A week after publishing this, I read this passage in "Braiding Sweetgrass":
Cattails grow in nearly all types of wetlands, wherever there is adequate sun, plentiful nutrients, and soggy ground. Midway between land and water, freshwater marshes are among the most highly productive ecosystems on earth, rivaling the tropical rainforest. People valued the supermarket of the swamp for the cattails, but also as a rich source of fish and game. Fish spawn in the shallows; frogs and salamanders abound. Waterfowl nest here in the safety of the dense sward, and migratory birds seek out cattail marshes for sanctuary on their journeys.
Not surprisingly, hunger for this productive land precipitated a 90 percent loss of the wetlands--as well as the Native people who depended upon them. Cattails are also soil builders. All those leaves and rhizomes return to the sediments when the cattails die back. What hasn't been eaten lies beneath the water, only partially decomposing in the anaerobic waters, building up peat. It is rich in nutrients and has the water-holding capacity of a sponge, making it ideal for truck crops. Decried as "wastelands," marsh draining for agriculture was carried out on a huge scale. So-called "muck farms" plow under the black soil of drained marshes, and a landscape that once supported some of the world's highest biodiversity now supports a single crop. In some places the old wetlands are just paved over for parking. A true waste of land.