World Oceans in Extreme Danger #1
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3. World Oceans in Extreme Danger
Oceanic problems once found on a local scale are now pandemic. Data
from oceanography, marine biology, meteorology, fishery science and
glaciology reveal that the seas are changing in ominous ways. A
vortex of cause and effect wrought by global environmental dilemmas
is changing the ocean from a watery horizon with assorted regional
troubles to a global system in alarming distress.
The oceans are one, say oceanographers, with currents linking the
seas and regulating climate. Sea temperature and chemistry changes,
along with contamination and reckless fishing practices, intertwine
to imperil the world's largest communal life source.
In 2005, researchers from the Scripps Institution of Oceanography
and the Lawrence Livermore National Laboratory found clear evidence
that the ocean is quickly warming. They discovered that the top
half-mile of the ocean has warmed dramatically in the past 40 years
as a result of human-induced greenhouse gases.
One manifestation of this warming is the melting of the Arctic. A
shrinking ratio of ice to water has set off a feedback loop,
accelerating the increase in water surfaces that promote further
warming and melting. With polar waters growing fresher and tropical
seas saltier, the cycle of evaporation and precipitation has
quickened, further invigorating the greenhouse effect. The ocean's
currents are reacting to this freshening, causing a critical
conveyor that carries warm upper waters into Europe's northern
latitudes to slow by one-third since 1957, bolstering fears of a
shut down and cataclysmic climate change. This accelerating cycle of
cause and effect will be difficult, if not impossible, to reverse.
Atmospheric litter is also altering sea chemistry, as thousands of
toxic compounds poison marine creatures and devastate propagation.
The ocean has absorbed 118 billion metric tons of carbon dioxide
since the onset of the Industrial Revolution, with 20 to 25 tons
being added to the atmosphere daily. Increasing acidity from rising
levels of CO2 is changing the ocean's pH balance. Studies indicate
that the shells and skeletons possessed by everything from
reef-building corals to mollusks and plankton begin to dissolve
within 48 hours of exposure to the acidity expected in the ocean by
2050. Coral reefs will almost certainly disappear and, even more
worrisome, so will plankton. Phytoplankton absorb greenhouse gases,
manufacture oxygen and are the primary producers of the marine food
web.
Mercury pollution enters the food web via coal and chemical industry
waste, oxidizes in the atmosphere and settles to the sea bottom.
There it is consumed, delivering mercury to each subsequent link in
the food chain, until predators such as tuna or whales carry levels
of mercury as much as 1 million times that of the waters around
them. The Gulf of Mexico has the highest mercury levels ever
recorded, with an average of 10 tons of mercury coming down the
Mississippi River every year, and another ton added by offshore
drilling.
Along with mercury, the Mississippi delivers nitrogen, often from
fertilizers. Nitrogen stimulates plant and bacterial growth in the
water that consumes oxygen, creating a condition known as hypoxia,
or dead zones. Dead zones occur wherever oceanic oxygen is depleted
below the level necessary to sustain marine life. A sizable portion
of the Gulf of Mexico has become a dead zone—the largest such area
in the United States and the second largest on the planet, measuring
nearly 8,000 square miles in 2001.
It is no coincidence that almost all of the nearly 150 (and
counting) dead zones on earth lie at the mouths of rivers. Nearly 50
fester off U.S. coasts. While most are caused by river-borne
nitrogen, fossil-fuel-burning plants help create this condition, as
does phosphorous from human sewage and nitrogen emissions from auto
exhaust.
Meanwhile, since its peak in 2000, the global wild fish harvest has
begun a sharp decline. Progress in seagoing technologies and
intensified fishing have stimulated unprecedented decimation of sea
life. Long-lining, in which a single boat sets line across 60 or
more miles of ocean, each baited with up to 10,000 hooks, captures
at least 25 percent unwanted catch. With an estimated 2 billion
hooks set each year, as much as 88 billion pounds of life a year is
thrown back to the ocean either dead or dying.
Additionally, trawlers drag nets across every square inch of the
continental shelves every two years. Fishing the sea floor like a
bulldozer, they level an area 150 times larger than all forest
clear-cuts each year and destroy seafloor ecosystems.
Aquaculture is no better, since 3 pounds of wild fish are caught to
feed every pound of farmed salmon. A 2003 study out of the
University of Nova Scotia concluded, based on data dating from the
1950s, that in the wake of decades of such onslaught, only 10
percent of all large fish (tuna, swordfish) and ground fish (cod,
hake, flounder) are left anywhere in the ocean.
Other sea nurseries are also threatened. Fifteen percent of sea
grass beds have disappeared in the last 10 years, depriving juvenile
fish, manatees and sea turtles of critical habitats. Kelp beds are
also dying at alarming rates. While at no other time in history has
science taught more about how the earth's life-support systems work,
the maelstrom of human assault on the seas still continues. If human
failure in governance of the world's largest public domain is not
reversed quickly, the ocean will soon and surely reach a point of no
return.
Source: 'The Fate of the Ocean,' by Julia Whitty. Mother Jones
magazine, March/April 2006
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