A year after the volcanic explosion, many reefs in Tonga have gone silent

Jan 15 (Reuters) – A year after a massive underwater volcano erupted in the South Pacific, the island nation of Tonga is still dealing with damage to its coastal waters.

When Hunga-Tonga-Hunga Ha’apai erupted, it sent shockwaves around the world, produced a plume of water and ash that soared higher into the atmosphere than any other ever. recorded, and set off tsunami waves that ricocheted around the region – slamming into the archipelago that lies southeast of Fiji.

Coral reefs were turned to rubble and many fish perished or migrated.

The result is hardship for Tongans, with more than 80% of Tongan families relying on subsistence reef fishing, according to 2019 World Bank data. Following the eruption, the Tongan government said it would request $240 million for recovery, including improved food security. Immediately afterwards, the World Bank provided $8 million.

“In terms of the recovery plan…we are expecting funds to cover expenses related to small-scale fishing along coastal communities,” said Poasi Ngaluafe, head of the science division of Tonga’s Department of Fisheries.

SILENT REEFS

The vast majority of Tonga’s territory is oceanic, with its Exclusive Economic Zone spanning almost 700,000 square kilometers (270,271 sq mi) of water. While commercial fishing contributes only 2.3% to the national economy, subsistence fishing is considered essential to constitute a staple of the Tongan diet.

The Food and Agriculture Organization of the United Nations estimated in a November report that the eruption cost the country’s fisheries and aquaculture sector some $7.4 million – a significant figure for the economy of about 500 million Tonga dollars. Losses were largely due to damaged fishing vessels, with almost half of this damage in the small-scale fishing sector, although some commercial vessels were also affected.

Since the Tongan government does not closely monitor subsistence fishing, it is difficult to estimate the impact of the eruption on fish harvests.

But scientists say that, apart from the likely depletion of some fish stocks, there are other worrying signs that suggest the recovery of fisheries could take a long time.

Young corals are failing to mature in the coastal waters around the site of the eruption, and many areas that once had healthy and abundant reefs are now barren, according to the government investigation in August.

It is likely that volcanic ash smothered many reefs, depriving fish of feeding and spawning grounds. Investigation revealed that no marine life survived near the volcano.

Meanwhile, the tsunami that swelled in the waters around the archipelago toppled large rocky corals, creating fields of coral rubble. And while some reefs have survived, the crackling, snapping, and slapping sounds of shrimp and fish searching for food, a sign of a healthy environment, have disappeared.

“Tonga’s reefs were silent,” the survey report revealed.

AGRICULTURAL SURPRISE

Agriculture has proven a lifeline for Tongans faced with empty waters and damaged boats. Despite concerns that volcanic ash, which covered 99% of the country, would make soils too toxic to grow crops, “food production has resumed with little impact,” said Siosiua Halavatu, a soil scientist speaking on behalf of the Tongan government.

Soil analyzes revealed that the fallen ashes were not harmful to humans. And while yam and sweet potato plants perished during the eruption and fruit trees were scorched by the falling ash, they began to recover once the ash washed away.

“We supported recovery work through land preparation and planting vegetable and root gardens on farms, as well as export crops like watermelon and squash,” Halavatu told Reuters.

But long-term monitoring will be essential, he said, and Tonga hopes to develop a national soil strategy and upgrade its soil testing laboratory to help farmers.

WATER FROM THE SKY

Scientists are also taking stock of the impact of the eruption on the atmosphere. While volcanic eruptions on land primarily eject ash and sulfur dioxide, submarine volcanoes eject much more water.

Tonga’s eruption was no different, with the white-gray plume from the blast reaching 57 kilometers (35.4 miles) and pumping 146 million tonnes of water into the atmosphere.

Water vapor can persist in the atmosphere for up to a decade, trapping heat on the Earth’s surface and driving further global warming. More atmospheric water vapor can also contribute to ozone depletion, which protects the planet from harmful UV rays.

“This volcano has increased the total amount of water in the stratosphere by 10%,” said Paul Newman, chief scientist for Earth Sciences at NASA’s Goddard Space Flight Center. “We’re only starting to see the impact of that.”

Reporting by Gloria Dickie in London; Additional reporting by Kirsty Needham; Editing by Katy Daigle and Tomasz Janowski

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