WWF has a new edition of its Living Planet Report out. I promise to read it more carefully in the near future, but what bothers me about it already is their use of the ecological footprint to make their case. Economists have long criticized the use of the EF as a measure of sustainability. I'll get deeper into the reasons for that in future posts, but the bottom line for me is that it is often interpreted in a normative sense, even though it cannot be used for that purpose. In other words: it only tells you, in a simplified way, whether we can keep up our current way of life, but it says nothing about the consequences of living unsustainable. Therefore, you risk sounding the wrong alarm bells. By the same token, the way it is designed it is strongly biased against cities and trade: two things economists like and ecologists dislike. This goes some way in explaining its popularity but that does not mean it is an accurate indicator.
Anyway, I'll go deeper into this later.
Edited 13 June 2012: Changed the title. I should have known about the kind of connotations animal limbs can have (pandas, camels). That's what you get when you're not a native speaker.