Draining marshes and other wetlands could hasten climate change, a group of experts meeting in Brazil this week warned.
Wetlands contain 771 tons of carbon dioxide and methane, said scientists gathered in the central western town of Cuiaba for a four-day wetlands-preservation conference hosted by the United Nations University and Brazil's Federal University of Mato Grasso (UFMT). The world's remaining wetlands hold about one-fifth of the world's carbon, an amount equivalent to that currently in the atmosphere.
A UN University press release warns that continued destruction of these wetlands could unleash the stored carbon into the atmosphere:
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.
Wetlands are not just swamps: they also include marshes, peat bogs, river deltas, mangroves, tundra, lagoons and river flood plains.
Together they account for 6 percent of Earth's land surface and store 20 percent of its carbon. They also produce 25 percent of the world's food, purify water, recharge aquifers and act as buffers against violent coastal storms.
Historically, wetlands have been regarded as an impediment to civilization. About 60 percent of wetlands worldwide have been destroyed in the past century, mostly due to draining for agriculture. Pollution, dams, canals, groundwater pumping, urban development and peat extraction add to the destruction.
What's more, global warming can also cause wetlands to release greenhouse gases, creating a feedback loop in which rising temperatures beget more rising temperatures. As temperatures rise, more water in wetlands will evaporate, and the water is less likely to be replenished as glaciers recede and precipitation declines. Organic materials are likley to decompose faster in a warmer climate, releasing even more carbon dioxide.
The UN University press release quotes its rector, Konrad Osterwalder. "Too often in the past, people have unwittingly considered wetlands to be problems in need of a solution," he said. "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."