I firmly believe a new generation of pragmatic and committed leaders was hard at work at the conference in Rio. Our job now is to identify who these leaders are and how to work with them to ensure they succeed.

During my time at Rio+20, I was only able to attend a handful events. But even so, it was clear to me that the tremendous challenges our world is facing are being met with an equally impressive amount of energy and enthusiasm to find the right solutions.

Behind the concept of sustainable development lies a bold vision of the future. Standing in the way of the future we want are the environmental problems we continue to face.

Rio+20 is a historic chance to move away from business-as-usual and end environmental destruction, reduce poverty, jumpstart the green economy and chart a course to a sustainable future. But the outlook is bleak.

About 80 percent of the pollution that ends up in our oceans is plastic, including sandwich bags that choke sea turtles and monofilament fishing line that ensnares sea lions and seals. All the plastic talk culminates next Thursday, at an all-day conference at Rio+20 called Plasticity.

These years later, one group of the poor-wastepickers-have organized as the Global Alliance of Waste Pickers. These wastepickers are demanding a place of honor within the green economy -- a key theme is this year's Rio+20 meet.

So what has changed for the world since first Earth Summit in Rio twenty years ago -- and what new challenges and opportunities will be on the table at the end of June when the UN again convenes its members?