Next June, world leaders will gather in Rio de Janeiro, Brazil, for Earth Summit 2012, to discuss (again) how to steer the planet towards a more sustainable future. The gathering marks the 20th anniversary of the 1992 Rio Earth Summit, at which heads of state agreed on a set of principles intended to guide sustainable global economic growth — including the precept that environmental protection should be central to development.

Little progress has been made on this in the two decades since the summit. Rather, countries have continued to pursue relatively unrestricted economic development, with limited attempts to minimize environmental impacts. So, will next year's summit do any better?

Those who attend will be forced to confront a string of failures to meet international green goals, including a pledge to stem the loss of biodiversity by 2010 — as agreed under the Convention on Biological Diversity — and to set new binding targets to reduce greenhouse-gas emissions under the United Nations Framework Convention on Climate Change. The chances of meeting the UN's Millennium Development Goals to halve poverty by 2015 look equally unpromising.

It does not help that the UN has been lacklustre in its preparations for the Rio summit. A panel of senior politicians and business heads has been put to work to draw up a plan (again) for global sustainable growth that will set the agenda for much of the discussion. But the panel was announced only last August, and it is not clear that such an important task can be completed in so little time.

Continued damage to factors such as biodiversity will increasingly affect economic growth.

Still, many scientists and environmental economists remain hopeful. Last month, Nature joined a group of 17 Nobel laureates in Stockholm as they drew up their own vision of the key challenges to sustainable development. Given the size of the task, the mood was surprisingly upbeat. Central to the proposals that the group came up with was the need (again) to change the mindset of world leaders. Rather than keeping to the traditional view that economic development and environmental conservation sit in opposition, the laureates stressed that continued damage to factors such as biodiversity, soil quality and indigenous people's land rights will increasingly affect economic growth.

There are encouraging signs that, in some places, the necessary change in attitudes is under way. For example, late last month at the Global Energy Partnership in Rome, 23 governments agreed on holistic indicators to assess the sustainable production and use of bioenergy. These include the price and supply of food and the net creation of jobs, as well as water quality and greenhouse-gas emissions. The current biofuel fiasco, in which policies on the use of such fuels have been introduced ahead of the proper checks and balances, could have been avoided had these wider factors been given proper consideration.

Similarly, the Organisation for Economic Co-operation and Development in Paris has launched the Your Better Life Index, a tool to evaluate livelihoods using indicators that go beyond gross domestic product. They include housing, environment, safety and work–life balance. As the Nobel laureates noted, such welfare indicators are needed to account properly for natural capital and the social aspects of progress in economic decisions.

Governance remains a major issue with the implementation of environmental goals. Part of the reason that the 1992 Earth Summit failed to have the hoped-for impact was that no international body was given responsibility to monitor and enforce its decisions. This remains the case, but suggestions on how to change the situation are maturing. Brice Lalonde, coordinator of the Rio summit, told a meeting in Brussels on 25 May that he wants to see the World Trade Organization's environmental remit strengthened, so that it can police any new global agreement. Others would prefer to see a beefed-up UN Environment Programme collaborate more with other relevant UN and international bodies. There could even be a role for the UN Security Council.

Political realities, or what are still viewed as political realities, remain a huge obstacle to sustainable development. But for those willing to listen, the global community now has at least a wider and more thorough understanding of the scale of the environmental problems it faces. This may yet spur political will to ensure that the Rio summit, and wider discussion on the vital decisions that it represents, are not a waste of time (again).