A year after the volcanic explosion, many of Tonga’s reefs lay dormant

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

When Hunga-Tonga-Hunga went off Ha’apai, it sent a shock wave around the world, producing a plume of water and ash that soared higher in the atmosphere than any other on record, and caused tsunami waves that ricocheted over the region – slamming into the archipelago that lies southeast of Fiji.

Coral reefs turned to rubble and many fish perished or moved away.

The result has left Tongans struggling, with more than 80% of Tongan families relying on subsistence reef fish, according to 2019 data from the World Bank. After the eruption, the Tongan government said it would seek $240 million for recovery, including improving food security. In the immediate aftermath, the World Bank provided $8 million.

“As far as the recovery plan is concerned, we are waiting for funds to cover the expenses related to small-scale fishing along coastal communities,” said Poasi Ngaluafe, head of the scientific division of Tonga’s Ministry of Fisheries.

QUIET RIFTS

The vast majority of Tongan territory is oceanic, with its exclusive economic zone extending over nearly 700,000 square kilometers (270,271 sq mi) of water. Although commercial fishing contributes only 2.3% to the national economy, subsistence fishing is considered crucial to form a staple of the Tongan diet.

The UN’s Food and Agriculture Organization estimated in a November report that the eruption cost the country’s fishing and aquaculture sector some $7.4 million — a significant amount to Tonga’s economy of about $500 million. The losses were largely due to damaged fishing vessels, with nearly half of that damage in the small-scale fishing sector, although some commercial vessels were also affected.

Because 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, in addition to some fish stocks likely to be depleted, there are other worrying signs that suggest fisheries may take a long time to recover.

Young corals fail to mature in the coastal waters around the eruption site, and many areas that once hosted healthy and abundant reefs are now barren, according to the government’s survey in August.

It is likely that volcanic ash has smothered many reefs, depriving fish of foraging and spawning grounds. The investigation found that no marine life had survived near the volcano.

Meanwhile, the tsunami that swelled in the waters around the archipelago knocked over large boulders, creating fields of coral rubble. And while some reefs survived, the crackling, snapping and popping sounds of foraging shrimp and fish, a sign of a healthy environment, were gone.

“The reefs in Tonga were quiet,” the research report said.

AGRICULTURE RULES

Agriculture has proven to be a lifeline for Tongans faced with empty waters and damaged boats. Despite concerns that the volcanic ash, which covered 99% of the country, would make the soil 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 testing showed that the fallen ash was not harmful to humans. And while yam and sweet potato plants perished in the eruption, and fruit trees were burned by falling ash, they began to recover once the ash washed away.

“We have supported recovery efforts through land preparation and the planting of backyard gardening and root crops on the farms, as well as export crops such as watermelon and squash,” Halavatu told Reuters.

But long-term monitoring will be critical, he said, and Tonga hopes to develop a national soil strategy and upgrade their soil research lab to help farmers.

HEAVEN WATER

Scientists are now also taking stock of the impact of the eruption on the atmosphere. While volcanic eruptions on land mainly emit ash and sulfur dioxide, underwater volcanoes throw much more water overboard.

The Tonga eruption was no different, with the blast’s whitish-gray plume reaching 57 kilometers (35.4 miles) and injecting 146 million tons of water into the atmosphere.

Water vapor can linger in the atmosphere for up to ten years, trapping heat on the Earth’s surface and leading to more global warming. More atmospheric water vapor can also help break down ozone, which protects the planet from harmful UV rays.

“That one volcano increased the total amount of global water in the stratosphere by 10 percent,” said Paul Newman, chief scientist for earth sciences at NASA’s Goddard Space Flight Center. “We’re just now starting to see the impact of that.”

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

Our Standards: The Thomson Reuters Principles of Trust.

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