Rob Parsons is amazed when he travels to Oahu and sees all the plastic bags being handed out at stores left and right.

"We’re so over it," said Parsons, Maui County’s environmental coordinator.

With the plastic checkout bag banned on Maui 41⁄2 years ago, the Valley Isle has seen a dramatic difference along roadways, in trees and across the landscape, according to Parsons and others.

"Those windblown plastic bags are all but gone," he said.

It’s much the same story on Kauai, which outlawed plastic checkout bags the same time Maui County did, and on Hawaii island, where they were banned in 2013, according to folks on those islands.

Oahu?

Honolulu is about to become the last county in Hawaii to ban the plastic checkout bag. Starting July 1, businesses will be prohibited from giving out plastic bags and nonrecyclable paper bags to their customers at the point of sale for carrying groceries or other merchandise.

The law is being welcomed by those who see it as dealing with the impacts of plastic bags on the environment, which include litter, a growing burden on the landfill and threats to marine life.

Many merchants, on the other hand, warn that the ban will add to the cost of doing business — a cost that undoubtedly will be passed on to customers.

And then there are those who will miss the plastic "T-shirt" bag for its utility as a trash can liner, a pet cleanup bag, a lunch holder and a million other things.

First approved by the Hono­lulu City Council three years ago and signed into law by then-Mayor Peter Carlisle, the law was amended slightly last year and then signed by Mayor Kirk Caldwell.

Acceptable bags include compostable plastic bags, recyclable paper bags that contain a minimum of 40 percent post-consumer recycled content, and "reusable bags," which have handles and may be made of fabric or other durable material suitable for reuse, including plastic that is at least 2.25 mils or 0.00225 inch thick.

The law applies only to bags distributed at checkout. Plastic bags will still be OK for loose items such as fruits, vegetables, nuts, coffee, candy, or small hardware items, and for frozen foods, meat or fish, flowers or plants, medications, newspaper, laundry and pet items.

The city Department of Environmental Services recently distributed 9,000 bag ban information sheets and forms asking Oahu businesses how they plan to comply with the ordinance.

Of those businesses that indicated they were continuing to provide bags, 25 percent said they were going to compostable bags, 44 percent recyclable paper bags and 31 percent reusable bags, the city said.

Even though the ban’s July 1 start date has been set for three years, apparently not everyone’s ready.

"It’s crazy," said Adrian Hong, president of Island Plastic Bags in Aiea, one of Oahu’s few plastic bag manufacturers and distributers. "I’m getting five to 10 calls a day. A lot of people still haven’t figured out what they’re going to do."

That’s not the case at City Mill. Carol Ai May, vice president, said the retailer with eight stores on Oahu plans to provide two bag options: Customers can buy a heavy duty 2.25-mil plastic bag for 10 cents or a reusable "eco-bag" for 99 cents.

At Foodland, with 32 Foodland and Sack N Save stores on four islands, the plan is to continue a rewards program for those who use their own bags, offering either 5 cents credit or three Hawaiian Air frequent flier miles per bag.

The store will step up the program July 1 with weekly prize drawings for those who bring in their own bags. Also, the stores will sell a variety of reusable cloth bags, at prices from 99 cents to $8.99. And if shoppers choose no bags, clerks will offer to help customers carry out their groceries — and offer the credit, as well.

"We’ve been working on our plan for a long time," said Foodland spokeswoman Sheryl Toda, who added that restrictions on the neighbor islands helped prepare the company for the Oahu ban. "We learned a lot."

While Foodland has embraced the new law, many small- and medium-size businesses view the edict as a burden, said Sheri Saka­moto, president of the Hono­lulu-based Retail Merchants of Hawaii.

"When there’s a new fee here and a new fee there, plus a new regulation here and a new regulation there, it can add up to a lot of money, especially for a small business trying to make rent at the end of the month," Sakamoto said.

There’s a fear the law will create new opportunities for shoplifting, with customers armed with their own bags plying the aisles, she said.

The plastic bags that most retailers use now cost about 2 cents to make, while the choices of bags available under the new law will cost between 10 and 14 cents, according to Hong of Island Plastic Bags.

Jerry Masaki, general manager of Pukalani Superette, said bag costs at the longtime Upcountry store are up 25 percent since Maui County established its ban. With the big supermarkets offering free paper bags, his store has been compelled to offer the same.

Masaki said he thinks there should be a mandatory charge for bags not only to encourage the use of reusable bags but also to level the playing field for big merchants and small.

"It’s only fair," he said.

Kahi Pacarro, executive director of Sustainable Coastlines Hawaii, wants changes in the law, too. While he calls the Oahu ban a step in the right direction, he said the law needs some work.

"Retailers are finding ways around the ban by moving toward thicker plastic bags and compostable (plastic) bags, which, if you look on the bag, it says it’s compostable in a commercial composting facility," he said. "We don’t have one of those in Hawaii, so the two loopholes that they created still pose the same risks (to sea life) that we were trying to eliminate in the first place."

Pacarro said the compostable bags — which were included in the ordinance by the Honolulu City Council as a compromise — don’t break down in water and require heat from a composting facility.

The city is advising residents to put compostable bags in the gray cart with their regular refuse. All regular refuse on Oahu is sent to the city’s HPOWER waste-to-energy facility, where it’s incinerated to generate electricity, said Tim Houghton, deputy director of the city’s Environmental Services Department.

"It’s important to note that even without a separate composting system for compostable plastic bags, the plastic bag ban will significantly reduce the number of plastic bags being distributed by retailers on Oahu and reduce the number of plastic bags that are littered onto beaches and into the ocean, which is the ultimate goal," Houghton said in a statement.

Compostable bags are not an issue on the neighbor islands, where they are not allowed.

Former Maui County Councilman Mike Molina said he’s proud of the measure that he helped usher into law. He remembers taking a lot of flak from lobbyists and business folks at the time, with many of them saying it would push merchants out of business.

"The sky was falling and it was the end of humanity," recalled Molina, who is now an executive assistant to Mayor Alan Arakawa. "But it wasn’t the end of the world. And now Maui is a lot cleaner."

Maui’s ordinance has resulted in a "massive decrease" in plastic litter, said Michael Ratte, Maui County’s Solid Waste Division chief, thanks in part to nearly 100 percent of merchants complying with the law.

But apparently the initiative has fallen short in one area: encouraging the use of reusable bags. A 2014 survey of 1,634 Maui shoppers found that only 25 percent bring reusable bags to stores, with the rest taking a free paper bag.

That means the paper bag has become the shopping bag of choice once again, Ratte said.

On Hawaii island, by contrast, the number of folks shopping with reusable bags is up, according to surveys at local grocery and big-box stores in both East Hawaii and West Hawaii. Before the law went into effect in January 2013, the percentage of shoppers with reusable bags was about 20 percent. Within the first few months, the percentage shopping with reusable bags was 80 percent, said Linda Peters, Hawaii County recycling coordinator.

Peters credits the county’s outreach and education for helping to change habits, and she reports positive feedback from residents and a good deal of cooperation from the business community.

On Kauai, Allison Fraley, the county’s Solid Waste Program coordinator, said she’s seen a noticeable decline in plastic litter over the past few years. So has Maureen Murphy, president of the Kauai Outdoor Circle.

"It’s made a huge difference," Murphy said. "We used to see a lot of plastic bags blowing around, attached to chain-link fences. We don’t see that anymore."