Austin's bag ban is more than two years old, but a study finds it may need some work.

Environmental groups say they've seen a dramatic drop in plastic bags littering streams and creek banks, but an Austin Resource Recovery report found reusable bags may be getting thrown away before the end of their life span.

The city phased out the bags in an effort to clean up the environment. Rodney Ahart with Keep Austin Beautiful says he's seen a difference.

"We definitely have seen a decrease in the amount of plastic bags that our volunteers are collecting at cleanup sites,” he said.

Ahart says the bags were not just an eyesore; they were harmful to wildlife.

"If they make it to our waterways, they can potentially be confused for food by wildlife – whether it's birds, whether it is fish,” Ahart said.

That was before the bag ban. Now, Austin Resource Recovery’s report says more than half the plastic bags ending up at the city's recycling centers are the thick plastic reusable ones. Technically, those bags are not recyclable.

Andrew Dobbs with the Texas Campaign for the Environment says the study's missing a key component.

"That's not to say we've replaced single-use bags with reusable bags in our trash. We have seen a big decrease in bag pollution overall, and the composition of that little bit that is remaining is different,” Dobbs said.

He believes Austin's become more responsible as a city and expects habits will continue to change over time.

Rick Cofer with the Austin Bag the Bags Coalition also supports the bag ordinance, but he says he wants to see it improved.

"It's time to eliminate the option of using paper bags, and it's time to move toward only reusable bags,” he said.

The study finds while paper bags are rarely reused, they’re made of recycled paper that can be easily recycled. Plastic and canvas bags are often made new and need to be used at least 100 times to offset their carbon footprint.

Check out Austin Resource Recovery's full report below.