The Tribune

By KEILE CAMPBELL

Tribune Staff Reporter

kcampbell@tribunemedia.net

A UNIVERSITY of Miami study found that while rising sea levels have caused significant transformations in inland ecosystems, shorelines on the island of Andros in The Bahamas have remained surprisingly stable, challenging common assumptions about coastal erosion.

According to the study, the rising sea levels have caused dramatic changes to the island’s inland areas, including marshes and mudflats. Bacterial mats have shifted further inland, and tidal channels have grown wider and longer over the decades.

“One of the lessons from what’s happened on Andros is that the effects of sea level rise are not uniform or intuitive,” said University of Miami geologist Sam Purkis, a coauthor of the study. “While shorelines may stay in place, inland areas can expand and change dramatically, even hollowing out islands from within.”

The study relied on a unique set of data to uncover these changes, according to SciTechDaily. A collection of black-and-white aerial photographs taken by the British Royal Navy during World War II was discovered among the papers of late University of Miami geologist Robert Ginsberg in 2017. These photos, combined with modern satellite imagery from Landsat, allowed scientists to track how Andros island’s landscape has evolved over the past eight decades.

“By comparing these historic images to recent satellite data, we could see how much the marshes have shifted and how the tidal channels have grown due to rising sea levels,” Dr Purkis explained.

The data shows a steady rise in sea levels over the decades. Between 1985 and 2018, sea levels around Andros rose by about ten centimeters, aligning with global trends observed since the 1990s. Researchers estimate an average annual rise of 0.18 centimetres since 1950.

“Given the rapid rate of change, we expected to see significant coastal erosion,” Dr Purkis noted. “But instead, the shorelines remained stable, thanks to sediment replenishment in the area.”

While the shorelines showed little change, the study revealed dramatic shifts inland. The researchers observed bacterial mats, particularly Scytonema cyanobacteria, moving more than 200 meters (700 feet) inland in some areas. Tidal channels also widened, lengthened, and proliferated, reshaping the island’s interior.

The study found that hurricanes, despite their intensity, caused minimal lasting damage to the landscape. Andros storms had little effect on the structure of mudflats, marshes, or tidal channels. Instead, the gradual rise in sea levels was identified as the primary driver of significant inland changes.

“The effects of sea level rise are far from uniform,” Dr Purkis said. “Andros shows us that while shorelines may appear stable, the unseen transformations inland can hollow out islands and reshape their entire landscape.”