A low lying Pacific island.
Last week we sailed past a couple of the atolls in the
GilbertIslands. They were just over 10 miles away, but were so low
andflat, they didn't look like land at all, just wrinkles in the
horizon.Their fate has been sealed by our addiction to fossil
fuels. Thebillions of tons of carbon dioxide we pump into the
atmosphere everyyear are adversely impacting the Pacific.
The Intergovernmental Panel on Climate Change (IPCC) estimates
theaverage global temperature will have increased by 6 degrees
by2100. This may not sound like much but the phrase
'averageglobal temperature' conceals a lot.
The average global temperatureduring the last ice-age, when ice
sheets covered most of Scandinavia,reached as far south as northern
Germany and covered most of Canada theUpper Midwest and New England
in America, was only 6 degrees lower thantoday's average global
temperature. Even a small change hassignificant effects on the
world's weather systems, oceans andecology. Four effects of
climate change will have massive impactson the Pacific.
Sea level rise
One of the most widely publicised effects of climate change is
anincrease in sea levels. Current estimates predict an increase in
sealevel of around 1.5 - 3 mm per year. This doesn't sound so bad,
and theIPCC conservatively predict that by 2100, global warming
will lead to asea level rise of 110 to 880 mm.
However, if the ice sheets of Greenland and the Antarctic melt
then the sea level is expected to rise by a more drastic 68.3 m.
No one knows whether these ice sheets will melt entirely but a
2005British Antarctic Survey found 87% of the Antarctic Peninsula
glaciershave retreated over the past 50 years. In the past five
years,the glaciers have lost an average of 50 metres (164 feet) per
Greenpeace expedition to Greenland last year found the Arctic
tobe in a similar situation.
The implications of any sea level rise for the Pacific are
enormous.Rising sea levels will smother islands wholesale, drowning
mangrovesand coral reefs. The Gilbert Islands that we passed last
week are partof Kiribati, a country with a population of just over
105,000 peoplescattered amongst 33 low lying atolls.
The highest point in thecountry is only 81 metres high and is on
decimated island ofBanaba.
The Kiribati people have a good deal comparedto their neighbours
in Tuvalu. There the population of just under12,000 people is
clustered on 9 atolls. The highest point is 5 metresabove sea
level. When you add the
effect of storms and high tidesto the increase in sea level
most of the atolls of Tuvalu and Kribatiwill become uninhabitable.
Tuvalu already has a deal with the NewZealand government for all
its inhabitants to move there when theirhomes are drowned.
Mangroves serve as nurseries to juvenile reef and pelagic fish.
Mangroves may just look like muddy swamps but they are of
vitalimportance to island communities and marine ecosystems.
Theyprovide communities with food; protect the coastline from the
sea, andserve as nurseries for many juvenile reef and open water
ocean marinespecies. The United Nations estimates that 13% of
mangroves will be drowned by 2100. Many Pacific Island
countries, including Samoa and Fiji, are expectedto lose half of
their mangroves; this is likely to have a devastatingeffect on
local communities and ocean ecosystems.
Changes in ocean temperatures
Climate change is warming the oceans. Changes in ocean
temperature willalter the distribution, migration routes and
breeding cycles of marineorganisms. For example, Albacore tuna
exhibit a strong preference forwaters between 16°C and 21°C,
whereas Yellowfin tuna only spawn in waterabove 25.5°C. Other
organisms, such as oysters, rely on thetemperature of the
environment to determine their sex. Astemperatures increase these
creatures will have to alter their range,adapt or die. Their
decreasing population sizes, a result ofoverfishing, will also
reduce their ability to adapt to the rapidlychanging
When temperatures increase coral bleaching occurs. What wecall
coral is actually two co-dependent organisms, a coral polyp and
analgae, which live symbiotically. The algae photosynthesise
providingthe coralpolyp with nutrients while the coral provides the
algae with a safe andnurturing environment. Temperature increases
cause the coralpolyp to expel the symbiotic algae, this causes the
coral to lose it'scolour (hence the term bleaching). If the coral
does not re-establishits relationship with the algae (or another
species of algae) it soondies. A recent report suggests that
three quarters of the world's coral reefs may suffer from climate
change related bleaching. Some experts have gone so far as to
predict that Australia's
Great Barrier Reef will lose 95% of its living coral by
Changes in weather patterns
Oceanic currents pump nutrients from the ocean floor to the
lightsub-surface waters, where they are used by phytoplankon. These
are avital part of ocean ecosystems. Salinity changes in
differentparts of the ocean, primarily caused by differences in
rainfall (e.g.El Nino/El Nina in the Pacific) or melting glaciers
(e.g. the Gulfstream in Atlantic) drive these currents. Climate
change is alteringthese patterns of rainfall and glacial melt, and
these alterations willinevitably change the magnitude, locations,
directions and seasonalityof these life-giving currents. A 2005
study, predicted that changes inocean currents caused by global
warming will reduce the supply ofnutrients, slashing the oceans'
productivity by a fifth.
Climate modelling suggests that weather patterns will alter,
becomingmore extreme. This is expected to result in more severe
storms,meaning severe weather events, such as hurricane Katrina,
whichdestroyed New Orleans, will become the norm. In addition
changing storm patterns are expected to increase coastal
erosion - further exacerbating the effects of sea level
A less well known effect of climate change is ocean
acidification. Ouroceans are, and have been for millions of years,
slightlyalkaline. Some carbon dioxide from the atmosphere
dissolves inthe ocean forming a weak acid (carbonic acid). As the
volume ofcarbon dioxide in the atmosphere increases so too does the
amountdissolving in the sea. Carbonic acid's handiwork can be seen
in manylimestone caves. It is the leeching of carbonic acid through
thelimestone that results in the formation of the most
fantasticstalactites and stalagmites. Its work in the ocean will be
Coral reefs arevulnerable to climate change induced bleaching, ocean acidification andsea level rises.
As the oceans acidify, marine organisms with calcium carbonate
in theirinternal skeletons (bones) and shells will be in trouble.
At themoment their skeletons and shells are hard because the upper
layers ofthe oceans are supersaturated with calcium carbonate. As
the oceansacidify this concentration will be reduced. This
meanstheir shells and skeletons will become softer and, if the
level ofacidification becomes too high, their shells and skeletons
will startto dissolve.
This will have massive impacts all over the marineecosystem. It
will cause huge changes to the species compositionof the oceans
because key organisms at the bottom of the food web,critically some
phytoplanktons and most zooplankton, will no longer beable to
survive. Different species of plankton form the basis ofnearly
all ocean food chains. Further disruptions willoccur because the
corals that create the structure and provide nichesfor an array of
marine ecosystems will also be unable to survive.
A 2003 study calculated that increasing fossil carbon dioxide in
theoceans, could make them more acidic over the next few centuries
thanthey have been for 300 million years, excepting some rare
catastrophicevents. A2005 study into such events showed that 55
million years ago, a releaseof 4500 gigatons of carbon caused the
extinction of huge numbers ofdeep-sea creatures. It took over
100,000 years for the oceans to returntotheir normal alkalinity.
To put that time frame into perspective,Homo Sapiens
- us - have been around for between only200,000 - 400,000
What is to be done?
This is all very depressing both for marine organisms and on a
moreselfish level, for us. Overfishing and destructive fishing
hasalready impoverished most marine ecosystems, and left them
particularlyvulnerable to environmental changes. The rapid changes
that humaninduced climate change will bring about will exacerbate
the problems wehave already caused.
Climate change, overfishing and destructive fishing are more
than justpersonal responsibilities. Their causes are endemic to
oureconomic and social structures. These issues need to be
tackledon by every government, industry, corporation and
individual. Thenumber of collapsed fisheries around the world are a
dire warning toanyone thinking that politicians, self-interested
regulatory bodies andcorporations are an effective way to make
Don't be overwhelmed by the problems, there are still things we