Napoleon described Britain as a nation of shopkeepers, but with corporate interests having conquered where the Emperor failed, these days we're more like a nation of supermarket shoppers.
The Big Four of almost 30 supermarket chains operating in the UK control 80 per cent of the country's grocery market. Tesco has 2,715 stores, Sainsbury's 934, Morrisons 455 and Asda roughly 400. Add to that hundreds of regional and national distribution centres, and vast portions of land either earmarked for development or stockpiled to prevent it, and supermarkets cover a vast area.
Take the market leader's biggest stores: Tesco Extra hypermarkets - all 212 of them - have an average floor space of 120,000 sq ft. These aircraft hangars of the shopping world alone cover an area roughly the size of 300 football pitches.
All of which means, above the walls of glass and neon logos, there's a lot of roof space going begging - and that's something a pioneering scheme found on top of Thornton's Budgens supermarket in Crouch End, North London, hopes to rectify.
The Food from the Sky community growing project is a low-rise labyrinth of green recycling boxes packed with earth and bursting with all manner of fruit and vegetables. In an outbuilding, oyster mushrooms slowly shoulder their way out of plastic bags. In a far corner of the roof, beyond the wormeries and compost tumblers full of Budgens' out of date food, purple pod beans wave in the breeze. July's crop of salad, red mountain spinach, rocket, potatoes, peas, pak choi and much other fresh produce is already on sale in the supermarket aisles below.
But growing food is just one facet of the project, says its founder Azul-Valerie Thome. The roof garden is a community space, a place to educate children and young people, an insect sanctuary, a symbolic gesture... Its functions, in short, are as varied as most supermarkets' are uniform.
Azul's goal is to persuade more stores will take up the rooftop challenge, bringing the warmth of community back into sterile aisles and the heart back to Britain's supermarkets.
She isn't fazed by the fact that many consider them never to have had a heart in the first place. For her they are an untapped resource - not just their roofs but their focal positions in the lives of so many shoppers. Budgens, she points out, has 17,000 visitors a week: where and when better to capture people's imaginations, to remind them where their food comes from?
‘We're starting with the independents - one day there may be a quantum leap of some kind,' she says. ‘Hopefully this will be the first of many.'
Devil in the detail
There are practicalities to consider, however, which is why on October 1 Food from the Sky will release a 12-step template to help other people persuade their local shops to give over space to growing.
The idea is to give other community projects all the information and advice they need, to help them realise what's involved and how to make it work, says Budgens Crouch End's owner, Andrew Thornton.
‘For other stores to take this on they'd have to believe it wasn't going to be terribly onerous for them, and our work will help with that side of things.'
The major hurdle is weight load, particularly on newer, out-of-town supermarkets, says Dusty Gedge, founder of www.livingroofs.org. Commercial buildings like Budgens - solid structures from the first half of the 20th century - are ideal for purpose. But modern lightweight steel structures may not support even the simplest green roof. The carbon cost of adapting them would outweigh any benefit, says Gedge.
‘There is potential for retailers to have some kind of community growing projects on existing buildings, but only those that have the structural capacity,' he says.
While the first step for any new project is to engage the services of a structural engineer, Azul hopes all future buildings will one day be built with green roofs in mind. With new Big Four stores still going up at a rate of knots (577 over the past two years alone), roof garden opportunities are growing exponentially.
‘We need more space in cities to grow food,' she says. ‘It makes sense to have that designed in from the beginning rather than having to spend a fortune on reinforcing existing roofs.'
Policymakers in Europe and further afield are already leading the way: Switzerland has passed a law that stipulates 20 per cent of all roof space must be green. More than 10 per cent of Germany's flat roofs are already green, with several million extra square feet being planted every year. In Canada, industrial buildings must render 10 per cent of their roof space green by 2011.
Too little, too late?
In terms of PR, roof vegetable gardens could help improve the reputation of the big chains, which are often accused of harming community spirit - unless, that is, people unite in opposition to them.
And yet Morrisons says it has no plans to roll any out, despite owning the freehold on the vast majority of its flat-roofed buildings. A spokesman confirmed it was focusing on green energy generation rather than growing: ‘We think this is a much better use of our roofs. We're not likely to use them for putting garden facilities or allotments or anything like that.'
Sainsbury's - which has a store in Greenwich with a green roof - says it has installed sun tubes on top of its more modern stores to cut down on energy usage, ‘meaning we wouldn't be able to host community gardens. Most of our older stores have slanted roofs, which would also prevent this.'
Tesco points out that many of its 1,000+ Express stores are leased and so not theirs to plant on - neglecting to mention all the freestanding buildings it does own - and that ‘a number' of its stores already use roof space for harvesting rainwater, roof lights and solar panels. It left the door open somewhat by saying it was ‘always considering new and innovative uses of space' for its new and existing stores.
Dusty Gedge says it is ‘impossible' for a city to feed itself through roof farming alone, but hails Food from the Sky for being ‘a community activity that is raising awareness and highlighting the issue of food security.
‘It would be a complicated process to grow food on a huge supermarket - and certainly more costly to maintain than at ground level in terms of water and carbon. The ticket is for them to set aside a certain percentage on more structurally robust sections of their green roofs for small-scale community food projects.'
Azul too is encouraged by the fact that all businesses have a responsibility to their social and natural environments. Representatives from M&S paid Food from the Sky a visit last year and two or three other Budgens stores have expressed an interest in learning more.
Nor is the irony of community gardens piggy-backing on the destroyers of communities lost on her: the template is for nothing less than a supermarket rehabilitation scheme.
‘People are so sad in Tesco, you wonder: where is the heart in this place? It's obvious something isn't working. I think they can be encouraged to see the value in a community venture like ours, which feed people on so many different levels.'
Efion Rees is a freelance journalist
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