Climate

Wetlands destruction — another climate feedback

Wetlands are an essential ecosystem that promote biodiversity and flood control. They are also essential to maintaining a livable climate — since wetland destruction potentially accelerates global warming.

As reported in Science Daily, leading scientists are now meeting in Brazil at the 8th International Wetlands Conference, discussing actions to better understand, protect, and manage this key global resource.

How big a deal are the wetlands?

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.

So how much carbon are we talking about?

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.

Put another way:

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.

That’s significant. Of course it all depends how quickly the CO2 and/or the methane is released. And like the disappearing forests, disappearing wetlands hold a double whammy for climate change — as another carbon sink becomes a carbon emitter.

The irreplaceable nature of wetlands goes beyond carbon capture, of course:

“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.

What’s our track record in protecting this invaluable resource you might wonder?

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.

So what to do now?

German expert Wolfgang Junk says…”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.

Like a deforested northern hemisphere asking the tropics to save their forests, this familiar dynamic is unavoidably playing out with wetlands:

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.

In fact the conference is taking place in Cuiaba on the edge of the Pantanal wetlands: “… spanning 160,000 square km, is confronted by increasing development pressure. Its catchment area straddles Brazil, Bolivia and Paraguay, while Uruguay and Argentina are downstream.”

A bit of good news here in the U.S., since there’s been so little, should be noted: Not only has the U.S. largely stopped wetland destruction, it is undergoing significant wetland restoration, most notably in the Florida Everglades:

The US will spend $700 million over two decades to revive the Florida Everglades. It will include six artificial wetlands (“storm water treatment areas”), to receive and cleanse excess nutrients from neighbouring farm districts.

And the most threatened?

…those around the Mediterranean, where for two millennia the population has been draining wetlands and floodplains for agriculture — and more recently for urban areas, tourist developments, and to eradicate malarial mosquitoes.

Wetlands destruction is also an amplifying climate feedback. As we warm, the rising temperatures will destroy further wetlands. So far it is estimated that wetlands damage due to rising temperatures has been minimal, but according to UN University scientists: “… a warming of 3° to 4°C could eliminate 85% of all remaining wetlands in the world.”

Saving and restoring wetlands, like stopping deforestation and preserving the tundra, must be a first-tier climate change fighting effort.

Ken Levenson

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2 Responses to Wetlands destruction — another climate feedback

  1. Russ says:

    A bit of good news here in the U.S., since there’s been so little, should be noted: Not only has the U.S. largely stopped wetland destruction, it is undergoing significant wetland restoration, most notably in the Florida Everglades:

    The US will spend $700 million over two decades to revive the Florida Everglades. It will include six artificial wetlands (”storm water treatment areas”), to receive and cleanse excess nutrients from neighbouring farm districts.

    While the Everglades plan is great news (though I’ll hold off on the euphoria until I actually see the execution), I fear this assessment of the state of US wetlands may be too optimistic.

    Just like with everything else, the Bush admin has sought to gut the CWA and its wetlands protections. The law demands no net loss, with a strong preference for on-site preservation, and failing this mitigation must be in-kind and as close to the destruction site as possible.

    The enemy’s (illegal) replacement concept is “mitigation banking”, which would extend eligible mitigation over as vast area, with vastly fungible concepts of acceptable geography and wetland type.

    (This also creates a new parasite industry, specializing in Potemkin “wetland” creation. Disaster capitalism in action. But it looks great in the GDP!)

    Then we also have the Supreme court’s dubious wetlands decision. Resting on Kennedy’s splitting-the-difference between enforcing the law and allowing the enemy to gut it, this is hardly a strong foundation for wetlands preservation.

  2. kenlevenson says:

    Russ,
    Thanks for expanding the view on this…there is much for the next administration to tackle such as undoing Bush’s environmental crimes and reclaiming much more of what’s been lost.

    And while the Supreme Court decision was a blow against federal authority over wetlands, fortunately, it’s my understanding, that states can and do wield tremendous power over wetlands.

    Of course the Supreme Court’s decision on this is just another big illustration of why we need an Obama presidency.