The world was losing as much potential capital annually through the destruction of forests as was wiped off the major markets in last year's financial crisis, an economist warned on Friday.

Pavan Sukhdev, leader of the United Nations Environment Programme's (UNEP's) Green Economy Initiative, was addressing journalists on the final day of the Diversitas biodiversity conference in Cape Town

He said the current pace of forest loss meant a potential economic cost of the order of $2-trillion to $4,5-trillion a year.

"In other words, if we continue business as usual that's how much natural capital we are throwing down the tube," he said.

That was comparable to the amount of capital lost by Wall Street and City firms when the worst financial crisis in the history of the world hit last year.

"And we're losing that every year, in natural capital terms, every year for the last 20 years.

"And we'll continue to do that until something really breaks."

Sukhdev said just over one-third of the sustainable value of forests lay in carbon capture and storage, for climate change mitigation.

Next on the lists came their value as a source of fresh water, followed by food, fuel and other non-timber values for communities who lived in or near them, and bioprospecting in the search for new drugs.

Timber was not included in the calculations, as it was "not a sustainable value".

He said the world was drawing on its ecological capital at a rate never experienced before.

Humanity's ecological footprint was already 25 to 30 times higher than the Earth's capacity to produce.

"We are therefore drawing off its capital. We are not eating off its interest," he said.

He said a project he headed on the economics of ecosystems and biodiversity was seeking to show that there was an economic case for the conservation of biodiversity, and investment in it now would save significant losses in future.

"The underlying problem is that we are a society that is not in harmony with nature," he said.

"We do not seem to understand that natural capital is equally if not more important than physical and financial capital.

"When we invest, especially when we invest public money, we do not seem to understand that it is important to invest public money in creating public wealth, not just more and more private wealth.

"And we don't seem to understand that it is not the case that more production is always better than less production.

"We don't seem to focus on better production and more intelligent consumption. We just seem to think that more is better."

Sukhdev earlier presented findings to the conference, attended by some 650 scientists from across the globe, that an average hectare of coral reef provides annual services to humans worth $130 000.

In some places this rose to as much as $1,2-million.

The amount was made up of value in terms of recreation and tourism; climate regulation, water purification and biological control; food, raw materials and "ornamental resources"; and a catch-all category labelled maintenance of genetic diversity.

Taken together, coral reefs had an average annual value of some $172-billion, he said.

Previous studies had shown that investing $45-billion could secure nature-based services worth some $4,5-trillion to $5,2-trillion annually.

For example, planting mangroves along a coastline in Vietnam had cost $1-million, but saved $7,3-million a year in dyke maintenance.

The scientists attending the conference released a statement on Friday that the meeting had confirmed that the fabric out of which the Earth's system was woven was unravelling at an accelerating rate.

They called on governments to set up the proposed
Intergovernmental Platform on Biodiversity and Ecosystem Services as soon as possible.

The mechanism would allow quick communication of scientific evidence on biodiversity issues.

"We urge policy-makers to act swiftly and effectively on the already-established and future findings relating to ways of limiting further biodiversity loss and restoring ecosystem services," they said.