we don't think about the true value of biodiversity.
One billion people live off sea-fishing, and almost 300 million people depend on our forests, and that's not to mention the good that biodidversity does for pollination, medicine, fertile soils and clean water.