impacts > ecosystems >
Wetlands in a warmer world
Mike Anderson
Institute for Wetland and Waterfowl Research, Ducks Unlimited Canada
Wildfowlers have long been obsessed with the weather. After all, nothing has more impact on the fortunes of duck hunters than ice, open water, and tomorrow's wind. Although we can't discern the picture yet, it is clear that the tapestry of water 
and birds across the continent is likely to change in the years ahead. Coastal marshes are likely to lose birds as wetland losses mount; big waters inland may do better, but only if water quality can be protected. Warmer winters will mean birds, on average, wintering farther north, as long as they have water for roosting and adequate food. Having said this, there will always be warm years and cold years, wet years and dry, cold fronts and nor'easters to make average years exceptional.
The bigger question is whether waterfowl habitats in North America will be able to support historical numbers of breeding and wintering birds in the face of global climate change.
Earth's climate, so far as scientists can reconstruct it, has fluctuated markedly over the millennia. Glaciers have come and gone. Droughts and floods have waxed and waned. Whole continents have moved, and the seas changed with them. So, attributing every unusual weather event today to human modification of the atmosphere is nonsensical. But does that mean there is nothing to be concerned about? Hardly. If you ask instead what trends are evident in the climate record, how has the atmosphere been altered, or what changes are unfolding in the world's oceans, the answers are sobering.
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What's changing?
The earth's average temperature is the product of complex physical forces including the chemical composition of the atmosphere. Several compounds such as carbon dioxide (CO2) and methane are powerful greenhouse gases, in that they help trap heat in the atmosphere, preventing it from radiating back into space. If the atmospheric concentration of such gases increases, so does the temperature of the globe. Depending upon the future emission scenarios and climate models used, the Intergovernmental Panel of Climate Change has upped its projections for warming this century to 2.5° - 10.4°F.
While there is growing consensus about the general physical changes we might expect as a result of global warming, there is much less certainty about what the biological impacts of those changes might be. That's because the current climate models are designed to predict change over very large geographic areas - larger scales than biologists typically use to study wildlife. Second, the predictions are imprecise and depend greatly on what humans will do in the future. Finally, things like timing of precipitation, and variation from season to season and year to year, are hard to predict but can matter a great deal to critters like migrating ducks.
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Prospects for key waterfowl regions
DU believes that the prospects of climate change are serious, and we are taking steps to keep informed and do prudent contingency planning for conservation. There remains, however, a great deal of uncertainty about how this global drama will play out, and that too must be considered as we plan for the future. Here's a sampling of projections for some of DU's high priority conservation regions:
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What should conservationists do now?
People are challenged to make important environmental, social, and economic decisions in a world pervaded by uncertainties. The prospects of global climate change pose especially difficult challenges for conservation planners because of the scale and complexity of the problem, the long time required to learn about impacts, and the high degree of uncertainty associated with some of the predictions about future conditions. But uncertainty doesn't preclude the need for conservation decisions today. The immediate challenge for DU and like-minded organizations is to judge what adaptations to future conditions are prudent now, even if we are unsure, and, second, what should be done to improve our understanding of climate change and options for future adaptation. Scientific monitoring is essential in those systems that seem most vulnerable (e.g., Prairie Pothole Region, coastal zones, Western Boreal Forest). Improving our understanding of how current swings in climatic conditions affect wildlife populations and their habitats would allow us to anticipate climate impacts much better than we can today. Monitoring changes in other sectors that impact wildlife conservation (e.g., agriculture, forestry) should yield early signals of impending challenges or new opportunities.
DU will seek opportunities that might be lurking in the global greenhouse. Some regions might become a good deal wetter--and for ducks, where there is water there is opportunity. Conversely, where freshwater becomes scarcer, a wider segment of society should value the role that wetlands, grasslands and forests can play in ensuring that clean water flows from our watersheds. Some waterfowl habitats may have potential to help remove CO2 from the atmosphere and thereby bring new funding partners for habitat restoration (see sidebar).
Waterfowl habitats throughout the continent have been affected profoundly by human development. Any effects of climate change will be imposed on top of existing pressures. In most places one obvious adaptation would be to reduce existing stresses on wetlands (e.g., nutrient loading, toxic chemicals, filling, drainage, soil erosion, urban encroachment) and thereby reduce vulnerability to further climate-induced alterations. This may be the single most important and achievable thing that we can do today to prepare for a warmer but uncertain future.
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Carbon traps
Ducks Unlimited and its conservation partners are exploring opportunities for using wetlands, grasslands, and bottomland hardwood forests to take up, or sequester, atmospheric carbon. If this works as well as some scientists predict, it may provide added incentive for North American society to conserve and restore waterfowl habitat. Power producers, energy companies, and other private industries are already investing speculatively in international carbon credits. The basic notion is that industry or governments might be allowed to offset some portion of their carbon emissions by restoring natural habitats that remove carbon from the atmosphere and incorporate it in plant tissue and soil organic matter. Restoration of bottomland hardwood forests seems tailor-made for such a program. Carbon cycling in other habitats, like prairie wetlands, needs additional study to test their carbon storage potential. DU is actively exploring these opportunities and facilitating research needed to guide the way.
