A documentary by Nicolas Brown. Rating unavailable

Brit-based award-grabber Nicolas Brown has produced and directed scads of science-minded docs for TV, but The Serengeti Rules is the first he also wrote, and it’s obviously a labour of love. The swiftly moving effort is based on a book of the same name, and author Sean B. Carroll sometimes appears on-screen, explicating (and occasionally overselling) the theories that connect five scientists with a lot in common.

The most influential was University of Washington zoologist Robert Paine, dying of leukemia when this was filmed, but his enthusiasm for the intricacy of ecosystems remains undimmed, even when talking from his bed.

Fifty years ago, Paine started wondering if animal-habitat observers had things wrong; maybe loads of small animals didn’t support a few big critters atop the food chain, whether in the vast African savanna or in tiny tidepools. It was obviously easier to empty the latter of predators, for the sake of study. And he discovered that when your basic starfish were taken out of the equation, the pools lost their biodiversity.

His acolyte Jim Estes went to Alaska’s Aleutian Islands and discovered that a sudden dearth of sea otters meant an overabundance of urchins, thereby wiping out the vast kelp beds that act as the ocean’s lungs.

The title takes its name from the work of Tanzania-raised UBC professor Tony Sinclair, who applied Paine’s theory to the Serengeti, but found that wildebeests, not lions, were the “keystone species” keeping that system in balance.

Conservationist John Terborgh saw that the absence of jaguars and birds of prey in the Venezuelan jungle allowed leaf-cutter ants to, well, cut down every leaf in sight.

Mary Power, the only female in the group, came to science by accident, as a child. Saddled with unusually bad eyesight, she discovered that she could see much better underwater, and devoted most of her subsequent energies to exploring coastal and riverbed systems.

Throughout, the film intercuts the subjects’ stories with stunning, National Geographic–level footage, as well as reenactments of their early exploits—usually a kind of needless padding, but the actors are very well-matched with the scientists, and these scenes help convey the wonders they felt upon discovery.

The film is intent on passing the torch to young activists today, suggesting that now that we’ve figured out how the planet works, we could actually do something to protect it. If we, you know, want to.