Just how big will this number get when all other natural resource losses are taken into account? The rape of the seas, and the tragedy of bycatch and quotas, is well documented and could well run into the billions. And what happens when we include habitat and species losses through hunting, pollution, salinisation and desertification?

The world is nearly bankrupt. At what point is nature bankrupt?

To understand these figures it's important to understand just what nature does for us. For free. Forests filter entire water systems and circulate and soak up greenhouse gasses. If they are lost then we have to take counter measures such as building a reservoir (at great expense) or simply go without. Other tangible losses include the tourism cash that evaporates when forests are lost and the end result is always the same: it is very expensive. We have used up infinity and the depleting resources we rely on invariably cost more and more to get at, for smaller and smaller returns. 

Adam Dutton, a wildlife economist from Oxford University, says: "If when deciding how much forest to cut down the forester actually had to pay for the loss in ecosystem services along with the cost of the workmen, tools and land then logging might fall to sustainable levels. The purpose of an environmental evaluation is to make some attempt at working out how large this payment might be."

There are also a host of less tangible benefits, such as the sheer beauty that wild places provide us, that should be taken into account when calculating nature losses.

But are numbers like 5 trillion too big to be taken seriously? Will they scare politicians into a numbness of inaction, and what about the man on the street or the man in the forest? Can numbers this huge ever mean anything to them?