"This sends a very powerful message that conservation is not a marginal issue in the year 2004," said Achim Steiner, director-general of the Geneva-based organisation. "There has been a record level of interest."

One of the gathering's top events will be the unveiling of the IUCN's "Red List" of endangered animals, the most comprehensive scientific assessment of species at risk of dying out, and concrete measures to slow or reverse their extinction.

The prognosis is not good.

"Despite all our efforts in the conservation community and in governments, we have not really succeeded in stemming the loss of species," Steiner told Reuters.

"The number has now risen to over 15,000 threatened species on our planet -- and this is just the number we have been able to assess so far."

Threats to the environment from rapid economic and population growth -- a major issue in Asia, home to half of humanity -- will also feature prominently at the forum, which includes names from the world of big business.

Oil giants BP and Royal Dutch/Shell, mining conglomerate Rio Tinto and insurer Swiss Re are among multinationals putting in an appearance, reflecting the growing prominence of green issues in the boardroom.

"There has definitely been a shift in the big corporations, who now realise the importance of biodiversity," said IUCN spokesman Deric Quaile. "Most of big business now incorporates this as part of their strategic planning."

ONLY ONE WORLD

The theme of the Bangkok meeting, which opens on Wednesday, is "People and Nature -- only one world", to emphasise that conservation and the environment should not be at the expense of human development, and vice versa. Founded in 1948, the IUCN is the world's largest conservation organisation, bringing together more than 80 governments, over 800 non-governmental organisations (NGOs) and 10,000 scientists and experts from 180 countries.

It says its unique "union" structure adds to its effectiveness because it bridges the public and private sectors.

At the last Congress, held in the Jordanian capital Amman in 2000, environmentalists said a lack of political will was hampering efforts to preserve threatened species and ecosystems such as coral reefs.

Given the continued decline visible in the past four years, the time for talking was over, they said.

"What we are documenting today is an extraordinary loss of wealth, not only in biological terms, but also in historical terms and in financial terms," Steiner said.

"Every day that passes when we do not take the threat of losing species more seriously will cost us more and more."

Following are some facts about the IUCN:

- The IUCN is a huge umbrella conservation group which uniquely includes non-governmental agencies (NGOs) and states.

- Its stated mission is to: "influence, encourage and assist societies throughout the world to conserve the integrity and diversity of nature and to ensure that any use of natural resources is equitable and ecologically sustainable."

- Among its members, it counts 81 countries, 730 national non-governmental organizations (NGOs) and 77 international NGOs. Angola and Iran are the latest countries to join.

- According to latest audited figures, its total external operating income in 2003 was just over 102 million Swiss francs ($87 million), a sum that underscores the size of the global green movement.

- The IUCN has a number of specialist groups, for example on sharks and crocodiles, run by scientists who are noted experts in their fields.

- Since its founding in 1948, its databases, assessments and case studies have been among the world's most respected and frequently cited sources of information and reference on environmental issues.