Image caption The most threatened species tend to be relatively cheap to save because of small range sizes

Reducing the risk of extinction for threatened species and establishing protected areas for nature will cost the world over $76bn dollars annually.

Researchers say it is needed to meet globally agreed conservation targets by 2020.

The scientists say the daunting number is just a fifth of what the world spends on soft drinks annually.

And it amounts to just 1% of the value of ecosystems being lost every year, they report in the journal Science.

Nature just doesn't do recessions, we're talking about the irreversible loss of unique species and millions of years of evolutionary history Donal McCarthy, RSPB

Back in 2002, governments around the world agreed that they would achieve a significant reduction in biodiversity loss by 2010. But the deadline came and went and the rate of loss increased.

Significant cost

At a meeting of the Convention on Biological Diversity in Nagoya that year governments re-committed to a series of targets to be achieved by 2020.

But there is a marked lack of data on how much it would cost to protect species and landed areas. And some experts believe that uncertainty about financial information helps governments who are reluctant to commit to funding the targets.

Now researchers from a number of conservation organisations and universities have set out in detail the likely costs of preserving all threatened species. They've also worked out the cost of establishing and expanding protected areas to cover seventeen percent of land and inland water areas.

Image caption The Philippine Eagle needs relatively large tracts of pristine forest to survive

Environmental economist Donal McCarthy from the RSPB lead the study. He told BBC News that the amounts involved are significant.

"Reducing the extinction threat for all species would cost $5bn a year, but establishing and maintaining a comprehensive global network of protected areas would cost substantially more," said Mr McCarthy.

"It could be up to $76bn annually to meet both targets."

The researchers used the threat to birds as a model for working out the costs of extinction to all species. They asked experts around the world to estimate the costs of conservation actions required to move them down the IUCN list of those at greatest threat.

"A key finding of our analysis was that the most highly threatened species tend to relatively cheap to save on account of their small range sizes, such as the Razo lark, which lives on the island of Razo in the Cape Verde islands," said Mr McCarthy.

"Experts say conserving the species would cost less than one hundred thousand a year over the next ten years."

The costs for protecting land areas were worked out by including estimates of what would be needed to protect sites from threats including deforestation, poaching and over harvesting as well as improving existing conservation zones.

Donal McCarthy says that when compared to some global expenditures the $76bn price tag is a small price to pay.

"These are just a fraction of what we as consumers spend on soft drinks each year which is almost half a trillion dollars - the total required for species and sites is less than half of what is paid out in bonuses to bankers on Wall street's biggest investment banks," he explained.

Tough choices needed

Some scientists though are uncertain as to whether the world can afford such large sums in a time of economic crisis.

Prof Tim Benton from the University of Leeds says that tough choices may have to be made.

Image caption Cambodia's white shouldered Ibis is critically endangered. It only 10% of the estimated US$0.75 million annual investment needed to prevent its extinction.

"Some species in some places are absolutely crucial to the way the ecosystem works, but that may not the case in other places." he told BBC News.

"So rather than trying to save everything everywhere, I think we need to be more strategic, in a very money-limited world, to optimise conservation targets rather than to maximise all biodiversity everywhere."

Dr Andy Jarvis is with the International Centre for Tropical Agriculture in Colombia. He feels the targets and the finance will be hard to realise. He says that the growing global population and shifting consumption patterns are putting additional pressures on the food system, and so the pressure on land is only going to increase from that side.

"Whilst it would be fantastic if this money were to become available, and ensure that we do maintain critical ecosystem services, this is unlikely to happen," he said.

But Donal McCarthy argues that at the very least knowing the cost of the targets that governments have agreed to will bring some realism to the discussions.

"Nature just doesn't do recessions, we're talking about the irreversible loss of unique species and millions of years of evolutionary history that does need to be borne in mind."

"These total sums are essentially investments in natural capital. They are not bills."