Two rival communities come ­together to combat environmental disaster in a new children’s book co-authored by Hawaii’s Maya Soetoro-Ng, a well-known peace ­activist and academic.

Soetoro-Ng and her co-author, Todd Shuster, will present the book, “The First Day of Peace,” at Barnes &Noble bookstore at the Ala Moana Center at 5 p.m. Thursday and at the Hawaii State Public Library at 3 p.m. Friday.

Soetoro-Ng and Shuster are also co-founders of New York-based The Peace Studio, a project that acts as a hub for artists, educators, business leaders and others in an effort to rebrand peace as an “action-oriented” concept.

Soetoro-Ng, who is half-sister to former President Barack Obama, said the story is about two communities that are divided over resources, who are brought together by a girl who “makes the first move to persuade the adults in her life to reach out, to show compassion, to be generous, to give where needed and to begin opening a possibility for sustained dialogue.”

“I think there’s a lot of opportunity here to really work with young people, through teachers, through family, through community spaces and storytelling to really let young people know that they’re strong, that they’re brave, that they have things to contribute,” she said in a conference call.

Shuster, who has worked primarily as a literary agent in addition to his work with The Peace Studio, said “it was a joy and pleasure to create a book that shows a young person taking the small step … to bring these groups together who are quarreling.”

In the story, one community lives in the mountains and the other lives in the valley, a reference to concepts in Native Hawaiian and other Indigenous cultures.

“The idea of the ahupuaa, the idea of the division of land from mountain to the ocean, it’s really about the idea that we already know how to manage our resources,” Soetoro-Ng said. “We know how to share, to be in community. We have the guidance of our ancestors. We have the wisdom of the land itself, but we seldom listen carefully. … The idea is to really think about being reflective and mindful of the fact that we already know how to build peace with one another.”

“At the Peace Studio, we believe that there’s enough for everyone,” Shuster said. “There’s tremendous beauty in the natural world; there’s also enough resources in the natural world for all of us, if we can listen to each other and come together in common cause and share. So ‘The First Day of Peace’ illuminates what happens when we’re generous to one another.”

The book, which is illustrated by New York-based artist Tatiana Gardel, retails for $18.99 in hardcover.