Twenty years ago, a burst of sunny optimism radiated from Rio de Janeiro as world leaders staged a meeting that would prove pivotal. Amid post-Cold War euphoria and a desire to tackle the problems of the looming millennium, the UN’s 1992 Earth Summit inscribed protection of the planet on the world ’s list of foremost priorities.

Already, many in the green movement fear that Rio+20 will fall dismally short of guiding the planet towards better health and a brighter future 20 years from now

It set down a blueprint, Agenda 21, for sustaining nature rather than destroying it and created UN mechanisms designed to brake the oncoming juggernauts of climate change, desertification and species loss.

Leaders gather once more in Rio from June 20 to 22 for the 20-year follow-up to that great event. But how very different the world is today, and how much darker the mood.

By almost every yardstick, as the UN Environment Programme (Unep) reported in a landmark assessment last week, our planet is sicker than it has ever been.

Despite the rising prosperity in China, India and other emerging giants, billions of people remain in the rut of great poverty.

And as the fourth anniversary of the world’s financial calamity nears, the ability – and will – of countries to embrace green growth is evidently badly constrained.

“Governments are mired in crisis and their eyes are fixed on the present, whereas Rio+20 requires them to calmly draw up a future for the planet,” Brice Lalonde, a former French environment minister who is co-coordinator of the summit, told AFP.

“It’s hard to do the two things at the same time. But that, in principle, is what heads of state are there for.”

Around 115 leaders are expected for the summit, which will cap more than a week of meetings gathering as many as 50,000 activists, business executives and policymakers.

This frenzy of contacts and deal-making could well be more fruitful than the UN process itself, say some.

The nation-state system remains traumatised by the failures of the 2009 climate summit in Copenhagen.

There is “a risk of division among developed and poor countries, the risk of failure because there may be other pressing matters,” said France’s new president, François Hollande.

“The world is today turned towards the economic crisis, the financial crisis, and is worried about a certain number of conflicts, such as Syria ... might easily turn away from what is however the top priority.”

Already, many in the green movement fear that Rio+20 will fall dismally short of guiding the planet towards better health and a brighter future 20 years from now.

Behind the scenes there is incipient panic over the draft summit communique. The charter is supposed to sum up the challenges and spell out pledges to nurture the oceans, roll back climate change, promote clean growth and provide decent water, sanitation and electricity for all.

There have so far been three rounds of informal negotiations on the document. Out of 329 paragraphs, only 70 have been settled.

The rest of the text is lost in a sea of brackets, denoting discord, as countries squabble over the level of ambition.

The biggest divergences include action on climate change, protecting the oceans and achieving food security, and whether “Sustainable Development Goals” should replace the Millennium Development Goals when these objectives expire in 2015.

What’s on the table

Here are the main objectives at the June 20-22 UN Conference on Sustainable Development. The goals are scheduled to be incorporated in a statement called The Future We Want.

Green economy
Guidelines for promoting growth in a way that is environmentally sustainable and helps eradicate poverty.

Institutional changes
How to strengthen the international system for sustainable development, a constellation of agencies and programmes whose roles sometimes overlap.

Priority work
The conference will also look at seven critical areas needing priority attention:

• Green employment: Creating jobs that help preserve the quality of the environment

• Energy: Improving efficiency, encouraging cleaner and sustainable resources and providing universal access to modern energy supplies

• Cities: Better housing, transport, less pollution and poverty, to avoid slums and congestion

• Food: How to feed today’s 925 million hungry and the additional two billion mouths expected by 2050

• Water: Providing clean water for all and coping with droughts and shortages in the future

• Oceans: Better management of a resource suffering badly from overfishing and pollution

• Disaster preparedness: Work that can reduce the toll from earthquakes, floods, drought, storms and tsunamis