Environmentally, Moffett Field is more viable than Alviso, but it still presents problems. The channels become shallow far from roads. Birds nest alongside channels. Wakes from speeding ferries erode shoreline and damage birds' nests. If ferries are required to slow down, that can add a lot of time to a daily commute, Siegel says.
Development can fragment populations.
If you cut through a tidal marsh, species can't get across the channel. You isolate different populations from each other. Disease could wipe them out at any time. They need large blocks of habitat connected by large corridors. Dredging and cutting channels can also be problematic.