ROCKLAND, Maine — In an effort to boost dwindling year-round island populations, the Maine State Housing Authority is making $2 million in grants available to build affordable housing on offshore communities.

Not so long ago, 300 Maine islands had year-round communities, but that number has dwindled to 13, according to Roger Berle, chairman of the Maine Islands Coalition, a collaboration of island communities facilitated by the Island Institute.

“We’re running on the edge of survival and have been for a long time,” said Berle of Cliff Island, as islanders and supporters gathered Friday to announce the funding at press conferences at both the Island Institute’s headquarters and the ferry terminal in Rockland.

Berle said only three children attended the Cliff Island school this year.

Doug Boynton of Monhegan Island said enrollment in his community’s one-room schoolhouse would drop from four students to two next year.

Young people just can’t afford $500,000-plus houses, Boynton said.

“On Monhegan we have the highest cost of housing. It’s $500,000 for a house of any sort there,” Boynton said. “There’s no one there now who lives there year-round who could afford something on the housing market today.”

Boynton said the Monhegan Island Sustainable Community Association plans to apply for a couple of the grants that will become available in July.

“We did a lot of groundwork because we saw this coming,” he said.

So far, his association has bought an acre to build a house on and acquired another house to refurbish with grant money from the Maine Energy, Housing and Economic Recovery Program.

The 124th Legislature established the program within the Maine State Housing Authority to support, among other things, the construction and renovation of affordable housing in Maine. The program is funded by revenues from the real estate transfer tax, state revenue bonds and loan repayments to the program.

The $2 million in grant funding announced Friday resulted from revenue bonds issued by Maine State Housing Authority. Applicants can seek up to $400,000 per project to create multifamily rental properties that people who make 50 to 120 percent of the area median income can rent and, in some cases, rent to own. Eligible islands are: Isle au Haut, Matinicus, Monhegan, North Haven, Vinalhaven, Chebeague, Cliff, Frenchboro, Great Cranberry, Islesboro, Islesford, Long, Peaks and Swans. Grant awardees must match their grant by 20 percent.

Liza Fleming-Ives, the associate director at Genesis, a statewide nonprofit organization that helped advocate for the legislation the led to the program, said it is unusual for such affordable housing funding to be made available to people with 120 percent of median income. Fleming-Ives said this program is more flexible than most because it is so expensive to build homes on an island.

“It costs 20 to 30 percent more to live on an island. Food costs more. Transportation costs more. Building on an island costs more,” she said.

Building on an island can cost 40 percent more than building on the mainland, according to Rob Snyder, vice president of programs at the Island Institute.

Snyder said that if affordable housing is not created to entice young families to move to islands, the year-round communities could be in danger.

“The greatest challenge right now is finding ways for young families to move onto an island and getting a house from there,” Snyder said. “Without those families] the communities grow old much faster and their sustainability comes into question.”

Maine Speaker of the House Hannah Pingree of North Haven said all the islands are “losing young people, losing housing stock to summer people.”

“We have a ton of young people who’ve come back who can’t find a place to live,” Pingree said. “These are kids who want to work, who want to live on the island. They’re scrounging.”

The money from the grants will be available July 1.

For information, call the Maine State Housing Authority at 626-4634.