Two dead, Tongans told to stay indoors to avoid inhaling volcanic ash, as scientists warn of ongoing environmental devastation

Two people are dead and Tonga’s government is advising the public to remain indoors after the eruption of the Hunga Tonga Hunga Ha’apai volcano, the World Health Organization (WHO) says.

Key points:
Scientists say volcanic ash raises concerns about air pollution and contamination of food and water
They say ash could devastate foods sources and the environment for years
The WHO says more than 100 homes have been damaged and 50 destroyed
Around 2 centimetres of volcanic ash and dust has fallen on Tongatapu -Tonga’s main island- since Saturday’s eruption, which triggered tsunami warnings across the Pacific Ocean.

Ash in the air and on the ground has raised concerns about air pollution and the potential contamination of food and water supplies, the WHO said.

Locals have been advised to drink bottled water and wear masks outdoors to avoid breathing in the ash.

Satellite images of homes in Tonga before the volcano. One is clear and the other is blackened with volcanic ash.
The WHO says more than 100 homes were damaged and 50 others destroyed. (Supplied: Satellite image/©2022 Maxar Technologies)
“Thankfully, all health facilities on Tongatapu are fully functioning and clean-up efforts have been initiated,” the WHO said.

Why was the Tonga eruption so big?
Tonga tsunami
The volcanic eruption in Tonga on Saturday was massive. Here’s what we know about why it was so big, whether it’s going to erupt again soon, and if there are others we should be keeping an eye on.

It said initial reports were that around 100 houses had been damaged and 50 completely destroyed on Tongatapu.

“Many [Tongans] remain displaced, with 89 people taking shelter in evacuation centres on the island of ‘Eua and many more seeking shelter with relatives,” the WHO said.

“The Ha’apai and Vava’u island groups … remain out of contact with the capital [Nuku’alofa].”

There were particular concerns about the smaller and low-lying islands of Mango and Fonoi in the Ha’apai group, the WHO said.

Volcanic ash could ‘could deliver long-lasting damage’
Scientists have warned that volcanic ash could deliver long-lasting damage to coral reefs, erode coastlines and disrupt fisheries.

How the volcanic eruption near Tonga unfolded
Smoke on Tonga
Satellite imagery and social media posts capture the moments the underwater volcano off the coast of Tonga erupted, causing shock waves felt worldwide.

Since the initial eruption, the volcano has been releasing sulfur dioxide and nitrogen oxide – two gases that create acid rain when they interact with water and oxygen in the atmosphere.

With Tonga’s tropical climate, “there is likely to be acid rain around Tonga for a while to come”, according to volcanologist Shane Cronin from the University of Auckland.

Acid rain causes widespread crop damage, and could ruin Tongan staples such as taro, corn, bananas and garden vegetables.

“Depending on how long the eruptions last, food security could be compromised,” Professor Cronin said.

A satellite image of the Hunga Tonga Hunga Ha’apai volcano that shows plumes of volcanic ash.
Scientists warn the volcanic ash could devastate the natural environment for years to come.(Supplied: Satellite image/©2022 Maxar Technologies)
Satellite imagery shows the plume from the volcano spreading westward, which means Tonga could be spared some of this acid rain, although Fiji could then be in its path.

In a bulletin on Monday, the UN humanitarian affairs office said Fiji was monitoring its air quality, and had advised people to cover their household water tanks and stay indoors in the event of rain.

Tonga’s exclusive economic zone of nearly 700,000 marine square kilometres is 1,000 times larger than its land area.

And most Tongans get their food – and livelihood – from the ocean.

While scientists have yet to investigate on the ground, “the few pictures that are available seem to show a blanket … of ash” on land, according to Marco Brenna, a geologist from the University of Otago in New Zealand.

Marine life could be ‘poisonous or poisoned’
In the ocean, that ash can be harmful to marine life.

Weeks before Saturday’s eruption, Tonga Geological Services had warned that nearby seawater was contaminated with toxic volcanic discharge, and that fishermen should “assume fish in these waters are poisoned or poisonous”.

Inevitably, the weekend’s huge eruption has made the situation worse.

Murky, ash-filled water near the volcano will deprive fish of food and wipe out spawning beds.

Some fish will perish, and survivors will be forced to migrate, scientists said.

Further, changes in the structure of the sea floor could create new obstacles for fishing vessels.

“It will be a while before the same or new fishing grounds will be restored,” Dr Brenna said.

Coral ‘buried and smothered’ by ash
Falling ash can also smother coral reefs that, in Tonga, are the mainstay of a tourism industry that brought in up to $5 million per year before the COVID-19 pandemic.

Even before the eruption, Tonga’s reefs were threatened by disease outbreaks and the effects of climate change, including coral bleaching and increasingly strong cyclones.

Now, “vast areas of the reefs in the immediate impact area at Hunga Tonga are probably buried and smothered by large deposits of volcanic ash”, according to Tom Schils, a marine biologist from the University of Guam who has studied volcanic eruptions and corals in the Northern Mariana Islands.

Such eruptions also release more iron into the water, which can boost the growth of blue-green algae and sponges, which further degrade reefs.

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Reefs might have to begin again – a procedure that may take years, based on John Zgliczynski, a barrier reef ecologist in the Scripps Institution of Oceanography.

“Species more loving toward poor water quality will arrive first,” Dr Zgliczynski stated.

Meanwhile, hard corals and fish would take more time to come back, he added.

A loss of revenue of barrier reefs would also affect Tonga’s ability to handle rising waters and storm surges.

This can be a concern for Tonga, where global warming is driving the ocean level to increase by about 6 millimetres each year, double the amount global average.

Inside a 2015 report, Tonga valued its natural storm buffers – including barrier reefs in addition to seaside seagrasses and mangroves – at some $11 million yearly.

Using the latest eruption, a Tongan ocean-level gauge recorded a tsunami wave of just one.19 metres before it stopped reporting.

Tsunamis are recognized to cause rapid seaside erosion.And before communication systems went down, videos revealed damage to man-made seawalls.

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