Vote: Which is the biggest environmental threat?

On the right-hand side-bar, there is a (straw) poll on which you can cast your vote. The question is Which of these is the biggest threat to global bio-diversity? You may tick one or more of the answers provided.

The poll will run until the end of 2007, which, I hope, will allow enough time to accrue enough votes so as to have an accurate idea of what people think is the cause - or causes - of threat to bio-diversity.

Please take a few seconds to cast your vote - thank you!