Ocean damage 'is worse than thought'
A new report says the
world's oceans are changing faster than previously thought, which could
have dire consequences for both human and marine life.
by Alex Kirby
Marine scientists say the state of the world's oceans is
deteriorating more rapidly than anyone had realised, and is worse than
that described in last month's UN climate report from the
Intergovernmental Panel on Climate Change.
They say the rate, speed and impacts of ocean change are greater,
faster and more imminent than previously thought - and they expect
summertime Arctic sea ice cover will have disappeared in around 25
years.
Their review, produced by the International Program on the State of
the Ocean (IPSO) and the International Union for the Conservation of
Nature (IUCN) and published in Marine Pollution Bulletin , agrees with
the IPCC that the oceans are absorbing much of the warming caused by
carbon dioxide and other greenhouse gases.
But it says the impact of this warming, when combined with other
stresses, is far graver than previous estimates. The stresses include
decreasing oxygen levels caused by climate change and nitrogen run-off,
other forms of chemical pollution, and serious overfishing.
Professor Alex Rogers of the University of Oxford, IPSO's scientific
director, says: "The health of the ocean is spiralling downwards far
more rapidly than we had thought. We are seeing greater change,
happening faster, and the effects are more imminent than previously
anticipated."
The IUCN's Professor Dan Laffoley says: "What these latest reports
make absolutely clear is that deferring action will increase costs in
the future and lead to even greater, perhaps irreversible, losses."
The review says there is growing evidence that the oceans are losing
oxygen. Predictions for ocean oxygen content suggest a decline of
between one percent and seven percent by 2100.
The loss is occurring in two ways: through the broad trend of
decreasing oxygen levels in tropical oceans and areas of the North
Pacific over the past 50 years, and because of the "dramatic"
increase in coastal hypoxia (low oxygen) associated with eutrophication,
when excessive nutrient levels cause blooms of algae and plankton.
The first is caused by global warming, the second by increased
nutrient runoff from agriculture and sewage.
The authors are also concerned about the growing acidity of the
oceans, which means "extremely serious consequences for ocean life, and
in turn for food and coastal protection". The Global Ocean Commission
reported recently that acidification would make up to half of the Arctic
Ocean uninhabitable for shelled animals by 2050.
Methane a concern
Professor Rogers told the Climate News Network : "At high latitudes
pH levels are decreasing faster than anywhere else because water
temperatures are lower, and the water is becoming more acidic. Last
year, for the first time, molluscs called sea butterflies were caught
with corroded shells."
When atmospheric CO2 concentrations reach 450-500 parts per million
(ppm) coral reefs will be eroded faster than they can grow, and some
species will become extinct. Projections are for concentrations to reach
that level by 2030-2050: in May they passed 400 ppm for the first time
since measurements began in 1958.
With the ocean bearing the brunt of warming in the climate system,
the review says, the impacts of continued warming until 2050 include
reduced seasonal ice zones and increasing stratification of ocean
layers, leading to oxygen depletion.
It also expects increased releases from the Arctic seabed of methane,
a greenhouse gas at least 23 percent more potent than CO2 (the releases
were not considered by the IPCC); and more low oxygen problems.
Overfishing
Another stress identified is overfishing. Contrary to claims, the
review says, and despite some improvements, fisheries management is
still failing to halt the decline of key species and damage to
ecosystems. In 2012 the UN's Food and Agriculture Organisation said 70
percent of world fish populations were unsustainably exploited.
The scientists say world governments must urgently reduce global CO2
emissions to limit temperature rise to under 2°C - something which would
mean limiting all greenhouse gas emissions to 450 ppm. They say current
targets for carbon emission reductions are not enough to ensure coral
reef survival and to counter other biological effects of acidification,
especially as there is a time lag of several decades between atmospheric
CO2 emissions and the detection of dissolved oceanic CO2.
Potential knock-on effects of climate change, such as methane release
from melting permafrost, and coral dieback, mean the consequences for
human and ocean life could be even worse than presently calculated.
The scientists also urge better fisheries management and an effective
global infrastructure for high seas governance.
- Third World Network Features
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