A new study is warning the combined effects of global warming, population growth and continued environmental degradation could lead to the collapse of the ecosystem in just a few generations. A research paper published in the journal Nature says the world faces a “tipping point” of irreversible environmental damage as early as this century. On Wednesday, the head of the U.N. Environment Program, Achim Steiner, encouraged activists to seize on the report’s findings ahead of the key Rio+20 environmental summit in Brazil later this month.

Achim Steiner: “I would like those activists who are preparing to come to Rio+20 to protest and to also lament the inaction that they have seen, to open up a second fund and to take a report like this and say, 'Answer to the public: Why is it that we are not moving on these issues?'”