For a third of the population in the U.S., single-use plastic bags have become less of a convenient option—and this has had a positive impact on beaches, riverbanks, and lakeshores.

This is the conclusion of a study published on June 19 in Science. The study examined data from thousands of coastal cleanups across the U.S. and discovered that regions with policies either banning or charging for single-use plastic bags saw fewer of these items in their coastal debris compared to areas without such policies. This research provides some of the strongest evidence yet that these regulations are beneficial for the environment.

“I was not anticipating we’d see any significant findings,” admits Kimberly Oremus, an environmental economist at the University of Delaware and one of the study’s co-authors. “The results were quite surprising to me.”

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Oremus, along with her colleague Anna Papp, also an environmental economist soon to join the Massachusetts Institute of Technology as a postdoctoral researcher, initiated this study after coming across a vast dataset from the Ocean Conservancy. This organization had accumulated data from over 45,000 volunteer-led coastal cleanups from January 2016 to December 2023. Oremus and Papp were curious to see if they could trace any impact of local laws aimed at reducing the use of single-use plastic bags.

Indeed, they found significant evidence. Given the diversity of cleanup operations included in the dataset, counting individual plastic bags was impractical. However, they could assess the proportion of trash made up by these bags at different locations and how this changed over time. Unfortunately, the overall volume of plastic trash increased everywhere during the study period, and the proportion of single-use bags also grew. However, by correlating cleanup data with local regulations, they found that places with bag fees or bans had notably lower percentages of these bags in their beach trash.

“This research is crucial for lawmakers looking to enact environmental policies,” states Kara Lavender Law, an oceanographer at the Sea Education Association in Massachusetts, who was not involved in the study. “It’s one of the rare studies that shows the direct environmental impact of such policies.”

The researchers also delved deep into the effectiveness and limitations of these policies. They questioned whether a general reduction in plastic use might be occurring, independent of any specific policies. When examining other common plastic waste items, such as straws, water bottles, and bottle caps, they observed no changes.

Moreover, they analyzed the policies in greater detail to determine which were most effective. They concluded that complete bans were more impactful than partial prohibitions. The most significant changes occurred in areas that initially had high concentrations of single-use bags in their coastal trash.

The data also included some instances of wildlife entanglement in plastics. Here, Oremus and Papp noticed that areas with targeted plastic bag policies appeared to have fewer such incidents, though they plan to investigate this further.

Overall, the findings suggest that while bag bans and fees are not a cure-all for plastic pollution, they play a significant role. “These policies are focused on just one specific item,” explains Papp. “They help reduce pollution from that item but are far from solving the broader issue of plastic pollution.”

Law warns against the temptation to broadly apply such policies to other products. “We need narrowly focused, item-specific policies,” she advises. “A one-size-fits-all approach could lead to unintended consequences.”

Yet, facing a problem as widespread as plastic pollution, the researchers agree that any effective measures are valuable. “Given how prevalent and heavily used single-use plastics are, no single policy, like those targeting straws or bags, will solve everything,” Law remarks. “But it’s crucial that we start somewhere, especially with policies that are showing positive impacts.”