India, July 12 -- On a Saturday evening in Thane, nearly 50 young people, most of them in their 20s, gathered after work to watch a documentary. For the next 75 minutes, they barely moved. As The Last Mangroves of Mumbai unfolded, the room fell silent. Familiar faces of activists, lawyers, researchers, fisherfolk and ordinary Mumbaikars appeared on screen, speaking calmly but passionately about a campaign to protect the city's mangroves. By the time the credits rolled, the audience seemed less like spectators and more like participants in a movement.

The opening scene sets the tone. As a group of citizens sing in protest against the proposed Mumbai Coastal Road (North), the documentary makes it clear that this is not merely a film about ...