Sealevels are rising in the South Pacific and set to rise higher.
Patrick Nunn explains why the islands are so vulnerable.
GERARD & MARGI MOSS /
The Pacific most tourists see is the stuff of fantasy. Behind the veneer, however, lie environments under considerable stress. The worst symptoms of this stress have been caused by resource mismanagement and the never-ending search for export dollars. But another problem looms large over Pacific island nations as they struggle to sustain themselves into the twenty-first century – and that is global warming.
The evidence that our planet’s surface has been warming for the past 100 years or so is overwhelming. Yet the data on which this evidence is based comes largely from industrialized countries – not from small Pacific islands with only minuscule industrial sectors. Long-term, regularly monitored climate stations are few in the Pacific and data quality is often suspect. So there has been some doubt about whether global warming has indeed affected this vast region.
Yet the three best sites – in Fiji, Hawai’i and Aotearoa/New Zealand – all show an unequivocal result. The Fiji data from Government House in Suva, for example, show a net rise of around 0.5ÞC from 1884 until 1986, when the recording station was relocated. There seems little reason to doubt that the Pacific has been warming at approximately the same rate as almost everywhere else. Throughout history climate has been changing. So too has the surface of the oceans. The connection is twofold. Just as water expands slightly when heated, so does the upper part of the ocean when its temperature rises. Ice will melt when heated – but, if it is floating, the sea level will not change. This will happen only if the ice is on land. When temperatures rise, through both thermal expansion of ocean water and land-ice melt, the sea- level will rise.
The sealevel in the Pacific is undoubtedly rising and has been for at least 100 years – probably twice as long. The few long-term tide-gauge records that we have suggest that it has been rising at a rate of around 1.5 millimetres per year. This may not sound very threatening. But on a gently sloping coastline a rise of around 15 centimetres, similar to that of the past 100 years, can cause flooding of tens of metres of shoreline.
This is a depressingly common story throughout the Pacific islands. On several occasions over the past ten years I have organized my students – who come from 12 different Pacific island nations – to conduct interviews with elderly, long-term residents of long-established coastal settlements in their home countries. These people were asked how their coastlines had changed during their lifetimes. With a few exceptions the results demonstrate widespread inundation, over the past 60-70 years at least, throughout the south and west Pacific.
Admittedly the hard evidence is not as good as that for temperature. Sceptics have tended to latch onto tide-gauge records. Because they are too short – less than 30 years – and/or because the place where the tide gauge is located is itself moving, they do not show a clear pattern of sealevel rise.
Sitting in their offices, some government planners are keen to deny the reality because to admit it means recognizing a problem which demands more dollars than they can afford. Yet, back in their home village drinking kava with their relatives, they hear about the receding shoreline and look worriedly at the foundations of their grandparents’ house, poking out of the water 100 metres from shore.
Projections by the sophisticated computer models of the Intergovernmental Panel on Climate Change (IPCC) – the group of some 700 experts given this task in 1987 by the UN – suggest that the rates of temperature and sealevel rise will increase three- to five-fold in the next 100 years or so. The effects of the past century will be dwarfed by those of the next. To understand what this means for the Pacific islands we need to appreciate something of their variety.
The nations of Kiribati, Marshall Islands, Tokelau and Tuvalu are not particularly populous, nor do they have great land areas. Yet all the land they have rises less than about four metres above mean sealevel. Not only are their islands low but they are built largely from loose sand and gravel chucked up during large storms onto the reefs which surround them.
Traditionally the people of these islands have been dependent on what they can catch to eat from nearby reefs. Parts of Tarawa atoll in Kiribati, for example, now have a population density similar to that of Hong Kong. In some places reefs are becoming over-exploited. Root crops are also grown in pits sunk into the shallow freshwater lens beneath the island surface. Sealevel rise is causing erosion of these islands and also – because the surface of the lens is controlled by that of the sea surface – increased freshwater flooding.
Most other Pacific nations comprise largely high islands. This is another reason for the common perception of their governments that sealevel rise is ‘not our problem’. Yet 90 per cent or more of the people live along their coasts. Their traditional use of coastal resources is much the same as in the low islands. Many of the coastal plains have equivalent problems of erosion and freshwater flooding. The latter effect is exacerbated by rivers bursting out of their channels at the same time as high tides are raising water-table levels.
Economic activity is mostly located along the coasts. Take commercial agriculture in Fiji, for example. Sugar cane – the third-biggest foreign-currency earner – is grown mostly on flat areas along coasts or in low-lying river deltas. Over the last 50 years or so increasing seawater penetration of coastal aquifers has been identified as a reason for falling sugar content in cane. Research is currently being pursued to develop more salt-tolerant strains of sugarcane and other crops.
Or take tourism – increasingly important as a source of revenue throughout the Pacific islands. Tourists are attracted by sun, sand and sea. But tourist beaches are being eroded by sealevel rise. Some resort owners spend huge amounts of money maintaining a beach which 50 years ago maintained itself. Ambitious schemes for tourist resorts built on reclaimed land throughout the Pacific islands seek investors’ dollars oblivious, it seems, of the estimates of the IPCC.
The coral reefs which surround most tropical Pacific island groups are not only important sources of sustenance for islanders, but also provide physical protection to many island shores. Huge waves whipped up by storms or driven across the ocean by undersea earthquakes would cause massive damage to island coasts were it not for the buffering effects of offshore reefs. I remember an old man telling me about the 1953 Suva earthquake and tsunami (wave). When the second wave – the big one – hit the barrier reef it was as tall as a coconut tree. Yet when it reached the Suva shoreline – from which my informant had quickly fled – it was just the height of a tall man.
Many coral reefs are under stress for human-associated reasons. If ocean temperatures and sealevels rise as predicted then this stress will increase, perhaps to such a degree that entire reefs might die or be unable to act as such effective buffers. The cause of future stress is not simply that sealevel rise will drown reef surfaces, denying sunlight to photosynthetic reef organisms. Rising temperatures will combine with other sources of stress to cause widespread coral death by ‘bleaching’. When the water surrounding a coral is heated beyond about 32ÞC that coral is prone to eject the symbiotic algae which live within it and give reefs such glorious colours. In this way they become ‘bleached’ and die. Incidents of coral bleaching have already been recorded in French Polynesia and on Aitutaki in the Cook Islands.
Optimistic but unrealistic observers have been quick to assure Pacific island governments that, if sealevel does rise as fast as the IPCC contend, then ‘don’t worry’, all the reefs will grow upwards just as fast. This will not happen. For although some Pacific reefs have done so in the past, this was not a Pacific-wide phenomenon and happened long before people entered the picture and created such high levels of stress in these fragile ecosystems.
Fate has conspired to create an impression among many Pacific island governments that global warming poses less serious problems to their nations than is likely, given the present state of knowledge. Many island governments have adopted a ‘wait-and-see’ policy. They argue that, before they commit resources which are earmarked for other, potentially more pressing, problems they should have some concrete evidence.
There are other reasons behind this attitude. Many government decision-makers see global warming as a problem which was not created in the Pacific islands but in the metropolitan countries of north-west Europe and the Pacific Rim. These countries should bear the financial brunt of mitigating the undesirable effects of their profligacy in the Pacific islands.
There is some justification for this view and it has already been translated into aid money. Detailed surveys have been funded by the United States, Japan and Australia. Projects with more tangible benefit include artificial shoreline-protection structures – witness the magnificent seawall protecting Nuku’alofa, the capital of the Kingdom of Tonga, designed and funded by Japan.
Yet, perhaps inevitably, politics and ignorance have also played a role. Distant rumblings are coming from the Australian Government about continued funding for a multi-million-dollar tide-gauge project in the Pacific islands, only a few years after the last gauge was installed – despite the fact that the project needs to function for at least 30 years to produce useful results.
Short of funds, many island governments encourage rural communities to build artificial structures to protect eroding shorelines. I remember talking to a planner in one of the government departments intended to help rural dwellers to do this. He explained all about the materials he advised people to use, about where they should purchase them from. Then I asked what he advised them about seawall design. He looked askance at me. ‘A wall is a wall,’ he said, gesturing to the side of his office. Seawalls built like house walls cause far more problems than they solve, and invariably collapse after a couple of years.
If the future holds what the IPCC believes is the most probable scenario – and this is what most other countries are assuming – then Pacific islands are going to be among the parts of our world that are most adversely affected by climate change.
Patrick Nunn is Professor and Head of Geography at the University of the South Pacific. As Leader of its Climate Change Researchers’ Group, he has been involved in climate-change issues in the Pacific islands for more than a decade. He is the author of Oceanic Islands (Blackwell, 1994).