At tens of thousands of shoreline cleanups across the United States in recent years, volunteers logged each piece of litter they pulled from the edges of lakes, rivers and beaches into a global database.
One of the most common entries? Plastic bags.
But in places throughout the United States where plastic bags require a fee or have been banned, fewer bags end up at the water’s edge, according to research published Thursday in Science.
Lightweight and abundant, thin plastic bags often slip out of trash cans and recycling bins, travel in the wind and end up in bodies of water, where they pose serious risks to wildlife, which can become entangled or ingest them. They also break down into harmful microplastics, which have been found nearly everywhere on Earth.
Using data complied by the nonprofit Ocean Conservancy, researchers analyzed results from 45,067 shoreline cleanups between 2016 to 2023, along with a sample of 182 local and state policies enacted to regulate plastic shopping bags between 2017 and 2023.
They found areas that adopted plastic bag policies saw a 25 to 47 percent reduction in the share of plastic bag litter on shorelines, when compared with areas without policies. The longer a policy was in place, the greater the reduction.
“These policies are effective, especially in areas with high concentrations of plastic litter,” said Anna Papp, one of the authors and an environmental economist and postdoctoral associate at the Massachusetts Institute of Technology.
The research accounted for different types of policies, including complete bans, partial bans that allow some thicker plastic bags considered “reusable,” and charging shoppers fees for bags at checkout. Bans considered complete, like New York’s, may allow exceptions such as for food takeout. They found that complete bans and fees led to greater reductions in bags on shorelines than partial bans.
The total amount of plastic bag debris found on shorelines in areas with and without policies increased over the study period but the increase in areas with plastic bag bans and fees was significantly less than those without.
“It’s blowing down the rate of plastic bag litter,” said Kimberly Oremus, another author and an environmental economist and associate professor at the University of Delaware. “It’s not reversing it, it’s not eliminating it.”
To test overall trends in each area, the researchers also tracked other items like bottles and straws. They did not find decreases in those, reinforcing the finding that the decline in the percentage of plastic bags was tied to area bag policies.
The findings also suggested the policies may reduce wildlife entanglement with plastic bags on shorelines, based on reductions in the numbers of entangled animals found dead or injured during cleanups. But more information is needed to determine the connection concretely, the researchers said.
Hundreds of state and local governments have adopted single-use plastic bag bans or fees, while some states have moved to preemptively block local governments from regulating bags. Globally, plastic bag policies have been adopted in several countries. The timing of the study is relevant as countries around the world negotiate a United Nations treaty designed to tackle plastic pollution.
Zoie Diana, an environmental scientist and postdoctoral fellow at the University of Toronto who has studied plastic pollution and was not involved in the research, said the study is exciting because researchers were able to link the plastic bag polices with reduced plastic litter.
“It shows that this trend wouldn’t have happened anyway,” Dr. Diana said, “that these policies are working,”
Using data collected by volunteers gave researchers the ability to track plastic bag litter in the environment over time, making robust before and after comparisons possible, said Dr. Papp.
“This is not a once-in-time snapshot of plastic litter, but really is something that keeps happening again and again,” she said.
The Ocean Conservancy collects data from volunteers at shoreline cleanups around the world, primarily through its mobile app, and makes that data public for use by researchers.
Erin Murphy, manager of ocean plastics research at the organization, said the work demonstrates the potential for data gathered by volunteers to contribute toward a better understanding of environmental problems.
“When we have these members of the community who care about an issue and are willing to collect data for us, it allows us to learn so much more about what’s happening in our environment,” Dr. Murphy said.
The researchers emphasized that while plastic bag bans and fees are not a complete solution to plastic bag pollution, they’ve found them to be productive in leaving fewer bags on the beach.
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