A bill which has been quietly making its way through the state house could dramatically affect the future ownership of some of the Vineyard’s pristine barrier beaches, moving them from private hands to public.

The bill, which consists of just a single paragraph, relates to the barrier beaches that separate the Island’s Great Ponds from the ocean. Many of these beaches are privately owned and also are retreating into the ponds as they are eroded on their seaward side.

Sponsored by a Brookline representative, the bill would prevent private ownership from moving with the sand. Because the Great Ponds are public land, any barrier beach which retreated to a place which formerly was the bottom of a pond, would become a public beach. The property rights of the former owners would be fixed to a GPS location, and extinguished when their sand shifted.

Designed H254 and technically an amendment to Chapter 91, the state law governing navigable waterways in the commonwealth, the bill has broad implications not only for the Vineyard, but also Nantucket and other areas across the commonwealth where there are Great Ponds and barrier beaches. But it would be felt most sharply on the Vineyard, which has the greatest concentration of Great Ponds in the state — 17 of them.

The main sponsor of the bill, Rep. Frank I. Smizik, a Democrat from Brookline, says the measure would simply ensure that if nature took the property, the owners could not move their claim to a new beach formed by the same natural process, on what is already state land.

The bill is now at the third reading stage in the house, having been reported out of the natural resources committee with a positive recommendation. If it passes the third reading committee, it could go to the house floor for a vote this fall. It would still have a long way to go before it could be signed into law, and among other things would have to pass the state senate.

Owners of barrier beaches, initially caught unawares by the bill, now are organizing to lobby against it. Several who might be affected said they were caught by surprise and were still studying it.

Questions have been raised about whether the bill threatens legal rights established over hundreds of years that an upland landowner also owns any adjoining beach down to the mean low water line. As long as that beach is attached to property they own, regardless of how it accretes or diminishes or moves over time, it remains theirs.

A group of landowners, including some riparian owners on the Edgartown Great Pond and called the Great Ponds Coalition, has formed in recent weeks to oppose the bill.

In a statement the group of unidentified landowners said the bill would “dramatically change the common law of Massachusetts as it has existed for hundreds of years.” The statement was released by James McManus of Slowey McManus Communications in Boston.

As well as transferring private land to public, the statement said, it would bring potential negative ecological consequences and lead to a serious loss of revenue to cities and towns through lost property taxes.

The statement also warned of “a likely due process challenge under the Massachusetts and United States Constitutions.”

Yesterday the chairman of the house committee on bills in the third reading, Rep. Vincent A. Pedone, said he planned to visit the Vineyard later this month, at the invitation of Cape and Islands Rep. Timothy Madden, to visit the likely areas to be affected by the bill and talk to Islanders, including local elected officials, about it.

“There are strong feelings around this bill. It’s a hot one,” said Mr. Pedone, a Democrat from Worcester.

“There are many legislators who have contacted my office in support of this — Democrat, Republican, conservative, liberal, all across the political spectrum,” he said. “On the other side there have been some who have contacted me saying this bill should not move forward.

“So I am doing some research, looking at the pros and cons. There are a lot of questions. Could this amount to a land taking by the commonwealth? And if so, are we responsible for paying fair market value? Who maintains this public land? Is there access to this land? There are a whole host of questions that have been raised by the other side.

“I don’t have a view. I just got focused on this bill last week.”

The committee on third readings will decide if the bill goes to the house for a vote; if it does it would not occur at least until the fall.

The main sponsor of the bill, Rep. Frank I. Smizik, a Democrat from Brookline, said its intent was to protect the rights of the state over its land.

“We’re not trying to devalue anyone’s property; we’re trying to say this is public water, and you as part of the public will have access, but you’re not going to take it over,” he said. He said he believed the change in the law was all the more important because climate change would accelerate natural erosion.

“It should be made very clear to avoid future confrontations, because the water’s rising. It’s pushing back the beaches, including the beaches before the Great Ponds. And we ought to have a system to deal with it, which shouldn’t be, ‘Let’s go to court and fight it out, ’ ” Mr. Smizik said.

He acknowledged the potential for enormous impact to the owners of barrier beaches. “They might lose their ownership of the beach, but they’ll still have access,” he said.

Mr. Madden underscored the same point and said the issue was not about access, but ownership. “My only concern is that it is not taking away any public rights or access,” he said, adding: “Right now if I had to vote, on the information I have been provided so far, I would vote in support of the bill.”

Mr. Madden compared the issue to the legal situation which exists on beaches other than barrier beaches.

“If there is a property in front of your property, and it erodes away, well, now you’re waterfront,” Mr. Madden said. “In layman’s terms, if you take a Great Pond and draw a line around the pond, that is the property line. If you have a barrier beach in front that was not part of the bottom of the pond it was therefore not commonwealth property.”

But if the original barrier beach went away and reformed on what was the bottom of a Great Pond, it would become public, he said.

Mr. Madden said he is very much still gathering information on both sides of the issue.

Cape and Islands Sen. Dan Wolf said he thinks the intent of the bill is positive, but that he had made no judgment ahead of discussion with affected parties.

The bill is set against the realities of a rapidly changing shoreline around the Great Ponds especially in the face of sea level rise, higher storm surges and greater rates of erosion.

Robert Woodruff, a West Tisbury resident who is the science and education director for the Great Pond Foundation, cited studies showing erosion rates of 10 feet or more per year on parts of the south shore.

“At Squibnocket and Lucy Vincent it’s about seven feet; by the time you get to the Edgartown Great Pond it’s about 10 feet, and it gets greater the farther east you go,” Mr. Woodruff said.

As barrier beaches move inland, he said the Great Ponds are decreasing in size. He estimated the Edgartown Great Pond had shrunk by around 40 acres in the past 40 years.