Geoscience Reference
In-Depth Information
8
Global ChanGe in the biosphere
plants and animals of
the nearshore Zone
often line the shores of estuaries, sounds,
and lagoons or, as in the Great Barrier Reef,
in the sheltered waters behind coral reefs.
Coral reefs are found on open ocean shore-
lines and thrive in the open ocean wave
environment, where their location is of-
ten marked by a telltale offshore white line
of breaking waves. Coral reefs and man-
groves are found in warm waters, while salt
marshes flourish from the temperate zone
all the way north into the Arctic.
Two important groups of organisms live in
the zone between the high and low tides and
in the world's shoal waters just offshore.
These are the salt marshes and mangroves.
A third organic community, the coral reefs,
lives in shallow water below the low tide
line. All have several things in common.
They are all important and widespread
habitats for large numbers of species of
marine organisms. All three are quite ca-
pable of moving landward or seaward as the
sea level rises and falls, and they have his-
torically migrated to the north or south as
nearshore waters cooled or warmed during
past climate changes. Unfortunately the
three communities have another thing in
common: their vulnerability to the activi-
ties of humans. All are threatened by global
change and even more by the response of
humans to global change. Like so many bio-
logical systems, left to their own responses
they would probably survive quite well.
Generally mangrove forests and salt
marshes are found on shorelines that are
protected from direct wave attack. They
threatened by acidification,
Warming, and people: the Future
of coral reefs
Tropical coral reefs exist in a broad band
circling the globe, between latitudes 30 de-
grees north and 30 degrees south. They are
found in clear, well-lit, warm, shallow wa-
ter. Globally an astounding three million
species of marine organisms live in, on, or
very near the world's coral reefs, perhaps
one-third of all such critters. The greatest
of all is the Great Barrier Reef of Austra-
lia, 2,000 kilometers (1,240 miles) long. In
the absence of humans, coral reefs should
