By Mike Anderson, Ph.D.
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. 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.
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 years, and 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.
What Is 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.