Rising sea levels – Disappearing islands, threatened settlements

BORN in a seaside town on the furthest southwestern peninsula of England, I have been aware of the curse of rising sea levels for well over 70 years. However, their acceleration has been amplified by rising heat levels worldwide.

I frequently think of the future of the cities of Kuching, Kota Kinabalu, and other coastal urban areas in Sarawak and Sabah. Most major settlements in these two states are located on rivers and their many tributaries flowing into the open seas.

From the turn of the 20th century to 2018, the average global sea level rose by between 15cm and 25cm, or put another way averaging 1mm to 2mm per annum. Alarmingly, between 2013 and 2022, an acceleration occurred at a rate 4.62mm per annum.

Around our planet, sea level rise is not uniform as some landmasses are rising up in response to the removal of ice sheets of the Pleistocene glaciations and other landmasses sinking. By 2100, the National Oceanic and Atmospheric Administration (NOAA) of the USA has predicted that sea levels will rise by at least 0.3 metres.

Causes of sea level rise

There are many reasons for this. As a result of global warming caused by anthropogenetic greenhouse gas emissions, the oceans, which absorb 90 per cent of these emissions, are heating up and thus seawater is expanding. Water input from melting glaciers and the icecap of Greenland and the sea ice of the Antarctic ice sheet has added to this rise.

Should global warming be contained at 1.5 degrees Celsius, sea level rises would be up to two to three metres. Should projected global warming rise to 5 degrees Celsius, the sea level would rise on average by 20.5 metres by 2100. Much depends on worldwide governments to slow down and eventually cease their emissions of heat warming gases.

Our climates, however, take time to respond to heating and thus sea levels will continue to rise for several thousand years after the cessation of harmful gaseous emissions.

Disappearing islands

Already five Solomon Islands in the Pacific Ocean to the Southeast of Papua New Guinea have been drowned in an area where, in the last 20 years, sea level has increased by 10mm annually. Fortunately, these very small islands of one hectare to five hectares in size were not inhabited. It has been reported that another six islands of the same group have experienced huge chunks of land washed into the sea. Two of the islands saw villages destroyed and their inhabitants forced to relocate to higher ground.

Nuatambu Island in this archipelago was home to 25 families, which has lost 11 houses and half its habitable area since 2011. Relocation planning is a major part of that nation’s annual budget. Australia has set an example to the world by accepting such ‘climate change refugees’.

The Maldives islands in the Indian Ocean contain 1,200 coral islands, housing just over half a million people. Its average elevation is just 45cm above the present sea level and it will lose 77 per cent of its land by 2100. Kiribati, a small Pacific island, again possesses a very low elevation of 1.8 metres above sea level. Should sea level rise by one metre, two thirds of the land area, affecting 120,000 people, will be lost.

In short, nearly all inhabitants of Pacific islands are likely to be affected by rising sea levels for climate change is affecting the strength of sea surges with more destructive waves caused by more typhoons and tropical cyclones heightening the plane of wave attack. To date, 65 million people in East and South Asia are at risk from flooding by the sea, which will worsen in future years. The densely populated coastal areas of Bangladesh, China, India, Indonesia, Japan, Pakistan, the Philippines, and Vietnam are most threatened by 21st century rising seas.

Coastal city threats

Of the 20 cities in the world most likely to suffer from the greatest flood losses, 13 have been identified in Asia. Nine of these are Bangkok, Guangzhou, Ho Chi Minh City, Jakarta, Kolkata, Nagoya, Tianjin, Xiamen, and Zhanjiang. A rise in sea level combined with high tides could see potential flooding on a large scale.

Already several towns in Sabah and Sarawak have suffered the effects of king tides.

Jakarta (population: 10 million people) has been dubbed ‘the fastest sinking city in the world’ and is subsiding at a rate of between 5cm and 10cm a year owing to excessive groundwater drainage. Together with rising sea levels, it faces a major flood disaster.

The Indonesian government has taken a wise decision to relocate its capital to a new site in Kalimantan.

In 76 years’ time, Dhaka, in Bangladesh (22.4 million people), Lagos, Nigeria (15.3 million people), and Bangkok, Thailand (nine million people) could be totally drowned, or have huge swathes of land under water. No coastal place in the world will escape, and 36 of the 50 of the most prone cities to flooding are in the state of Florida, USA.

The two questions to be asked of national and local politicians are ‘what plans are in force to combat rising sea levels’, and ‘what are the plans for the relocation of those most affected’.

Answers to these questions must be at the top of their agendas. One country in the world, the Netherlands, has most of its land below sea level as it is reclaimed land and is certainly investing heavily in coastal defences and has vast coastal barriers already in place. Such plans of any government in power will provide headaches with rising monetary inflation.

Implications of rising sea levels on our societies

Rice farming exists on many river delta floodplains in Asia. Such areas face crop destruction as seawater penetrates the groundwater and seeps inland with the ultimate effect of the abandonment of farms. Farms on the Californian coastline have already experienced the salinisation of their soils.

Crops need to be developed to be more tolerant of salt particles in the soil and no doubt the Rice Institute is ahead of the game in this field. Fishermen may see tidal changes and the migration of shoals of fish from traditional fishing of inshore fishing grounds; thus, affecting their income. Seaside holiday resorts built at or near sea level may collapse owing to a rise in the plane of wave attack and also the erosion and drowning of present-day beaches

What of the future?

There are two old adages that regularly spring to mind in trying to answer this question. The first is, quite literally, ‘time and tide waiteth for no man’, and the second, ‘prevention is better than cure’.

As I stated earlier, cutting greenhouse gas emissions is an enormous step for mankind, but it will not affect the damage already done by the accumulation of such in our atmosphere and seas immediately.

The accumulation of these since the start of the ‘Industrial Revolution’ will take many thousands of years to dissipate and meanwhile sea levels continue to rise. The answer lies in coping with the inevitable by building coastal protection defences in terms of dams, fortifying, and even building sea walls and levees.

Building standards applied to coastal areas need updating to reduce flood damage and storm water valves placed in the outlets of rivers to contain frequent and severe flooding at high tides.

Whilst immediate construction costs in coastal defences may be high the costs of the damages incurred by the intrusion of the sea will prove more expensive in the long run.

However, island developing nations are the ones in our world who most need the greatest help and support from the wealthier nations. Sea level rises are with us now and will continue for many moons well beyond our lifetimes and younger generations.

We need to act now, rather than trying to pick up the bitter consequences of inaction.