interesting thought on wetlands being plowed...
most wetlands are relatively good at soil building and carbon sequestration. cattails are especially good at it. i am having trouble finding any good sources. but, lets say only .5 inches/year (i would just venture a good cattail slough is actually closer to 1 inch)... even at that rate, had these marginal wetlands not been plowed for the last 75-100 years, they would have accumulated enough soil (3-4 feet) to not be wet any more.