Infrastructure development pushing islands to ‘tipping point’

Human-driven pressures on island-reef systems is pushing a majority of Maldives islands to a threshold beyond which it cannot naturally adapt to climate risks such as sea-level rise, scientists have found.

According to findings published on Nature, researchers Virginie K. E . Duvat and Alexandre K. Magnan concluded that “20.1% of inhabited and exploited islands (eg: resorts, airport islands) have already reached a tipping point and that 46.2% may reach it over the coming decade(s).”

The pair conducted fieldwork and studied a sample of 608 Maldivian islands from 23 natural atolls, comparing high-resolution satellite images between 2006 and 2016.  They studied disturbances caused to coral reefs – which form the bedrock of Maldivian islands – and shorelines due to expansion by reclamation as well as harbour construction and reef dredging.

“This study constitutes the first detailed, nationwide assessment of human-driven undermining of the coastal protection services provided by the reef ecosystem to island communities,” the paper noted. “It confirms that over the last decade, human activities have been a major driver of reef-island morphological change.”

Islands were classified into five categories (T1 to T5) based on shoreline and reef disturbances to show how many were close to reaching a critical threshold beyond which natural coastal protection services were irreversible. 

Protection provided by the reef ecosystem – wave energy attenuation and sediment provision – are “absolutely essential for risk reduction and to the persistence of these islands and of the whole country over time,” the researchers warned.

“Anthropogenic tipping point”

According to the results, only 12% of inhabited and exploited islands preserved natural defences and 16.7 % of these islands have suffered limited undermining whilst 46.2% of islands suffered a “partial but significant” undermining of coastal protection services.

In 20.1 % of cases where defences were “highly or very highly” undermined, the islands have either “entirely or almost entirely” lost their natural capacity to respond and adjust to ocean climate-related pressures.

“The fact that 20.1% of inhabited and exploited islands (T4, T5) have already reached this tipping point and that 46.2% (T3) of these islands may, in regard to their trajectory of change, reach it over the coming decade(s), raises serious concerns in the context of sea-level rise and increased flooding events,” the paper observed.

Artificial armouring was the only solution to maintain these islands in the face of sea-level rise, researchers concluded. “Yet, there is high uncertainty on the future habitability of such armoured islands, which would lie below sea level and therefore likely lose not only their freshwater underground supply but also all cultivable land, due to saltwater intrusion,” they added.

Climate adaptation strategies

Researchers advised that the degree of human disturbance needed to be taken into account in climate adaptation strategies. 

Islands which still have natural capacity to adjust should make it a priority to preserve and sustain the natural protection services, they said. Islands that have surpassed the tipping point meanwhile require hard-engineered measures and adequately designed and calibrated protections without further delay.

But in 2019 alone, the Maldives government announced plans to reclaim 17 islands and kicked off projects to either build, design or extend approximately 50 harbours.

In May, the Maldives was classified at the ‘warning’ alert level by a satellite monitoring programme of the United States National Oceanic and Atmospheric Administration. The local Marine Research Centre at the time advised the government to suspend projects that affect the health of reef ecosystems, such as dredging, land reclamation and beach nourishment projects.

While coral reefs in the Maldives recovered relatively quickly after mass bleaching events, the MRC said stressors that damage reefs could slow the rate of regeneration.