Climate change in the Pacific

Feature story - 21 October, 2006
Last week it was 37°C in Sydney and 19°C in London. I’ve lived in both cities. Sydney’s 33° south of the equator, London’s 51° north. These temperatures are unseasonably warm for both cities and that's wrong. When it’s hot in Sydney it should be cold in London, and vice versa. That’s supposed to be part of the fun of having two homes. Anyone who thinks climate change isn’t real, or isn’t significant or that it won’t radically alter their lifestyle needs their head examined.

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 year. A 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 the 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 environment.

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 2050.

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 tofloods, changing storm patterns are expected to increase coastal erosion  -  further exacerbating the effects of sea level rises.

Ocean acidification

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 much moredestructive.

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 years.

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 change.

Don't be overwhelmed by the problems, there are still things we can do.