Why is the City Council considering a plan to slap a 10-cent fee on every plastic and paper carryout bag New Yorkers use?

Part of the answer is blowing in the wind.

New York City residents use about 5.2 billion plastic bags a year -- most of which aren't recycled.

Instead they frequently fly off into the breeze -- hanging on power lines, catching on fences, clogging up storm drains, endangering fish and littering landscapes.

Maybe they biodegrade over 500 years, or maybe over a millennium. They've only been around en masse for 50 to 60 years, so no one knows their life span.

But we do know they pose an environmental threat. And it costs the city $10 million a year to haul about 100,000 tons of them to landfills in other states.

The council's bill makes sense. While no one welcomes another charge in one of the most heavily taxed cities in America, the 10-cent-per-bag levy is relatively modest.

And there's a way to avoid it entirely.

The council members who are backing the measure hope it persuades shoppers to switch to reusable bags.

That's why paper bags also would cost 10 cents. While paper sacks aren't as tough on the environment as plastic ones, they're not as green as reusable bags.

So the measure, sponsored by Councilmembers Brad Lander of Park Slope and Margaret Chin of lower Manhattan, is environmentally and financially smart.

When Los Angeles County banned plastic bags and put a 10-cent charge on paper ones not long ago, it saw the use of paper bags drop by 35 percent. The overall use of nonreusable bags, meanwhile, dropped 95 percent.

One quarrel with the New York City bill: Storekeepers would be allowed to keep the entire 10-cent-per-bag fee for administrative costs. That's an overreaction to a 2008 bill that failed in part because it was seen as a tax.

Here's a better idea. Set aside a few cents per bag for shopkeeper costs while using the rest to underwrite a city program to make cheap reusable bags readily available to everyone who needs one. Green is good.