What might the Rio+20 summit deliver?

We have a little more idea now, following publication of the "zero draft" outcome document for the June summit.

It's been compiled by the chairs of the preparatory process, following a huge amount of dialogue and input from governments and other interested parties.

But with much more dialogue due, a lot can change between now and then.

This Rio summit, like the last one 20 years ago, isn't part of the UN negotiations on climate change or biodiversity or desertification or anything else.

It's bigger than that. It's a chance for world leaders to take a long view of where the global society is heading, and whether they're happy with that.

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