The reaction to Sharkwater, a debut film by  Rob Stewart, made the Toronto documentary maker into an optimist.

Made at great personal cost including a lost relationship, a stint in prison and a mountain of debt, Sharkwater became one of the highest-grossing Canadian documentaries ever made.

But more important to Stewart, who has loved fish ever since he was a child, it inspired hundreds of shark conservation groups and led to bans on shark fin soup around the world.

On Wednesday, Stewart talked to Jian Ghomeshi, host of CBC’s Q current affairs show, about his newest projects – the  documentary Revolution that will screen at the Toronto International Film Festival and the memoir Save the Humans, released last week.

This time the Canadian conservationist is trying to use his higher profile to save nothing less than humanity itself.

Stewart told Q he began thinking of saving more than just the sharks after attending environmental film festival and conservation conventions in support of Sharkwater.

"At the time I thought saving sharks was  the most important issue on the planet -- we can’t undermine a form of life that’s 40 million years old," he said.

"But I met all these scientists and conservationists who said ‘What you’re doing with sharks is great, but you’re missing the point. We’re going to lose everything and if we lose everything we won’t have any sharks left.  By the middle of this century we could have no fish in the sea, no coral reefs, no rainforests and a planet that can’t sustain many forms of life.’"

Stewart believes that if he can educate people about their impact on the planet, and what they stand  to lose, they'll make the personal changes needed to save humankind from itself.

With Revolution, Stewart says he wants to infuse others with his own love of the sea and its wonders – and point out the long-term effects of both climate change and human consumption of fish on marine ecosystems.

His memoir, Save the Humans, talks about the making of Sharkwater and how he became so interested in life under the sea, but goes one step further – pointing out that we will not be able to feed ourselves soon unless we change our patterns of consumption.

He’s confident that message will get through, he tells Q, despite Canadian government policies that disregard the environment.

"Studies have shown that the thing that’s going to change our behaviour the most is the actions of our peers. Until our peers start recycling everything, we are not going to start recycling, By educating everybody and letting everybody know what’s going on, our actions are going to change," he said.