It seems obvious. If we buy food that is grown locally, we can help combat global warming. This is the concept of "food miles" - surely food flown or even shipped around the world must contribute far more to carbon emissions than food grown nearby? I believe it's not as simple as that. For instance, there are two Farmers' Markets held on Saturdays within driving distance from my home. The food is locally grown - more or less - after all the farms are not within the city boundaries, but on the outskirts. The stalls are small. So each grower is driving perhaps 30 km in a small car or van to bring their produce to the market. And if I shop there, it is a longer drive than my nearest supermarket, which is just around the corner. Or even a no-so-close supermarket which I can stop at on my way home from work. I am fairly sure that each kilogram of produce sold at the Farmers Market is responsible for more carbon emissions than the equivalent produce sold at the supermarket - even though the latter may be driven several hundred kilometres to get there. It's the economies of scale - moving a large quantity of produce in a large truck to a supermarket closer to the target market.
I worry about what will happen to New Zealand if the concept of food miles catches on. Or if long-range tourism declines due to fears of global warming. It's what our economy relies on. So I was interested to read some figures in this article. (If you are interested, bookmark it. In the interests of selling magazines, the full text of the main feature articles are not available on line for a few weeks after the issue date). New Zealand farmers are not subsidised, unlike farmers in the European Union and other countries. They have to be efficient to survive. Apparently, in most cases, less total energy is used to produce food in New Zealand and ship it to the other side of the world than to produce it and sell it locally. Another interesting statistic was that half of all the energy used in transporting food is used in the journey from the supermarket to home. To reduce emissions you could choose the locally grown product, or you could combine your shopping list with your neighbour's and cut your trips to the supermarket in half for exactly the same effect. Or you could make sure to stock your pantry well, reducing your number of trips.
You can use a simplistic measure of emissions like food miles. Or you can investigate the true measure by researching all the emissions produced in the lifetime of the product. Unfortunately this takes a lot of research, so it is heartening to see that the UK supermarket chain Tescos plans to do it for us, and label goods sold in their shops with information on their total carbon footprint.
I hope that the world will keep buying our produce, and keep visiting us. Or will New Zealanders become an endangered species, starving at the bottom of the world? Perhaps then the World Wildlife Fund will mount a rescue campaign. One thing is for sure - we can't all emigrate back to Britain.