A Kiva for the Environment?

I’ve long been a fan of Kiva.org, a company that let’s you invest in micro-development projects around the world.  It has now topped $241m in loans.  Here’s a great data vizualization of its tremendous growth:

I wonder, could something similar be possible for environmental projects?

The trick would be providing an equitable non-financial return, since most environmental projects produce not $$ but other environmental benefits.  Perhaps pollution clean up projects whose success are measured in pounds of trash collected?