Geoscience Reference
In-Depth Information
breakwaters that reefs form will lead to
greatly increased rates of mainland shore-
line retreat.
The loss of reefs will represent a loss of an
important carbon sink, leading to increas-
ing carbon concentration of the atmosphere.
The loss of the reef fauna and flora will be
a loss to the fishing economy of many local
communities and the economy of numer-
ous tourist villages. Most important will be
the loss of a huge number of reef-dependent
species of marine organisms.
global warming have done. Mangrove
wood is used as lumber and firewood, and
large areas of mangroves have been cleared
to allow access to and a view of the sea.
Mangroves are considered ugly and are
inevitably cut down and replaced by palm
trees, as in south Florida during the 1920s.
The biggest global threat of all is the clear-
ing of mangrove forests to make way for
shrimp farms.
Like salt marshes, mangroves perform
important functions as a source of nutri-
ents to local waters and as a shelter (within
the root system) for a variety of organisms.
At the top of the mangrove forest food
chain are jaguars in Colombia and tigers in
Bangladesh. Mangroves have proved effec-
tive in reducing damage from storms and
tsunamis. Mangroves prevented wave at-
tacks on buildings in Homestead, Florida,
from Hurricane Andrew in 1995, and the
Rangong area of Thailand received rela-
tively little damage from the Asian tsu-
nami in 2004 because mangrove forests
remained intact. As sea levels rise, man-
groves must move inland with the retreat-
ing shoreline, and as climates warm they
must move to the north above the equator
and to the south below the equator. Devel-
opment will usually prevent this. On the
other hand, most mangroves have very ef-
ficient methods of long-distance seed dis-
persal, which is certainly a strong factor
in favor of survival. But the endurance of
continuous forests along the world's tropi-
cal shorelines seems a faint hope, except
for remote, undeveloped shorelines.
Mangroves: Disappearing Forests
Mangroves occupy a band circling the globe
roughly between 25 degrees north and 25
degrees south and are the warm-water
equivalent of salt marshes. There are at
least thirty-five species in this group of
plants that can tolerate salt water to vary-
ing degrees. They are referred to as man-
grove forests or mangrove swamps. Species
numbers are quite unevenly distributed.
For example, there are only three species
of mangroves in Florida Bay and perhaps
nineteen species in Australia. Along shore-
lines, individual species are typically ar-
ranged in shore parallel bands, determined
by the species' tolerance for tidal inunda-
tion, salinity, and waves.
Mangroves range in size from bushes to
trees as high as a hundred feet, with tan-
gled, almost impenetrable root systems. So
far humans have done much more dam-
age to mangroves than sea level rise and
