"Like no other generation before, we can choose the type of future that we will leave to the next generation. A transition to a safe and prosperous future is possible, but will require the full use of humanity’s extraordinary capacity for innovation and creativity... Tinkering at the edges will not do the job." Gro Harlem Brundtland writes in the International Herald Tribune as world leaders gather for the Rio+20 summit on sustainable development.

On Wednesday, world leaders will gather in Rio de Janeiro to review progress made in the 20 years since the 1992 UN Earth Summit and hopefully to chart a new path toward a more sustainable future. Protecting the planet and its people must be their first priority.

Our central concern is that governments are currently refusing to make the transformative changes needed to resolve the global sustainability crisis.

The scientific evidence is clear that the environmental dangers are rising quickly. Based on current trends, we are likely to move toward a world warmer by 3 degrees, and we may well cross tipping points with potentially catastrophic consequences.

Human activities are likely propelling the planet out of the climatically and ecologically stable state, the Holocene, which has sustained human development over the past 10,000 years. Science reports that we are now instead entering a new geological epoch, the Anthropocene, where humans have become the most potent force.

With our current growth and development model we are indeed changing the earth system, and as a result rapidly undermining the resilience of the planet and the future of humanity. The pressures of ecosystem decline, pollution and resource depletion have become immense, drawing down on the economic prospects of present and future generations.

We are the first generation with scientific understanding of the new global risks facing humanity. We must respond decisively, equipped with the best available evidence as a basis for decisions.

This new predicament is recognised in the report by the United Nations Secretary-General’s High-level Panel on Global Sustainability, of which I am a member, which maintains that tinkering at the edges will not do the job. If its recommendations are fully and rapidly implemented, we would be well on our way toward a more sustainable world.

Results from the Nobel Laureate Symposium Series on Global Sustainability also show that nothing less than a fundamental transformation will be needed, where human societies are reconnected with the biosphere to reverse global environmental change and move toward fair and lasting prosperity.

Twenty years after the Earth Summit it is clear that humanity has been a poor steward for the Earth.

Institutions must be developed and strengthened at all levels in order to integrate the climate, biodiversity and development agendas and help address the legitimate interests of future generations. Global governance must focus on ensuring that economic and social development evolves within a safe range of the carrying capacity of the planet.

A new contract between science and society is urgently required. World leaders are urged to support new integrated Earth-system research, which can facilitate the transition to global sustainability. Trans-disciplinary cooperation and innovation are also needed. Priorities for immediate action are meeting the global needs for food, water and energy, while at the same time avoiding dangerous climate change, safeguarding biodiversity and managing the oceans sustainably.

Science tells us global greenhouse gas emissions must peak no later than 2015 if we are to keep warming below 2 degrees and avoid dangerous climate change. For that to happen, governments must take action on many fronts.

While continued investments in innovation are needed, technology is not the obstacle. We also need to accelerate and scale up investments in poverty reduction, clean technology and ecosystem management, not to mention education.

Achieving equality for women must be a priority if we are to develop more sustainable livelihoods. Fulfilling the Millennium Development Goals, especially on women’s health, education, empowerment and economic status is a good and necessary first step.

There are compelling reasons to rethink the conventional model of economic growth. It is vitally important to de-couple growth from resource use, while simultaneously generating new employment opportunities. We should move beyond GDP as a measure of society’s progress, apply the “polluter pays” principle, ensure the full accounting of natural capital and ecosystem services in all economic decisions and greatly enhance resource efficiency by moving production systems toward a “circular economy” that is regenerative by design.

Our current development path is simply too risky for humanity. In the Anthropocene, all nations must learn to live within the safe operating space of Earth’s boundaries. This requires an agreement between the world’s governments for a fair and sustainable use of Earth’s natural capital.

The proposed Sustainable Development Goals, if aligned with the latest science, offer the prospect for a viable and equitable future for humanity.

Like no other generation before, we can choose the type of future that we will leave to the next generation. A transition to a safe and prosperous future is possible, but will require the full use of humanity’s extraordinary capacity for innovation and creativity.

Real leadership is required now to tackle these systemic issues. We therefore call upon world leaders to move beyond aspirational statements and exercise a collective responsibility for planetary stewardship, seizing the opportunity offered by the Rio 2012 summit to set our world on a sustainable path.

Gro Harlem Brundtland, a former prime minister of Norway, is a member of the UN Secretary-General’s High-level Panel on Global Sustainability and a member of The Elders.

This article was first published in the International Herald Tribune.