The global economic crisis cast its shadow over UN talks that closed in India on Saturday after two weeks of intense wrangling on funding to reverse the decline of Earth's natural resources.

A deal was finally signed a day later than planned, after a succession of late-night sessions that pitted rich countries reticent to fork out more cash as they try to balance the books, against poor ones.

Several traditional donor countries cited the world's economic troubles as a factor in the talks, held under the auspices of the UN's Convention on Biological Diversity (CBD).

"Countries like us in difficult financial times are making big sacrifices with taxpayers' money. We want to make sure... that we are not leaving ourselves open to putting greater burden on our taxpayers," British Environment Minister Richard Benyon told AFP on the penultimate day of the negotiations.

In the end, the deadlock was broken and developed states pledged to double by 2015 the aid they provide to poor countries for biodiversity projects, compared to a baseline of average annual aid in the period 2006-2010.

No figures were mentioned, but observer groups believed the new annual figure would amount to about $10 billion (8 billion euros) per year -- just 10 percent of what global consumers spent on chocolate last year.

Some negotiators, especially in the European Union, hailed the deal as a symbolic breakthrough in tough times.

"In the context of the financial crisis, this is a good deal," French Environment Minister Delphine Batho told AFP.

Yet CBD member countries lamented that "the lack of sufficient financial resources" was hampering progress on biodiversity, urging one another to "consider all possible sources and means that can help to meet the level of resources needed".

Many observers believe the pledge is not nearly enough, and warned a failure to pay up now could spell disaster.

"Efforts to conserve nature must be urgently scaled up if we want to meet the 2020 deadline to save all life on Earth," the International Union for Conservation of Nature said.

Earlier in the week, the union had added 400 animals and plants to its authoritative "Red List" of species at risk of extinction.

A quarter of the world's mammals, 13 percent of birds, 41 percent of amphibians and 33 percent of reef-building corals are now at risk of dying out, according to the list.

"If we do not invest in nature now, the cost will be tremendous in terms of the loss of our global biodiversity and the vital ecosystem services it provides for humanity," said Conservation International biodiversity head Lina Barrera.

Conservation group WWF said about $200 billion must be invested in biodiversity annually if the world is to meet the targets it set two years ago to turn back the loss of species and habitat that humans rely on for food, water and livelihoods.

"What's been agreed in Hyderabad represents less than half this number."

Environment talks in Rio de Janeiro in June and a succession of UN climate conferences have been marked by a failure to meet funding targets.

"We have a global economic crisis that is of course more urgent in Europe than anywhere else, and Europe has always been the leading political bloc in these negotiations," WWF executive director for conservation Lasse Gustavsson, told AFP.

"Environment negotiations have always been orchestrated by the EU. It is not happening here and it was not happening in Rio."

UN Environment Programme executive director Achim Steiner said economic woes had affected the global commitment to solving the planet's ills, "which risks eroding the ability of nations to act collectively in addressing fundamental environmental challenges".

Yet "the incentives to invest -- both economic and environmental -- are clearer than ever", he said.

The economic crisis hit at a time that environment issues were starting to gain serious ground on the global agenda.

While the environment, global warming and biodiversity may not have been completely abandoned, observers feel things have not moved as quickly as they should have.

Countries decided at the last CBD conference in Nagoya, Japan, two years ago on an ambitious 20-point plan to turn back the tide of biodiversity depletion by 2020.

The so-called Aichi Biodiversity Targets include 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.

But the plan has been hamstrung by a lack of cash for conservation, research, and the creation of green business alternatives.

"The need for the world's nations to come together to implement the Aichi Targets grows more pressing with widespread extinction increasing every year," said Conservation International president Russell Mittermeier.