From the Sydney Opera House to Rapa Nui: A New Map Shows Where Rising Seas Could Strike

The Sydney Opera House, the stone figures of Rapa Nui and coastal sections of the Great Wall of China share an uncomfortable fact: their relationship with the sea is changing. A new global dataset finally gives researchers precise digital boundaries for studying that exposure at scale.

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The database contains 1,250 individual heritage locations covering more than 235 million hectares.

The missing layer in climate-risk maps

Climate models can estimate where water may rise or storms may push inland, but those forecasts are useful only when the location and shape of what needs protection are known. For many World Heritage properties, researchers lacked consistent digital boundaries detailed enough for global comparison.

The Global Coastal Heritage Mapping Project, known as Glo-CoH, addresses that gap. Researchers from the University of East Anglia, Durham University and the University of Cape Town combined UNESCO site plans with satellite imagery to trace the boundaries of low-lying coastal properties.

The resulting study was published in Scientific Data on July 24, 2026. It covers cultural, natural and mixed heritage locations, ranging from individual monuments to large landscapes and ecosystems.

How researchers built the map

The team began with World Heritage records and identified properties situated along coastlines below 20 metres in elevation. Human digitisers then compared official plans with Google Earth imagery and converted the visible boundaries into geographic data that modelling software can use.

This is more demanding than dropping a pin on a famous building. A World Heritage property may include several separated zones, wide coastal habitats or a historic city with a protected buffer. Flood models need polygons that show the area, not just coordinates naming the place.

Each result was checked for the quality of its source material, the confidence of site identification and the precision of digitisation. According to the researchers, 92% of locations received scores representing the highest accuracy category.

What the map can reveal

Managers can overlay the boundaries with projections for sea-level rise, storm surge, wave exposure or coastal erosion. That can reveal which parts of a property may require closer monitoring, better drainage, a protective barrier or an emergency plan.

The dataset includes locations associated with the Sydney Opera House, Rapa Nui's Moai, coastal parts of the Great Wall and much of St Petersburg. It also covers natural areas where the threatened asset may be a coral reef, mangrove, rare species habitat or geological formation.

The team is already using Glo-CoH for global studies of sea-level risk and climate exposure affecting corals and mangroves. Because the data is public, other researchers can test different hazard models rather than rebuilding the heritage map from scratch.

Why mapping is an intervention

A digital boundary does not stop a flood, but it can change where limited protection money goes. Authorities can compare exposure across sites, identify missing local measurements and plan adaptations before damage becomes visible.

The work may also improve accountability. If governments, insurers and conservation groups use a common spatial reference, they can discuss the same property and measure how its condition changes over time.

What happens next

The planned update will add recently listed properties and correct boundaries as improved records become available. Researchers can then combine the map with higher-resolution terrain, ocean and storm data to produce site-specific risk assessments.

Not every mapped landmark will be lost, and a coloured polygon should not become a headline predicting disaster. The value of Glo-CoH is more practical: before the world can protect its shared coastal heritage, it must know exactly where that heritage begins and where the water may meet it.