Brevemente...numa praia perto de si!
"VANCOUVER, August 21, 2008 (GLOBE-Net) - Aquatic
dead zones - stretches of water where little or nothing can survive -
were once rare phenomena. Now they are commonplace and eco-systems upon
which marine life and humanity in general depend on are being destroyed
according to a new study in the journal Science, entitled "Suffocating
the Oceans."
According to Rutger Rosenberg
from the University of Gothenburg in Sweden and Robert Diaz from the
Virginia Institute of Marine Science, College of William and Mary in
the US, dead zones have increased to such an extent that they are now
considered to be the key stressor on marine ecosystems’ and rank with
over-fishing, habitat loss, and harmful algal blooms as global
environmental problems. More than 400 such areas covering a total ocean
area of 95,000 square miles were identified last year.
Dead zones
are areas that suffer from hypoxia, i.e. lack of oxygen, which
scientists believe is caused by agricultural nutrients such as nitrogen
and phosphorus that wash off the land and fertilize huge blooms of
algae. When dead, the algae are eaten by bacteria, which absorb oxygen
from the water as the algae decompose. Hypoxia can drive away tens of
thousands of marine animals and, in severe cases, kill them. The
expanding agricultural use of new fertilizers and other growth
stimulants is simply feeding the dead in the water.
Sewage,
animal wastes and atmospheric deposition from the burning of fossil
fuels, also contribute to oxygen depletion in the water.
Robert
Diaz stated in a Globe and Mail article that In Canada, oxygen
depletion in the lower St. Lawrence Estuary is killing cod and other
fish species. According to Inka Milewski, a marine biologist with the
Conservation Council of New Brunswick also quoted in the Globe and mail
article, in New Brunswick, dead zones resulting from nitrogen runoff
from fish farms have caused massive fish kills and the transformation
of complex and diverse coastal habitat into barren seascapes dominated
by a few species. Nearly every summer, the bottom waters of Lake Erie’s
central and western basins lose so much oxygen that fish can’t survive.
A major report released earlier this year by the United Nations
Environment Programme (UNEP) - "In Dead Water" - notes the number of
dead zones are increasing. Given their association with pollutants from
urban and agricultural sources, together with the projected growth in
coastal development, their numbers may multiply in a few decades,
unless substantial changes in policy are implemented.
While
the primary culprit creating dead zones in the marine environment is
nitrogen from agriculture, the other major contributor is the
consumption of fossil fuels. Burning gasoline and diesel creates
smog-forming nitrogen oxides, which subsequently clear when rain washes
the nitrogen out of the sky and, ultimately, into the ocean.
Technological
improvements, such as electric or hydrogen cars, could help solve that
problem but the agricultural question is trickier. "Nitrogen is very
slippery; it’s very difficult to keep it on land," Diaz notes in a
Scientific American article. "We need to find a technology to keep
nitrogen from leaving the soil."
Biotechnologies, such as the
nitrogen use efficiency (NUE) improvements, may allow farmers to reduce
the overall amount of nitrogen they require. Arcadia Biosciences,
a California-based company that pursues agriculture-based business
opportunities that improve the environment and human health, has been
engineering crops to absorb more nitrogen.
"It’s a big economic
benefit for farmers if they use only half as much nitrogen as well a
big beneficial impact on nitrogen runoff into waterways," Arcadia
president and CEO, Eric Rey in the same article. Rey hopes that this
product will be adopted as quickly as herbicide-resistant crops, which
only took five years from introduction in 1998 to become nearly 70
percent of the corn grown in the U.S., and is now nearly 90 percent. "A
reasonable expectation is that there would be a dramatic reduction,
maybe by 2018."
While these technologies will not solve the dead
water zone problem anytime soon, they do offer grounds for hope. This
problem took years to develop and it will take even longer before there
is any dramatic turnaround given the current pace of urban growth in
coastal regions, and the necessary expansion of agricultural production
needed to feed a growing world population.
Some hypoxic
ecosystems have improved in recent years due to better management of
pollutants. Dead zones in New York’s Hudson River and East River, for
example, have actually disappeared. But on a global scale only 4
percent of the dead zones are recovering, according to the Science
report.
While it may be unrealistic to try to return to
pre-industrial levels of agricultural nutrients flowing into coastal
waters, policy makers should seek ways to reduce pollution levels to
those seen in the middle of the 20th century, before the dead zones
began spreading, note the reports authors.
More information on climate change impacts on the world’s oceans is available in the UNEP Report."
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