The world's governments will fail to meet their agreed target of curbing biodiversity loss by 2010, according to experts questioned by BBC News.
Nearly 200 countries signed up to the target in 2002.
Ten leading conservationists asked here at the World Conservation Congress were unanimous that the goal cannot be met.
All the global indicators of progress are heading in the wrong direction, and few governments have even translated the target into national legislation.
Not all the experts questioned would go on the record, and some said there was a reluctance to embarrass governments over their failures on the matter.
Others suggested the target was unachievable even at its inception six years ago.
Ahmed Djoghlaf, executive secretary of the UN Convention on Biological Diversity (CBD), told BBC News that the 2010 target was achievable if governments acted urgently, but conceded that "all indicators are telling us it is unlikely".
Last week saw the publication of the Red List of Threatened Species, showing that between a quarter and a third of mammals are at risk of extinction.
It also saw the head of an EU-commissioned review into the economics of biodiversity loss say that degradation of forests worldwide cost the global economy more each year than the current banking crisis.
The CBD was agreed at the Rio Earth Summit in 1992, but not until 10 years afterwards did it acquire a firm, supposedly binding target - "to achieve by 2010 a significant reduction of the current rate of biodiversity loss at the global, regional and national level as a contribution to poverty alleviation and to the benefit of all life on Earth".
Georgina Mace, director of the Centre for Population Biology at Imperial College London, said that on the worldwide basis there was absolutely no chance of achieving it.
"We don't have many measures of biodiversity at a global level, but there are a few," she said.
"They measure things like the rate at which species are moving down the categories of threat on the Red List towards extinction, they measure average trends in various populations that have been measured over time, they measure trends on habitat change."
"And at global level, all those data that we have show either continuing downward rates of loss or maybe continuing rates of loss - so some of them aren't getting worse, some are just staying at the same rate of loss - but none of them are getting better," she added.
In addition, virtually all of the trends that drive the loss of species and ecosystems are continuing at a global level.
"The biodiversity convention doesn't deal with cross-cutting issues such as logging, road building, climate change, pollution and the expansion of agriculture," said Gordon Shepherd, director of global policy at the environmental group WWF.
"In reality the people who own decision-making in those areas, be they in governments or in business, have much more power than environment ministers, who don't have tools to get to grips with over-use [of natural resources] or over-consumption."
However, Sebastian Winkler from the International Union for the Conservation of Nature (IUCN) said the time period from 2002 to 2010 was so short that we should not have expected to see any changes in the real world.
He suggested a different way of measuring the lack of progress - that only 16 governments have followed through on their commitment to integrate the 2010 target into national plans for tackling biodiversity loss.
Mr Winkler runs an IUCN initiative called Countdown 2010, which aims to engage stakeholders across the world such as local authorities and get them to commit to actions that could improve prospects in their own regions.
"Now the CDB is trying to use Countdown 2010 as a fig leaf for governments - we have 800 partners, they're each taking at least 10 actions, so that's 8,000 actions and that's what they hope to report back as progress," he said.
By March next year, governments must submit assessments of their own progress to the CBD, which will compile them into a global assessment.
Thomas Lovejoy, president of the Washington DC-based think-tank, the Heinz Center, said there were signs of progress in different corners of the world, citing Costa Rica and Bhutan among countries that were taking the issue seriously.
"In 43 years we've gone from one protected forest in the Amazon to 40% of the area under some form of protection," he said.
"It's not enough to maintain the integrity of the ecosystem but it's a huge achievement."
Europe is the continent which has made most progress towards the target. According to one recent study, it is on course to curb biodiversity loss - but by 2050, rather than 2010.
Mr Djoghlaf said the 2010 initiative had at least put the issue of natural decline into the political and public spotlight.
"There is more and more increased awareness, people are ready to be engaged, business behaviour is changing, biodiversity is becoming a business case because businesses know the market of tomorrow is green, and they have to adapt," he said.
Most of the other leading figures I spoke to here about the issue were not willing to go on the record, although all said in private there was no chance of achieving the target.
Sebastian Winkler said it was important to keep governments engaged with the issue.
"Martin Luther King said 'I have a dream', not 'I have a nightmare'," he said.
"And if we always paint nightmares, we will not engage the international community."
But Mr Lovejoy suggested that at the level of species and ecosystems, the nightmare was already unfolding.
"There's no longer a question whether there will be a sixth major extinction in Earth history," he said.
"It's already happening, and the question is how big we'll allow it to get."