Walking along the shore of Black Point Pond in Chilmark, Richard Johnson of Sheriff's Meadow Foundation is nearly dwarfed by a thick stand of 12-foot high reeds.

Also called phragmites, the reeds are an invasive species that have formed a dense monoculture over what was once an open diverse habitat of native pondshore plants. Dead reeds crunch beneath his boots, covering the ground so virtually nothing else can grow through.

One of the most widespread invasive wetland plants in the United States, phragmites have colonized and dominated much of the Delaware and New Jersey shoreline, and are found in virtually every state. At a rapidly growing pace, they are also now taking over many Vineyard ponds. Stands of phragmites can be found in Squibnocket Pond, in all of the southern Great Ponds, and in Crystal Lake in Oak Bluffs, just to name a few.

Concerned about the spread of the reeds and the corresponding loss of important pondshore habitats, Sheriff's Meadow Foundation last week received approval from the Chilmark conservation commission to remove about three acres of phragmites from Black Point Pond later this summer.

"We want to open this up and get the pondshore back," said Mr. Johnson, executive director of the foundation. "We're trying to restore the habitat back to a functioning, healthy system. The last time I was here we had three or four different species of shorebirds feeding. Now there's none."

Next to inappropriate development, invasive species pose the gravest threat to global biodiversity and habitat loss. Which is why Sheriff's Meadow Foundation and other groups, such as The Nature Conservancy and the Polly Hill Arboretum, have made controlling invasive species a top priority for the conservation work on the Island.

"I consider it the most important thing I can do. Here we've conserved all this land on the Vineyard, and yet we're losing what's unique about it," Mr. Johnson said. "In 10 or 15 years we're going to be looking at a very different Vineyard if we don't address this problem soon. And the changes are not only of biological or ecological importance - it's a character issue too. If we let these nonnative species take over, the Island is going to end up looking just like everywhere else."

Because of their aggressive tendencies, techniques for removing invasive species are often less than ideal. Robert Woodruff of West Tisbury cleared out a couple of acres of phragmites in a dredging project in Mink Meadows Pond a few years ago, but rhizomes remained in the sediment, and the reeds have already reappeared in force.

"I'm astounded by how much it has spread," Mr. Woodruff said this week.

Conservation groups agree that the most effective way to control phragmites is through the careful application of a small amount of herbicide, to the tune of roughly half a gallon per acre.

But unsurprisingly, the use of poison - sold under the commonly used brand name Roundup - has not sat well with some residents.

Christopher Murphy of Chilmark opposed the most recent Sheriff's Meadow proposal, and at a town meeting two years ago convinced his fellow voters to reject a town-funded phragmites project in Chilmark Pond. As a retired commercial fisherman and a current member of the Martha's Vineyard Commission, he said his main concern is the health of the ponds, which he believes will be degraded by the herbicide.

Mr. Murphy believes phragmites and other invasive species must be viewed from a broader perspective.

"Nothing stays the same in nature; even a rock gets worn down by weather over time," he said this week. "If we look out at these ponds and sometimes see cattails, and other times phragmites, is that necessarily bad? I don't think so. Nature has a way of balancing these things out in the long term."

The most recent proposal is modeled after a successful project last fall that removed half a mile of phragmites in Doctor's Creek near Abel's Hill; Sheriff's Meadow Foundation hopes it will become a pilot program that encourages other landowners to eventually tackle all the reeds in Black Point and Chilmark ponds. The initiative is also being watched closely by other conservation groups on the Vineyard - including The Trustees of Reservations and Great Pond Foundation - who would like to remove stands of phragmites spreading in other ponds on the Island.

Optimism for the effort is running high with the emergence of a new funding mechanism that allows for partnerships among private landowners, nonprofit conservation groups and public environmental officials. Recognizing that more than 80 per cent of land in the commonwealth is privately owned and that their conservation goals could not be reached by focusing on public lands, the Massachusetts Division of Fisheries and Wildlife in 2004 created a landowner incentive program that provides up to 75 per cent of funding for projects brought forward by private landowners interested in maintaining native wildlife habitat on their property.

Initiated by longtime Chilmark seasonal resident Jane Wilkie, the phragmites removal near Abel's Hill was one of the first 70 projects funded through the state program. After a series of ups and downs trying to get the project off the ground, the program provided some $20,000 to clear about four acres of phragmites from Doctor's Creek, which connects upper and lower Chilmark ponds and was almost fully choked with reeds last summer. The creek is now easily navigable for the first time in years, with some signs of native plants already making a return.

"Everybody's impressed with the results," said Mrs. Wilkie, a retired college professor who spent years working on the phragmites project. "It's back to looking like it did 15 years ago, before it was all filled in with reeds."

Mrs. Wilkie acknowledges that the project was not an easy sell to her neighbors, and that the main sticking point was the use of herbicide. She said she was skeptical too at first, but that after years of research she accepted that it was the best of other bad choices.

But Mr. Murphy said phragmites can have some positive side effects, such as providing cover for smaller birds hiding from predators. He also pointed out that the most damaging invasive species on the Island is the one to which we all belong.

"It's not like I'm a total tree hugger. I spent the earlier parts of my life hunting deer and duck down at Black Point," Mr. Murphy said. "I just know that the bottom line is, we almost always end up regretting what we've done in these cases. Every time we screw around with nature, we seem to get it wrong."

Mr. Johnson said the herbicide decision has weighed on him heavily, and he admits that he does not know for certain that what he is doing is right.

"Maybe in 10 or 20 years people are going to say I screwed up. But I feel strongly that we can't do nothing," Mr. Johnson said, adding that the Vineyard's coastal great ponds are some of the best preserved remaining habitats of their type in the world. "If we don't do some active management and give it a shot, I believe we're going to regret it."

An osprey screeched as it flew overhead to protect its nesting pole nearby.

"Either you do the best you can and hope you did the right thing," Mr. Johnson said, "or you step back and watch what was once beautiful disappear."