Three decades ago, Massachusetts became a darling of the environmental movement for requiring developers to replace virtually every square foot of wetlands they destroyed to build houses, parking lots and shopping malls.

The policy was designed to slow the destruction of one of nature’s most underappreciated resources: Swamps, marshes, seasonal ponds and other soggy places that filter pollution, host threatened species and control floodwaters.

Today, the state’s landscape is pocked with hundreds of examples of that policy’s failure, an examination by the New England Center for Investigative Reporting has found.

Some developers never followed through on promises to replace wetlands they destroyed. Many did, but the areas are now dry land, filled with invasive plant species, or are much smaller than intended. Others built are next to roads, sidewalks or other areas that can become degraded from pesticide runoff or foot traffic.

The rate of wetland construction failure is so well known among specialists in the field, that some joke that the best way to identify the sites is by the shopping carts and old tires inevitably dumped in them.

“It’s almost a blanket assumption that they don’t work," to replace the ecological function of what was destroyed, said Matt Schweisberg, former chief of the New England wetlands protection program for the U.S. Environmental Protection Agency, who now runs Wetland Strategies and Solutions, an environmental consulting firm in Merrimac.

Preliminary results of a new state and University of Massachusetts Amherst study highlight the problem. Of 91 wetland projects researchers were given permission to access, 12 never were built at all. In 28 cases, a wetland was attempted to be built but did not succeed. And 51 were created successfully, with some smaller or larger than originally planned.

Systemic, long-running problems plague the state wetlands program, including:

• Administration of the state’s wetlands regulations by local volunteer conservation commissions that can be ill-equipped to enforce the law and monitor the sites.

• State budget crunches that have delayed some long-planned improvements to the wetland system that would help identify and track scofflaws.

• Inherent scientific challenges in building wetlands, especially in smaller areas that were never wet to begin with.

Now, as development picks up with an improving economy and large tracts of affordable dry real estate become harder to find, regulators are rethinking Massachusetts’ wetland replacement policy. Under consideration is more emphasis on avoiding wetlands in the first place, having developers pay into a fund that would create larger, more meaningful wetlands elsewhere, and finding better ways to monitor projects over time.

A decision may be forced soon: The U.S. Army Corps of Engineers, which permits larger projects in conjunction with communities or the state, now allows developers to pay into a fund that will be used to preserve or build wetlands elsewhere. The Massachusetts requirement to replace wetlands on the same property where they were altered can conflict with that federal policy.

Yet developers are concerned that if Massachusetts moves toward the federal model, the administrative cost with such a program would be too expensive. Municipal officials worry that the wetland construction would not benefit the community that lost it.

“The replication areas need to be next to what was destroyed, said Michele Restino, conservation agent for the city of Taunton. “If it goes to Boston (or elsewhere), how does that do any good here?”

To be sure, there are many cases of thriving wetland replication projects filled with frogs, turtles and salamanders, among other species. Examples of reconstructions that have worked include a multi-acre wetland behind the MBTA Alewife station, and the area behind ForeKicks, a soccer complex, in Taunton.

But state officials acknowledge the program overall has not lived up to its original promise.

“There are plenty of places where things can go wrong,’’ said Lealdon Langley, director of the wetlands and waterways program at the Massachusetts Department of Environmental Protection. The state, he said, which was the first to adopt wetland regulations, does not allow as much wetland alteration as other states and is one of the few to even measure its loss.

“We think it’s important to put the emphasis on avoidance, and then (reconstruction). We want to keep wetlands intact,” Langley said.

A fragmented, pockmarked landscape

In Oxford, conservation commission members diligently reviewed a plan in 2007 for a four-home subdivision on a quiet cul de sac. Developer Mark Riel needed to disturb 870 square feet of a wetland, but promised to rebuild one twice the size on the same property.

But Riel never finished the wetland construction, light installation or paving the subdivision’s road, according to town officials. Riel was required by the town to put aside money in case anything went wrong, but most of it was needed to pave the road.

“(The wetland) never happened," said Judy Lochner, the conservation agent in the Worcester suburb. Now, town officials are trying to see if enough of Riel’s money is left for them to do the replication themselves. Lochner said the town now requires replication projects to be constructed as a building goes up and will not give an occupancy permit until the new wetland is complete. Attempts to reach Riel were unsuccessful.

Elsewhere, such as in Franklin and Bolton, wetland areas were designed or built poorly and have invasive species. At The Estate at Franklin, a senior community, nursery workers were busy on a recent frigid day planting swamp maples and summersweet in the third attempt by developer Wegman Companies Inc. to get a wetland replication area working. The wetlands were disturbed to build a road to the complex.

Dan Murphy, the local Wegman representative, did not return calls or an email for comment.

“(They are) trying to do the right thing," said George Russell, Franklin’s conservation agent. “But (these areas) can be hard to build.”

Indeed, recreating a wetland that took nature thousands of years to form, wetland specialists say, is complex. The site must connect to other wet areas. It must have the right soils to support wetland vegetation. And it has to be in the right place so water doesn’t merely drain out of it like a sieve. Wetland replication can add as much as $10,000 to $15,000 for even a relatively small project, wetland scientists say.

The state allows wetland disturbances of up to 5,000 square feet — roughly an eighth of an acre. Anything larger must undergo additional review and must be for the purpose of crossing a wetland to get to a higher area, or for purposes related to health, safety or others projects in the public interest.

Many communities have tougher bylaws than state regulations and some require developers or homeowners to build replication areas twice the size of the area disturbed. Based on state guidance, most require a check in after two years to ensure the area is mostly covered in vegetation.

"When we write an order for replication we want to make sure it’s successful," says Chuck Tirone, part-time conservation administrator in Reading and the assistant administrator in Boxford.

But many conservation agents agree that what happens after that monitoring ends is uncertain. Only about half of the conservation commissions in Massachusetts have paid staff, according to the Massachusetts Association of Conservation Commissions, and many of those are part-time or work on other conservation issues such as open space.

Fixing a hard problem

In many ways, Massachusetts is a victim of its own success. Other states' threshold for requiring wetland construction for disturbed areas is larger. Maine, for example, doesn’t often require replacement until 15,000 square feet, or a third of an acre, is altered.

Massachusetts passed the nation’s first wetland protection law in 1963. Since the 1990s, the state has promoted a goal of “no net loss” of wetlands and conducts aerial surveys to find illegal wetland filling and gives technical help to communities to meet that goal.

But while state officials say that “no net loss” acreage goal is met each year, they and wetland specialists agree the goal is not met in terms of creating wetlands of the same environmental value as those destroyed.

“If you look at the natural system the wetland is in the middle in the woods, its not in the middle of pavement," said Mark Kern, a wetland scientist with the EPA.

State wetland staff levels have been fairly stable — between 40 and 45 people over the past 12 years, according to state officials, in part because the state gets about 5,000 applications a year requesting to work near a wetland or to disturb some portion of it.

Yet budget cuts have taken a toll: While the state is now able to geo-locate permitted projects and enforcement actions, it ran out of money to provide that access to local conservation commissions. Officials also created a program called eDEP that allows on-line filing of permit applications and orders of conditions from local conservation commissions, but the system is over capacity and no new permits can be filed.

State wetland officials, and wetland specialists, did not dispute NECIR’s tally of hundreds of constructed wetland sites that have failed in some manner, given the longevity of the program and findings of studies looking at wetland success rates.

Still, while the wetland replacement rate is far from perfect, it is improving. A 2001 UMass Amherst study found that developers never bothered to construct 22 percent of required wetland projects; its recent study found that the rate had dipped to only about 13 percent.

Still, officials are discussing how the process should be fixed. One option is to avoid more wetland destruction altogether, although that may not always be possible given development pressure.

Another idea is for developers to focus more on restoring historically wet areas, such as agricultural land, where success is usually better. But there are not many available sites in New England, wetland scientists say.

The state is evaluating options, including improving monitoring efforts on site or some version of the federal model, where developers can choose to replicate on site or pay into a pool to construct or save wetlands elsewhere.

We would “like to have both options," said Chip Nylen, an environmental attorney and regulatory counsel with NAIOP, the commercial real estate development association. “The policy still makes sense to allow wetland fill to take place. It’s up to the conservation commissions and the owners to get it right.”

No timetable exists for creation of a new plan. But officials, locally and elsewhere, say one is needed before even more wetlands disappear.

“It involves difficult political decisions," said Schweisberg, the former EPA wetland chief. “And no solution is perfect.”

NECIR intern John Hilliard contributed to this report. Beth Daley is a reporter at the New England Center for Investigative Reporting, an independent, nonprofit news center based at Boston University and WGBH News. She can be reached Follow her on twitter @bethbdaley.

Environmental attorney Chip Nylen and environmental consultant Matt Schweisberg discussed the issue on Greater Boston: