Michael Bywater: Welcome back. Sorry we ruined the planet

An open letter to the woman who is back home after 19 years lost in the jungle

My dear Rochom P'ngieng

If it's true that you spent 19 years in the Cambodian jungle, you'll have realised by now that changes are like assumptions: we don't know we're making them, and they creep up on us while our back is turned. It's also said (though in the Information Age we take nothing for granted) that you're thinking of heading back to the wild.

There's plenty for you to think about. Plenty for the rest of us, too, because it's only when we step back and look afresh that we spot the changes all around us.

"Hello," we cry in alarm, "nobody smokes! Everything beeps! Everyone is earplugged, nodding! And the Commies have gone!" Then we start to notice. GM food, rucksack bombs, rows about stem cell research, global warming, iPods, email burnout, anti-depressants, obesity, the Middle East, spam, porn, the iPhone... These things probably don't mean that much where you are. But the world has changed. You turn your back for two decades and things are different.

Not that materially different, mind you. Even if the post-modern world only impinged on you from a distance, you were born into it, its infrastructure complete if not yet fully realised. Jet planes, napalm, bubble gum, trainers, radar, nylon, the Pill, hypertext, the atomic bomb, the microwave, credit cards, superglue, bar codes, McDonald's, fibre optics, modems, Valium, computer games, silicone breast implants, CDs, food processors, word processors, ethernet, laser printers, liposuction, inkjets, cellphones, personal computers: all there, waiting, on the day you vanished.

And while you've been away? Not that much dramatically new; it's more that existing things have improved. The internet, DNA- testing, the human genome project, broadband, cellphones - all the biggest changes have been either natural, political or cultural. And, of course, Communism, which packed its bags and stole away into the night of the 11/12 November 1989 when the Berlin Wall came down, just two years after they say you ran away to hide.

The effects were global. Even China changed its mind and has become the world's factory, scaring the hell out of everyone else with its economic growth and its hunger for energy. The world you step back into is a different place. The most unexpected triumph is that of the internet, thought up by the Americans when we were all terrified of the USSR (except for people such as yourself, who had things closer to home to be terrified of). In the West, thanks to the net, much of life is now spent staring into a screen. Globalisation is on the march and coming soon to a village near you.

Television is losing the plot, diluted into a thin, diffuse stream. Thanks to GPS, nobody need get physically lost, though we're culturally lost much of the time.

People know more and more and understand less and less, and in the face of this (among other causes) religion is back, and this time it's armed. The world's divide, from where I am standing, is no longer Communism vs. capitalism (such a shame; how Communism would have loved the surveillance opportunities offered by the internet) but Islamism vs. Western materialism.

Which, of course, is immaterial to you and to the majority of the world's people, who still live much as they have for centuries: in relative poverty, from day to day. But not for much longer, because while you've been away, we discovered we seem to have buggered up the planet. Now it's turning against us, probably irrecoverably. Sorry about that.

Still, your experience in the forest may stand you in better stead in the years to come than a 60Gb iPod and a working knowledge of Web 2.0 design. However, if you do decide to go back, we'll know about it. Because there's nowhere to hide any more.