London must invest in its great outdoors

I did just that earlier this month, sitting under the stars in the magnificent courtyard of Somerset House, joining 2,000 others for an outdoor movie screening. The film was the Johnny Cash biopic, Walk the Line, but that was a secondary pleasure. The real delight was seeing a beautiful London landmark in a new, bright light. A warm evening, a good film, a picnic atmosphere and all in the lap of one of this city's great buildings. It was Cinema Paradiso via the Strand. (All credit to Film4 which organised a whole week of movies al fresco.)

But it felt like a rarity, and not only for this summer. Too often we treat London as an essentially indoor town, either beavering away inside buildings or jammed into trains underground. Then those who can afford it get away, either fleeing to the countryside for the weekend or abroad for their holidays. But it doesn't need to be that way.

Obviously, good weather makes the London outdoors more enticing, as it did last weekend, but there are some simple and relatively cheap steps both we and our municipal masters could take which would enhance the environment we inhabit no end - giving all of us a little shot of that outdoor high I felt at Somerset House.

Start with the simplest landscape improvement of all: trees. The effect on human beings of seeing a tree is almost chemical. A tree-lined street appeals to everyone who sees it, whether it's The Mall or a suburban Acacia Avenue. When trees are missing, the whole area looks desolate. A leafless street is a lifeless street.

Not that London is some concrete desert. Visitors speak of the capital as one of the greenest cities in the world, thanks to the abundance of parks, the endurance of London's villages - from Hampstead to Blackheath - and our leafy suburbs. Indeed, those born outside Britain seem to appreciate London's great outdoors almost more than the natives: witness the Babel of languages to be overheard in any of the city's parks over the bank holiday.

It is no coincidence that the definitive urban tree, found in Paris and New York, is known as the London Plane. No matter what our scuzzy urban environment throws at a plane tree, it copes by shedding its bark: like any good Londoner, it picks itself up, dusts itself down and starts all over again.

So you would think trees would have few enemies. But no. When someone proposed a planting scheme at my local residents' association in Stoke Newington, the objections came tumbling out. Where on the pavement would they stand? Too near the curb and they could make it difficult to open a car door. And what about the risk of subsidence, as roots start spreading, undermining the foundations of nearby houses? Battles like this are under way all over London. Even when residents agree that they want trees, they can't always get them. Councils are strapped for cash, with no money to prune existing trees let alone plant new ones. Not to mention the perils of "'elf 'n' safety". Where you and I might see the majesty of an oak or elm, the ever-cautious health and safety commissar sees only bent pavements, cracked walls and an obstruction of the top decks of buses. Trees are risky: they might fall over and hit someone.

Once health and safety send out a warning, local councils feel compelled to act: otherwise they might be vulnerable to a compensation claim. Erring on the side of caution, the trees get the thumbs down.

This is a mistake. The LSE's Tony Travers puts it beautifully when he says that one of the joys of London, and Britain, "is that it's nobbly, wobbly and asymmetrical, that it is not neat. It's all about bent walls and crooked streets, a world created and bent by nature." Put simply, we need more trees, not fewer.

But people yearn not just for green, but blue too. Think of it as another elemental human need: to see water. Which is why folks in Hackney cheered when the London Fields lido reopened last year after two decades of closure, boasting the city's only Olympic-sized outdoor heated pool. Lambeth residents feel just as warmly about Brockwell lido, fending off multiple attempts at closure.

We may not need them the way we did back in the 1920s, when they were the closest many poor Londoners would ever get to the sea. But the aspiration behind the lidos - to have a taste of the seaside in the city - remains alluring. I still haven't given up on the plans, much discussed two years ago, to convert a stretch of the South Bank into a sandy beach. They've done a Paris plage and one in Berlin, too. So why not London? Alternatively, and perhaps cheaper, we might construct a swimming pool in the Thames. It sounds outlandish, but it could be done easily - just sink four walls by the shoreline, forming a box, and fill it with water. And the effect would be magnificent, as if you were bathing in the river that defines this city.

There is no shortage of schemes that would make the outdoor environment of London a joy. But how to make them reality? It would help if local authorities could raise more money, so they could do more than simply funding the front-line services which currently gobble up all the cash - education taking half and social services nearly a third. As things stand, improving the landscape we all live in barely ranks, counting itself lucky if it gets a percentage share of the local budget that reaches double figures.

But this shouldn't be a task for government alone. There are now people of stratospheric wealth living in London, drawn by a tax regime that asks next to nothing of them. Let them make a contribution to the city whose delights they enjoy. Why shouldn't the hedge fund managers or private equity boys follow the lead of an Andrew Carnegie, who endowed libraries from Luton to Herne Hill, and decide to stump up for a London plage or line the streets of London's poorest boroughs with gorgeous trees?

If they ask for a reason, there's a simple reply: they should get out more.