The low winter sun that blinded me from behind the City buildings did look strangely like the end of the world that morning. Or the beginning of a new one? I couldn’t decide at the time.

In any case, there was something very different about that breakfast event, where a Deutsche Bank economist addressed the mostly business audience with the words “I’m here today because of my personal irritation with GDP growth.”

There in the midst of the credit crunch, Pavan Sukhdev wanted to talk to us instead about the value of the goods and services that fall between the cracks of conventional spreadsheets: the clean air, water and biodiversity that are ‘worth’ so much less than gold and diamonds in monetary terms – until you don’t have them.

He came up with the sobering calculation that while Wall Street had already lost $1-$1.5 trillion by then, we are losing natural capital worth between $2-$5 trillion every year.

But it wasn’t so much the figures in his report, ‘The Economics of Ecosystems and Biodiversity’, that struck me. Sukhdev said himself that his job wasn’t to come up with a new value for the Earth – that’s impossible. Actually, it was the way in which everything that the environmental movement has been banging on about for years – disappearing forests, dying coral reefs – was talked about with a serious business head on. As he said, the only reason to put a value on these resources is that they’d get overlooked if they weren’t given a price tag.

I’ve never been a great believer in number crunching, but he won me over to the force of economics that morning. And to believing that it’s essential to package up the solutions to our disappearing resources – you know, straightforward things like forestry projects in Costa Rica or ecotourism schemes in Uganda – into neat financial tools. ‘Wetland banking’, ‘forest securitisation’, ‘endangered species credits’, they’re all going to float an investor's boat. In the end, it’s about speaking the right language.

As I stepped out in the crisp air, with the sun now high in the sky, I think I’d answered my own question.