There is a mighty sycamore tree in Scotland that has swallowed a bicycle. The story goes that a local boy left his bike propped against the trunk when he went to war in 1914, and never came back. Over the decades, the tree embraced the old bicycle, growing around and over it, gathering the machine into its woody heart. Today, all you can see of the bicycle are the handlebars poking out from the trunk.

The Bicycle Tree of Brig o’Turk is a fitting testament to the symbiotic relationship between man and tree: the tree has not suffered from absorbing the bicycle; the plant and the man-made object are successfully growing old together. But now the local residents are calling for a preservation order to protect their iron-eating tree.

Trees forced to live in proximity to urban humans are in danger as never before. A report yesterday by the London Authority gave warning that the capital’s seven million trees face “a chainsaw massacre”, with some 40,000 full-grown trees cut down by councils in London over the past five years.

Some were old and dying. Many were simply seen as a nuisance. Our attitude towards urban trees is weirdly ambivalent. We claim to love them, but barely notice as they vanish, while demanding that the council hack them down without mercy if they impinge on our daily lives or, worse, our house prices.

William Blake had it right: “The tree which moves some to tears of joy is in the eyes of others only a green thing which stands in the way.” We are both tree-huggers and tree-muggers. City trees are accused, often wrongly, of causing subsidence; the pigeons in their branches bespatter our cars; their leaves cause mud and blockages; we fear their rotten limbs might fall on us; their foliage obscures the CCTV cameras that must now follow us everywhere.

Insurance companies are quick to blame the nearest tree for every crack in every ceiling. Councils, facing claims and fearful of litigation, swiftly reach for the chainsaw. Some 40 per cent of the trees felled are due to insurance claims, according to the assembly report, of which perhaps 1 per cent were justified.

More trees are being planted, but the great Georgian and Victorian urban plantings are ageing and instead of replacing grand old broadleaf trees with similar species, local authorities increasingly turn to smaller, ornamental trees, which are cheaper, easier to maintain and less “threatening” to nearby properties. The treescape is being transformed. Britain once boasted an urban forest canopy; today we have city shrubberies, overpruned and understated.

The gritty city tree that hangs around on street corners has been abused for so long we barely even see it. Battered by pollution and passing trucks, used as a goalpost, peed on, carved into, starved of oxygen in earth compacted by acres of paving slabs, brutally hacked back and sprayed by winter road salt, this tree somehow lives on the meagre sustenance from leaking water pipes, surviving the rattling of its roots every time the road is dug up to lay yet another pipe or cable. But city trees are tough. This is vegetation with attitude; even the most bedraggled, scabby specimen of indeterminate parentage clings patiently to life. Lean your bike against a city tree for too long, and it will be eaten.

Like the human inhabitants of cities, trees suffer from stress and obscure ailments, but their workload on our behalf is phenomenal. A tree-lined street produces only 10 per cent of the dust found in a treeless street, and is up to 10 degrees cooler. Trees protect against flash-flooding and sunburn, sucking up smog and chemicals, reducing noise, providing free air-conditioning and keeping us sane. An invalid with a view of a tree recovers more quickly. A large beech tree produces enough oxygen for the daily requirements of ten people.

The Victorians cleverly imported tough plane trees, able to grow in the meanest soil, which not only survived the pea-soup fog but fought back, absorbing air pollution in their bark and then shedding it. The bark patterns on a London plane are not just beautiful, but evidence of a tree working its skin off to help us all to breathe easier.

The uncomplaining plane even makes you richer. A recent survey found that the presence of trees near a building increases property prices by up to 18 per cent. If properly pollarded, even large trees should present little danger to buildings. For every dollar spent on a tree in New York, the city benefits to the tune of $5.60 in terms of property values, reduced pollution. Presumably it also lower hospital fees since the calming effect of trees discourage New Yorkers from attacking each other.

We mourn the shrinking Amazonian rainforest; we suffered a national nervous breakdown over Dutch elm disease; we painfully tot up the number of trees lost in storms. Yet the steady deforestation of our towns and cities passes without comment. Harrow, for example, has lost some 5,000 trees since 2002, according to the London Assembly, but replanted only one third of that number.

Carl Linnaeus, the father of modern taxonomy, observed 300 years old this week: “If a tree dies, plant another in its place.” If a city tree dies, plant three. Great oaks from little acorns grow, but slowly. Urban reforestation, however, is a matter of urgency. A gardener employed by the French marshal Hubert Lyautey once objected to planting a particular species of tree, complaining that it would not reach maturity for 100 years. The marshal replied: “In that case, there is no time to lose; plant it this afternoon!”

There is only one sight more uplifting than a tree, and that is a grimy town tree: defying the concrete and soot, bringing green to the grey, and proudly sprouting, among its ancient boughs, a pair of rusting handlebars.

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