There were seven of us, all squeezed into a cramped semi in a west London suburb. We rarely saw the horizon, and the main wildlife event was a daily visit of a flock of parakeets to our bird feeders. When we upped sticks and moved down to the Somerset Levels six years ago, my two older sons stayed put but the younger trio, Charlie, George and Daisy, came along with us.
Our new home could hardly have been more different. We now live in an 18th-century farmhouse with assorted outbuildings, hot and cold running mice and more than an acre of garden. I say garden, but 'gone-to-seed-meadow' would be nearer the truth. Gardening has never been my strong point, so the grass is now longer, the brambles thicker and the hogweed taller than when we first arrived. It's a world away from our previous suburban existence.
My children – now aged eight, seven and seven – take their rural surroundings for granted. And like all children their age, the rival attractions of CBBC and computer games do sometimes prevent them getting off the sofa and venturing outside. But when they do, they are transformed from couch potato kids into free-range children.
As I watch them racing off, nets in hand, to hunt down unsuspecting insects, I am filled with pride and joy. Pride that my children are rapidly turning into genuinely knowledgable naturalists, able to identify buzzards and bullfinches, catch gatekeepers and grasshoppers, and enjoy rare visitors such as the hummingbird hawkmoth that graced our buddleia bush last summer. Joy that they are, little by little, learning to love the natural world. For me, it was this passion that enabled me to turn my childhood hobby into my life's work as a naturalist.
Yet I am also worried. Not for my own children, because nature will always be an important part of their lives. My concern is for other children up and down the country – in cities, suburbs, towns and villages – for whom the natural world is a closed book.
I've spent the past six months writing a report for the National Trust, Natural Childhood, on what we can do to reconnect our nation's children with nature. It's made me realise that the issue is both a lot more complex, and a lot more important, than many people assume.
This social condition now even has its own quasi-medical name, Nature Deficit Disorder. This refers to the now default state of affairs in which children are hardly allowed into the natural world at all, and when they are, only under strict supervision. The days when our mums sent us out with the instruction to 'be back home for tea' are long gone.
The world is now divided into two camps, separated by whether you were born before about 1970, or after. When I meet people in their seventies or eighties they often tell me about their childhood nature experiences, sometimes going back before the start of the second world war. They are often surprised that I share their memories: that I, too, collected frogspawn and tiddlers in jam jars, picked bunches of wild flowers to take home to Mum, and even – shock horror – took the odd bird's egg.
But when I meet younger people, even those who have embarked on a career at the BBC Natural History Unit, I am often amazed at the lack of freedom they had as children. If they do know about British wildlife, it is usually because one or both of their parents are naturalists. Those who, like me, came from a family where we were the first to take an interest in nature, are few and far between.
Why this has come about is obvious to any parent. Whereas we, and previous generations, had the freedom to roam where we liked at weekends and during school holidays, today's children have their lives organised, planned and controlled to a military degree. Even if they do encounter wild animals or plants, this is usually as part of a 'nature experience': a guided walk, a school lesson, or via a TV or computer screen.
Richard Louv, author of the classic work Last Child in the Woods, is the man who coined the phrase Nature Deficit Disorder. He has pointed out that today's children now know more about the wildlife of the Amazon rainforest than they do about their own backyard. My own children may be avid fans of Steve Backshall and his Deadly 60, but they also enjoy their own hands-on encounters with nature, even if they do suffer the occasional sting, prick or bite.
But does it really matter if our children are disconnected from the natural world? Well, apart from the obvious benefits to their physical and mental health (there aren't many obese naturalists), there is also the sheer joy that these experiences – often unexpected, sometimes scary, but always fulfilling – bring.
There are other, less tangible benefits to getting outdoors. Being allowed to roam free with your friends is a fantastic way to learn about yourself and about risk, which we all appreciate when we climb a tree – and even more so when we fall out. It also teaches children about working together as a team, a valuable lesson for later life.
So short of giving every child the opportunity mine have enjoyed to roam freely around their own safe and secure wildlife haven, what can we do to reverse the tide and reconnect this generation of cotton-wool kids with the great outdoors?
Getting our children back to nature has to start with us parents. There are lots of ways to help them explore the natural world without feeling tied to our apron strings. I've taken my children to a local wood and simply told them to 'get lost'. Seeing their expressions waver between fear and delight, and hearing their tales of what they did when we weren't watching over them, is incredibly fulfilling.
And please, please don't stop your children touching, picking, catching and collecting what they find; whoever coined the conservationists' mantra "take only photographs, leave only footprints" had clearly forgotten what it is like to hold a frog, pick a bluebell or catch a butterfly.
Finally, as they reach the teenage years, allow them the freedom to explore wild places without adults following their every footstep. Scary, perhaps – for you and them – but incredibly rewarding too. By letting go a little, you will enable them to learn a lot.
• The National Trust wants to hear your ideas about how to reconnect children with the natural world. Email firstname.lastname@example.org or tweet @outdoor_nation.
guardian.co.uk © Guardian News and Media 2012