It sounds like a good idea, but...

[N]ot everyone agrees that organic farming is better for the environment. Perhaps the most eminent critic of organic farming is Norman Borlaug, the father of the “green revolution”, winner of the Nobel peace prize and an outspoken advocate of the use of synthetic fertilisers to increase crop yields. He claims the idea that organic farming is better for the environment is “ridiculous” because organic farming produces lower yields and therefore requires more land under cultivation to produce the same amount of food. Thanks to synthetic fertilisers, Mr Borlaug points out, global cereal production tripled between 1950 and 2000, but the amount of land used increased by only 10%. Using traditional techniques such as crop rotation, compost and manure to supply the soil with nitrogen and other minerals would have required a tripling of the area under cultivation. The more intensively you farm, Mr Borlaug contends, the more room you have left for rainforest.

What of the claim that organic farming is more energy-efficient? Lord Melchett [Peter Melchett of the Soil Association, Britain's leading organic lobby group] points out for example that the artificial fertiliser used in conventional farming is made using natural gas, which is “completely unsustainable”. But Anthony Trewavas, a biochemist at the University of Edinburgh, counters that organic farming actually requires more energy per tonne of food produced, because yields are lower and weeds are kept at bay by ploughing. And Mr Pollan notes that only one-fifth of the energy associated with food production across the whole food chain is consumed on the farm: the rest goes on transport and processing.

What about Fairtrade? Its aim is to address “the injustice of low prices” by guaranteeing that producers receive a fair price “however unfair the conventional market is”, according to FLO International's website. In essence, it means paying producers an above-market “Fairtrade” price for their produce, provided they meet particular labour and production standards...

The standard economic argument against Fairtrade goes like this: the low price of commodities such as coffee is due to overproduction, and ought to be a signal to producers to switch to growing other crops. Paying a guaranteed Fairtrade premium—in effect, a subsidy—both prevents this signal from getting through and, by raising the average price paid for coffee, encourages more producers to enter the market. This then drives down the price of non-Fairtrade coffee even further, making non-Fairtrade farmers poorer. Fairtrade does not address the basic problem, argues Tim Harford, author of “The Undercover Economist” (2005), which is that too much coffee is being produced in the first place. Instead, it could even encourage more production...

Another objection to Fairtrade is that certification is predicated on political assumptions about the best way to organise labour. In particular, for some commodities (including coffee) certification is available only to co-operatives of small producers, who are deemed to be most likely to give workers a fair deal when deciding how to spend the Fairtrade premium. Coffee plantations or large family firms cannot be certified... Yet limiting certification to co-ops means “missing out on helping the vast majority of farm workers, who work on plantations,” says Mr Wille of the Rainforest Alliance, which certifies producers of all kinds.

...perhaps the most cogent objection to Fairtrade is that it is an inefficient way to get money to poor producers. Retailers add their own enormous mark-ups to Fairtrade products and mislead consumers into thinking that all of the premium they are paying is passed on. Mr Harford calculates that only 10% of the premium paid for Fairtrade coffee in a coffee bar trickles down to the producer. Fairtrade coffee, like the organic produce sold in supermarkets, is used by retailers as a means of identifying price-insensitive consumers who will pay more, he says.

“Local is the new organic” has become the unofficial slogan of the local-food movement in the past couple of years. The rise of “Big Organic”, the large-scale production of organic food to meet growing demand, has produced a backlash and claims that the organic movement has sold its soul. Purists worry that the organic movement's original ideals have been forgotten as large companies that produce and sell organic food on an industrial scale have muscled in.

This partly explains why food bought from local producers either directly or at farmers' markets is growing in popularity, and why local-food advocates are now the keepers of the flame of the food-activism movement. Local food need not be organic, but buying direct from small farmers short-circuits industrial production and distribution systems in the same way that buying organic used to. As a result, local food appears to be immune to being industrialised or corporatised. Organic food used to offer people a way to make a “corporate protest”, says Mr Pollan, and now “local offers an alternative to that.”

Buying direct means producers get a fair price, with no middlemen adding big margins along the distribution chain. Nor has local food been shipped in from the other side of the country or the other side of the world, so the smaller number of “food miles” makes local food greener, too. Local food thus appeals in different ways to environmentalists, national farm lobbies and anti-corporate activists, as well as consumers who want to know more about where their food comes from.

Obviously it makes sense to choose a product that has been grown locally over an identical product shipped in from afar. But such direct comparisons are rare. And it turns out that the apparently straightforward approach of minimising the “food miles” associated with your weekly groceries does not, in fact, always result in the smallest possible environmental impact.

The term “food mile” is itself misleading, as a report published by DEFRA, Britain's environment and farming ministry, pointed out last year. A mile travelled by a large truck full of groceries is not the same as a mile travelled by a sport-utility vehicle carrying a bag of salad. Instead, says Paul Watkiss, one of the authors of the DEFRA report, it is more helpful to think about food-vehicle miles (ie, the number of miles travelled by vehicles carrying food) and food-tonne miles (which take the tonnage being carried into account).

The DEFRA report, which analysed the supply of food in Britain, contained several counterintuitive findings. It turns out to be better for the environment to truck in tomatoes from Spain during the winter, for example, than to grow them in heated greenhouses in Britain. And it transpires that half the food-vehicle miles associated with British food are travelled by cars driving to and from the shops. Each trip is short, but there are millions of them every day. Another surprising finding was that a shift towards a local food system, and away from a supermarket-based food system, with its central distribution depots, lean supply chains and big, full trucks, might actually increase the number of food-vehicle miles being travelled locally, because things would move around in a larger number of smaller, less efficiently packed vehicles.

Research carried out at Lincoln University in New Zealand found that producing dairy products, lamb, apples and onions in that country and shipping them to Britain used less energy overall than producing them in Britain. (Farming and processing in New Zealand is much less energy intensive.) And even if flying food in from the developing world produces more emissions, that needs to be weighed against the boost to trade and development.

There is a strand of protectionism and anti-globalisation in much local-food advocacy, says Gareth Edwards-Jones of the University of Wales. Local food lets farming lobbies campaign against imports under the guise of environmentalism. A common argument is that local food is fresher, but that is not always true: green beans, for example, are picked and flown to Britain from Kenya overnight, he says. People clearly want to think that they are making environmentally or socially optimal food choices, he says, but “we don't have enough evidence” to do so.