Photograph: © SAF – Coastal Care
The first global assessment of mangroves in over a decade reveals that 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.
About one fifth of all mangroves are thought to have been lost since 1980. Although losses are slowing at 0.7 per cent a year, the authors warn that any further destruction due to shrimp farming and coastal development will cause significant economic and ecological decline.
Economic assessments provide some of the most powerful arguments in favour of mangrove management, protection or restoration. Studies estimate that mangroves generate between US$2000-9000 per hectare annually, considerably more than alternative uses such as aquaculture, agriculture or insensitive tourism.
The new atlas also underscores 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.
Achim Steiner, UN Under-Secretary General and Executive Director, UN Environment Programme (UNEP), said: “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. 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”.
“Together, the science and the economics can drive policy shifts. 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,” he added.
“Mangrove forests are the ultimate illustration of why humans need nature,” says 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. What’s more, 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 provided the bulk of funding for the Atlas. This book goes a considerable way to communicating that message.”
“The Nature Conservancy is an organization with its feet firmly on the ground in 30 countries,” said Mark Terceck, CEO of the Conservancy. “Already we have teams working to protect and restore mangroves from Florida to Indonesia, Palau to Grenada. This book raises the stakes and engenders urgency, but it also offers hope. These are robust and resilient ecosystems. Get things right for them and the payback will be immense: security for rich biodiversity and a lifeline to many of the world’s most vulnerable people.”
Key Findings from the Atlas
Loss and restoration
The global area of mangroves, 150 000 square kilometers, is equivalent to the area of Suriname, or the state of Illinois, or half the area of the Philippines. Mangrove forests straddle land and sea and are found in 123 countries in tropical and subtropical regions.
The nations with the largest mangrove areas include Indonesia with 21 per cent of global mangroves, Brazil with 9 per cent, Australia 7 per cent, Mexico 5 per cent and Nigeria with 5 per cent.
The greatest drivers for mangrove forest loss are direct conversion to aquaculture, agriculture and urban land uses. Coastal zones are often densely populated and pressure for land intense. Where mangroves remain, they have often been degraded through over harvesting.
Where vast tracts of mangroves have been cleared for shrimp aquaculture, fast profits often left a legacy of long-term debts and poverty, which are hard to reverse.
According to the FAO (Food and Agricultural Organization) mangrove losses have been considerable and are continuing. Some 35,600 square kilometers were lost between 1980 and 2005.
While there are no accurate estimates of the original cover, there is a general consensus that it would have been over 200,000 square kilometers and that considerably more than 50,000 square kilometers or one-quarter of original mangrove cover has been lost as a result of human intervention.
Mangroves have now been actively planted or encouraged to grow through activities such as site clearance and the removal of waste. Examples include Australia, Bangladesh, Benin, Brazil, Cuba, India, Indonesia, Pakistan, Philippines, Thailand and Vietnam.
Use and ecological niche
Mangroves contribute to livelihoods locally and globally by providing forest resources such as timber, firewood and thatching materials as well as non-timber products.
They are also recognized as an important greenbelt and carbon sink that protects coastal areas from natural disasters such as tsunamis, cyclones and erosion resulting from sea-level rise especially in small island countries.
There is good evidence that mangroves even reduced the impact of the 2004 Indian Ocean tsunami in a number of locations.
There is also considerable storage of organic carbon in mangrove soils, meaning they may have an important role to play in the process of mitigating climate change. Preliminary estimates indicate that the total above-ground biomass for the world’s mangrove forests may be over 3700Tg of carbon, and that carbon sequestration directly into mangrove sediments is likely to be in the range of 14-17Tg of carbon per year.
Mangroves are also among the most important intertidal habitats for marine and coastal fisheries. Mangrove related species have been estimated to support 30 per cent of fish catch and almost 100 per cent of shrimp catch in South-East Asian countries, while mangroves and associated habitats in Queensland, Australia support 75 per cent of commercial fisheries species
Policy and solutions
The destruction of mangroves is often prompted by local decisions, market forces, industrial demand, population expansion or poverty. However, in many countries, the fate of mangroves is also determined by high level policy decisions.
In the Philippines, as an example, state-wide encouragement of aquaculture dating back to the 1950s led to massive losses. In Malaysia, by contrast, state ownership of mangroves prevails. While there have still been losses, large areas remain in forest reserves, managed for timber and charcoal production, with concomitant benefits for fisheries.
Trends of mangrove gain or loss can be rapidly and quite dramatically reversed. Laws addressing the placement of aquaculture standards or water quality pollution minimization have greatly altered the shape of new aquaculture developments in many countries.
New policies and projects have led to widespread mangrove plantation across the Philippines. Policies have led to the offsetting of mangrove loss by replanting or restoration with examples in Florida (US) and Australia.
Many countries, such as Mexico, Belize, Tanzania and Mozambique, have also established general legal protection for mangroves, controlling destructive activities through strict licensing systems.
The atlas brings together an unprecedented partnership of organizations, from forestry and conservation sectors and from across the United Nations, and includes a new and comprehensive map and account of mangrove forests.
Mangroves worldwide: a global loss of tidal forests, The National Geographic
Mostly because of coastal development, Earth has already lost perhaps as much as a quarter of its mangrove forests, and many species of mangrove plants are edging toward extinction. The remaining mangrove zones add up worldwide to no more than the area of the U.S. state of Illinois, and they shrink every year under the onslaught of development, pollution, and climate change.
The World Atlas of Mangroves published July 14th 2010, is the most comprehensive assessment of mangroves yet. It reveals “drastic loss to global economy and livelihoods,” the publishers said in a news release about the book.
More than 100 top international mangrove researchers and organizations provided data, reviews and other input. Spanish and French versions of the Atlas are being prepared.