What is a wetland?

Wetlands have been called the "kidneys of the landscape" because they:

They've also been called "biological supermarkets" because of their:

They are found on every continent except Antarctica, from the tropics to the tundra.

About 6% of the surface of the land on earth is wetland.

Note on the map that we are in sort of a "hot spot" for wetlands.

(From Mitch and Gosselink, 1993)

Lots of cultures have lived in harmony with wetlands and get a lot out of them.

So if they're so good.....?

In Dante's Divine Comedy, a marsh of the River Styx in upper hell is the final

resting place for the wrathful

Carl Linnaeus (you know, the guy responsible for binomial nomenclature in biology) in 1732 describes peatlands in Lappland:

"These we have had to cross for miles, think with what misery, every step up to our knees. Never can the priest so describe hell because it is no worse."

Survey of Dismal Swamp on the VA/NC border described in the 18th century:

"...horrible desert, the foul damps ascend without ceasing, corrupt the air and render it unfit for respiration."

And then there are these negative images:

"bogged down in detail"

"swamped with work"

"The Creature from the Black Lagoon" and "Swampthing"

Since it's not easy to hike through or boat through these places, they've tended to impede "progress" and so they have been misunderstood.

Even wetland science is hard to sort out because of the huge geographical extent and wide variety of hydrologic conditions in which wetlands are found. They are usually at an interface between terrestrial systems (upland forests and grasslands) and aquatic systems (lakes, rivers, oceans). They don't fit into aquatic or terrestrial ecology. They are different from these, but entirely dependent upon them. As a transitional zones or ectone they have characteristics and species typical of the communities they divide, and thus are especially rich in diversity.

(From Mitch and Gosselink, 1993)


Defining Wetlands

Precisely defining wetlands became important when we decided to start protecting them. Finding the edge or delineating in the U.S. has major political consequences.

Distinguishing Features:

1. Presence of water either at the surface or within the root zone

2. unique soil conditions

3. hydrophytic (water loving) vegetation adapted to flooding and a lack of flood

intolerant vegetation


So why is defining a problem?

1. How much water and for how long? Wetlands aren't necessarily wet at any given time.

2. Wetland species (plants, animals, and microbes) range from those that can be wet or

dry--facultative--to those who can only be wet--obligate.

3. Wetlands can be very small to very large.

4. There are huge differences in the functioning of different wetland types--saltmarshes vs.

prairie potholes vs. forested wetland.

5. There can be major human impacts-easily drained, created by increased run-off due to

alterations (beavers can take some credit/blame for this too)


Formal Fish and Wildlife Service definition is typically used in ecological studies and


Wetlands are lands transitional between terrestrial and aquatic systems where the

water table is usually at or near the surface or the land is covered by shallow

water...Wetlands must have one of the following three attributes: (1) at least

periodically, the land supports predominantly hydophytes, (2) the substrate is

predominantly undrained hydric soil, and (3) the substrate is nonsoil and is

saturated with water or covered by shallow water at some time during the growing

season of each year.


Juristictional Wetlands--those legally defined as wetlands by the US Army Corps of Engineers definition:

The term "wetlands" means those areas that are inundated or saturated by surface

or ground water at a frequency and duration sufficient to support, and that under

normal circumstances do support, a prevalence of vegetation typically adapted for

life in saturated soil conditions. Wetlands generally include swamps, marshed,

bogs, and similar areas.

Wetlands in the US

(From Mitch and Gosselink, 1993)

Since the late 1700's we've lost about 53% of our wetlands. The area around the Mississippi River offers a stark picture of what this means:

(From Mitch and Gosselink, 1993)

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