Aerial survey finds mostly plastic, limited tsunami marine debris in Hawaii

Photo: DLNR


A new study reveals where marine debris is washing up in Hawaii.

The study was funded by the Ministry of the Environment of Japan, and commissioned by the Hawaii Department of Land and Natural Resources and North Pacific Marine Science Organization (PICES), so that officials could see how much debris washed up from Japan’s 2011 tsunami.

According to high-tech aerial imagery and analysis, not a lot.

“We ended up finding actually very little Japanese tsunami debris, but we did find a lot of plastics,” explained Brian Neilson, aquatic invasive species biologist, DLNR Division of Aquatic Resources. “This plastic comes from other places in the Pacific. It comes off fishing boats, other islands, other countries, and because of the way Hawaii is situated and the currents, it just accumulates on our shores here in Hawaii. So it’s an ongoing problem and  a problem we’re going to be dealing with for a while since we can’t really control the source of it.”

The images were taken between August and November 2015 by Resource Mapping Hawaii, then analyzed and cataloged by the University of Hawaii’s Hawaii Coral Reef Initiative. More than 20,000 individual pieces of debris were identified.

The study found that 38 percent of the total debris identified is on Niihau.

“We didn’t study the actual currents around the island of Niihau, but because it’s located at the most extreme point of the island chain, the northern most point, what you can see is it kind of is impacted moreso by the currents that bring about the substantial amounts of debris to the state of Hawaii,” said Kirsten Moy, Marine Debris Coordinator, DLNR Division of Aquatic Resources.

All other islands had 14 percent or less of the debris identified, with Oahu having the least density at only five percent.

“Fortunately, we’ve got some very active community groups, like Sustainable Coastlines, (Surfrider Foundation), and just individuals that are out there all the time, cleaning up debris off the beach, so if you’re fortunate enough to find a beach that doesn’t have much debris on it, you can probably thank those organizations and volunteers that are out there cleaning it up,” Neilson said.

The following is a breakdown of marine debris pieces found on each island:

  • Oahu: 984. Most common type was plastic (63%). Marine debris was concentrated on the northern tip of the island, particularly around Kahuku.
  • Maui: 1,749. Most common type was plastic (40%). Marine debris was concentrated on the northern side of the island, particularly around Kahului.
  • Hawaii: 2,200. Most common type was plastic (52%). Marine debris was concentrated on the southeastern tip of the island, particularly around Kamilo Point.
  • Kauai: 1,849. Most common type was plastic (49%). Marine debris was concentrated on the eastern shores of the island, particularly at the northern and southern extents.
  • Molokai: 2,878. Most common types were plastic (37%) and buoys & floats (35%). Marine debris was concentrated on northwestern shores and a small area on the northeastern corner of the island.
  • Kahoolawe: 1,298. Most common type was plastic (47%). Marine debris was concentrated on the northern tip of the island and in the Keoneuli area on the eastern coast.
  • Lanai: 1,829. Most common type was plastic (53%). Marine debris was concentrated on the northeast coast of the island.
  • Niihau: 7,871. Most common type was plastic (46%), followed by buoys and floats (25%). Niihau had the great debris densities on east-facing shores.

In addition to plastic, buoys and floats, the surveys identified derelict fishing gear, foam, tires and “other” types of debris, including wood, metal, cloth and vessels.

View the full report online here.

Officials hope to use these results to better manage and control marine debris accumulation in the islands.

“It’s a hazard to our wildlife. It causes entanglement of whales, turtles,” Neilson said. “Our birds and fish ingest it, so it’s a major problem for our wildlife, but also it tarnishes our idea of paradise here. No one wants to go to the beach and see a bunch of debris land on their pristine white sand beach.”

Photo: DLNR
Photo: DLNR

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