Here’s how Tonga’s volcanic eruption could damage the environment for years

Tonga’s massive underwater volcanic eruption could cause long-term damage to coral reefs, destroy coastlines and disrupt fisheries, say scientists studying satellite images and Looking to the past to project the future of the remote region

Acid rain

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

With Tonga’s tropical climate, “acid rain is likely to occur around Tonga for some time to come,” said volcanologist Shane Cronin at the University of Auckland.

Acid rain causes widespread crop damage and can ruin Tongan staples such as taro, corn, bananas and garden vegetables. “Depending on how long the eruption lasts, food security could be compromised,” Cronin said.

Satellite imagery shows the plume spreading westward, meaning Tonga may be shielded from some of this acid rain, although Fiji may be on its way.

The United Nations Office for Humanitarian Affairs said in a bulletin on Monday that Fiji was monitoring its air quality, and advised people to cover their domestic water tanks and stay indoors in case of rain. .

Fish die-off

Tonga’s exclusive economic zone of approximately 700,000 nautical square kilometers (270,271 sq mi) is 1,000 times larger than its land area. And most Tongans get their food – and livelihood – from the sea.

While scientists have yet to investigate on the ground, “the few pictures that are available show what looks like a blanket of ash on the ground”, said geologist Marco Brenna of the University of Otago in New Zealand.

That ash in the ocean can be harmful to marine life. Weeks before Saturday’s eruption, Tonga Geological Services warned that nearby seawater was contaminated by toxic volcanic discharge, and that fishermen “should assume that the fish in these waters are poisonous or poisonous.”

Obviously, the explosion has made the situation worse. Murky, ash-laden waters near the volcano will deprive fish of food and wipe out spawning beds. Scientists said some of the fish would perish and the survivors would be forced to flee. Further changes in the composition of the ocean floor could create new obstacles for fishing vessels.

“It will take some time to restore the same or new fishing grounds,” Brenna said.

Repressed corals

Falling reefs can also disturb coral reefs, a mainstay of a tourism industry in Tonga that brought in up to $5 million per year before the coronavirus 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, “huge areas of rock in the immediate impact zone in Hunga Tonga are buried and disturbed by large deposits of volcanic ash,” said Tom Shils, a marine biologist at the University of Guam who studied volcanic eruptions and corals. The Northern Mariana Islands.

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

Reefs may have to start over again — a process that can take years, said Brian Zaglizinski, a coral reef ecologist at the Scripps Institution of Oceanography. “Species more tolerant of poor water quality will come first,” while hardy corals and fish will take longer to return, he said.

Cut coast

The loss of coral reefs will also affect Tonga’s ability to cope with rising waters and storm surges. This is a concern for Tonga, where climate change is causing sea levels to rise by about 6 millimeters (0.2 inches) per year – more than twice the global average.

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