High tide threatens Nukutoa island, Takuu. Photo Professor Richard Moyle Creative Commons
Sea Level Rise is Real
It is now widely accepted that sea level rise (SLR) due to climate change is real. The International Panel on Climate Change’s most optimistic calculations predict a minimum rise of 38 cm (1.25 feet) by 2099. But according to Dasgupta et al in World Bank Policy Research Working Paper 4136, “The impact of sea level rise on developing countries: a comparative analysis,” the continued growth of greenhouse gas (GHG) emissions and associated global warming could well promote SLR of 1-3m (3-10 feet) in this century. The most pessimistic scenarios would have GHG emissions and ice shelf melting passing a tipping point and resulting in a rise of five metres (15 feet).
However, current average sea level rise is 3mm (.118 inches) per annum, so how worried should we be?
Low Lying Islands Have Cause for Concern
Nukutoa village, Takuu Atoll, Papua New Guinea, in the year 2000. A village scene on a Polynesian outlier island. Photo courtesy Hamish MacDonald
Many low-lying regions of the world have cause for concern. The Papua New Guinean (PNG) Carteret islands and Takuu Atoll are among several Pacific islands to be severely affected by salination of their aquifers and increased tidal storm damage.
Takuu, an obscure, difficult to reach atoll, is the ancestral home to 600 Polynesian people living a subsistence lifestyle based exclusively on the sea. Part of Papua New Guinea and 200 kilometres north-east of Bougainville, the atoll is made up of 13 islets with a combined land area of less than a square kilometre (.38 sq. miles), none of it now more than one metre (3.3 feet) above mean sea level. Many food gardens were completely destroyed by king tides in 2010 and the islanders now have to rely mostly on taro and coconuts for survival.
In the Carterets, 86 kms (35 miles) northeast of Bougainville, a similar scenario is threatening the 2500 inhabitants of the five diminutive islands. They have progressively become uninhabitable, with an estimate predicting their total submersion by 2015. The islanders have fought a twenty-year battle, building a seawall and planting mangroves. However, storm surges and high tides have already washed away homes, destroyed vegetable gardens and contaminated fresh water supplies. The natural tree cover on the island is also being impacted by the saltwater contamination of the fresh water table, and the islands have been receiving aid since 2007.
According to PNG’s Post Courier, forty families are ready to move to their new location on the far north of Buka Island. Bougainville President John Momis said that the Bougainville administration was now working on a proposal to immediately help the islanders, because during his recent visit to the Carterets, he witnessed the island in a very bad state and said that the main island would now be cut in half from the rising sea level.
Far-Reaching Economic, Human and Geographical Implications
Whilst causing personal distress and upheaval and having cultural implications, in these cases, sea level rise affects only a small number of people in areas of little global economic importance. A one-metre sea level rise however, according to the World Bank, could have far-reaching economic, human and geographical implications. A one-metre rise in sea levels would force about 60 million people in developing countries to abandon their homes, as waters submerged large swaths of coastal areas.
Rich green vegetation lines the fertile banks of Egypt’s Nile River, culminating in the green fan of the river’s delta. Image courtesy Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC
In Egypt, a one-metre rise in sea level would affect 10 percent of the population, mainly in the Nile Delta. In South East Asia, 10.8 percent of the Vietnamese population would be affected by a one-metre rise, mainly in the Mekong and Red River Deltas. Most of the land southwest of Ho Chi Minh (Saigon) would be severely affected. The vast, humid expanse of the delta is home to more than 17 million people, who have relied for generations on its thousands of river arteries. But rising seawater caused by global warming is now increasing the salt content of the river water and threatening the livelihoods of millions of poor farmers and fishermen. Such a rise could leave a third of the Mekong Delta underwater and lead to mass internal migration and devastation in a region that produces nearly half of Vietnam’s rice.
Land Areas Affected Globally
Concerning land area, around the world, the Bahamas would be by far the most impacted country, with close to 12 percent of its area affected. Approximately 10 percent of Vietnam’s and the Arab Republic of Egypt’s populations would be impacted with a one-metre SLR. Nearly 28 percent of Vietnam, Jamaica and Belize’s wetlands would be impacted by a one-metre SLR. “If there was a one-metre rise, we estimate 40 percent of the delta will be submerged,” says Tran Thuc, director general of the Vietnam Institute of Meteorology, Hydrology and Environment.
Mekong Delta. By Teijo Hakala cc-by-sa-2.0 via Wikipedia Commons
Vietnam would also see 10 percent of its GDP affected and Mauritania’s GDP would be impacted by 9.5 percent. The impact on Egyptian agriculture would be particularly severe, with a one-metre rise hitting 12.5 percent of Egypt’s agricultural production, (this figure increases to 35 percent with a five-metre rise). This would be compounded by the fast-increasing Egyptian population, placing a huge strain on the region’s main breadbasket.
According to a report produced for the Organization for Economic Development by Agrawala et al, the Nile Delta is already subsiding at a rate of 3-5 mm (.12-.19 in) per year. Just a .25-metre rise in sea level would devastate the populous cities that drive Egypt’s economy. Forty percent of Egyptian industry is located in Alexandria alone; a .25-meter (.82 ft) rise in sea level would put 60 percent of Alexandria’s population of four million below sea level, as well as 56.1 percent of Alexandria’s industrial sector. A rise of 0.5 metres (1.6 ft) would be even more disastrous, placing 67 percent of the population, 65.9 percent of the industrial sector, and 75.9 percent of the service sector below sea level. Thirty percent of the city’s area would be destroyed, 1.5 million people would have to be evacuated, and over 195,000 jobs would be lost.
Alexandria is not the only Egyptian city that would be hit by even a 50 cm (1.6 ft) rise in sea level. Agrawala et al cite a study that finds that a half-metre rise would cost over two billion dollars and eliminate over one-third of the jobs in Rosetta. Other cities threatened by a rising sea level in the delta include Port Said, Matruh City, and Arish City.
Port Said. Image courtesy Daniel Csörföly
Higher sea levels will also have a significant impact on Egypt’s tourism sector, as the Nile Delta is home to much of Egypt’s tourism. In cities like Alexandria or Matruh City, rising sea level will reduce both their capability to sustain tourism and of course, their attractiveness to tourists. With a fifty-centimetre rise, 49 percent of Alexandria’s tourism industry would be underwater. Last, but not least, saltwater infiltration in the lakes of northern Egypt, home to 60 percent of Egypt’s fisheries, will have a significant impact.
Whilst there is no certainty to the extent of future sea level rise, the World Bank Policy Research Working Paper’s authors state “these results are not speculative: The current atmospheric concentration of GHG’s is sufficient to drive global warming well into the next century, and much higher concentrations will undoubtedly be reached before any global agreement can be implemented. For precautionary planning purposes, SLR in the range of one-metre – 3m should therefore be regarded as realistic”.
