Disappearing Ducks:

The Effect of Climate Change on North Dakota's Waterfowl

By Alice LeBlanc, Staff Economist,
Daniel J. Dudek, Senior Economist,
Luiz Fernando Allegretti, Agronomist/Consultant,
Environmental Defense Fund

Originally published in February 1991

Summary

North American waterfowl are among the most important wildlife on the continent. In addition to being indispensable to a recreational hunting industry worth an estimated five hundred million dollars per year, they provide aesthetic enjoyment and other intangible benefits to millions of people. Because of their great value, a major conservation program and management plan between the United States and Canada focuses on regulating recreational harvest and protecting and managing key habitats. Harvest variations from year to year have been largely influenced by weather conditions and agricultural activities that affect waterfowl breeding.

This paper examines and quantifies the expected impact of climate change on the duck population of North Dakota. Direct climatic changes together with an increase in land used for agriculture are estimated to bring about a decline of 22% in duck productivity in North Dakota. This conclusion could reasonably be extended as an approximation to the entire prairie pothole and parkland region of the U.S. and Canada.

The next half century is likely to reveal a new set of stresses on waterfowl and a new set of challenges to waterfowl management. Climate change as a result of the accumulation of greenhouse gases such as carbon dioxide, nitrous oxides, methane and chlorofluorocarbons in the atmosphere will result in changes in weather patterns and temperatures. The primary effects of the increased concentrations of greenhouse gases over the next fifty years include an increase in average global temperature of 3 to 8 degrees F, a rise in sea level and subsequent flooding of coastal cities, damage to coastal lands and estuaries, changes in precipitation and evapotranspiration and in the frequency and severity of storms. Secondary effects of climate change are its impacts on agricultural productivity, water resources and location of cropland. The expansion of agriculture in response to climate change may encroach upon wildlife habitat. In conjunction with direct climatic stresses, this may be devastating to the ecological systems that support waterfowl.

The prairie wetlands or prairie pothole region of the U.S. and Canada combined contributes more than 50% of this continent's waterfowl production. North Dakota is a predominantly agricultural state that lies squarely within the pothole region and contributes 25% of U.S. duck production. On average, about three million ducks use the pothole wetlands of North Dakota to breed. In addition most of the continent's mallards pass through North Dakota and use its wetlands in transit on their way to breeding grounds farther north. North Dakota was chosen as the study area in order to look more closely at the interactions between agriculture, climate change and waterfowl breeding habitat including both wetlands and upland nesting areas. Moreover, it was assumed that North Dakota would be representative of changes brought about by the greenhouse effect in the prairie duck breeding habitats of the entire continent.

A series of models are used to estimate the effect of climate change on ducks in North Dakota. Results from the general circulation model (GCM) of the Goddard Institute for Space Studies (GISS) were obtained under the assumption that the atmospheric concentration of CO2 has doubled. GCMs are sophisticated computer models designed to predict changes in weather based on changes in the concentration of gases in the atmosphere. Climatic predictions from the GCM and changes in CO2 levels were input into a national agricultural model to forecast changes in crop yields and agricultural land use based on climate change. The agricultural model employs baseline data from 1982 for major crops in the U.S. and allocates resources and crop production among regions in the U.S. so as to maximize measures of consumer and producer welfare. The changes in agricultural production that it yields are based on climate change, agricultural resources, and economic factors. Results for North Dakota are an increase of 423,000 acres of cropland.

Data collected by the U.S. Fish and Wildlife Service on wetland availability, number of adult ducks, and brood indices in North Dakota were used to specify regression equations to estimate the pond count, which is an indication of the extent of wetlands, and duck productivity. The factors used to explain the pond count are precipitation as measured by a soil moisture index, evapotranspiration as measured by pan evaporation and a cropland variable. When results under a doubling of CO2 from the GISS GCM and from the agricultural model were used in the equation, a decline of 30% was observed in the pond count. Duck productivity, or the measure of young ducks produced, is explained by the pond count and the number of adult birds in the state in May. When results from the pond count equation and the increase in cropland from the agricultural model were used, the duck productivity measure declined by 22%.

Climate change related to the greenhouse effect has the potential in all its ramifications to affect an enormous range of natural systems as well as human activities. This paper traces the impact on the waterfowl breeding habitat of North Dakota of climate change as well as secondary land use adjustments as agricultural activity responds to first round changes. The duck breeding habitat of North Dakota is an example of a valuable natural system, subject to human management and investment, that will be negatively affected by climate change directly as well as by secondary effects as agriculture adjusts. Effective conservation of waterfowl in the next century may well depend on the early formulation of management strategies that recognize the gravity of the changes that could occur as a result of the alteration of the earth's climate. Those governmental agencies and private groups most interested in the conservation of North American waterfowl should recognize their stake in the emerging public policy discussion of what to do about the threat of climate change. Recommendations focus on policies that would alleviate rather than worsen the effects of climate change on waterfowl habitat and would help achieve a planning process that includes the potential impacts of climate change. They include the completion of wetlands inventories; continuing research on climatic stresses on waterfowl; strengthening of the swampbuster provisions in the farm bill; removal of federal subsidies in agriculture and in water programs; creation of water markets and the encouragement of alliances to restore drained wetlands and expand wetland acquisition programs. There is general agreement among scientists that if recent trends in the release of carbon dioxide and certain trace gases into the atmosphere continue, dramatic climate change is inevitable. On the other hand, international cooperation to avoid or postpone climate change through controls on releases of climate-altering gases may be attainable. A recent international protocol to reduce the production of chlorofluorocarbons, trace gases partly responsible for the atmospheric changes expected to result in climate change, may provide a framework for a more ambitious international effort to curb other activities contributing to climate change. In the meantime, potential effects of climate change should be included in the management processes for those ecological systems that will be affected.

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