"Isolated" Wetlands

Information & Ecology

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We may call them pond-breeding amphibians, but a more apt name might be woodland-for-9/10-of-their-lives-except-for-brief-periods-of-breeding-in-water amphibians. Quality terrestrial habitat surrounding the actual wetland is essential. Remember, even in the word W-E-T-L-A-N-D, 4/7ths of the word is LAND. Unfortunately, state regulations protect very little of this wetland buffer zone. 

Also for amphibians (there seems to be a recurring theme here), it is not simply the wetland habitat itself that is essential to species survival, Pond-breeding amphibians, as well as many invertebrates, have a complex life cycle that involves aquatic young, followed by a transition (metamorphosis) to juvenile and adult life stages. For amphibians in particular, terrestrial habitat surrounding a wetland is essential for life.

One animal group that, for obvious reasons, fares poorly in seasonally drying wetlands is fish. With a small number of exceptions, fish are the bane of most amphibian species, as fish are extremely effective predators on aquatic larval and even adult amphibians. For example, in the Southeast--an area of very high diversity of pond-breeding amphibian species--more than half of the 40+ pond-breeding species show a strong preference for fish-free isolated wetlands.

Isolated wetland names differ depending on region--New England vernal pools, midwestern prairie potholes, southeastern Carolina bays, southwestern desert depressions, swale ponds, snow melt ponds, pocosins, sandstone potholes, alpine ponds, karst sinkhole ponds. With the usual caveat that there are MANY exceptions, they are all isolated seasonal wetlands. As such their hydrology--the timing of pond filling and drying, the total time they hold water (hydroperiod)--is paramount. The hydrological factors are the driving force that help determine the biological factors--what species occur in which wetlands, how many species coexist, how often and how successfully species breed. The annual cycle of pond filling and drying determines which species live and which die in this temporary aquatic environment. This is especially true for plant, invertebrate, and amphibian (frog, toad, salamander) species.

Isolated Wetland Ecology