What is a wetland?

To put it simply, wetlands are the "kidneys" of the world.  They are in-between areas that have both dry uplands and open water environments.  They are neither land nor water, rather a transition zone, which is why they are so interesting. 

Wetlands are hard to define because of their transitional nature.  It is important to note that an area does not have to be wet all year long to be considered a wetland.  As few as three consecutive weeks of wetness a year is all that is required for an area to be recognized as a wetland.  How much water it gets and how long it stays there is the most important factor that determines a wetlands character.  Because oxygen does not move very fast in water, water saturation very quickly results in a soil condition known as anaerobiosis, which refers to very low oxygen content.  A lack of oxygen kills most plants, and hydrophytic or wetland vegetation is the only kind of vegetation that can survive in these conditions. 

Excerpt from Texas Coastal Wetlands Guidebook, by Daniel W. Moulton and John S. Jacob, Texas Sea Grant Publication TAMU-SG-00-605, p.1-2.