Molokai’s Righteous Reef

Landmark USGS study culminates in colorful report

By Sean Aronson

Molokai’s coral reef is famous for its clear waters and abundant marine life. Visitors travel from all over the world to snorkel and take in its beauty. It is full of colorful fish and brilliant coral.

But the reef is also famous for the amount of degradation it has endured because of sentiment washing from the land.

Now a landmark report by the United States Geological Survey documents this degradation in an attempt to save the threatened reef. The report, “The Coral Reef of South Molokai: Portrait of a sediment-threatened fringing reef,” is the first of its kind for Molokai.

According to the Preface of the report, “Today the Molokai reef is at a crossroad – the evidence of damage from heavy land-use is clear, and yet procedures for its protection through improved land-use practices are already underway.”

The report gathers the work of more than a dozen scientists and researchers and is the culmination of more than five years of intense studies of the reef. It is a comprehensive, engaging publication that incorporates science, culture and history of the Molokai reef.

The impetus for the report comes from USGS Senior Marine Geologist Mike Field. In 1998, he was taking a sabbatical at the University of Hawaii. He used that time to talk to fellow scientists about an environmental approach to studying coral reefs. It was then he learned that the major threat to corals is sedimentation, the introduction of land particles to the reef.

Sedimentation is especially damaging in places where there is increased erosion. Any land-based pollution is washed on to the reef. With the increase in silt, the reef is blocked from sunlight and all the marine life is effectively ‘choked’ out.

Field set out to find a place where he could learn about sedimentation’s effect on a reef. Molokai was the best choice available, said Field. The reason is much of Molokai’s land was plowed for pineapple and thus erosion is incredibly high. It is also one of the longest continuous reefs in the Hawaiian Islands.

“Molokai is a superb natural laboratory,” says Field, “I think it’s a state treasure.”

Field explains that it is the broad shallow nature of the reef that makes it such an ideal study subject. The sediment is trapped on reef flat and it just stays there, he says. The sediment keeps getting stirred up and continues to impact every time a wave washes over the reef.

“It becomes the gift that keeps on giving,” says Field.

The report includes satellite photos of various parts of the island as well as documentation of the effects of erosion. It features chapters on fish ponds, geology and the history of the reef.

“We are all extremely pleased with the final product,” says Field.

Field says the report has three audiences in mind. First off is Molokai residents. They are the caretakers of the reef and the island, says Field. Second are the resource managers of reefs. And third are scientists from other disciplines that can apply some of the same methods to study their ecosystems.

Primarily, Fields says, we made it for the people of Molokai. “It is the people of Molokai who will ultimately decide the fate of their coral reef,” he continues.

Field says it is incredibly important that Molokai reefs be protected. Coral reefs are the rainforest of the sea. Reefs occupy a small amount of land, but contain an amazing amount of species. Their biological diversity is unparalleled.

The report does not mean the end of studies for the USGS team. In April, Field and other research will return to Molokai to conduct a 10 day experiment. They will be trying to understand how fast the reef will clean-up. Specifically, they want to understand what the rate of sediment exit from the reef is.

Field says the report has tremendous educational opportunities. He is encouraging anyone who would like a copy of the report to contact him. The report will be sent to Molokai High School and other island organizations.

“It’s a resource for the people of Molokai – for the entire country,” says Field

To receive a copy of the report, contact Mike Field at Or to browse the report online head to



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