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Climate Change and Wetlands: Droughts and Floods

One of the reasons why climate change effects can be difficult to predict is that there are many variables that determine how climate change will impact a given area. Not all regions will be affected in the same way. One of the more serious consequences of global warming is the disruption of rain and snowfall patterns throughout the world—changes that could cause both persistent drought and severe flooding. But the forecast varies depending on where you are looking. According to the Intergovernmental Panel on Climate Change, tropical and high-latitude environments will see an increase in precipitation, while subtropical areas will experience less rainfall. In other words, global warming is causing the wet to get wetter and the dry drier. This has far-reaching consequences for wetland ecosystems.

Drought is of particular concern to the northern Great Plains states, which contain a vast network of lakes, wetlands, and grasslands known as the prairie pothole region. This area is named after the unique “pothole” wetlands that dot the landscape, which are remnants of glacial retreat during the last Ice Age. The prairie pothole region provides vital habitat for countless numbers of birds during their migration and breeding cycles, and is estimated to produce more than half of North America’s duck population. However, climate change is bringing catastrophic changes to the region. Decades of agricultural and commercial development have already destroyed over half of the region’s wetlands, and prolonged drought could further reduce both their size and number. The Wildlife Society, the association for professional wildlife managers, warns that if current warming trends continue, up to 90 percent of the prairie potholes could be lost, which would cause a 69 percent drop in America’s duck population.

The Great Lakes region is also being affected by climate change-induced drought. According to the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory, water levels in Lake Superior have dropped by 10 millimeters (.4 inch) every year since 1978. In 2007, the water level was almost 20 inches below average, its lowest recorded water level since 1926. Water levels in Lakes Michigan and Huron are about 2 feet below average. Lakes Ontario and Erie are suffering less dramatic declines, but they are also several inches below normal. Scientists attribute these declines primarily to higher evaporation rates. Warmer air and water temperatures have led to less snow and ice cover on the lakes over the winter, which allows more water to evaporate. Additionally, the entire watershed has been experiencing lower than average rainfall during the summer months. The result has been devastating to the region’s wetlands. Natural beds of wild rice growing in the lakeside marshes have been steadily drying as the shoreline recedes. This impacts several Native American communities that rely on wild rice harvests for subsistence, as well as local waterfowl populations. Shallower waters are also preventing fish from accessing coastal marsh vegetation, which provides essential spawning habitat for at least 32 out of the 36 species of fish found in the lakes.

In other parts of the country, flooding is a major concern. In the northern United States and Canada, scientists are worried about the thawing of the permafrost that underlies peatlands and forests. As these frozen layers of soil melt, they could flood entire bog ecosystems. This not only results in the loss of a unique and increasingly rare variety of wetland, it may also exacerbate the process of global warming by causing the release of large amounts of greenhouse gases stored in the roots of bog plants. In the Rocky Mountain states and Alaska, earlier and more rapid snowmelt threatens to increase flash floods. Meanwhile, in the Southeast, storms are becoming more frequent and severe. Because warmer air can hold greater amounts of water vapor, precipitation events are projected to get a lot more intense in many parts of the country. Coastal and riparian wetlands already weakened by development and logging would be unable to absorb the excess water of intense storms and hurricanes. The increasing severity of storms is an issue of great concern for many states, and will be the focus of the next issue of Wetland Sights & Sounds.

As catastrophic droughts and floods increasingly plague many parts of the country, many individuals and communities across the country are choosing to take action not only to prevent climate change, but also to protect wetland habitat. Healthy wetlands can lessen the effects of drought by storing rainwater and recharging groundwater reserves. Wetlands also protect homes and property from flood damage by absorbing excess water and acting as a physical buffer between communities and flooded waterways. In Placer County, California, local developers are teaming up with conservation groups and federal agencies to protect and restore the area’s unique vernal pool grasslands. These increasingly rare wetlands fill with water during fall and winter rains, providing essential habitat for a rich variety of plants and wildlife. The Wallkill Valley Land Trust in Ulster County, New York, is fighting to protect 425 acres of land, including Pine Hole Bog and surrounding swamplands and drainage areas. Recognizing the importance of these wetlands for flood protection and water purification, they are reaching out to local residents and policymakers to educate them about the importance of protecting these valuable lands. So far they have achieved protection for 300 acres of wetland habitat through land preservation agreements with landowners. Community conservation efforts like these are becoming increasingly common, and are an important step toward reducing the effects of global warming on our communities and ecosystems.

Critter Corner
Surviving southwest drought: Chiricahua leopard frog

When it comes to environmental change, frogs are often thought of as the proverbial “canary in the coal mine.” As amphibians, they are vulnerable to both waterborne and airborne pollutants; and their moist, permeable skin makes them more sensitive than other species to changes in their environment. What happens to frogs is often an indicator of an environmental stress that may affect other wildlife, and even humans, in the future. Global warming is no exception. Rising temperatures have been blamed for drastic declines, and even extinctions, in amphibian populations around the world. This is raising red flags for scientists and outdoor enthusiasts alike, many of whom are concerned about the effects of global warming on both the landscape and resident wildlife. In one small corner of the Southwest, the plight of the Chiricahua leopard frog is revealing just how catastrophic climate change can be for wetland ecosystems.

Commonly reaching lengths of over 4 inches, the Chiricahua leopard frog is one of the Southwest’s largest leopard frogs. Its distinctive snoring call was once heard at more than 400 aquatic sites throughout central and southeastern Arizona, southwestern New Mexico, and northern Mexico. Today, that number has shrunk to fewer than 80. Listed as a federally threatened species in 2002, the Chiricahua leopard frog faces many obstacles along its road to recovery. This species needs permanent water to reproduce. But many of the desert streams, springs, and wetlands that provide essential habitat for the frogs have been destroyed by cattle grazing, groundwater pumping, and water diversion. Invasive species, such as bullfrogs and crayfish, have also taken a toll on frog numbers. With populations already dwindling and weakened, global warming is threatening to provide the fatal blow to the Chiricahua leopard frog. As temperatures in the Southwest soar, drought is drying up what little habitat remains for these amphibians. Warmer temperatures may also be causing the spread of chytridiomycosis, a fungal disease that is killing frogs and toads around the globe.

But the Chiricahua leopard frog is not without friends. These days, the Chiricahua leopard frog is mostly found in the man-made stock tanks that dot the modern landscape of the Southwest. Although these concrete watering holes are a poor substitute for natural streams and wetland habitat, they are helping this threatened species eke out a living in the increasingly dry landscape. And the ranchers themselves are proving to be an important part of the conservation effort. One family voluntarily transported 1,000 gallons of water every week to keep a tank populated by the frogs from drying out. Another rancher transported several frogs from a desiccated reservoir to a new home in an artificial pond. In southeastern Arizona's San Bernardino Valley, the University of Arizona and San Bernardino National Wildlife Refuge are working with local ranchers to create and restore wetland habitat for the frogs. According to the U.S. Fish and Wildlife Service, these and other community-based conservation efforts could lay the groundwork for a regional Chiricahua leopard frog recovery plan..

Click here to listen to the sounds of a desert spring.

VOLUME FOUR
Issue No. 4