Clemson,
SC (9/16/99)- As hurricane Floyd roared along the eastern coast of the
US, biologists and engineers were ready, putting in place lessons learned
from previous large scale storms and conducting new studies of Floyd and those
that come after.
left:
enhanced satellite imaging has improved storm tracking
Researchers at Clemson University have conducted a vast amount of research
on the effects of hurricane Hugo, a storm that caused billions of dollars
in damage in 1989. The day after Hugo passed through South Carolina, with
winds of 121 miles-per-hour and reported gusts up to 147 miles-per-hour, a
forest disaster was declared. More than one-third of the state's forest land
(4.5 million acres) was damaged by the high winds and a tidal surge up to
20 feet above sea level that swept saltwater inland. Hugo affected a larger
area and downed more timber than any previous natural catastrophe in the United
States-- more than Hurricane Camille (1969), Mount Saint Helens (1980) and
the Yellowstone fires (1988) combined.
The research revealed that while hurricanes cause massive damage to man-made
structures and wildlife habitats, the storms also create new habitats for
wildlife and provide much need water after long summer droughts.
"Only now are scientists beginning to recognize the critical importance
of natural catastrophes in ecosystem dynamics," said William H. Conner, a
Clemson University forestry scientist who is studying the effects of hurricanes
on coastal environments in South Carolina and Louisiana.
"We will be much better prepared to respond to forest disasters because of
Hugo," added Roy L. Hedden, a Clemson forest resources scientist. "Now we
know how many people and what equipment it takes to salvage the downed timber,
what timber is salvageable, how to store the timber and how to rehabilitate
the remaining forest."
Hurricanes
cause natural destruction by numerous mechanisms. While wind is the most obvious
problem, seawater storm surges can cause extensive damage as they push into
inland freshwater systems. Saltwater storm surges seen during hurricane Huge
reached as high as 20 feet above sea level and destroyed large areas of coastal
forest and the wildlife that lived there. Flying insects and birds were the
first to return; but six months after Hugo, the number of reptiles and amphibians
remained significantly lower than before the storm.
right: tracking
hurricane Floyd
The Santee Experimental Forest in the Francis Marion National Forest north
of Charleston showed the effect such storms can have on endangered species.
. Before Hugo, that area had 477 colonies of endangered red-cockaded woodpeckers.
After the storm, only 100 family groups could be found. Forest salvage operations
included drilling new nesting cavities for the birds.
"One of the risks of current methods of protecting rare and endangered species
by confining them to a few protected areas is that the destruction of one
such area can severely damage an entire population," said Allan P.C. Marsinko,
a Clemson forest resources scientist.
| A hurricane is defined as intense tropical weather system with a well
defined circulation and maximum sustained winds of 74 mph (64 knots) or
higher. In the western Pacific, hurricanes are called "typhoons," and
similar storms in the Indian Ocean are called "cyclones." Hurricanes are
products of the tropical ocean and atmosphere. Powered by heat from the
sea, they are steered by the easterly trade winds and the temperate westerlies
as well as by their own ferocious energy. Around their core, winds grow
with great velocity, generating violent seas. Moving ashore, they sweep
the ocean inward while spawning tornadoes and producing torrential rains
and floods. |
While destroying habitats for some species, the storm improved habitats
for others. For example, the downed trees created open spaces for new plant
growth for deer herds and increased insect populations for wild turkeys. The
remains of larger fallen trees and logs now provide habitat for wildlife and
support the growth of other plants by releasing nutrients into the soil. Interestingly,
three species of trees native to the area weathered the hurricane with less
damage than others, the live oak, cypress and longleaf pine.
"Nature abhors a vacuum," said Charles A. Gresham, a Clemson forest ecologist
who has tracked the recovery process since Hugo hit. "Within 10 years, we
have seen significant recovery-- back to a fully functional, productive forest
with a lot of habitat for wildlife."
Silver Lining?
Another huge storm, Hurricane Andrew, has also taught some valuable lessons.
That storm caused $25 billion in damage to South Florida in 1992. Subsequent
research showed that it may have had a sliver lining for the ecosystem.
"Hurricanes break up dead zones of oxygen-poor water by vertically mixing
the water column," says Dr. Craig Mattocks of the US National Oceanic and
Atmospheric Administration. The mixing disperses pockets of fresh water that
are infested with bacteria from stream run-off. In addition, the strong currents
created by hurricanes flush out sediment, rubble and weeds from coral reefs,
and blast away fungal diseases that damage coral, not to mention drawing up
nutrient-rich water from below which provides a major food source for sea
life.
Hurricane Andrew also did some ecological housecleaning, removing a majority
of non-native Australian pines from Bill Baggs State Park on Key Biscayne.
Now the area is being replanted with native vegetation which is better for
maintaining local wildlife. The Everglades, which have are draining because
of man-made canals, may also benefit from these big storms. Mattocks points
out that "hurricanes can create standing water and sheet water flow in the
Everglades which restores the natural water cycle." This water revitalizes
plant and animal life, and can help prevent and extinguish wildfires.
Dr. Thomas Michot, from the United States Geological Survey agrees, saying
that "hurricanes keep certain types of habitats from being dominated by species
that thrive in a more stable environment." Michot is studying the after effects
of Hurricane Georges on Louisiana's Chandeleur Islands. The hurricane's impact,
while initially devastating to nesting and wintering birds, may in the long
run maintain the islands' high quality as a wildlife habitat. Georges completely
eliminated some nesting islands, but by scouring the vegetation off some of
the areas of higher elevation, it also created new habitats favored by certain
types of nesting birds. In addition, many sea grass beds were buried by the
storm. But Michot says that the new sediment is being quickly colonized by
a sea grass species that is highly valued as a food source to redhead ducks
that winter in the area.
Long Range Problems
Climatologists report that a hurricane rushing up the east coast of the US
has a significant impact on world weather patterns, creating impacts on everything
from salmon conditions in the Pacific Northwest to rainfall in the drought-stricken
Sahel region of Africa.
This process, called a thermohaline circulation pattern or "conveyor belt"
of ocean waters, has implications for El Ninos, La Ninas and countless other
global impacts, said George Taylor, the state climatologist at Oregon State
University and president of the American Association of State Climatologists.
"This hurricane season started late, but it's already had about an average
amount of hurricane activity and it's only halfway over," Taylor said. "It's
going to be a very busy hurricane season, just as four of the last five years
have been. And the Pacific Northwest is going to have its sixth year in a
row of wetter than average weather. This is not a coincidence. If you want
to understand what is happening, you have to look at some of the climate forces
that are driving it."
Taylor believes that a conveyor belt of ocean circulation which operates
over vast distances has kicked into a higher level of activity - a pattern
that began about 1995 and generally lasts around 20 to 25 years before it
quiets down again. This pattern is not related to the other bad news climate
story, global warming caused by the greenhouse effect.
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