Jack and Laura Dangermond spent their honeymoon in a pup tent on a remote and spectacular stretch of southern Californian coast. They were students, idealistic and broke.We both fell in love with that place – Jack DangermondOver the next 50 years the Dangermonds grew into billionaires, and all through those years they witnessed the unabating march of suburbia up and down the coast. Their old honeymoon haunt became part of a vast property owned by a hedge fund that develops coastal real estate.We just thought, ‘Well, we just have to do this' – Laura DangermondSo Jack and Laura spied a chance and swooped, shelling out $225 million to save for all time a 10,000 hectare tract of pristine coast and its hinterland of oak forests, hills, canyons and grasslands.I didn't believe what I was hearing. This was a big piece of good news – Mike Bell from The Nature Conservancy, the environmental NGO which was handed the land, its biggest gift ever, by the DangermondsJack and Laura Dangermond are private people who rarely talk to media. But they open up to Foreign Correspondent about how they pulled off this big green deal, and why. They hope their gift will inspire similar acts, big and small, and there is urgency to their message.Time is running out. It's not dark yet but it's late in the day – and people are going to have to move to do this kind of thing in small ways and large ways all over the planet, really quickly – Jack DangermondNow they're challenging Australia's richest people to take a lead as well.I want everybody in Australia getting this idea. I want those who really have large means to look at the amazing places in Australia before it's too late. And everybody else in Australia to plant one more tree, protect one more thing, to play at all levels - Jack DangermondThe Dangermonds' conservation coup has come against the run of play, with the Trump administration seeking to roll back environmental safeguards and open up new territory for commercial development.As North America correspondent Zoe Daniel discovers, Jack and Laura are no left-wing ideologues. Their environmental passion is founded on the hard data that drives their business. Founded nearly 50 years ago, their company ESRI leads the world in digital mapping, its software used by 350,000 organisations to predict flash floods, ease traffic snarls, help the homeless or plot the next Starbucks.I like maps. They're a kind of language, the language of geography, the language of human activities, the language of understanding – Jack Dangermond