Mangroves are converted to shrimp farms worth US$200 per ha.
Article includes a good review of threats to wetlands
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By TAN CHENG LI / the Star Online / Tuesday February 2, 2010WORLD Wetlands Day is celebrated every Feb 2. It marks the date of the signing of the Convention on Wetlands in 1971 in the Iranian city of Ramsar. Celebrated for the first time in 1997, it is a time to recognise the importance of wetlands and learn about their values and benefits to man. This year’s theme is “Caring For Wetlands – An Answer To Climate Change”.
Wetlands encompasses bogs, marshes, peat swamps, freshwater swamps, lakes, mangroves and river systems, and are generally considered low-value lands, making them susceptible to reclamation for agriculture and other purposes. In truth, however, they are rich in species and provide man with numerous ecological services.
The benefits people obtain from wetlands are varied and include water supply, habitats for wildlife, fish breeding grounds, water purification and waste treatment, flood control, storm protection and recreation. These ecosystem services have been valued by some economists at US$14 trillion (RM49 trillion) annually.
In Thailand, intact mangroves are valued at US$1,000 (RM3,410) per ha based on the sale of mangrove fish and the additional value of non-marketed services such as storm protection and the sequestration of carbon. On the other hand, if the mangroves are converted to shrimp farms, their worth plunges to only US$200 per ha.
We cannot afford, for environmental, social or economic reasons, to lose wetlands; yet we have been doing just that. Losses range from 53% in the United States to a staggering 90% in New Zealand. The world has lost half its wetlands and still is, especially in developing countries.
What are we doing to cause losses in wetlands?
■ Habitat loss through wetlands claimed for agriculture and for urban and industrial development.
■ Excessive freshwater withdrawals especially for irrigation, and for domestic and industrial water needs. This leads not only to less freshwater availability inland but less freshwater.
flow to coastal areas from rivers, thereby impacting coastal ecosystems.
■ Siltation in coastal areas from the outflow from silt-laden rivers.
■ Invasive species have disrupted the abundance and survival of native species. These alien species can arrive as “hitch-hikers” on ship hulls and in ship ballast waters or as escapees from the aquarium and ornamental plant trades. Sometimes species are introduced for agricultural, aquaculture and forestry purposes.
■ Pollution through: agricultural runoff that releases pesticides and fertilisers into rivers; toxic industrial wastes; and untreated or partially treated sewage.
■ Over-exploitation of fish, shellfish, prawns, seaweed and wetlands timber, which reduces the capacity of the ecosystem to function.
■ Nutrient loading from nitrogen, phosphorous and other chemicals – mostly from agriculture but also from poorly treated domestic waste – causes excessive algal growth and the resulting reduction in other species.
The effect of climate change on wetland ecosystems and species
Wetlands found in prairies, tropical and boreal forests, arctic and alpine ecosystems, and coral reefs and mangroves, will be especially vulnerable to climate change because they have a limited capacity to adapt to change.
■ Expected increases in sea surface temperature of about 1°C to 3°C are likely to result in more frequent coral bleaching events and widespread mortality of corals.
■ Coastal wetlands, including salt marshes and mangroves, are likely to be negatively affected by sea-level rise, especially where there are inland physical barriers (such as sea walls and dykes); many areas will be damaged by coastal flooding through storms and tidal surges.
■ Changes in the timing and volume of freshwater runoff from inland wetlands will affect salinity, nutrient levels and moisture regimes in coastal ecosystems – all of which will impact coastal ecosystem functions.
■ Certain invasive species might spread further with increasing temperatures.
What can be done for wetlands?
■ Maintain the health of our intact wetlands.
■ Address the key drivers of wetlands loss and degradation (habitat loss, pollution, excessive water withdrawals, invasive species and over-exploitation).
■ Identify vulnerable species and ecosystems, and implement action plans for their recovery.
■ Prioritise and plan wetlands management and restoration programmes for more variable climate in future.
■ Restore degraded wetlands since healthier wetlands are more resilient than degraded ones.
■ Address the additional impact of climate change on wetlands species and ecosystems through climate change mitigation and adaptation strategies.
(Mitigation requires us to reduce greenhouse gas emissions and to encourage the removal of such gases already in the atmosphere by “trapping” them in soils and vegetation.
Wetlands species under threat
■ Waterbirds are more threatened than all birds and their status has deteriorated faster in the last 20 years.
■ Of the 1,138 waterbird populations whose trends are known, 41% are in decline. Some 140 out of 826 waterbird species are threatened.
■ 38% of the freshwater-dependent mammal species that have been assessed are globally threatened; these include groups such as manatees and river dolphins.
■ 33% of the world’s freshwater fish species are threatened.
■ 26% of the world’s freshwater amphibian species are considered threatened and at least 42% of all amphibian species assessed are declining in population.
■ 65 of the 90 freshwater turtles species that have been assessed are globally threatened. Six of the seven species of marine turtles are threatened.
■ Three out of five crocodile species assessed are threatened.
■ 27% of coral-building species that have been assessed are considered threatened.
■ Source: Ramsar Convention Secretariat / Data from the IUCN Red List, BirdLife International and Wetlands International