If you do not hear the wetlands sounds playing, make sure you have the Quicktime plug-in, which is available online at www.apple.com/quicktime/download.
You must also have scripts set to run automatically on your computer.

If you still can't hear the wetland sound, click here.

Climate Change and Wetlands: Invasive Species

From temperature increases and drought to flooding and severe storms, climate change impacts are directly affecting wetland ecosystems in a number of ways. Some wetland plants and wildlife will be able to adapt to these rapid environmental changes. In fact, some species may even thrive under new climatic conditions. Unfortunately, many of the species will be plants and animals that are not native to the United States, posing an additional threat to native species. One of the reasons that some plants and animals become invasive when introduced to new areas is because they are “generalists,” which means that they can thrive in a wide variety of environmental conditions. Climate change favors these species, because they are best able to adapt to rapid environmental changes. On the other hand, many of the native species that are threatened by invasives require specific environmental conditions in order to thrive. Climate change will make it even more difficult for these native species to compete with invasive species.

Of all the planet’s ecosystems, wetlands are the most vulnerable to invasive species. Wetlands may only cover 6 percent of the Earth’s land mass, but they are host to 25 percent of all invasive species. The diversity of habitat found in wetlands makes them a vulnerable target to a greater number of non-native invasive species. Climate change threatens to greatly expand the threat of aquatic invasives by increasing the range in which they can survive, and by reducing competition from native species. For a more comprehensive look at how wetlands across the country are being affected by invasive species, take a look at Wetland Sights & Sounds 2006. This eight-part series highlighted the threat of aquatic invasive species to our wetlands and waterways with a special theme: Alien Invaders: Invasive Species and Wetlands. You can access previous years’ Wetlands Sights & Sounds by clicking here.

Scientists fear that many of the aquatic invasives that are already problematic in the wetlands and waterways of the United States will become even more widespread as the climate warms. The New Zealand mud snail is one example. First discovered in the 1980s in Idaho’s Snake River drainage, this invasive mollusk can now be found in many lakes and streams throughout the West. These tiny snails form massive colonies that devour enormous quantities of algae and plankton, leaving little behind for native snails and aquatic insects. The repercussions extend further up the food chain as well, since fish populations depend on native snails and insects as a primary food source. One of the barriers that has kept the New Zealand mud snail from invading even more streams is that it cannot tolerate very cold waters. Global warming, however, would cause stream temperatures across the country to rise, allowing this species to become even more widespread.

Horticulturalists are noticing that some non-native plants that had previously been unable to overwinter in their areas are now surviving into the next growing season, such as the rapidly spreading water hyacinth. Water hyacinth is one of the fastest-growing plants in the world. Originally from the Amazon river basin of South America, this species grows so rapidly that it can double its population in just 12 days. It was first introduced to Louisiana in the 1880’s as a pretty novelty plant. Since then, it has spread throughout the southeastern United States, where it is causing severe economic and ecological damage. Its thick, floating mats of vegetation can weigh up to 200 tons per acre, and are so dense that a person could walk on top of them from one end to the other. These mats prevent sunlight and oxygen from penetrating the water column. As the mats decay, the increase in nutrients causes algae populations to bloom, which depletes the oxygen supply even further. As a result, native fish and other aquatic wildlife are smothered. The rapid growth of water hyacinth also crushes and displaces native vegetation, prevents waterfowl from landing on the water, and makes boating and fishing impossible. Until now, its spread into northern states has been prevented by severe cold. But as global warming causes winter temperatures to rise across the United States, water hyacinth is poised to march further northward. This species has already made an appearance as far north as New Jersey, Delaware, and New York. Other invasive plants that are beginning to expand their ranges include purple loosestrife, kudzu, giant salvinia, and Japanese honeysuckle.

People can help stem this trend by keeping non-natives out of their yards and communities, and by learning about ways to use strictly native species. You can obtain lists of known invasives from state and federal agencies, as well as non-profit groups such as The Nature Conservancy and local Native Plant Societies. You can also visit the U.S. Department of Agriculture’s Natural Resources Conservation Service Web site, which maintains a comprehensive plant data base that includes invasive species. (See “Links” section on the right-hand sidebar.) You can also join an effort to eradicate invasive species in your community. Many parks and nature reserves rely on volunteers to help them manually remove troublesome invasive species. Another important way to prevent non-native species from spreading throughout our waterways is to properly clean all boating and fishing equipment between visits to lakes and streams. To learn more about keeping aquatic invasives out of your favorite boating and fishing spots, and enter a contest to win valuable prizes, visit the Izaak Walton League’s Clean Boats Campaign Web site at www.cleanboats.org.

Critter Corner
Paradise Lost: Puaiohi

For many people, the Hawaiian islands conjure up images of pristine beaches, lush rainforests, and gorgeous displays of plant and animal life. Due to an increasing number of environmental woes, however, this tropical landscape is no longer a paradise for many of its native wetland species—many of which are teetering on the brink of extinction. Between habitat destruction, pollution, and invasive species, Hawaii’s unique plants and wildlife are facing an onslaught of human-induced environmental change. Global warming is now threatening to tip the scale further against their continued survival. Because of their easily distinguished songs and plumage, the plight of Hawaii’s birdlife has been especially noticeable. The puaiohi bird could be a poster species for the problems that plague many of the birds that are endemic—or found exclusively—on the Hawaiian Islands.

Also known as the Kauai thrush, the puaiohi is a small, olive-brown thrush that is found only on the island of Kauai, within streamside forests in Alaka`i Swamp above 4,000 feet. Though puaiohi populations have historically been confined to a small area, these birds have suffered drastic declines in both numbers and distribution over the past 25 years. Today, only an estimated 200-300 individuals remain. This shy, drab-colored bird does not have flashy plumage, nor is its song particularly melodious—yet, it has become the focus of a major research and conservation effort among federal and state biologists, as well as several private organizations. Why? Because the puaiohi is the only native frugivorous (fruit-eating) bird still surviving on the island of Kauai, and several plants depend on this species for seed dispersal.

Like many of Hawaii’s endemic species, the plight of the puaiohi can be largely blamed on the introduction of several non-native species, including cats, rats, alien plants, and—worst of all—mosquito-borne pathogens. Avian pox and avian malaria are transmitted by a non-native mosquito species, which first arrived on the Hawaiian Islands in 1826, as a stowaway onboard the ships of European explorers. Since then, these two diseases have single-handedly wiped out virtually every native bird below 4,000 feet in elevation. Cooler weather above this elevation prevents the mosquitoes from becoming established. However, global warming is threatening to increase the range of the mosquito, which could devastate the remaining populations of native Hawaiian forest birds, including the puaiohi. The loss of these native species is not only a tragedy from a naturalist’s perspective, it would be catastrophic effects on the entire ecosystem. Warmer temperatures would also increase the likelihood of severe hurricanes hitting the Hawaiian Islands—a worrisome scenario since Kauai’s dwindling puaiohi population suffered heavy losses during two large hurricanes in 1982 and 1992.

Fortunately, efforts to save the puaiohi have met with remarkable success. In 1995, the Puaiohi Recovery Project was started, with the participation of the U.S. Fish and Wildlife Service, the U.S. Geological Survey’s Biological Resources Division, Hawaii Division of Forestry and Wildlife, and The Peregrine Fund. These efforts included an intensive study of puaiohi ecology; the development of captive-breeding and release program for the puaiohi; and the eradication of non-native species within its habitat. The first captive puaiohi were released into historic habitat in 1999, and were confirmed successfully breeding in the wild. Since then, 132 puaiohi have been released in the Alakai Swamp. Though these birds still face an uphill battle for survival, the Puaiohi Recovery Project is giving them a fighting chance. You, too, can be a part of the puaiohi recovery effort by helping reduce the greenhouse gas emissions that contribute to global warming. Next week’s issue of Sights & Sounds will show you how, so stay tuned.

Click here to hear an audio clip of puaiohi birds in the wild from the CD "Voices of Kauai Forest Birds," by David Kuhn. The CD can be purchased at www.soundshawaiian.com.

VOLUME FOUR
Issue No. 7