"We cannot continue to live as we do now." Writing as Global Ambassador for Oxfam International as Rio+20 begins, Desmond Tutu reflects on the achievements of the first Rio Earth Summit twenty years ago and calls for strong, unequivocal political commitment to re-orient the global economy in a way that meets the needs of the poorest while respecting the earth’s limits.

1992 was a momentous year. In South Africa we had the final whites-only referendum in which the vast majority voted to end apartheid and create a power-sharing multi-racial government. In Maastricht the European Union was formed. While in Rio de Janeiro, in response to the growing pressure to protect the future of the planet and its people, the landmark Earth Summit delivered new treaties to tackle climate change and conserve biodiversity.

This week world leaders will be back in Rio once again. Twenty years on the need for global action is more urgent than ever. Rio+20 must tackle one of most critical issues facing humanity today – how to end poverty and achieve prosperity for all while living with the earth’s rapidly diminishing natural resources. Despite the scale of these challenges, the negotiations have until now lacked the ambition and commitment to action shown in 1992. As leaders engage, they must deliver.

The world's poorest people are denied their fair share

We cannot continue to live as we do now. Climate change is threatening food production and creating more extreme weather. Fresh water is drying up. Fertile land is running out. Plants and animals are becoming extinct at alarming rates. Our seas are over-exploited. Inequality is increasing as the incomes of the poorest fall even further behind those at the top, and the current economic crisis is pushing millions into deeper poverty. The lifestyles and choices made by the wealthiest threaten all our future security and prosperity, while almost a billion people go to bed hungry every night.

The world’s poorest people who are denied their fair share of our limited resources of land and water, are suffering most from our collective failure to live within the earth’s boundaries. But they won’t be the only ones. Oxfam warned last year that the spiraling prices of staple foods could drive human development into reverse in the future.

In Rio we need strong and unequivocal political commitment to re-orient the global economy to meet the needs of the poorest while respecting the earth’s limits. We need concrete action to ensure that we have sustainable food supply particularly by helping the half a billion of small scale producers who currently feed two billion people – one in three of us.

Supporting small farmers is key

With the right support and techniques these small farmers can help feed our growing population without doing further damage to the environment and sending our climate out of control. For lessons on how to do this, we need look no further than Brazil where millions no longer go hungry thanks to the government’s successful Zero Hunger campaign which recognized that reducing poverty, combating hunger and support for small scale farming are inextricably linked.

We need to find new ways to deliver energy and cut emissions in a way that benefits the poorest. This is not an impossible task. Bringing electricity to the almost one fifth of the world’s population who currently lack it could be achieved with a less than one per cent increase in global carbon emissions.

We must create a future safe from the risks of a changing climate and water, land and food shortages. A future with a more equal and just society, where the poorest have access to their fair share of the earth’s natural resources and all of us are living within the earth’s environmental and social boundaries. Conference themes don’t come more important than that. Our leaders must prove that they are up to the task.

This blog was first published on the Oxfam website.