Conservation International

Some 39 chief executives of banks, investment funds and insurance firms Saturday pledged at a Rio+20 business forum Saturday to integrate the Earth's natural capital into loans and investments.

Twenty years after the first Earth Summit highlighted the importance of the natural environment, they unveiled a "Natural Capital Declaration" that commit their companies also to reporting or disclosing on the theme of natural capital and accounting for natural capital in accounting frameworks.

What is a sip of clean water worth? Is there economic value in the shade of a tree? And how much would you pay for a breath of fresh air?

That study, started in 2007, has estimated the world economy suffers roughly $2.5 trillion to $4 trillion in losses every year due to environmental degradation. That's up to 7 percent of global GDP.