Is local food more sustainable?

One argument against suburban sprawl is that it sterilises agricultural land. A particular variation on this contention is that land should be preserved for agriculture so that carbon emissions in transporting food from farm gate to plate – “food kilometres” – can be minimised.

A frequently cited estimate is that food in the US travels on average 2,400 km from where it is produced to where it sold to consumers. We should therefore seek to grow as wide a range of food as possible as close to Melbourne as possible.

From Weber and Mathews, Food Miles and the Relative Climate Impacts of Food Choices in the US

All things being equal that makes sense. But of course it’s never that simple. Here are some pertinent issues to consider.

First, transport is not a major component of the total carbon emissions from agriculture. These researchers estimate that on-farm production accounts for 83% of the average US household’s carbon emissions from food whereas delivery from producer to retail outlets accounts for just 4%.

Second, most food can’t be grown locally without resorting to potentially environmentally damaging practices like excessive application of fertiliser, irrigation or artificial heating of greenhouses. This article cites a British study which found that because British tomatoes are grown in heated greenhouses, they emit 2.4 metric tons of carbon dioxide per ton grown whereas Spanish tomatoes emit 0.6 tons. Further:

Another study found that cold storage of British apples produced more carbon dioxide than shipping New Zealand apples by sea to London. In addition, U.K. dairy farmers use twice as much energy to produce a metric ton of milk solids than do New Zealand farmers.

Third, even where the local area is suitable for growing certain foods, it might not be the most “environmentally efficient” location for a particular food. For example, the impact on the environment of growing tomatoes in a more distant location might be lower than it is locally because the former has more hours of solar energy (sunlight), or higher rainfall or soil that requires fewer additives.

Fourth, producers in more distant locations might have superior farming practices to local growers. They might, for example, husband the land or protect biodiversity with greater care.

Fifth, the environmental and economic cost of moving people is higher than the cost of transporting their food. To the extent that some proportion of residential growth occurs on the fringe (and even Melbourne 2030 anticipated that proportion would be 30% of all commencements), it is accordingly preferable where there is a conflict with farming to give housing priority.

In short, “food kilometres” tells us how far food has travelled but little about its effect on the environment. The way to minimise the environmental impact of the food production chain at the personal level is to think primarily in terms of what you eat and how it is produced rather than in terms of “food kilometres”. These researchers illustrate the importance of what you eat:

Dietary shift can be a more effective means of lowering an average household’s food-related climate footprint than “buying local.” Shifting less than one day per week’s worth of calories from red meat and dairy products to chicken, fish, eggs, or a vegetable-based diet achieves more GHG reduction than buying all locally sourced food.

Yes, all other things being equal, it is better to buy local, but proximity is likely to be only a very small part of the environmental benefits that come from eating wisely.

Suburban sprawl already has enough real downsides without it being necessary to exaggerate the issues associated with agricultural land. Agriculture in Australia is in little danger from urban encroachment – the total area of land used for urban development in Australia is equivalent to less than 1% of all land used for farming and the productivity of agriculture has doubled over the last 30 years.

In any event it is interesting to note that some key agricultural areas within Melbourne’s border are “spared” from urban development. Lettuce and broccoli are grown in large quantities in the 3,000 hectare Werribee Irrigation District (it produces 70% of Australia’s lettuce) using recycled water pumped from the Western Treatment Plant and the Werribee River. The largest cattle farm in Victoria, where cattle feed on grass that is flood-irrigated with recycled water, is located on the Western Treatment Plant – it grazes 15,000 cattle and 40,000 sheep. This doesn’t mean however that they are necessarily the best options for reducing the food footprint of Melburnians – farmers in the Irrigation District have long been accused of exhausting the soil of nutrients and of relying excessively on fertiliser.

UPDATE: I’ve looked at the impact of sprawl on agricultural land here.

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16 Comments on “Is local food more sustainable?”

  1. TomD says:

    Heard a great interview about this whole area one time on the radio.

    And yes things are definitely not as simple or straightforward and logical as they might at first seem, in the way of pluses and minuses for each approach.

    Always the rebel against conventional thinking, Alan!

  2. Greg says:

    All sensible arguments for the status quo Alan. However, the idea that concentrating our food production to the areas most suited economically and apparently environmentally [assuming climate change is still an issue!] for production ignores the resilience of our predominantly centralised food system. Large ‘economies of scale’ production can be highly vulnerable to shock that can have an enormous impact on the market. Three historically recent examples spring to mind; poisoned tomatoes in Queensland, storm ravaged bananas in the same state and a lack of lettuce after storms in WA in March. All led to price spikes. Granted these are rather minor as they are all isolated incidents but they prove that centralised systems of scale are highly vulnerable to any shock. Imagine what a more far reaching threat such as peak oil would do to these highly transport dependent centralised systems?

    I agree, food miles is a distracting argument. The real question is; how vulnerable are these highly concentrated food systems to breakdown? I would argue they are extremely vulnerable.

    • Alan Davies says:

      Intersting point,Greg. I suppose we need to be confident that the savings in economies of scale from large, centralised systems (compared to decentralised production systems) outweigh the expected costs in the longer term from the sorts of disruptions or shocks you mention.

      It seems to me that Melbourne has, on balance, unambiguously benefitted from its centralised water, sewerage, gas, train, tram, etc, systems. Our dams are looking shaky at the moment, but I expect they’ve more than paid for themselves. The water distribution and treatment systems have performed flawlessly. In all the decades we have had reticulated gas supply, I’m only aware of one major disruption.

      And centralised infrastructure in some applications appears to be coming into its own. In the face of risks from climate change and peak oil, many cities are looking increasingly to highly centralised public transport systems and away from (largely) decentralised systems like cars.

  3. Mike says:

    I’m usually a fan but not sure you really understand agriculture, nor have spoken to too many farmers.

    For a balanced view of this topic, see

    http://www.parliament.vic.gov.au/osisdc/inquiries/article/980

    The 1% stat you quote is so jejune as to be laughable.

    • Alan Davies says:

      I derived my “less than 1%” figure from the Australian Government’s Australian Natural Resources Atlas (see here). It shows that the area of land used for urban development in Australia amounts to 0.5% of the area of land used for the sum of irrigated agriculture, dryland agriculture and livestock grazing. Here’s another estimate via the Australian Collaborative Land Use Mapping Program (see here).

      Thanks for the referral, but I’m cautious about the weight I give to reports by Parliamentary committees. The kerfuffle over the recent nakedly political Report of the Select Committee of the Legislative Council on Train Services is a case in point.

      In any event, I note the Committee you refer to received evidence from a number of sources that food miles is a problematic concept and that the emphasis should be on sustainability. The Committee’s support for food miles per se seems lukewarm e.g. “as a measure of sustainability, food miles is now considered simplistic, even misleading” (p269).

      Let me add that I don’t know a lot about tilling the soil, but I do know a bit about the subject of this post, which is public policy and economics.

  4. [...] Monday I looked at the idea of “food kilometres” but today I want to look at whether productive agricultural land should be converted to urban [...]

  5. Alan Davies says:

    Another view on sourcing locally (more than just food)

  6. Russell says:

    I think this article needs to be based a lot more on reality – the Australian situation and what really happens, eg. where is the evidence that “most food can’t be grown locally without resorting to potentially environmentally damaging practices like excessive application of fertiliser, irrigation or artificial heating of greenhouses”.

    Please give examples where food is being produced in that damaging way, and which could be sourced from some other place where it is grown in an ecologically superior way. Take into account that if that other place has natural advantages in growing said crop, that hasn’t or wouldn’t lead to ecologically damaging moonoculture of that crop (think of palm oil in Indonesia and Malaysia).

    I agree that simply ‘local’ is not all that has to be considered. I’ve heard of mangoes that were grown in Queensland, bought up by one of the big supermarket chains, trucked down South to their huge distribution centre, then trucked out to all their stores, including the ones in the area where said mangoes had been grown!

    Your use of the phrase ‘most food’ also makes me think that we don’t need access to all foods, all the year – if we have to accept limits on what’s available because it’s seasonable and local, we can live with that. Just as we can pay much more for better quality food than the rubbish that so many Australian eat.

    I think the key to expanding housing on (possible) food producing land is to have those residences producing a reasonable amount of food: I have a very small yard but it produces a lot of my fresh fruit and vegetables.

    • Alan Davies says:

      You might want to have a look at the report of the Victorian Parliamentary Committee (that Mike linked to above). They went one better than looking at the Australian situation and actually examined food production around the Port Phillip and Westernport regions.

      Of course its a political report but here’s what they say: “The Committee notes that the debate about the environmental impact of food is moving away from ‘a simplistic debate about food miles – good or bad’- towards attempts to factor in the intensity and sustainability of production systems in different locations”.

  7. [...] argued before (here) that buying local food is probably the least sustainable basis on which to base your food buying [...]

  8. [...] that it would double the amount of locally-sourced produce on its shelves. And while there is some legitimate debate about whether shortening distances alone really reduces the environmental footprint, [...]

  9. [...] that it would double the amount of locally-sourced produce on its shelves. And while there is some legitimate debate about whether shortening distances alone really reduces the environmental footprint, [...]

  10. [...] that it would double the amount of locally-sourced produce on its shelves. There’s some legitimate debate about whether shortening distances alone really reduces the environmental footprint (a fascinating [...]

  11. [...] that it would double the amount of locally-sourced produce on its shelves. There’s some legitimate debate about whether shortening distances alone really reduces the environmental footprint (a fascinating [...]

  12. [...] Melbourne Urbanist had a lot of hits last month from the US on a piece I wrote about the value of ‘food miles’.  The interest was generated by an article on Wal-Mart published in The Huffington Post, the [...]

  13. [...] a major effect, as I’ve discussed in various contexts before (see here, here, here, here, here, here, here and here). These are not fundamentally issues of land use [...]


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