A 2018 UN Environment Programme report on plastic pollution lists Japan as the second highest producer of single-use plastics per capita worldwide after the United States. Plastic waste from Japan (and other East and Southeast Asian nations and the U.S. west coast) has accumulated into large, belt-like areas in the northern Pacific Ocean. Approximately 30,000 to 50,000 tons of plastic waste are collected from Japan’s coastline annually. From 1988 to 2016, Japan had the third highest rate of global plastic waste exports, with 70 percent of its exports transported to China.
Most large-sized marine plastic waste does not biodegrade but instead breaks apart into smaller plastic pieces called microplastics. Microplastics negatively impact the marine environment, seabirds, and other organisms. Approximately one-half of all seabird species have experienced population declines, with one-third of species threatened with extinction worldwide by marine plastic pollution as one of the main causes.Recent scientific research also shows that seabird species, like shearwaters that migrate to Japan seasonally, are becoming contaminated by toxic chemicals found within and adsorbed to microplastics and other marine plastic debris.
To reduce Japan’s global plastic footprint, the Japanese government has recently enacted the Act on the Promotion of Resource Circulation for Plastics (Purasuchikku ni kakaru shigen junkan no sokushin-tō ni kansuru hōritsu) (hereinafter referred to as the Plastic Resource Circulation Act or PRCA). This article discusses marine microplastic pollution’s impacts on the world’s seabirds, including two shearwater species that migrate to Japan, briefly analyzes some of PRCA’s main provisions, and addresses a significant weakness in the new law. This article concludes with some recommendations to improve PRCA to further protect seabirds and the marine environment.
Microplastics' Impacts on Seabirds
There are two types of marine plastic waste: 1. large, commonly used plastic items or “macroplastics” measuring greater than five millimeters (mm) long that retain their shape when discarded (e.g., PET bottles); and 2. small plastic fragments called “microplastics” measuring less than five mm long. Microplastics constitute most plastic waste in the ocean. “Primary microplastics” include small plastic particles designed for commercial use in cosmetics and toiletries (e.g., scrubbing agents), plastic pellets used as raw material in industrial plastic manufacturing, or fragments produced from the abrasion of plastics during use (e.g., lost fishing gear or synthetic textile fibers shed during laundry). In contrast, “secondary microplastics” constitute small plastic fragments resulting from the breakdown of macroplastics from the sun’s ultraviolet rays and the ocean’s wind and wave action.
Microplastics and other plastic debris adversely affect seabirds. Abandoned, lost, or derelict fishing gear (ALDFG) such as lines and netting, and other plastic waste can entangle seabirds and cause them to become injured, drown or suffocate, and serve as a source of microplastics. Seabirds ingest microplastics through the food chain. Marine invertebrates like zooplankton consume microplastic fragments. Crustaceans, cephalopods, and fish eat the zooplankton and eventually become seabirds’ primary prey. Seabirds may also ingest microplastics directly by mistaking colored plastic pieces as food. Because seabirds cannot digest these plastic pieces, the microplastics accumulate in a bird’s stomach and gastrointestinal tract and may result in bowel blockages, ulcers, and intestinal tears. Moreover, as microplastics build up in a bird’s stomach over time, seabirds eat less food, depriving themselves of vital nutrients leading to starvation and death.
Microplastics also have less visible, nonlethal effects on seabirds. The Flesh-footed Shearwater (Ardenna carneipes), which spends the summer foraging in the Sea of Japan and the North Pacific and then migrates in the autumn to breed on Lord Howe Island, New Zealand, shows these effects. This shearwater population has declined approximately 20 to 29 percent in three generations, with plastic ingestion as one leading cause. The International Union for the Conservation of Nature’s (IUCN) Red List of Threatened Species has designated the Flesh-footed Shearwater as “Near Threatened.” In a 2019 study, scientists found that Flesh-footed Shearwater fledglings have significant health problems from ingesting even a few pieces of microplastics or other plastic debris in their stomachs. Flesh-footed Shearwater adults often mistakenly regurgitate microplastics and feed them to their young. Fledglings that consume these plastics have low blood calcium levels, small body mass, and reduced wing, head, and beak lengths. Plastics in young birds also cause increased amounts of uric acid, cholesterol, and amylase that adversely affect the birds’ kidney function and may lead to other illnesses.
Moreover, microplastics can transmit toxic chemicals to seabirds. Since microplastics are hydrophobic and have a large surface area-to-volume ratio, heavy metals and persistent organic pollutants in the marine environment such as polychlorinated biphenyls (PCBs) and per- and polyfluoroalkyl substances (PFAS), become easily attached to microplastics’ surfaces. When seabirds consume microplastics directly or prey containing microplastics, these chemicals enter the birds’ bloodstream and negatively impact their growth and health.
Seabird contamination also occurs through toxic chemical accumulation in seabird tissues from the leaching of additives found within microplastics. In a joint study published in October 2021, an international team of scientists found plastic additives in the tissues of 52 percent of the world’s seabirds. The scientists analyzed the oily fluid secreted from the preen gland near the tail base of 145 birds from 32 species in 16 different areas worldwide. Seabirds use this fluid to waterproof their feathers. The researchers detected plastic additives in 76 birds and estimated that 10 to 30 percent of the birds analyzed had accumulated plastic additives in their tissues from plastic ingestion. The scientists detected additives in several species, including the Flesh-footed Shearwater and the Streaked Shearwater (Calonectris leucomelas), which breeds and nests mainly on offshore islands of Japan like Awashima Island, Niigata Prefecture, and the Korean Peninsula in the warmer months and then migrates south during the winter. Streaked shearwater populations are also declining and designated as “Near Threatened” on the IUCN Red List.