Blame It on Leo: DiCaprio is a colorless pitchman for green thinking.

It’s sometimes suggested that Al Gore—globe-trotter, overeater, and big-house owner—is not a credible advocate for reducing carbon emissions. But he’s a desert hermit compared to the cause’s new spokesman, international playboy and Hollywood screen star Leonardo DiCaprio. Narrating The 11th Hour, which he also co-produced, he stalks various picturesque landscapes while glaring at the viewer and demanding that “our pivotal generation” make changes. Sibling writer-directors Leila Conners Petersen and Nadia Conners apparently thought Leo would inject some urgency into their redundant broadside, but he actually comes across like a washed-up ’90s child star who’s now paying the bills by doing infomercials: “You can save the Earth for only $9.99 a month! Act now and we’ll throw in a plan to terraform Venus with recycled Evian bottles!” The bulk of the film consists of brief remarks by more than 50 experts on ecology, architecture, oceanography, economics, land use, “slow food,” and more; among the celebs are astrophysicist Stephen Hawking, former CIA director R. James Woolsey, one-time Soviet dictator Mikhail Gorbachev, and new-age hacks Dr. Andrew Weil and Deepak Chopra. To lessen the film’s classroom vibe, the directors include occasional enviro-shock inserts—a baby seal’s bludgeoning, Hurricane Katrina horrors—which sometimes accumulate into world-gone-wrong segments that suggest Godfrey Reggio’s 1982 Koyaanisqatsi. (The music is a little more disjointed. Where Reggio had an exclusive deal with Philip Glass to score his film, the soundtrack to The 11th Hour taps Sigur Rós, Mogwai, Harold Budd, Cocteau Twins, Coldplay, Dirty Three, and German lyrical-techno act Triola.) After an hour of attempting to eco-terrorize the viewer, the directors switch into a prescriptive mode, which is just as dull as their alarmism. “Things are the thieves of time,” warns the film, but that’s unlikely to sway a generation that’s pivotally besotted with iPhones, SUVs, and plasma-screen TVs. An Inconvenient Truth delivered this flick’s message more clearly and more intelligently—and with more wit, as well. Big Al may be a pudgy old guy, but he’s a far sharper lecturer than Little Leo.