Scientists believe that Tonga’s volcanic explosion could have long-term effects on the environment.

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Tongas massive underwater volcanic eruption https://www.reuters.com/business/environment/impact-assessment-aid-efforts-underway-world-responds-tonga-tsunami-2022-01-16 could deliver long-lasting damage to coral reefs, erode 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 eruption, the volcano has been emitting sulfur dioxide and nitrogen oxide. These gases are acid rain-causing compounds that react with water and oxygen in their atmosphere.

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Tongas’ tropical climate means that acid rain will likely be around Tonga for some time, according to Shane Cronin, University of Auckland volcanologist.

Acid rain can cause extensive crop damage and could destroy Tongan staples like corn, bananas, taro and garden vegetables. Cronin stated that food security could be compromised depending on how long the eruptions continue.

Satellite imagery shows that the plume is spreading westward. This means that Tonga may be spared some of the acid rain, but Fiji could be in its path.

Monday’s bulletin from the U.N. humanitarian Affairs office stated that Fiji was monitoring air quality and has advised residents to cover their tanks and stay indoors if it rains.

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FISH DIE OFFS

Tongas’ exclusive economic zone, which covers nearly 700,000 square kilometers (270.271 square miles) of ocean, is 1,000 times greater than its land area. Tongans depend on the ocean for their food and livelihood.

Marco Brenna, a geologist at Otago University in New Zealand, stated that scientists have yet to investigate the ground but that the few photos available seem to show a blanket of Ash on the land.

This ash can cause damage to marine life in the ocean. Weeks before Saturdays eruption, Tonga Geological Services had warned https://matangitonga.to/2022/01/04/toxic-seawater-at-hunga-volcano-may-poison-fish that nearby seawater was contaminated with toxic volcanic discharge, and that fishermen should assume fish in these waters are poisoned or poisonous.

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The eruption made matters worse. The volcano’s ash-rich water will contaminate the river and kill fish. Scientists predicted that some fish may die, while others will migrate. Fishing vessels could face new challenges if the seafloor structure changes.

Brenna said that it will be some time before the same or even new fishing grounds can be restored.

SMOTHERED CORALS

Falling ash can also cause coral reefs to be destroyed. Tonga’s mainstay tourism industry brought in as much as $5 million annually prior to the coronavirus pandemic.

Tongas reefs were already under threat from disease outbreaks and climate changes, such as coral bleaching or stronger cyclones.

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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, said Tom Schils, a marine biologist at the University of Guam who has studied https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0046639 volcanic eruptions and corals in the Northern Mariana Islands.

Additionally, such eruptions can release more iron into the seawater, which can encourage the growth and development of blue-green algae as well as sponges that further degrade the reefs.

Brian Zgliczynski at Scripps Institution of Oceanography, a coral reef ecologist, said that the process of rebuilding reefs could take many years. He stated that species more tolerant of low water quality will be first to arrive, while hard corals, fish, and other hard corals will take longer to return.

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ERODED COASTLINES

Tongas’ ability to withstand rising waters and storm surges would be affected if coral reefs are lost. This is a concern in Tonga where climate change is driving sea level rise by 6 millimeters (0.2 inch) per year, twice the global average.

In a 2015 report https://www.researchgate.net/profile/Leanne-Fernandes/publication/317341776_National_marine_ecosystem_service_valuation_summary_Tonga/links/5bbe5828299bf1010178adac/National-marine-ecosystem-service-valuation-summary-Tonga.pdf, Tonga valued its natural storm buffers including coral reefs as well as coastal seagrasses and mangroves at some $11 million annually.

Tongan’s sea level gauge recorded the tsunami wave at 1.19 meters (nearly 4″) during the latest eruption. The gauge stopped reporting after it stopped reporting. Tsunamis can cause coastal erosion. Videos showed damage to man-made seawalls before the internet was down.

Cronin stated that tsunami waves could make coastal defenses and reclaimed ground more vulnerable.

(Reporting by Gloria Dickie, Editing by Katy Daigle & Howard Goller).