Image caption Delegates will consider adopting new set of targets for 2020 that aim to tackle biodiversity loss

The UN biodiversity convention meeting has opened with warnings that the ongoing loss of nature is hurting human societies as well as the natural world.

The two-week gathering aims to set new targets for conserving life on Earth.

Japan's Environment Minister Ryo Matsumoto said biodiversity loss would become irreversible unless curbed soon.

Much hope is being pinned on economic analyses showing the loss of species and ecosystems is costing the global economy trillions of dollars each year.

Ahmed Djoghlaf, executive secretary of the UN Convention on Biological Diversity (CBD), described the meeting in Nagoya, Japan, as a "defining moment" in the history of mankind.

"[Buddhist scholar] Daisetsu Teitaro Suzuki said 'the problem of nature is the problem of human life'. Today, unfortunately, human life is a problem for nature," he told delegates in his opening speech.

Referring to the target set at the UN World Summit in 2002, he said:

"Let's have the courage to look in the eyes of our children and admit that we have failed, individually and collectively, to fulfil the Johannesburg promise made by 110 heads of state to substantially reduce the rate of loss of biodiversity by 2010.

"Let us look in the eyes of our children and admit that we continue to lose biodiversity at an unprecedented rate, thus mortgaging their future."

Earlier this year, the UN published a major assessment - the Global Biodiversity Outlook - indicating that virtually all trends spanning the state of the natural world were heading downwards, despite conservation successes in some regions.

We are about to reach a threshold beyond which biodiversity loss will become irreversible Ryo Matsumoto, Japanese environment minister

It showed that loss and degradation of forests, coral reefs, rivers and other elements of the natural world was having an impact on living standards in some parts of the world - an obvious example being the extent to which loss of coral affects fish stocks.

In his opening speech, Mr Matsumoto suggested impacts could be much broader in future.

"All life on Earth exists thanks to the benefits from biodiversity in the forms of fertile soil, clear water and clean air," he said.

"We are now close to a 'tipping point' - that is, we are about to reach a threshold beyond which biodiversity loss will become irreversible, and may cross that threshold in the next 10 years if we do not make proactive efforts for conserving biodiversity."

Climate clouds

In recent years, climate change has dominated the agenda of environmental politics.

And Achim Steiner, executive director of the UN Environment Programme, suggested there is a lack of understanding at political levels of why tackling biodiversity is just important.

Image caption 2010 is the International Year of Biodiversity

"This is the only planet in this Universe that is known to have this kind of life," he said.

"This fact alone should give us food for thought, But more importantly, we are destroying the very foundations that sustain life on this planet; and yet when we meet in these intergovernmental fora, society somehow struggles to understand and appreciate what it is what we're trying to do here, and why it matters."

On the table in Nagoya is a comprehensive draft agreement that would tackle the underlying causes of biodiversity loss, as well as setting new targets for conservation.

At the heart of the idea is the belief that if governments understand the financial costs of losing nature, they can adopt new economic models that reward conservation and penalise degradation.

A UN-sponsored project called The Economics of Ecosytems and Biodiversity (TEEB) calculates the cost at $2-5 trillion per year, predominantly in poorer parts of the world.

Jane Smart, head of the species programme at the International Union for the Conservation of Nature (IUCN), said that although the problem was huge and complex, there were some encouraging signs.

"The good news is that when we carry out conservation, it does work; we increasingly know what to do, and when we do it, it works really really well," she told BBC News.

"So we need to do a lot more conservation work, such as protected areas - particularly in the sea, in the marine realm - we need to save vast areas of ocean to protect fish stocks - not to stop eating fish, but to eat fish in a sustainable way."

Triple win

Governments first agreed back in 1992, at the Rio Earth Summit that the ongoing loss of biodiversity needed attention. The CBD was born there, alongside the UN climate convention.

It aims to preserve the diversity of life on Earth, facilitate the sustainable use of plants and animals, and allow fair and equitable exploitation of natural genetic resources.

The UN hopes that a protocol on the final element - known as access and benefit sharing (ABS) - can be secured here, 18 years after it was agreed in principle.

However, the bitter politicking that has soured the atmosphere in a number of UN environment processes - most notably at the Copenhagen climate summit - looms over the Nagoya meeting.

Some developing nations are insisting that the ABS protocol be signed off before they will agree to the establishment of an international scientific panel to assess biodiversity issues.

The Intergovernental science-policy Platform on Biodiversity and Ecosystem Services (IPBES) is due to be signed off during the current UN General Assembly session in New York.

Many experts - and Western governments - believe it is necessary if scientific evidence on the importance of biodiversity loss is to be transmitted effectively to policymakers.