UN member states were urged Tuesday to give financial backing to their pledges to rescue Earth's natural resources from catastrophe as more bad news emerged on the state of biodiversity.

Estimates vary, but experts say hundreds of billions of dollars will be required to achieve targets set two years ago to turn back biodiversity loss by 2020.

Current conservation spending is estimated at about $10 billion (eight billion euros) per year.

"We need to work together and act before a catastrophe is upon us," Indian Prime Minister Manmohan Singh told delegates to a conference in Hyderabad of the UN's Convention on Biological Diversity (CBD), which marks its 20th anniversary.

As conservationists unveiled new data on the decline of Earth's wetlands, a key source of irrigation and drinking water, Singh said India was pledging $50 million (40 million euros) to boost biodiversity conservation.

The money will be spent on capacity-building at home, he said, urging other nations to back up their political commitments with hard cash.

"Humankind should understand the importance of preserving biodiversity," said the premier.

"The diversity of life forms on Earth is... nature's insurance against extreme events that may disturb the delicate balance of life on this planet."

Nearly half of amphibian species, a third of corals, a quarter of mammals, a fifth of all plants and 13 percent of the world's birds are at risk of extinction, according to the "Red List" compiled by the International Union for Conservation of Nature (IUCN).

After two weeks of talks between policy makers from 184 CBD signatories, the Hyderabad conference will kick into high gear from Wednesday with three days of ministerial-level talks, with more than 70 ministers expected to attend.

Hailing progress made in recent days, India's environment minister Jayanthi Natarajan said money remained the biggest obstacle.

"I urge the parties to the CBD to agree to some measures, commitments and targets of resource mobilisation, even if on an interim basis, so as to infuse confidence in parties and also to generate momentum," she said.

The last CBD meeting in Nagoya, Japan, in 2010, agreed on a swathe of targets to be met by 2020 -- halving the rate of habitat loss, expanding water and land areas under conservation, preventing the extinction of species on the threatened list, and restoring at least 15 percent of degraded ecosystems.

A report released at the conference said an alarming 50 percent of the world's wetlands had been destroyed in the last 100 years to make space for housing, factories and farms, threatening human welfare at a time of increasing water scarcity.

"Our choices have for a long time been skewed in not recognising the value that nature delivers to our societies, to our economies, to our communities every day," said Achim Steiner, executive director of the UN Environmental Programme.

"We still do not fully appreciate the consequences of the actions we are taking today."

Steiner told AFP the effects of the financial crisis on many of the traditional donor countries was playing a big role in the Hyderabad talks.

"As expected, it is on questions of financing that we are stuck," agreed Sandrine Belier, one of three European Parliament negotiators in Hyderabad

"The European Union has not succeeded in forming a common position, and so it is silent."

Natarajan said the world had already failed to achieve an earlier CBD target to halt the rate of biodiversity loss by 2010.

"Future generations will not forgive us if we fail again in 2020."