Author(s): Sanjay Srivastava

Tonga eruption: a reminder of the cascading risks and vulnerabilities of SIDS

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Illustration of Anak Krakatau volcano's eruption, Indonesia.
Dariush M/Shutterstock

On January 14, 2022, the South Pacific experienced the incredible force of the submarine volcano Hunga Tonga–Hunga Haʻapai. The plume reached 30 kilometers into the stratosphere, and the eruption was heard across the South Pacific, Australia, New Zealand as well as in parts of the United States of America. The volcano ranks among the world’s biggest undersea volcanos and the eruption was comparable to that of Mount Pinatubo in the Philippines in 1991, which caused several hundred fatalities.

The volcano in Tonga created a powerful shock wave and displaced huge amounts of water, triggering a far-flung tsunami that raced across the vast Pacific Ocean and reached as far as the coasts of Japan and the Americas. As of 26 January, three deaths have been confirmed in Tonga, while many people remain missing. Some of the most exposed people are those on smaller islands hard-hit by the eruption and the tsunami. Many islands were covered by volcanic dust and ash, which raises concerns of air, water and food pollution. Tonga’s undersea cable – its main connection to the Internet - was also disrupted, and the country was faced with ‘digital darkness’.

The eruption in Tonga is illustrative of a cascading risks scenario where one disaster triggered another, exposing and exacerbating multiple critical vulnerabilities. The following key lessons present a way forward on building a resilient future for small island developing States (SIDS).

Understanding the science of cascading risk

For a cascading risk of this magnitude on a tiny island in the vast South Pacific basin, earth observation satellites are the only means to collect data and develop scenarios. The Himawari-8 satellite showed the rapid expansion of a volcanic cloud following the explosive eruption. It captured an abrupt shock wave that propagated radially outward in all directions. The Geostationary Operational Environmental Satellite 17  captured the images of a vast plume of material that created what volcanologists call an ‘umbrella cloud’. Powerful waves ringing through the atmosphere after the eruption were unlike anything ever seen before as satellite data showed that the volcano provoked an unusual pattern of atmospheric gravity waves. Information and knowledge acquired from multiple earth observation satellites helped understand the science of cascading risk.

Early warning for volcanoes and tsunamis

On genesis of a volcano, it can be noted that the magma inside is under enormous pressure from gases trapped within. A fracture in the rock allows the gases to expand and blast the magma, releasing huge energy through a volcanic eruption. The understanding of this scientific background resulted in the development of volcano early warning systems. Field reports highlight that at-risk communities in Tonga were warned about the increased activity at the volcano a day before the eruption and also about the incredibly loud bang when it erupted. These warnings allowed many people to scramble to higher grounds in time.

Further, the underwater volcano off Tonga also triggered tsunami warnings and evacuation orders in several South Pacific islands as well as in Australia, Japan, New Zealand and the United States . Japan's meteorological agency issued tsunami warnings in the Amami islands in the south, where waves of more than a metre were recorded. Tsunami waves also hit the capitals of Tonga and American Samoa. Fiji also issued a tsunami warning, whereas a tsunami advisory was in effect for the US’ and Canadian Pacific coasts and high waves were reported in Alaska and Hawaii earlier.

Real-time impact mapping

The recent advances in geospatial and earth observation systems in conjunction with drones, connected devices data, internet of things (IoT) and social media have been extensively used for impact assessment of the Tonga volcano eruption and tsunami. Enabled through cloud computing and big data analytics techniques, these technologies provided near real time impact mapping and risk visualization. For example, Maxar Technologies used artificial intelligence to integrate satellite imagery and data with other forms of data (for example, social media sentinel data or drone footage). It enabled them to capture the real time spectacular eruption, with the plume of ash, steam and gas rising like a giant mushroom above the South Pacific. ESCAP contacted space faring countries of its Regional Space Applications Program for satellite imagery while the United Nations Satellite Centre activated its Emergency Mapping service. Its first analyses published on 18 January 2022 highlighted the damages to roads and buildings on nearby inhabited islands and provided before-and-after images of the volcano. The real and near real time impact mapping helped more effective and targeted emergency responses and guided the post-disaster recovery and reconstruction.

‘Digital darkness’

Tonga gained connectivity to the global submarine telecommunication network in the last decade.  Volcanic processes (such as the tsunami, submarine landslide or other underwater currents) have now snapped the fibre-optic cable that connects Tonga to the rest of the world. Consequently, the country is now facing weeks of digital darkness as a repair ship prepares to make its way from Papua New Guinea.

Key takeaways

The ESCAP Risk and Resilience portal estimates that across the Asia-Pacific region, the Pacific SIDS stand out with some of the highest disaster losses as percentage of their GDP. The estimated cost of adaptation is also the highest for the SIDS. As a share of GDP, the adaptation cost is recorded at 9.1 per cent in Vanuatu and 7.4 per cent in Tonga.

The adaptation priorities for Tonga include protecting mangroves, improving dryland agriculture crop production, resilient water resource management as well as strengthening early warning systems and making new infrastructure resilient. Ground reports from Tonga highlight that reefs, lagoons and other natural features have protected parts of Tonga, while amplifying the waves in certain areas.

International and regional cooperation in science-based risk assessment and early warning, as seen in case of the Tonga eruption, is a welcome trend. Moreover, early warning systems can be well complemented by nature-based solutions.

Finally, resilient ICT infrastructure is a crucial need for addressing the Pacific’s critical vulnerability. Here, the ESCAP initiative on e-resilience can help address the vulnerability of ICT systems. The launch of the Infrastructure for Resilient Island States (IRIS) initiative at COP 26 in November 2021, in the presence of Heads of Governments from Australia, Fiji, India, Jamaica, Mauritius and the United Kingdom, signals an encouraging trend to facilitate building resilience in the region.

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Hazards Volcano
Country and region Tonga
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