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Planning

Nov 28, 2016

Is sprawl a serious threat to food security?

We're often told suburban sprawl replaces agricultural land and is a serious threat to future food security, but the evidence suggests it's not such a big deal

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The irrigation district at Melbourne's Werribee South
The irrigation district at Melbourne’s Werribee South – an area worth saving

A new report by researchers at Melbourne University finds Melbourne’s foodbowl produces 47% of the vegetables consumed in Victoria. But population growth and continuing urban sprawl is putting the city’s foodbowl at risk. In Melbourne’s Food Future, the authors argue:

As Melbourne grows to a population of 7-8 million people by 2050, it will need at least 60% more food. If the city’s footprint continues to grow as it has in the past, the capacity of Melbourne’s foodbowl to meet the city’s food needs could fall to around 18% by 2050…

They say other state capitals also have productive foodbowls that contribute to fresh food supplies, but are under similar pressure from population growth and urban expansion.

The instinctive reaction of many will be that preserving local food supply is of paramount importance and shouldn’t be sacrificed to suburban sprawl. While urban development is a “higher and better” use, the argument goes, there are alternatives to sprawl, like stopping fringe expansion and redeveloping established areas at higher densities. There are a number of issues to consider here, including whether policy interventions intended to limit outward expansion work or have undesirable consequences; whether locally grown food is more sustainable than imported food; and whether the impact of urban development on agriculture is a critical issue.

My immediate interest is in the last issue; before we can begin to understand how food security relates to sprawl we need some baseline information about the importance of agriculture in peripheral-urban areas. As with most political discussions, the other side of the argument is often neglected.

Here are some pertinent figures, mostly drawn from an article I wrote in 2010 on this issue, about the impact of urbanisation on farming:

  • The Australian Natural Resources Atlas shows the area of land used for urban development amounts to just 0.5% of the area of land used for agriculture in Australia.
  • An estimate by the Australian Collaborative Land Use Mapping Program puts the ratio of urban land to agricultural land at 2.8%.
  • According to this report, between 1976 and 2009, the area of land in Australia devoted to farming and grazing declined by 33%, while the population grew from 13 million to 22 million. Most of the reclaimed land was shifted into a “conservation and natural environment classification”.
  • At the same time, the productivity of agriculture in Australia has increased markedly – by 2.8% p.a. over the last 20 years, double the rate at which the wider market economy grew.

Looking specifically at Victoria and Melbourne, a detailed study of the value of agriculture production in peri-urban areas by Peter Houston shows that:

  • The area of land used for agriculture in Melbourne’s Green Wedges comprises just 1.7% of all agricultural land in Victoria.
  • Most of the urban expansion of Melbourne isn’t at the expense of prime agricultural land. That’s because most of the land in Melbourne’s vaunted Green Wedges comprises extensive areas of protected natural bushland, particularly in the East, as well as semi-rural uses like hobby, lifestyle and part-time farms. Large areas of the Green Wedges are also devoted to other uses, including airports, sewage works, prisons, sporting facilities, quarries and more.
  • The report of Victoria’s Parliamentary Inquiry into sustainable development of agribusiness in outer suburban Melbourne found the average value of agricultural operations across Melbourne’s Green Wedges is only $3,101/ha p.a., varying from less than $1,000 per ha in the Western and Sunbury wedges to a high of $7,507 in the Yarra wedge.

It’s not a foregone conclusion that a city must have its own dedicated food bowl on its door step. It’s usually less costly – in financial, resource and environmental terms – to bring food to people rather than the other way around (see Is local food more sustainable?).

That’s not to say all peri-urban farming land should be fair game for urban development. As a community I think we put a high value on the scenic quality of bucolic landscapes. Melbourne’s Werribee Irrigation District, for example, is an area I wouldn’t want to see replaced by any form of urban development. I don’t think it’s essential for the city’s food security but it has high landscape value (and uses recycled water from the Western Treatment Plant). Fortunately, it’s protected from urban development.

Food security is an important issue but the impact of sprawl on the ability to feed future populations needs to be understood and kept in perspective..

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2 thoughts on “Is sprawl a serious threat to food security?

  1. Jacob HSR

    Because who cares if houses are built on top quality soil.

    Another problem that high speed rail can solve – build houses on poor quality soil and have people commute in via fast train.

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