All it takes is a license and a cutting rake to harvest rockweed anytime and anywhere along most of Maine’s long coast. But other than in a large bay in far eastern Maine, there’s no fisheries management plan for the common seaweed.

Work is now under way to develop a statewide plan to manage rockweed, which is processed in Maine into fertilizer, animal feed supplements, food and other products with an estimated value of $20 million a year.

A team tasked with developing the plan says rockweed isn’t being overharvested, but that it’s time to develop a strategy to establish sustainable harvesting guidelines and adopt harvesting practices to minimize habitat and ecosystem impacts as the industry grows.

Rockweed landings in Maine have risen from less than 4 million pounds a decade ago to more than 15 million pounds in each of the past two years.

“Rockweed is becoming a much more important commercial species,” said Brian Beal, a marine ecology professor at the University of Maine at Machias. “With increased levels of harvest, we want to make sure there’s a plan in place to ensure it’s sustainably harvested.”

Seaweed has been commercially harvested in Maine for decades, with rockweed accounting for more than 90 percent of the total seaweed harvest and kelp, dulse, nori and other kinds of algae making up the remaining 10 percent. Four major rockweed companies operate in Maine, buying raw product from locals who use mechanical harvesters or speciallydesigned, hand-held rakes.

Besides its commercial value, rockweed is important because it provides food, shelter and habitat for a wide variety of animals and organisms including lobsters, mussels, snails and periwinkles.

Yet for the most part, the industry is largely unregulated.

All harvesters have to be licensed and are required to cut rockweed at least 16 inches above where it holds onto rocks, to allow the plants to survive and regenerate. In Cobscook Bay — a sprawling body of ocean water tucked against the Canadian border in far eastern Maine — a management plan in place since 2009 divides the bay into 36 zones, caps the harvest at 17 percent of the biomass estimates and mandates that harvesters file harvest plans with the state.

The new statewide plan could incorporate a variation of some elements of the Cobscook Bay plan, said Dave Preston of North Atlantic Kelp in Waldoboro, which makes specialty fertilizer and animal feed supplements.

There’s no evidence rockweed is being overharvested, said Preston, who’s serving on the plan’s development team.

More than 2 billion pounds of it grow in the Gulf of Maine, with less than 1 percent harvested annually, according to the Department of Marine Resources.

But critics such as Robin Hadlock Seeley, a marine ecologist, think harvesting should be banned until there’s evidence that shows it’s ecologically sustainable and doesn’t affect other fisheries. Critics also want a court to determine whether rockweed is a public resource that’s legal to harvest.

“It’s absolutely essential,” she said. “It’s too important to risk since we don’t know how much you can take and still have a functioning intact ecosystem.”

Others say more rockweed is lost to nature each year — through storms, ice scouring, degradation and the like — than is taken by harvesters.

Studies also show that rockweed regenerates fairly quickly, in two to four years, said Linda Mercer, director of the Bureau of Marine Science of the Department of Marine Resources.

“It’s not like we’re clearcutting,” she said.

A draft is scheduled for delivery to the Legislature’s Marine Resources Committee in January and could be in effect a year from now.