The first nationwide examination of plastic litter removal from Japanese rivers was carried out by a research team headed by Assistant Professor Mamoru Tanaka of Tokyo University of Science (TUS) and published in the Marine Pollution Bulletin on November 1st, 2024.
A look into plastic litter removal from rivers in Japan. Plastic litter recovery from rivers is a rather understudied topic in Japan. To tackle this knowledge gap, researchers conducted an in-depth analysis of plastic removal from over 100 important river basins. Their findings reveal important correlations between plastic litter recovery and demographic and natural factors, which could help improve organized cleanup efforts. Image Credit: Mamoru Tanaka from Tokyo University of Science, Japan
Plastic pollution is a major problem worldwide since most cultures rely too heavily on plastics for packaging, medical supplies, and everyday items. Plastic litter accumulation in the ocean, whether through purposeful dumping or transportation from a river, presents substantial environmental issues.
This plastic degrades into tiny fragments known as microplastics, which influence a variety of marine and land ecosystems by moving up the food chain and into most living organisms. Though their detrimental impacts on cell health are still being investigated, several countries have chosen a precautionary approach, intensifying efforts to reduce plastic usage and prevent pollution.
Japan’s position in the North Pacific means that it contributes significantly to and is severely affected by plastic litter in the ocean. As a result, the government and local communities must launch aggressive cleanup efforts to retrieve plastic waste from river basins. Regretfully, not much research has been done on the rate at which plastic litter is being removed from Japanese river basins, despite the fact that this information is crucial for comprehending the dynamics of plastic movement and developing more efficient solutions.
According to their most recent study, the team used a dataset from the Ministry of Land, Infrastructure, Transport, and Tourism to quantify the yearly plastic waste recovery from river banks and water surfaces. Additionally, Ms. Yumena Okada, a 2022 TUS graduate, participated in the study.
The information comprised the amount of plastic recovered from 109 river basins between 2016 and 2020. The researchers examined this data and looked at potential correlations with other elements such as basin population, the size of neighboring urban regions, and geographical characteristics. The overall plastic recovery rate ranged from 763 to 1,177 tons per year, with an average of 938 tons.
Given the emission estimates from previous studies, Japan's annual plastic emissions are approximately 10,000-20,000 tons. The plastic recovery in river basins of approximately 1,000 tons/year estimated in this study represents approximately one-tenth to one-twentieth of this total. This is a non-negligible contribution toward reducing nationwide plastic emission, though not a decisive amount.
Mamoru Tanaka, Assistant Professor, Tokyo University of Science
According to the team's analysis, the Yodo River system collected 91.6 tons of plastic waste annually, followed by the Yoshino River system with 85.8 tons, the Tone River system with 78.8 tons, the Tama River system with 72.0 tons, the Oto River system with 69.2 tons, and the Abukuma River system with 53.9 tons. These made up around half of all the plastic collected in Japan.
By examining the data more closely, the researchers discovered that natural disasters and extreme weather events were strongly linked to increases in the amount of plastic litter collected from rivers.
Tanaka added, “The Ota and Kiso River systems saw a significant rise in plastic waste collected in 2018. Both systems were affected by heavy rains in western Japan that year. Similarly, the Abukuma River system saw a rise in plastic collection in 2019, which can be attributed to the impact of Typhoon No. 19 in 2019, which caused substantial water damage.”
These findings offer insight into the potential link between climate change, which causes more extreme weather events, and plastic pollution.
The team also discovered additional intriguing correlations. For example, the Yodo and Tone River systems, which have among the greatest recovery rates, serve nearly 10 million people, but this increases waste generation and requires more collaboration from various municipalities. As a result, there is a positive relationship between the basin population, plastic trash recovery, and the number of persons involved in cleanup initiatives.
Taken together, the findings of this nationwide analysis will help authorities and volunteer-based organizations plan future cleanup initiatives.
“Currently, the Ministry of the Environment scientifically estimates plastic litter levels across various areas of Japan. Our estimates cover where and to what extent plastic waste is generated, how much is collected, how much is deposited in soil and riverbeds, and the amount discharged into the ocean, thereby providing key data to support these estimates,” Tanaka concluded.
With any chance, this research will pave the way for more effective strategies to achieve sustainable plastic management, decreasing the terrible consequences of plastic pollution on wildlife and public health.
The Environmental Restoration and Conservation Agency of Japan funded this study through its Environment Research and Technology Development Fund [JPMEERF21S11900]. The River Foundation, Japan [2024-5211-060] and [2022-5211-028] contributed partial funding.
Journal Reference:
Tanaka, M., et. al. (2024) Country-wide assessment of plastic removal rates on riverbanks and water surfaces. Marine Pollution Bulletin. doi.org/10.1016/j.marpolbul.2024.117218