More than half of the world's coastal settlements are retreating inland to avoid rising sea levels, study finds

Having a house on the coast used to be a sign of wealth and status.

But a new study suggests it could now be a sign of foolhardiness. 

Scientists say that coastal properties around the world are vulnerable to flooding – and it seems people are finally realising the risk. 

The researchers found more than half of the world's coastal settlements are retreating inland to avoid dangers such as storms, erosion and sea-level rise.

However, the poorest regions are being forced to stay put or even move closer to danger. 

Professor Xiaoming Wang, lead study author at Monash University in Australia, said people now 'face increasingly severe risk in a changing climate'. 

'For the first time, we've mapped how human settlements are relocating from coasts around the world,' he said. 

'It's clear that moving inland is happening – but only where people have the means to do so.' 

Previous studies have shown that global warming is causing glaciers and ice sheets worldwide to melt, adding more water to the ocean. 

What's more, the volume of the ocean is expanding as the water warms – further raising the global average sea level. 

Coastal communities are of course not the only ones threatened by rising sea levels, as scientists think settlements further inland could go underwater in future too, but when seawater encroaches the land, coastal communities are first to feel the effects.

Scientists also think global warming is causing more extreme weather, which is generally more dramatic nearer the coast, while coastal erosion means coastal properties can suddenly drop into the sea. 

Although these factors have been known about for decades, researchers wanted to investigate if they've had an effect on the global public's habitation patterns.  

The team, based in China, Indonesia and Denmark, analysed nearly three decades (1992–2019) of satellite nighttime light data across 1,071 coastal regions in 155 countries.

The light data acted as a fingerprint of settlement patterns – so not necessarily the location of cities and towns, but the whereabouts of human habitation.

This is a subtle difference, because more humans could be living in new buildings further from the coast, while towns and cities, although still in existence, could be emptier. 

Overall, human settlements in 56 per cent of the regions analysed relocated further inland, 28 per cent stayed put and 16 per cent moved closer to the coast, the researchers found. 

Human settlements shifted most towards coastlines in South America (up to 17.7 per cent) and Asia (17.4 per cent), followed by Europe (14.8 per cent), Oceania (13.8 per cent), Africa (12.4 per cent) and North America (8.8 per cent).

Oceania had some of the closest settlements to the coast globally, reflecting the region's reliance on coastal economies.

In Australia, for example, the vast majority of major cities were founded close to water, away from the arid desert landscape at the centre. 

Taking into account various global locations, researchers also concluded that the poorest groups are more likely to move closer to, rather than further from, the coast.

This is being driven largely by the growth of informal settlements clustered around the coast and the search for better livelihoods – such as job opportunities like fishing and shipping.  

High-income groups also showed a high likelihood to remain on coastlines, such as in Europe and North America, due to wealth accumulated in coastal areas, Wang said.

But equally, such wealth would give people the opportunity to move away from the coast under the threat of danger – a luxury poorer groups will not have.  

The team also share concerns that overconfidence in protective infrastructure has encouraged risky development close to the coast. 

Such infrastructure can range from sandbags and seawalls, to more advanced projects like the Thames Barrier in London. 

The study, published in Nature Climate Change, shows that retreating from coastlines is a real human response to the increasing threats posed by coastal climate hazards. 

And according to Professor Wang, it'll increasingly become necessarily in the years to come.

'Relocating away from the coast must be part of a long-term climate strategy,' he said. 

'The rationale for policy and planning to relocate people requires meticulous consideration of both economic and social implications across individuals, communities and regions.

'Alongside climate change mitigation, it needs to be combined with efforts to reduce coastal hazard exposure and vulnerability, improve informal settlements, balance coastal risks with livelihoods and maintain sustainable lifestyles in the long-term.

'Without this, coastal adaptation gaps will continue to be widened and leave the world's poorest behind.'