By Richard Black
Environment correspondent, BBC News website
Coral reefs can provide fish and a sea defence, or be excavated for building
Damage to forests, rivers, marine life and other aspects of nature could halve living standards for the world's poor, a major report has concluded.
Current rates of natural decline might reduce global GDP by about 7% by 2050.
The Economics of Ecosystems and Biodiversity (TEEB) review is modelled on the Stern Review of climate change.
It will be released at the Convention on Biological Diversity (CBD) meeting in Bonn, where 60 leaders have pledged to halt deforestation by 2020.
"You come up with answers like 6% or 8% of global GDP when you think about the benefits of intact ecosystems, for example in controlling water, controlling floods and droughts, the flow of nutrients from forest to field," said the project's leader Pavan Sukhdev.
"But then you realise that the major beneficiaries [of nature] are the billion and a half of the world's poor; these natural systems account for as much as 40%-50% of what we define as the 'GDP of the poor'," he told BBC News.
The TEEB review was set up by the German government and the European Commission during the German G8 presidency.
The two institutions selected Mr Sukhdev, a managing director in the global markets division at Deutsche Bank, to lead it.
At the time, in an article for the BBC News website, Germany's environment minister Sigmar Gabriel wrote: "Biological diversity constitutes the indispensable foundation for our lives and for global economic development.
"[But] two-thirds of these ecosystem services are already in decline, some dramatically. We need a greening of globalisation."
The document to be released at the CBD is an interim report into what the team acknowledges are complex, difficult and under-researched issues.
The 7% figure is largely based on loss of forests. The report will acknowledge that the costs of losing some ecosystems have barely been quantified.
The trends are understood well enough - a 50% shrinkage of wetlands over the past 100 years, a rate of species loss between 100 and 1,000 times the rate that would occur without 6.5 billion humans on the planet, a sharp decline in ocean fish stocks and one third of coral reefs damaged.
However, putting a monetary value on them is probably much more difficult, the team acknowledges, than putting a cost on climate change.
The report highlights some of the planet's ecologically damaged zones such as Haiti, where heavy deforestation - largely caused by the poor as they cut wood to sell for cash - means soil is washed away and the ground much less productive.
'Too little, too late'
There are some indications that biodiversity and ecosystem issues are now being heard at the top tables of politics.
G8 environment ministers meeting in Japan last weekend agreed a document noting that "biodiversity is the basis of human security and... the loss of biodiversity exacerbates inequality and instability in human society".
Ecosystem damage is likely to reduce food supplies in vulnerable areas
It also emphasised the importance of protected areas and of curbing deforestation.
At the CBD on Wednesday, 60 countries signed pledges to halt net deforestation by 2020.
But the main CBD target agreed by all signatories at the Rio de Janeiro Earth Summit in 1992 - to "halt and begin to reverse" biodiversity loss by 2010 - is very unlikely to be met.
An early draft of the TEEB review, seen by BBC News, concluded: "Lessons from the last 100 years demonstrate that mankind has usually acted too little and too late in the face of similar threats - asbestos, CFCs, acid rain, declining fisheries, BSE and - most recently - climate change".
The Stern Review talked to governments in a way that earlier climate reports could not, because it was written by and for economists; and the architects of TEEB hope it will eventually do the same thing for biodiversity.