It’s easy to look at the long list of problems facing the environment–mass extinction, dying oceans, climate change–and wonder whether things might have gone a little too far to fix. A recent study argued that we’ve already passed four out of the nine “planetary boundaries” needed for Earth to keep working the way that it has for the last 12,000 years.

But despite the scale of the problems, one of the authors of that study believes that the world as we know it–the only conditions that have ever supported humans–can still be saved.

Photo by: Mattias Klum

“The window is still open, barely open, to transition back into a safe operating space,” says Johan Rockström, executive director of the Stockholm Resilience Center in Sweden. In a new book, Big World, Small Planet, Rockström lays out the case for hope, and explains how we can transition to a fully sustainable world–energy, food systems, cities, transportation–without sacrificing quality of life.

The technology that can make that happen is ready to scale now. “We know, for example, that to get back to a stable climate future we need to basically decarbonize the world economy by 2050 or 2060,” he says. “Just five years back, that was utopian. Now we can actually say we know we have the solutions.”

He calls it a “Montreal moment” for climate. In the 1980s, the world managed to agree to phase out the CFCs that were putting a hole in the ozone layer. “It worked because three criteria were fulfilled,” says Rockström. “The science was established and accepted, the technologies were available and scalable, and there was a very good substitution. Human well-being was not sacrificed. For the first time, we can say that actually applies for climate.”

Borneo Photo by: Mattias Klum

In the book, he argues for need for a “mind shift” that reconnects societies and economies with natural systems–a reminder that we rely on those systems for survival, and they have limits.

That’s something that wasn’t obvious in the recent past, as resources like freshwater, or ocean fisheries, seemed inexhaustible. Rockström calls it a planetary subsidy. “It actually worked quite well,” he says. “You cut down forests, it was an economic subsidy, and you delivered economic growth. You didn’t have to pay anything. The planet didn’t send any invoices back. It was a free ride. That free ride is over.”