The first global assessment of mangroves in over a decade has revealed that the rare and critically important mangrove forests continue to be lost at a rate three to four times higher than land-based global forests, despite positive restoration efforts by some countries.

The study said although losses are slowing at 0.7 percent a year, the authors of the study warned that any further destruction due to shrimp farming and coastal development will cause significant economic and ecological decline.

The World Atlas of Mangroves has been published by Earthscan said about one fifth of all mangroves are thought to have been lost since 1980.

"The Economics of Ecosystems and Biodiversity, which is hosted by UNEP is bringing to the fore the multi-trillion dollar value of the world's nature-based assets," said Achim Steiner, UN Under- Secretary General and Executive Director of the United Nations Environment Program (UNEP).

"This atlas brings our attention onto mangroves and puts them up front and central, plotting where they are, describing where they have been lost, and underlining the immense costs those loses have had for people as well as nature."

Stainer said together, the science and the economics can drive policy shifts, adding that some 1,200 protected areas are now safeguarding around a quarter of remaining mangroves and many countries are now embarking on major restorations, a positive signal upon which to build and to accelerate a definitive response in 2010, the UN's International Year of Biodiversity.

Economic assessments provide some of the most powerful arguments in favour of mangrove management, protection or restoration.

Studies estimate that mangroves generate between 2,000 to 9, 000 U.S. dollars per hectare annually, considerably more than alternative uses such as aquaculture, agriculture or insensitive tourism.

The new atlas also underscored positive trends. Restoration efforts now cover some 400,000 hectares, as foresighted countries make the link between these coastal forests and economically-important services from flood defenses and fish nurseries to carbon storage to combat climate change.

"Mangrove forests are the ultimate illustration of why humans need nature," said Dr. Mark Spalding, lead author of the World Mangrove Atlas and senior marine scientist with The Nature Conservancy. "In place after place the book details the extraordinary synergies between people and forests. The trees provide hard, rot- resistant timber and make some of the best charcoal in the world. The waters all around foster some of the greatest productivity of fish and shellfish in any coastal waters."

Spalding said mangrove forests help prevent erosion and mitigate natural hazards from cyclones to tsunamis. "These are natural coastal defenses whose importance will only grow as sea level rise becomes a reality around the world."

"Given their value, there can be no justification for further mangrove loss. What's urgently needed is for all those working in fields of forestry, fisheries and the environment to work together and communicate their worth, both to the public and to those with the capacity to make a difference," said Emmanuel Ze Meka, executive director of the International Tropical Timber Organization (ITTO) which provides the bulk of funding for the Atlas.