Polar bears and howler monkeys and charismatic megafauna galore. If this sounds a little overwhelming to you — and you have no idea what charismatic megafauna means — you are not alone.

“The Great Immensity,” a new musical created by theater company The Civilians that is currently playing at the Public, is filled with long words and complicated concepts that can easily leave an audience feeling swamped with information about climate change, activism and the future of the earth.

“Immensity” tells the story of a nature videographer, Karl, who is forced to face the reality of the changing climate when confronted by Julie and her group of teenage UN ambassadors who want to save the world. When Karl disappears, his wife Phyllis chases him from Panama to Canada in an attempt to figure out where he is and what he is doing.

Along the way, the audience is presented with some smart, socially conscious musical interludes on topics such as the history of the UN Climate Summit and the process by which animals go extinct.

The production, written and directed by Steven Cosson, feels neither wholly complete nor wholly disjointed. Certain aspects, such as the video projections that play a central role in the story’s development, are skillfully woven into the narrative, creating a multimedia experience. The four ensemble members slip from one role to another seamlessly, creating a varied cast of characters surrounding Phyllis, Karl and Julie.

However, parts of the musical are fragmented. The narrative is not chronological, which can make it hard to follow at times and has a tendency to muddle the play’s message, which is somewhat unclear to begin with.

“Immensity” makes the point that people must act to prevent further damage to the climate, and it even shows characters who are doing just that by taking extreme measures to force the United Nations to move forward with environmental reform. But because the audience follows Phyllis throughout the musical, it is primarily focused on her search for Karl. As a result, the message of climate change gets lost among the more accessible relationship drama of the main characters.

The exception to this is the musical interludes, which pepper the scenes of the main story.  Performed out of character by the ensemble members, they are witty and thought-provoking. The score, by Michael Friedman, is at its strongest during these moments.

Ultimately, the musical does come together nicely. As Karl and his band of teenage UN ambassadors take a stand for climate change, the play’s message — that action is not only a necessity but also a responsibility, a promise we can make to the future — shines through.

Without serious change, the polar bears and howler monkeys and other charismatic megafauna will die out, and so will humans. The world is a big place — great and immense, as the title suggests — and it is our job to keep it safe.

“The Great Immensity” is playing at the Public Theater, 425 Lafayette St., through May 1.

A version of this article appeared in the Tuesday, April 22 print edition. Dylan Jarrett is books and theater editor. Email her at [email protected].