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Fragilariopsis kerguelensis, a type of phytoplankton on the Kerguelen plateau that has a silica shell - Source: Reuters -
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To some entrepreneurs, the wild and icy seas between Australia
and Antarctica could become a money spinner by engineering nature
to soak up carbon dioxide and then selling carbon credits worth
millions of dollars.
To some scientists and many nations, though, the concept of using
nature to mop up mankind's excess CO2 to fight global warming is
fraught with risk and uncertainty.
An analysis by a leading Australian research body has urged caution
and says more research is crucial before commercial ventures are
allowed to fertilise oceans on a large scale and over many years to
capture CO2.
"I don't think the scientific community has even sat down and made
a list of the things we need to check before we feel comfortable
that this would be a low-risk endeavour," said one of the
Australian report's authors, Tom Trull.
"We never even designed measurement programmes to look at
ecological change and the risks," said Trull, Ocean Control of
Carbon Dioxide programme leader at the Antarctic Climate and
Ecosystems Cooperative Research Centre (ACE CRC) in Hobart.
Scientists say sprinkling the ocean surface with trace amounts of
iron or releasing other nutrients over many thousands of square
kilometres promotes blooms of tiny phytoplankton, which soak up
carbon dioxide in the marine plants.
When the phytoplankton die, they drift to the ocean depths,
along with the carbon locked inside their cells where it is
potentially stored for decades or centuries in sediments on the
ocean floor.
Firms eyeing this natural carbon sink hope to commercialise it to
yield carbon credits to help industries offset their
emissions.
The problem is no one knows exactly how much carbon can be captured
and stored in this way, for how long, or the risks to ocean
ecosystems from such large-scale geo-engineering.
Some scientists fear such schemes could change species composition
in the oceans, increase acidity or cause oxygen depletion in some
areas, even promote the release of another powerful greenhouse gas,
nitrous oxide.
Blooming
"Ocean fertilisation may cause changes in marine ecosystem
structure and biodiversity, and may have other undesirable
effects," says the ACE CRC position analysis on ocean fertilisation
science and policy, soon to be publicly released.
"While controlled iron fertilisation experiments have shown an
increase in phytoplankton growth, and a temporary increase in
drawdown of atmospheric CO2, it is uncertain whether this would
increase carbon transfer into the deep ocean over the longer-term,"
it says.
It also says the potential for negative impacts is expected to
increase with the scale and duration of fertilisation.
There are doubts that any damaging effects could be detected in
time.
"It is very important to recognise that if deleterious effects
increase with scale and duration of fertilization, detection of
these cumulative effects may not be possible until the damage is
already done," said John Cullen, professor of oceanography at
Dalhousie University at Nova Scotia in Canada.
"It is extremely important to look at the ecological risks of this
kind of activity," he said.
Oceans soak up vast amounts of CO2 emitted by nature or through
burning of fossil fuels and deforestation and the Southern Ocean
plays the greatest role of all the oceans.
But much of the Southern Ocean is depleted of iron and experiments
have shown even small amounts of the nutrient can trigger
phytoplankton blooms that can last for up to two months.
Companies such as California-based Climos and Australia's Ocean
Nourishment Corp are planning small-scale experiments to test their
ocean carbon capture and sequestration projects.
Ocean Nourishment uses ammonia and urea, delivered via a marine
pipeline to a region deficient in nitrogen, to boost phytoplankton
growth and boost fish stocks. Climos uses iron and plans
experiments in the Southern Ocean in 2010.
"Iron fertilization is no silver bullet for climate change - which
underscores the severity of the problem we have, and the urgency
for immediate emissions reductions worldwide," Climos founder and
CEO Dan Whaley told Reuters in an email interview.
But he said it was premature to judge iron fertilisation as
dangerous.
"Phytoplankton are nature's way of sequestering CO2 to the deep
ocean, where nearly 90 percent of earth's carbon lies. Further,
most everything we put up in the air is going to the deep ocean
eventually. The only question is how long it takes," he said.
Many nations, though, remain cautious and member states of two
treaties that govern dumping of wastes at sea passed a non-binding
resolution in October calling for ocean fertilisation operations to
be allowed only for research.
Parties to the London Convention and related London Protocol, part
of the International Maritime Organisation, signed the resolution
that said member states were urged to use utmost caution to
evaluate research proposals to ensure protection of marine
life.
Absorption limit
Trull, who participated in the first ocean fertilisation experiment
in 1999, one of a dozen since conducted globally, said commercial
ventures would need to operate over huge areas of ocean for many
years.
The ACE CRC report also says ocean fertilisation just using iron
would likely hit an absorption limit of about one billion tonnes of
carbon (3.7 billion tonnes of CO2) annually, or about 15% of
mankind's total carbon emissions.
"That really puts the risk in context. We're talking about altering
ecosystems of planetary scale for a benefit that won't actually
relieve us from dealing with all the other issues, such as
conservation or alternative energy generation."
Cullen of Dalhousie University said studies suggested that to
sequester large amounts of carbon would require fertilisation of
most of the Southern Ocean for long periods of time.
"The question is can we assess those large-scale and long-term
effects on the basis of experiments 100 by 200 km in size. I have
not seen evidence it can be done."
