The Prince of Wales has warned climate negotiators in Copenhagen that the "eyes of the world" are on them and that "our planet has reached a point of crisis", leaving only seven years before "we lose the levers of control" on the climate.

The prince was addressing ministers at the formal opening of the high-level talks. "It is no understatement to say that, with your signatures, you can write our future," he told them.

And in an apparent reference to disagreements between rich and poor nations he said that all countries needed to work together — climate change was not resolvable "in terms of 'them and us'", he said.

The prince, who has long campaigned for the survival of rainforests, said that forest protection would be key to a successful deal. "It seems the quickest and most cost-effective way to buy time in the battle against catastrophic climate change is to find a way to make the trees worth more alive than dead," he said.

But even as he spoke, plans for a revolutionary agreement to end deforestation and pay poor countries to protect their forests were hanging in the balance after leaked papers showed that a new proposed text has removed many of the scheme's safeguards.

It emerged that the negotiating text leaked to NGOs late last night showed that the language meant to cut the approximately 20% of global greenhouse gases from deforestation in developing countries — the so-called Reducing Emissions from Deforestation and Degradation scheme (Redd) — has now removed all targets for ending deforestation and significantly weakened other areas.

"Without targets, Redd becomes toothless," said Peg Putt of the Wilderness Society. "The so-called safeguards will be nothing but fancy window-dressing unless they are given legal force."

Forests protection is crucial to an ambitious deal at Copenhagen because it will not only save up to 20% of emissions which come from deforestation, but the forests provide a massive store of carbon against which countries can offset emissions at home.

In return, it was hoped that it could provide up to $40bn a year for some of the poorest countries in the world, including Congo DRC, Papua New Guinea, Indonesia and Gabon. In addition, countries which have already cut down their forests stand to benefit from money for reforestation.

Nobel peace prize-winning environmentalist Wangaari Maathai, whose efforts have resulted in more than 1bn trees being planted by individuals worldwide in the last few years, urged countries to set ambitious targets.

She told the Guardian: "We realise now that forests are much more important for services such as regulating the flow of water, climate medicine and food. We appeal to leaders to protect the forests." Targets for deforestation in the earlier text aimed to cut deforestation by 50% by 2020 and eliminate it by 2030. These targets have now been lost.

Start-up costs for Redd are estimated to be £13.6-22.7bn from 2010-15 to support preparatory activities, although some experts challenge those figures as far too low.

Forest groups reacted with clear disappointment. "It's hardly surprising that developing countries won't commit to global targets for deforestation when rich countries haven't yet provided the necessary financing for Redd or global targets for deep reductions of industrial emissions," said Nathaniel Dyer of Rainforest Foundation UK.

Of equal concern to forest-protection NGOs, language ensuring critical safeguards for biodiversity, forest conversion, indigenous rights, and monitoring has moved from operational text. Protection of natural forests does appear explicitly in the text for the first time, and a safeguard on conversion of natural forests to plantations has reappeared, but neither are mandated.

"Limiting safeguards to the preamble weakens the agreement and deprives it of any assurance of compliance," said Dr Rosalind Reeve of Global Witness.

"Global demand for forest commodities like illegal timber and palm oil is one of the leading causes of tropical deforestation around the world," said Andrea Johnson of Environmental Investigation Agency. "If we don't address the causes of the problem, how can we find a solution?"

Also missing from the negotiating text is any provision to protect and restore the world's peat soils, which account for 6% of all global C02 emissions. "Peat soils are a key part of many countries' plans to reduce their emissions, including large emitters like Indonesia," said Susanna Tol of Wetlands International.

"Currently, an acre of forest is cut down every second, depriving the world of critical carbon reservoirs and creating huge emissions bursts into the atmosphere," said Stephen Leonard of the Australian Orangutan Project. "A Redd deal without global deforestation targets or safeguards makes it much more likely that the orangutan and other critical species that rely on the forest will become extinct."

While text can still be changed, ministerial level actions will probably now be needed to reinsert targets and strengthen safeguard language. "Clearly, everyone agrees that the world's tropical forests need to be protected," said Bill Barclay of Rainforest Action Network. "But good intentions aren't enough, they have to be paired with action. Ministers must act to strengthen the Redd text if we have any hope of a Redd that will be effective in protecting tropical forests."