Louv was brought up on the edge of Kansas City, and would escape from his backyard into cornfields and woods "that seemed to go on forever". A still a special place in his heart. All children needed one and it didn't have to be beautiful, or rural. "A damp, mysterious edge of a vacant lot will do."
Being there took children away from their families and allowed them to generate creative games in their own world.
US children were now subjected to "industrial-strength day care" and rarely played outside. Ninety per cent of children in inner-city San Diego, where he lives, cannot swim; 34 per cent had never been to the sea despite living within 15 minutes reach of it.
New US subdivisions were mainly "gated communities" in which community associations set the curtain colour and banned tree huts in the yard. Some schools were cancelling playtime, to spend more time preparing children for exams.
Louv said this trend had been going on for 30 to 40 years, and it was an academic scandal that it took people so long to realise the harm it did.
Children needed exposure to the natural world to shape their brain development, and adults needed it to relieve stress.
Being outdoors made children's play more creative and more sharing, and increased their ability to be their own boss.
The symptoms of children with attention-deficit disorder were relieved by exposure to nature. "Nature therapy" should be prescribed for them as well as Ritalin.
"Green" schools had better exam results, regardless of their students' socio-economic level. And school-yard games were smarter and more creative on a field than on asphalt.
Louv wasn't against technology, but said the more children used it the more nature they needed. Single-minded concentration on screens closed off other senses and made children "less alive".
By now, most people imagined a dystopian future divorced from nature, "where not even the vampires are having a good time".
But New Zealand didn't have to go that way. It was blessed with generous amounts of nature. He advocated nature-rich cities, towns and schools, filled with other species.
"There's no reason cities can't become engines of biodiversity. New Zealand could lead the world on this."