For a keynote speaker at a conference on wilderness conservation, Pavan Sukhdev possessed a strange job title: banker. Sukhdev, a high-ranking executive of Deutsche Bank who helped build India’s modern financial markets, had a fiscal message to deliver. The loss of forests is costing the global economy between $2.5 trillion and $4.5 trillion a year, he said. Many trillions more in costs arise from the loss of vegetation to filter water, bees to pollinate crops, microbes to break down toxins, and dozens of other “ecosystem services.”

For centuries, economies have risen and collapsed based on the market value of the products extracted from nature-timber, coal, metals, game. And yet the value of much of what nature supplies hasn’t been reflected in the numbers. A new movement now seeks to put this right by attaching an economic value to the services nature provides. The idea is predicated on the notion that since a paper mill, say, needs water as well as trees, there should be some kind of economic mechanism whereby it pays to help keep the water flowing. The same is true for dozens of other ecosystem services across a wide range of industries. There’s scarcely a business in the world that doesn’t rely in some way on natural features that help control flooding, disseminate seeds, fend off pests, and hold soil in place. According to a study Sukhdev is conducting for the United Nations, protecting and restoring damaged ecosystems can deliver extraordinarily high rates of return on investment-40, 50, even 80 percent. “People need to start thinking of ‘ecological infrastructure’ as something they can and should invest in,” Sukdhev said at the conference.

It sounds radical even to talk about nature in the language of finance, but it’s quickly becoming a mainstream practice. One of the few tangible achievements expected from the climate talks in Copenhagen this month is agreement on a program called REDD, or Reducing Emissions From Deforestation and Forest Degradation, a complex set of regulations that would help developing countries keep their rainforests standing by turning their carbon-storing capacity into a source of income. Trees, after all, absorb carbon dioxide from the air, which can be seen as a service that offsets tailpipe and smokestack emissions. REDD would establish a market in which wealthy countries can pay countries with old-growth forests, such as Brazil, Indonesia, and Guyana, for their carbon stocks, thereby creating an economic incentive to preserve the jungle.