Researchers who examined Maui’s nearshore waters in a study of changing sea depths discovered a remarkable amount of seafloor and coral reef erosion — enough sand, rock and other material over nearly four decades to fill up the Empire State Building 81 times.

The finding by a team of U.S. Geological Service scientists is part of a study published last week in the journal Biogeosciences. The study examined five large coral reef tracts in Florida, the U.S. Virgin Islands and Maui.

Each of the study areas was found to be experiencing seafloor erosion, increasing water depths and coral reefs unable to keep pace with sea level rise.

“The magnitude of the seafloor loss was surprising,” said Kimberly Yates, the lead author and a biogeochemist at the St. Petersburg Coastal and Marine Science Center in Florida.

Scientists say coastal reefs around the world are declining due to a variety of factors, including coastal development, overfishing, pollution and coral bleaching. In Hawaii the reefs are also under stress from the nutrients found in coastal runoff that cause algae growth that can smother corals.

Without the full protection of their coral reef barriers, coastal regions are more vulnerable to the damage caused by storms, waves and erosion as sea level rise worsens.

The combination of human impacts to reefs and unprecedented rates of global climate change is likely to intensify the coastal hazard risks over the next century, according to the study.

Of all the study areas, Maui’s reefs were found to have the greatest volume of loss over the shortest period of time: 38 years. The researchers calculated that seafloor losses around Maui amounted to 81 million cubic meters of sand, rock and other material. They also figured the mean seafloor elevation decreased by more than 2.6 feet during that same period.

Yates said the scientists weren’t surprised Maui had the greatest amount of erosion. In contrast to Florida’s wide, shallow coastal shelves, Maui’s narrow shelves drop off precipitously and are punished by powerful open-ocean waves.

“It’s much easier for the materials to deposit into deep water,” she said.

But the magnitude of the change was surprising, Yates said.

The study also examined two reef tracts in Florida’s Upper Keys and Lower Keys and two at St. Thomas and Buck Island in the Virgin Islands.

For each of the five coral reef ecosystems, the research team obtained National Oceanic and Atmospheric Administration seafloor measurements taken between 1934 and 1982 and compared them with U.S. Geological Service surveys from the late 1990s to the 2000s.

A computer model was developed using the elevation changes to figure out the volume of seafloor material lost.

Previous studies have predicted global sea level rise between 19 inches and 3 feet, 3 inches by 2100. The problem is that they didn’t factor in seafloor erosion, Yates said.

Yates said that at current rates, seafloor erosion could increase water depths by two to eight times what was projected by 2100, placing nearby communities “at elevated and accelerating risk to coastal hazards.”

Yates was reluctant to say whether the Maui results were applicable to the other major Hawaiian Islands, saying each coastal area has its own variables.

As for Maui, the results of the study back up recent research that found coastal seafloor sediments move away from the shore rather than adding to the beaches. A 2003 study of beach erosion along the Maui coastline found that beach width narrowed by 19 percent islandwide over the last half of the 20th century.

According to various studies, coral reef ecosystems at all the study sites, including Maui, experienced losses in live coral cover over the past couple of decades.