Ocean acidity threatens islands
2008-06-02 21:15
Sydney - Rising acidity in the
ocean caused by seas absorbing greenhouse carbon dioxide could
make low-lying island nations like Kiribati and the Maldives
more vulnerable to storms as their coral reefs struggle to
survive, say scientists.
Carbon dioxide in the atmosphere is at its highest level in
the past 650 000 years, possibly 23 million years, and half has
now been dissolved into the oceans making them more acidic.
Ocean acidification, which is projected to spread
extensively north from the Antarctic by 2100, makes it
difficult or impossible for some animals, like coral and
starfish, to produce their shells and skeletons.
Reefs will become marginal
"If ocean acidification weakens the structure of
reef-forming corals and algae, tropical systems (islands) will
be more vulnerable to physical impacts from storms and
cyclones," said a new report by some of the world's leading
marine scientists.
"By 2100, it is expected that some reefs will become
marginal and reef calcification will decline," said the report,
by the Antarctic Climate & Ecosystems Cooperative Research
Centre.
Oceans absorb half of human emissions
Ocean acidification is when carbon dioxide dissolves in the
sea forming a weak acid, carbonic acid. Human-induced carbon
dioxide has largely been produced by burning fossil fuels,
agricultural practices and concrete production.
"The ocean is a major sink for CO² emissions and has
absorbed about 48% of the CO² emitted by human
activities since preindustrial times," said the report.
The report said atmospheric carbon dioxide levels are expected to
reach about double pre-industrial levels within this century,
resulting in an acidification of oceans three times the level
experienced during the last major rise in carbon dioxide during
the last glacial period 15 000 years ago.
Marine life may not adapt
"Many (marine) species have taken millennia to evolve and
it is unknown whether they can (or will) be able to adapt to
the relatively rapid rate of ocean acidification, in the order
of decades not millennia," said the report.