THE 11TH HOUR has all the hallmarks of a can't-miss hit: debut at Cannes in May, red-carpet premieres in New York and L.A. in August, and star Leonardo DiCaprio. But that's where the Hollywood pretty picture ends. "This movie is about human extinction," says Leila Conners Petersen, who co-directed the 90-minute film with her sister, Nadia Conners. (DiCaprio narrates and co-produced.) "We're talking about a species creating the conditions for its own demise."

Due out in wide release this fall, the newest Hollywood eco-doc will inevitably be compared to Al Gore's An Inconvenient Truth. But while Gore's global-warming extravaganza aimed to educate (the world is melting), DiCaprio's multi-issue approach is out to shock (destroying nature equals destroying human life). Whereas Gore's film rose and fell on the strength of his personality, DiCaprio appears only periodically in The 11th Hour, ceding the stage to 54 academics, environmental advocates, entrepreneurs, designers, and others, including physicist Stephen Hawking, former CIA director James Woolsey, and architect William McDonough. "The scholarship and content behind this had to be bulletproof," says Conners Petersen, alluding to the skepticism that can greet celebrity-driven projects. (The Conners sisters and DiCaprio teamed up on two previous environmental shorts, "Global Warning" and "Water Planet.")

Brace yourself: The film draws you in but can be damn depressing, especially in its first half, when various experts opine on everything from dying oceans to mass extinctions to weather gone mad around the world. DiCaprio narrates from nonspecific natural settings, then cuts to the talking heads, their voices overlaid by a rapid-fire succession of beautiful shots of Mother Nature interspersed with violently degraded ones. Much of the bad news we've heard before, but seeing all the dots connected compounds the impact. While the film gets a little lost in leftover hippie clichés during the anti-corporate second act—"What we need to do is find a harmony between people and nature," says one commentator—it convincingly portrays the ongoing conflict between environmental and economic progress.

The 11th Hour comes most alive in its final half-hour, offering cautiously upbeat avenues toward sustainability, from simple tips like using compact fluorescent lightbulbs to more complex solutions like carbon taxes and biomimicry (industrial design inspired by nature). One esoteric example: a nightclub powered by the energy of human movement on the dance floor. "We get to reimagine every single thing we do," marvels environmentalist Paul Hawken. "What a time to be alive."

Al Gore established that Americans have an appetite for green documentaries, but will people turn out for another one? "We're always saying, ‘OK, they're out on a date, and they're looking at the marquee. Are they going to see this environmental movie?' " Conners Petersen says. My bet is they will. What remains to be seen is if they'll really listen.