A MAJOR UN conference on how to slow species loss and the destruction of the world's ecosystems entered its final hours Friday with a half-dozen proposals on the table but virtually nothing decided.

"This is crunch time," said James Leape, the head of World Wildlife Fund International (WWF), an influential environmental group monitoring the negotiations.

"Everything depends on what comes out at the end of the day," he said.

More than 6,000 representatives from 191 countries gathered here since May 19 have struggled to hammer out a road map for saving Earth's vanishing flora and fauna, much of it in tropical rain forests and the sea.

Biodiversity advocates, inside and outside government, say the rapid disappearance of species -- some 150 every day -- and environmental damage pose no less a threat to human welfare than climate change.

The first major economic assessment of ecosystem degradation, released Thursday, calculated the cost to the world economy at between 1.35 and 3.1 trillion euros ($2.1 to $4.8 trillion) every year.

But the call to action has only recently gathered momentum, and concrete measures remain the exception rather than the rule.

The conference will vet a slew of proposals before adjourning Friday.

One calls on industrialized countries to boost funding for biodiversity conservation, by 50 percent for national programs and by 100 percent for international initiatives.

German Chancellor Andrea Merkel pledged this week to stump up 500 million euros ($785 million) before 2013, and another half-billion euros annually thereafter, but so far few other advanced economies have indicated they will follow suit.

The adoption of binding standards for biofuel development and a certification regime for applying those standards, are also under review.

Carbon-fuel substitutes made from grain and non-food crops were widely hailed until recently as a silver bullet in the fight against global warming.

But critics say some biofuels use nearly as much energy to produce as they save, and have helped drive up world food prices for corn and soy.

Large swathes of CO2-absorbing tropical forests -- especially in Brazil, which is hostile to the proposal -- have been converted to biofuel production.

"The careless pursuit of biofuel technologies can wind up doing more harm than good," said Leape.

The goal of "zero net deforestation" -- assuring that any forests felled are replaced -- by 2020 is also on the table. Environment ministers from sixty countries signed an informal pledge to support the measure earlier in the week.

Creation of the first protected areas in the high seas looks likely to be approved, said Julia Marton-Levevre, executive director of the International Union for Conservation of Nature (IUCN), which groups governmental and non-governmental organizations.

Less the one percent of oceans are currently under protection, and only in coastal areas, she said.

The Conference will also likely validate a new road map toward an agreement to compensate poorer countries for "genetic resources" transformed by advanced economies into drugs, cosmetics or other value-added products.