One Rare Plant in Wetlands

One rare plant found in drier wetlands is... the bulrush, specifically the Alkaline Bulrush. This plant provides food, cover, nesting, and shelter for ducks and other water creatures in wetlands. The seeds of this plant are eaten mostly by ducks and birds, while other organisms eat their rhizomes and baby shoots. There are several species of bulrushes, including the Alkaline. Bulrushes are perennial grass-like plants and can grow to 10 feet tall in shallow water or in moist soils. Flowers usually occur just below the tip of the stem. Bulrushes have not adapted much to these circumstances; over the many years they have existed, they mostly have not changed a lot, since their conditions are pretty good.

If this plant is eaten so often, why do you think it is still very abundant in wetlands; and it has not vanished completely?

Information: (http://www.uen.org/utahlink/tours/tourImage.cgi?image_id=1207&tour_id=1006&category_id=1010), and (http://aquaplant.tamu.edu/database/emergent_plants/bulrush.htm)