Are Beach Clean-ups Actually Effective Against the Colossal Problem of Marine Debris?

Nine years of citizen science from community groups across Hawaiʻi is helping researchers understand the scale and scope of marine debris

North Shore Oʻahu: Ghost nets hauled off the beach and waiting to be loaded for transport. (Image by author)

James Campbell National Wildlife Refuge covers 1,100 acres on the northeastern shore of O’ahu. Established in 1976, this refuge encompasses one of the few surviving wetland ecosystems on Oʻahu and provides critical habitat for four species of endangered Hawaiian waterbirds as well as a place of respite for migratory birds, endangered monk seals, and threatened sea turtles. This wildlife refuge is also one of the most polluted beaches on the island, receiving a regular influx of marine debris such as derelict commercial fishing gear and other swarms of plastic pollution. This strip of coastline consistently receives such a shocking volume of debris that for years several community groups have conducted clean-ups of the area multiple times a month, working tirelessly to remove large and small debris while collecting data throughout the process. From 2013 to 2022, similar efforts have taken place at other sites on the eastern shores of Kauaʻi and Big Island — coastlines that are hit particularly hard by debris due to the strong easterly and northeasterly trade winds. These volunteers exhibit a special type of dedication as they spend all day cleaning a beach while knowing that in a matter of days, weeks, or months, more debris will likely return in full force.

Map of typical trade wind directions around the main Hawaiian Islands. Wind maps and other ocean condition reports are publicly available through the Pacific Islands Ocean Observing System (PacIOOS).

In recent years, however, community groups across all islands have started to notice a difference. They show up expecting to remove thousands of pounds of debris, yet their clean-ups total hundreds of pounds or even less. They find mostly plastic fragments rather than the usual bulky fishing buoys or “ghost nets” — massive conglomerates of discarded fishing nets that accumulate more material as they float across the open ocean. This conspicuous absence of debris poses the question: Has the majority of marine debris bound for Hawaiʻi finally been captured and removed? The temptation to be optimistic is strong, but the seasoned beach clean-up crews are cautious with their hope. A near decade of clean-ups and citizen science has provided an important long-term data set on patterns of marine debris accumulation in the Hawaiian Islands, and that data is helping scientists understand and predict the movements of debris masses in the ocean.

Unfortunately, this data informs grim conclusions. A recent study in the Marine Pollution Bulletin transposed this nine-year data set of marine debris collection against a model of ocean currents across the northern region of the Pacific Ocean Gyre. The study sought to investigate if the reduced presence of shoreline debris noted during some years in Hawaiʻi is due to an overall reduction in ocean-wide marine debris, or the result of a shift in ocean currents that keeps the debris from reaching land. This is a pertinent research question given the Hawaiian Island chain’s proximity to the infamous Pacific garbage patch. The garbage patch is a loose, drifting convergence of marine debris swirled together by a circulation of ocean currents, and this entire convergence can migrate large distances when spurred by changes in the North Pacific Ocean system.

Map displaying the position of the Hawaiian Islands relative to the garbage patch. Image courtesy of NOAA.

Debris that peels away from this convergence zone may be guided to the shores of Hawaiʻi by the complex interaction of forces that create relatively stable ocean currents or it may be guided by smaller temporary events such as passing storms. Researchers developed a computer model to simulate the predicted drift of debris from the garbage patch based on changes observed in large-scale in ocean currents. The data collected from shoreline clean-ups between 2013 and 2022 showed similar debris trends to the model predictions that took the position of the garbage patch into account, supporting the hypothesis that variations in the volume of debris washing ashore are due to shifts in the position of the garbage patch rather than a change in the overall amount of debris in the ocean.

Figure 9 from original publication. The three colors indicate the years of debris totals on the island of Kaua’i and the corresponding contours of the garbage patch boundary.

It is a disheartening task to clean a beach — to remove thousands of pounds of material — and know that the impact is only temporary. The fact that the vast majority of this debris does not originate in Hawaiʻi also hits particularly hard and contributes to a feeling of frustration that these small, geographically remote islands are suffering the effects of far-off industries. These clean-up efforts may seem fruitless in the face of an inevitable return of debris, but they are a viable short-term tool to use in what is sure to be a long, globally complicated battle against the blight of commercial fishing and plastic manufacturing.

Though the visual impact of a recently cleaned beach may be temporary, the ecosystem benefits are not.

A study in the September 2024 issue of Science noted that decades of marine debris removal across the main and Northwestern Hawaiian Islands have significantly reduced the number of entanglement events for Hawaiian monk seals, an endangered species whose population is estimated at only 1,600 individuals. Similarly, every heavy net hauled off the beach by a team of volunteers is a net that will not float back out to sea and smother a section of coral reef. Every bottle cap removed from the sand is a bottle cap that will not end up in the stomach of an endangered bird.

Even if every piece of debris does not directly save the life of some beloved sea creature, these beach clean-ups led by dedicated citizen science community groups are a valuable source of broad, long-term data sets that cannot be feasibly collected under traditional rigorous scientific study. Information gleaned from this meticulous, ongoing battle with debris supports the much needed expansion of research and spurs discussions on future marine debris management and prevention strategies.

In that sense, every little piece of plastic at these clean-ups does actually count.