They come with speeches, placards, power point presentations and drums. Some with body paint and bows and arrows. Others with suits and business plans. Almost all driven by a desire for radical change.

“Come re-invent the world” is the call to the People’s summit, which has opened in Rio de Janeiro to counter what many participants see as the malign influence of capitalism at the Rio+20 United Nations sustainable development conference now taking place on the outskirts of the city.

Two hundred civil society groups – including environmentalists, unions, religious groups and indigenous tribes – will take part in the nine-day event, which is expected to climax with a rally of 50,000 people on the 20th June.

On that day, more than 110 world’s leaders will fly in for the Earth summit, marking the two decades that have passed since the original Rio gathering in 1992 set in place a system of international conventions and policy documents designed to bring the human economy back into balance with the global environment.

Despite those measures, the decline of ecosystems has accelerated. Negotiators at Rio+20 aim to address this with new measures to promote a green economy, strengthen global environmental governance and encourage nations to commit to a new set of sustainable development goals.

But the People’s summit – which is funded to the level of $5m by the Brazilian government – is designed to foster alternative ideas and provide an outlet for discontent at UN member countries’ failure to preserve biodiversity, eliminate poverty and cut greenhouse gas emissions.

Organisers expect 15,000 people daily at the gathering, which is supported by Greenpeace, Oxfam, the Via Campesina international peasant movement and a panoply of other participants including Ukranian green education pioneers, survivors of the Fukushima nuclear disaster, organic food organisations, the 100 Million Trees programme and ITPA, a Brazilian conservation group.

Most eye-catching are the hundreds of representatives from Brazil’s many indigenous groups, who performed a ritual on the opening day. Their appeal for protection of land rights and compensation for ecological services are only briefly mentioned in the official negotiating text, but they take central position at the People’s summit.

2012 Guardian News and Media Limited