The Martha’s Vineyard Land Bank Commission voted unanimously Monday not to delay construction of a protective fence around the Trade Wind Fields Preserve in Oak Bluffs, but to design the fence as close to the open sandplain grassland as environmental restrictions allow.

In practical terms, that means the fence surrounding the preserve will be abutting the field in about half the area, and at least 10 feet into the woods in the other half of the preserve.

The land bank commissioners vote rejected the advice of the Oak Bluffs land bank advisory board, which voted last week to delay the fence construction for six months to evaluate and explore other options.

Land bank ecologist Julie Russell said a delay risks losing endangered species.

“This fence is necessary to save this habitat,” Ms. Russell said. “If we want to save the sandplain grasslands, the diversity of species in it, and do it justice, then the fence is what’s necessary. Our signs have not kept people out, our information has not kept people out.”

Ms. Russell said the land bank decision to fence off the preserve triggered an application to the Massachusetts Natural Heritage and Endangered Species Program (NHESP). That organization agreed with the land bank request to put up a fence, but required it to be at least 10 feet from any endangered species.

Sarah Thulin, a land bank commissioner from Aquinnah, questioned whether a delay was a wise decision, in light of the NHESP restrictions.

“They do give you time frames,” said Ms. Thulin. “I don’t know if delaying the fence puts us in jeopardy of losing good graces with this organization.”

Land bank commissioner Mary Ravitch from West Tisbury called the fence a reasonable course of action.

“I am not quite seeing that that use would change all that much,” Ms. Ravitch said. “It would move the trail, but the people would still use the trail. There would still be a fence but you would still view the grass plain area. It wouldn’t be open to people crossing it. I think it’s a reasonable thing to do.”

Land bank commissioner Pamela Goff of Chilmark agreed. “You have to look to the future population that is going to use the property in question,” she said. “If there is something really in jeopardy, then you have to act for the property.”

The decision did little to appease about a dozen Island residents who oppose the fence plans and attended the meeting. Some disputed the ecologist’s contention that lack of attention to signage has further damaged the conservation parcel.

“She says the signage hasn’t worked,” said Jane Hawkes of West Tisbury. “It has, that’s exactly our point.”

“She herself said she could not speak to whether it has improved or not improved because she hasn’t surveyed it in two years,” said Idalyn Gilstad of Vineyard Haven.