这里出没的国外XDJM应该比较多吧？所以跑过来求助一下555，就要开题了@@，狂找资料中……
导师说：你要先给我搞清“孤岛湿地”（isolated wetland）的定义！>_<为虾米国内湿地资料就只有浮于表面的那些大道理捏？

American Wetlands Campaign 2002-2003:
Isolated Wetlands Types: Prairie Potholes and Vernal Pools

Prairie Potholes

For most people, potholes are pockmarks in the pavement that range in size from mildly annoying to downright dangerous. Prairie potholes are a different story. These small isolated wetlands decorate portions of five northcentral states and three Canadian provinces, capturing precious water in a relatively dry prairie landscape. The states with the highest concentration of prairie potholes are South Dakota, North Dakota, Montana, Minnesota, and Iowa. Potholes were formed as glaciers moved across this region and scoured out millions of low spots in the landscape. Retreating glaciers carved out nearly 25 million prairie pothole wetlands across the region. This amazing density of wetlands ?an average of 83 potholes per square mile 朿an be found nowhere else in North America (U.S. Fish and Wildlife Service).

Prairie Pothole Region

From piping plovers to bald eagles, more than 300 bird species rely on these small wetlands as resting places and feeding grounds. Ducks and geese that migrate do not simply take off in Mexico and land in Canada. During their difficult migratory journeys, waterfowl stop to rest and feed (re-fuel) at a variety of small wetlands found along the route. Migratory birds depend upon the insects, insect larva, crustaceans, algae, submerged plants, and other life within the prairie potholes for food. The shallowest potholes melt early in the spring and provide food for birds until the deeper ponds have time to thaw. Almost three quarters of the waterfowl, including many species of ducks and geese, in North America are hatched in the prairie pothole region.

Prairie potholes are in danger of being destroyed as more land is used for agriculture and development. So what would happen if these potholes were to disappear? Imagine if thousands of airplanes took off from airports around the world, and before they reached their destinations, half the airports were removed. Where would all of those planes land? When prairie potholes are destroyed, migratory birds have fewer places to land and less food to eat. This may lead to an earlier death for many birds. For example, from the 1970抯 to the early 1990抯, northern pintails had declined by more than 63 percent, blue-winged teal by 31 percent, lark buntings by 55 percent, and grasshopper sparrows by 69 percent (U.S. Fish and Wildlife Service).

Vernal Pools

Vernal pools are small, shallow low spots in grasslands or forests that are dry during most of the year. Vernal means spring in Latin, which is a good name for these wetlands because they become pools of water in late winter and early spring when snow melts and rainfall is heavy, or when the groundwater table rises. Forested vernal pools are common in the eastern and mid-western United States while grassy pools are more common on the West Coast.

West Coast vernal pools are found in grasslands and provide habitat for rare plants and animals. Eastern and mid-western vernal pools often are forested and support many species of amphibians.

Many types of frogs and salamanders rely on vernal pools for reproduction. Frog and salamander eggs that are laid in vernal pools are safe from hungry fish that cannot survive in these shallow ponds. Even when vernal pools do not completely dry up, they are too shallow to support breeding fish populations. Some of the species that rely on vernal pools in the northeastern United States include mole salamanders, red-spotted newts, wood frogs, spring peepers, green frogs, fairy shrimp, and many types of insects. Turtles, including spotted, painted and snapping turtles visit the pools regularly to dine on frog and salamander eggs and insects.

Vernal pools face increased development pressure, especially because these wetlands are so small. More than 90% of California’s vernal pools have already been lost. Great efforts are being made to protect the remaining vernal pools, as their disappearance marks the loss of rare and important habitat and some of the associated plant and animal species as well.