Wall on the wild side

Journeying north from Beijing, Robert Macfarlane discovers a leafy reminder of humanity's fragile ex

I spent last autumn and winter living in Beijing, my second long stint in the city. My activities included eating, writing, teaching and walking. Not a bad set of gerunds to live by. But come mid-November, I was beginning to miss the British landscape. The symptoms were all there: listening to Vaughan Williams, reading John Buchan, and spending hours on British weather-forecasting sites. The diagnosis was unmistakable: nostalgia in the 19th-century sense of the word - a missing of one's homeland. And the cure? Well, as I couldn't go home, I needed to get out of Beijing. So I made plans to head "up country", one of those Raj-style phrases that sets my spine tingling with a mixture of excitement and imperial guilt. My father was visiting, so I decided that we would travel north to the mountains, and spend a day on the wild wall.

The wild wall. The phrase was coined by the British sinologist and explorer William Lindesay to describe those sections of the Great Wall of China that haven't been officially "restored". And, by that rule, most of the surviving wall is wild, as only a fraction of its immense length has been reconstructed. In the deserts of Xinjiang, the grass steppes of Mongolia and the plains of Shanxi, thousands of miles of the wall are lapsing back into the landscape, eroded by earthquake, wind, freeze-thaw and plant growth.

A few days before my father and I travelled to the wall, the first snows fell on the mountains. About the same time, braziers were being lit on the Beijing roadsides to roast sweet chestnuts by the hundred in deep cast-iron woks. In that winter atmosphere, my father and I drove north out of Beijing. Within an hour we were up into Miyun County, much of which is taken up by a reservoir the size of a small English shire, which supplies most of Beijing's water. From Miyun, the ground steepened, the road began to climb, and the temperature dropped.

We reached Mutianyu - a restored section of the wall - by ten in the morning. The restoration there has been done handsomely, with greystone masonry, sharp and regular crenellations, and white, limey mortar. The restored section runs for more than three continuous miles, and at times the wall is wide enough for four horses to ride abreast down it. If you squint so that the chairlift disappears, and if you clamp your hands over your ears to shut out the piped Chinese muzak, you might just get a sense of how the wall looked in its defensive prime midway through the reign of the Ming dynasty.

Dad and I walked for two miles west along the restored wall, labouring up what felt like, and probably was, thousands of brick steps to reach a high watchtower. The last section was on a near-vertical ladder, and we popped up into the watchtower like gophers.

At the western end of the watchtower was an open doorway, half-blocked with a metal sign. "No Tourist!" it read, and "Wall Not Restored Past Point". There was a diagram showing a man being crushed by falling rocks. To my father and me, it was an unmistakable invitation to proceed. So we ducked under the low lintel of the doorway, squeezed past the sign, and found ourselves entering another world.

The wall beyond the sign was shattered, steep and fissile under foot. The bricks here, 400 years old or more, were rounded as used bars of soap. The thick mortar was crumbling, white and fractious. To either side of us the ground fell steeply away into oak, walnut and prunus forest, and snow lay in windrows between the trees, white against brown. A light wind rattled the last hanging oak leaves like copper charms.

But the forest did not stop at the wall's foot. No! It had marched on up on to the wall itself - achieving what the Mongols never did. The summit of the wall was thick with scrub and trees. We had to duck, push and scrape our way along it. Vegetation was rife. A blond, punk-headed grass flourished at ankle level. Weeds rioted in every cranny and fissure. There were ring-barked cherry saplings, and a spiny scrub that might have been acacia, with thorns long as sail needles and sharp as snakes' teeth.

We were, I realised, walking through a linear forest. The Great Wall had here become the great hedge. Nature was gradually and thoughtlessly dismantling what human beings had gradually and conscientiously put together.

A mile or so on, we stopped in a watchtower, and each sat astride a crumbling crenellation, eating bread and crisps, watching the land. Away to our south, I could dimly see Beijing in its dark halo of smog, like an extraterrestrial city that generated its own atmosphere. It was a city - with its near-birdless skies and its pollution-thickened water and air - from which the wild had been almost totally rinsed by human action.

I looked back along the shattered wall, with its prospering wildwood. It reminded me of other human structures, from other epochs, that were now sinking back into the land and being reclaimed by wildness.

Perhaps such abandoned places provide us with visions of the future. For as the climate warms and as human populations begin to fall, increasing numbers of settlements and structures will be abandoned. Inland drought and rising sea levels on the coasts will force exoduses. And wildness, in the form of vegetable and faunal life, will return to these forsaken places.

As my father and I pushed our way back down through the wooded wall, I thought of what the poet and forester Gary Snyder said in his book The Practice of the Wild. "A ghost wilderness hovers around the entire planet," Snyder wrote there. "The millions of tiny seeds of vegetation . . . hiding in the mud on the foot of an arctic tern, in the dry desert sands, or in the wind . . . each ready to float, freeze or be swallowed, but always preserving the germ."

This is an extract from Robert Macfarlane's Radio 3 essay series "Wild China", broadcast from 23-26 June at 11pm each night

This article first appeared in the 23 June 2008 issue of the New Statesman, Truly, madly, politically