Biology Reference
In-Depth Information
PLUG THE GATE?
Building a tidal barrier across the Golden Gate might help the bay region
stave off the early impacts of sea level rise, but over time the loss of the
tides could harm coastal fisheries, shrink tidal marshes, create navigational
nightmares for shipping, and degrade water quality. The low-lying nation of
Holland, long at the mercy of high seas, once focused solely on building
storm-surge barriers, but the country now realizes the value of natural buffers
and its leaders acknowledge that they can't just build their way out of the
problem.
ecological buffer along the edge,” says San Francisco Estuary Institute's
historical ecologist Robin Grossinger.
As sea level rises, wetlands either migrate inland or grow in place. The
most urbanized estuary in the world, however, offers little space for wet-
lands to migrate. In most areas, wetlands abut the hard edge of freeways,
railroads, and buildings. If wetlands can't grow out, then they have to grow
up. By collecting sediment and growing vegetation, which in turn helps
them trap more sediment and build up organic matter, wetlands can sus-
tain themselves in place.
“The bottom line is we have to keep as much mud in the system as we
can,” says wetland builder Michelle Orr. “It helps to have an overall plan
for which areas you're going to maintain for some time, and which you're
going to let erode, and let those be sources of sediment for the rest of the
system.”
Orr and others involved in restoring tidal wetlands are now trying to
figure out how to maintain what they've created. Researchers are experi-
menting with wetland-friendly flood-protection methods. But most ecol-
ogists and engineers agree that without its ring of wetlands the bay would
be in a much more dire position in terms of sea level rise.
“There's a lot we can do to make the wetland landscape more resilient
to sea level rise—by ensuring good sediment supply from the local water-
sheds, restoring wetlands in strategic places, and providing buffer areas for
wetland migration,” says Grossinger.
Experts are increasingly worried about coastal squeeze conflicts, and
calling for the upland edges of the bay not yet filled with commercial, ag-
ricultural, or residential developments to be reserved as undeveloped land
so that estuarine marshes can migrate upslope. “We need to shift our pri-
mary focus from restoration of subsided baylands to conservation of de-
fensible future estuarine-margin space, so that twenty-first-century tidal
marsh habitats can survive,” says coastal ecologist Peter Baye, formerly of
the U.S. Fish and Wildlife Service.
