Massive greenhouse gases may be released as destruction, drying of world wetlands worsens: UN

Leading world scientists convene in Brazil July 21-25 amid growing concern that evaporation and ongoing destruction of world wetlands, which hold a volume of carbon similar to that in the atmosphere today, could cause them to exhale billows of greenhouse gases. Meeting in the city of Cuiaba on the edge of South America's vast Pantanal, the largest wetland of its kind, some 700 experts from 28 nations at the 8th INTECOL International Wetlands Conference will prescribe measures urgently needed to better understand and manage these vibrant ecosystems, ranked among the planet's most threatened, and slow their decline and loss.

Warming world temperatures are speeding both rates of decomposition of trapped organic material and evaporation, while threatening critical sources of wetlands recharge by melting glaciers and reducing precipitation.

Covering just 6% of Earth's land surface, wetlands (including marshes, peat bogs, swamps, river deltas, mangroves, tundra, lagoons and river floodplains) store 10-20% of its terrestrial carbon. Wetlands slow the decay of organic material trapped and locked away over the ages in low oxygen conditions.

These waterlogged (either seasonally or year-round) areas contain an estimated 771 gigatonnes (771 billion tonnes) of greenhouse gases – both CO₂ and more potent methane – an amount in CO₂ equivalent comparable to the carbon content of today's atmosphere.

"Humanity in many parts of the world needs a wake-up call to fully appreciate the vital environmental, social and economic services wetlands provide – absorbing and holding carbon, moderating water levels, supporting biodiversity and countless others," says conference co-chair Paulo Teixeira, Co-ordinator of the Cuiaba-based Pantanal Regional Environmental Programme, a joint effort of the United Nations University and Brazil's Federal University of Mato Grasso (UFMT), which will host the event.

Says UN Under Secretary-General Konrad Osterwalder, Rector of UNU: "Too often in the past, people have unwittingly considered wetlands to be problems in need of a solution. Yet wetlands are essential to the planet's health – and with hindsight, the problems in reality have turned out to be the draining of wetlands and other 'solutions' we humans devised."

If the decline of wetlands continues through human and climate change-related causes, scientists fear the release of carbon from these traditional sinks could compound the global warming problem significantly, says Prof. Paulo Speller, Rector of UFMT. Drained tropical swamp forests release an estimated 40 tonnes of carbon per hectare per year. Drained peat bogs release some 2.5 to 10 tonnes of carbon per hectare per year.

Adds Prof. Speller: "This landmark conference beside the Pantanal will gather an overview of the status of global wetlands, identify knowledge gaps, create greater collaboration and consistency in wetland science worldwide, and offer a plain-spoken policy prescription for decision makers with an appeal to adopt it with urgency."

German expert Wolfgang Junk says the impact of climate change on wetlands is small so far compared to the damage caused by poor management at the local level.

"Lessening the stress on wetlands caused by pollution and other human assaults will improve their resiliency and represents an important climate change adaptation strategy," he says. "Wetland rehabilitation, meanwhile, represents a viable alternative to artificial flood control and dredging efforts that may be needed to cope with the larger, more frequent floods predicted in a hotter world."

Prof. Junk, of the Max-Planck-Institute for Evolutionary Biology, notes that maintenance of wetlands is much cheaper than rehabilitation and that poorer countries will have fewer means to rehabilitate their wetlands to cope with climate change. Wetland-friendly development alternatives must be elaborated in developing countries, therefore, to minimize losses of their many benefits, he says.

He notes too that while pressure on wetlands in poorer countries has risen dramatically in recent years, they have not suffered nearly as much damage as those in the developed world.

Some 60% of wetlands worldwide – and up to 90% in Europe – have been destroyed in the past 100 years, principally due to drainage for agriculture but also through pollution, dams, canals, groundwater pumping, urban development and peat extraction.

Notwithstanding recent efforts in such countries as Australia and the U.S. (which has lost 50 million of an estimated 90 million hectares of wetlands 500 years ago) to protect wetlands and reverse past damage, at a world scale they continue to shrink.

"Wetlands act as sponges and their role as sources, reservoirs and regulators of water is largely underappreciated by many farmers and others who rely on steady water supplies," says Prof. Junk. "They also cleanse water of organic pollutants, prevent downstream flood inundations, protect riverbanks and seashores from erosion, recycle nutrients and capture sediment."

Typically high in nutrients, wetlands also offer rich habitats for small organisms which feed fish and other water life, which in turn nourish mammals and birds. Many wetlands feature biodiversity comparable to that of rainforests or coral reefs.

Conference organizers say efficient protection of wetlands requires complex, long term management plans that cover their entire catchment areas, often involving agreements between states or countries. These agreements need to cover activities that affect wetlands both directly and indirectly, such as the use of water and soils, development, waste treatment and disposal, but also harmonization of environmental legislation for protection of wetlands and all that lives in them.

Source: United Nations University