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.
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.
If they’re not - and there’s a welter of evidence showing that we’re doing a pretty poor job of looking after the liveable bits of Planet Earth, let alone many of its inhabitants - it’s a chance to agree some new principles.
At its most basic, the zero draft is basically a set of ingredients for changing direction onto a new sustainable course.
If environmental decline is a major driver, others are the lack of resilience in the global economy shown up by the current extended financial crisis, and the continuing lack of development in the world’s poorest countries.
So - what might the Rio+20 summit deliver?
The zero draft sets out principles of universal access to the essentials - food, water and energy.
A major goal is “to free humanity from hunger and want through the eradication of all forms of poverty and strive for societies which are just, equitable and inclusive, for economic stability and growth that benefits all”.
In order to provide “proper nutrition” for all, it calls for “sustainable intensification of food production” - expanding the food supply without expanding the amount of land, water and other resources needed.
Another goal is to provide “universal access to a basic minimum level of modern energy services” by 2030.
And to make that sustainable from an environmental perspective, the proportion of energy coming from renewable sources should double by the same date.
One of the routes to achieving these aims would be to phase out “market distorting and environmentally harmful subsidies that impede the transition to sustainable development, including those on fossil fuels, agriculture and fisheries…”