One year after volcanic blast, many of Tonga’s reefs lay silent

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

When Hunga-Tonga-Hunga Ha’apai set off, it sent a shockwave around the world, produced a plume of water and ash that rose higher into the atmosphere than any in history, and sent tsunami waves ricocheting across the region – crashing into the archipelago that lies southeast of Fiji.

Coral reefs were reduced to rubble and many fish disappeared or migrated.

The result has hurt Tongans, with more than 80% of Tongan households relying on reef fishing, according to 2019 data from the World Bank. After the outbreak, the Tongan government said it would seek $240 million for recovery, including improving food security. Shortly thereafter, the World Bank provided $8 million.

“In terms of the recovery plan … we are awaiting funding to cover the costs associated with small-scale fishing along the coastal communities,” said Poasi Ngaluafe, head of Tonga’s Fisheries Ministry’s science division.

SILENT SIGNS

The vast majority of Tongan’s territory is ocean, with its exclusive economic zone spanning about 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 crucial in creating a staple of the Tongan diet.

The U.N.’s Food and Agriculture Organization estimated in a November report that the outbreak cost the country’s fisheries and aquaculture sector about $7.4 million — a significant figure for Tonga’s roughly $500 million economy. Losses were mainly due to damaged fishing vessels, with almost half of this 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 assess the impact of the outbreak on fish harvests.

But scientists say that, in addition to some fish stocks likely to be depleted, there are other worrying signs that suggest it may take a long time for the fishery to recover.

Young corals are failing to mature in the coastal waters around the eruption site, and many areas once home to healthy and abundant reefs are now barren, according to a government survey in August.

Volcanic ash likely drowned many reefs, depriving fish of feeding grounds and spawning beds. The survey found that no marine life had survived near the volcano.

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

“Reefs in Tonga were silent,” the survey report found.

AGRICULTURAL PRIVATE LIMITED

Farming has proved 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 at name of the Tongan government.

Soil tests revealed that the fallen ash was not harmful to humans. And while candy and sweet potato plants were destroyed in the eruption and fruit trees were burned by falling ash, they began to recover after the ash washed away.

“We have supported recovery works through land preparation and planting backyard gardening and root crops on farms, as well as exporting crops such as watermelon and pumpkin,” Halavatu told Reuters.

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

HEAVENLY WATER

Scientists are also assessing the impact of the explosion on the atmosphere. While volcanic eruptions on land release mostly ash and sulfur dioxide, underwater volcanoes spew much more water.

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

Water vapor can stay in the atmosphere for up to a decade, trapping heat at the Earth’s surface and leading to more general warming. More atmospheric water vapor can also help deplete ozone, which protects the planet from harmful UV radiation.

“That one volcano increased the total amount of global water in the stratosphere by 10 percent,” said Paul Newman, principal 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; Editing by Katy Daigle and Tomasz Janowski

Our Standards: The Thomson Reuters Trust Principles.