With forests and fish stocks declining, water demand rising and lack of action on climate change, humanity's path is anything but sustainable, the UN warns.
The Global Environmental Outlook says significant progress is seen on only four out of 90 environmental goals.
Meanwhile, a team of scientists warns that life on Earth may be on the way to an irreversible "tipping point".
The UN Environment Programme (Unep) urges leaders to agree tough goals at this month's Rio+20 summit.
Where governments have agreed specific treaties, it says, major change has transpired.
However, negotiations leading up to the summit appear mired in problems, with governments failing to find agreement since January on issues such as eliminating subsidies on fossil fuels, regulating fishing on the high seas and obliging corporations to measure their environmental footprint.
"GEO-5 reminds world leaders and nations meeting at Rio+20 why a decisive and defining transition towards a low-carbon, resource-efficient, job-generating 'green economy' is urgently needed," said Achim Steiner, Unep's executive director.
"If current trends continue, if current patterns of production and consumption of natural resources prevail and cannot be reversed, then governments will preside over unprecedented levels of damage and degradation."
More than 40% of the Earth's land is used for human needs, including cities and farms; and with the population set to grow by a further two billion by 2050, that figure could soon exceed 50%.
Rising demand for resource-expensive foods such as beef could mean it happens by 2025, Prof Barnofsky's modelling suggests....
The summit - which marks 20 years since the Rio Earth Summit and 40 years since the very first UN environmental gathering in Stockholm- is likely to agree to develop a set of sustainable development goals (SDGs), a concept that Unep endorses.
It points out that factors such as air pollution and climate change are also imposing costs on the global economy - in the US, for example, air pollution is calculated to cut crop yields by $14-26bn each year.
"The moment has come to put away the paralysis of indecision, acknowledge the facts and face up to the common humanity that unites all peoples," said Mr Steiner.
"Rio+20 is a moment to turn sustainable development from aspiration and patchy implementation into a genuine path to progress and prosperity for this and the next generations to come."