Reefs around the world are in for another  "difficult century", it would
seem - but global warming, which is what many are most concerned about,
is not the only threat.  Sediments from runoff is a major problem,
largely caused by de-forestation and poor agricultural practices which
don't conserve the soil well.  We should remember these things in our
personal activism campaigns.... threats to marine environments very
often begin on the land, and governments and land owners must be made
more aware that how they manage development, agriculture, forestry and
other land use has a major influence upon marine environments.

http://www.planetark.com/dailynewsstory.cfm/newsid/40457/story.htm

River Run-Off Threatens Great Barrier Reef

AUSTRALIA: February 22, 2007

SYDNEY - Satellite images of Australia's Great Barrier Reef show that
sediment from river run-off is threatening the reef at a greater rate
than previously realised, Australia's peak scientific body said on
Wednesday.

The images, taken this month by NASA and US National Oceanic and
Atmospheric Administration satellites, show sediment creating a hazy
cloud over the reef, blocking sunlight and hindering photosynthesis, the
process that keeps coral alive.

"The run-off from torrential rainfall goes into the Great Barrier Reef
lagoon and straight into the ocean at speeds which were not thought to
occur before we saw the images," said Arnold Dekker, from the
Commonwealth Scientific and Industrial Research Organisation (CSIRO).

Scientists say global warming is already a major threat to the Great
Barrier Reef, which stretches 2,300 km (1,400 miles) down the northeast
coast, with rising sea temperatures expected to cause more frequent
coral bleaching.

Global warming is also expected to result in more frequent storms, such
as cyclones that lash Australia's tropical north and flood rivers
flowing into the Great Barrier Reef lagoon.

The satellite images, of a 100 km (62 miles) stretch of reef off the
tropical city of Cairns, show sediment from rivers recently flooded
during a cyclone. The water was travelling at one kilometre per hour
onto the reef, Dekker told Reuters.

"The conventional wisdom was that this kind of water would stay quite
close to the coast ... and would slowly diffuse across the Great Barrier
Reef," he said.

"What these images are showing is that the plumes of river water would
go straight through the reef out into the outer reef, which is something
which we hadn't seen before."

Dekker said the sediment run-off also carried pesticides washed off
farmlands, which might threaten the reef's ecology.

"The satellite images seem to indicate that it is diluting quickly and
that after a week the direct effects are gone," Dekker said.

"However, we don't know how resilient the outer reef organisms are to
the large body of sediment which is re-suspended all the time with wave
and current action," he said.

Story by Suheil Damouny

REUTERS NEWS SERVICE

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