Sometimes it is good to remember that when you live on an Island, intimacy with the water doesn’t end when you step off the ferry.

Last week on Arbor Day, Mitchell Posin of the Allen Farm in Chilmark described his newest project: converting pasture to forest. The effort demonstrates how people working the land on the Island can make waterways healthier for their bivalve residents and all the species of ocean fish that venture inside them to breed.

“It’s called silvopasture,” Mr. Posin said. “It’s thousands of years old.”

This spring Mr. Posin is planting more than 100 chestnut trees on his property. He plans to turn sections of the Allen Farm’s rolling oceanfront pastures into a forest underneath on which his animals can graze.

When soil dries out, its constituent parts can easily wash away in a sudden rain. On an Island, everything those sheets of water carry becomes toxic pollution when it hits a sparkling body of water. Damp soil, like a wet sponge, doesn’t easily float away.

This effect is well described by scientist J. Russell Smith, in a book originally published in 1929 called Tree Crops: A Permanent Agriculture. Mr. Smith illustrates how intercropping with trees not only contributes food for animals when the trees fruit, but can actually make the grass underneath them grow better. Iberian ham and Greek lamb are raised on different silvopasture systems that incorporate trees to preserve moisture in the soil, provide fodder and shade for animals and furnish hundreds of goods for human and wildlife uses.

Chestnut tree saplings will need to grow to about six feet before being transplanted. — Ray Ewing

“Chestnut wood is beautiful. It’s also rot resistant, on par with black locust,” Mr. Posin said of his choice of tree. “People used it for fence posts that are still around.”

In 1904 chestnut blight was first observed in North America in a New York zoo. In China where the blight is native, it doesn’t kill the tree; their unique species of chestnut has inborn resistance. By 1950 chestnut blight had moved through the entire range of chestnut forests from Georgia to New Hampshire. Trees that weren’t quickly infected were cut down. People figured they might as well get the wood before the blight reduced it to a yellow gooey mess.

“Twenty-five per cent of the trees were American chestnut,” Mr. Posin said, referring to the forests of northeastern North America.

Mr. Posin is planting trees of the Chinese species, and American trees from both the American Chestnut Foundation, that have been bred to resist the specific ascomycetes fungus that we eventually recognize as blight, and 26 seeds from a vigorous, blight free, second-generation Island chestnut. He has constructed special beds for growing the trees that will encourage aggressive growth. And when it is time to shift the trees into larger containers, the specially designed beds will allow him to move them without destroying their elaborate root systems.

“They’re air-prune beds,” he said. “The roots get to the bottom of the bed and they prune themselves.”

Pasture land to chestnut tree forests.

After a season in his air-prune beds the trees will go into knobby pots made of recycled plastic.

“They’re called air pots,” he continued “They encourage the tap roots to branch over and over, so the trees will be really ready to grow when I put them into the field.”

A sapling in a forest has the trees around and above it to ameliorate the heat of the sun and the drying effect of the wind. On the Allen Farm’s south-facing seaside pastures, the trees will need to be especially resilient to survive.

“When I plant these out in the field they’ll be six feet tall,” Mr. Posin said.

He stressed that if they are going to survive herds of browsing deer and hungry farm animals they will need to be.

Every tree that takes root is a dynamic biological machine for gathering water and nutrients before they can leech into ponds where they suffocate fragile ecosystems and instead, aggregate resources to share with people and animals. From the soil in his beds to the nursery he has prepared in a corner of his yard, below a stout platform where his grandchildren play, every decision has been motivated to give these 106 trees every advantage to speed their growth.

“I’m 65 years old,” Mr. Posin said. “I want to see this happen.”