Understanding Urban Agriculture – Part 3, Calculating the Food Production Potential of a City
It has been well said that we do not see things as they are, but as we are ourselves. Every man looks through the eyes of his prejudices, of his preconceived notions. Hence, it is the most difficult thing in the world to broaden a man so that he will realize truth as other men see it.
Samuel Silas Curry, 1891
What does it take to convince a person that something can be done, when in the world of their mind’s creation they’re convinced it can’t be?
With the rise of Urban Agriculture (UA) worldwide we’re seeing the restoration of localized agriculture. Something that has always been done in human communities is being done again as a backlash against what is our current anomalous state of being – living apart from our food in urban food deserts created intentionally by local governments.
In my previous articles on the subject, I discussed how urban agriculture is a growing phenomenon worldwide and research released by the United Nations estimates that approximately 800 million people worldwide engage in urban agriculture. The figures are quite significant.
The UN estimates that “72 percent of all urban households in Russia raise food, and 68 percent do so in Tanzania. Berlin has over 80,000 urban farmers, while in China the 14 largest cities produce 85 percent or more of their vegetables” (1)
Despite reality, we’re seeing UA critics express opinions suggesting that UA can’t be carried out in cities for a myriad of reasons.
The obstacles to urban agriculture, textbook style
The textbook arguments centre around three main barriers to the uptake and expansion of UA in cities – legislative, regulatory and resourcing barriers. A lot of effort and discussion on UA centres on convincing authorities and regulators to support urban food growing. This makes sense, after all, the biggest obstacles to UA are regulations, by-laws and an entrenched hostility from the landscape architecture profession, especially from those employed by local government to design public spaces.
The question about resources is usually secondary and often more of an academic concern. It is this concern that I wish to address, to those ‘experts’ who claim that UA won’t work for reasons of resource limitations.
The real world obstacles to urban agriculture, a better distinction
I prefer to classify the obstacles to UA into two different categories, the first being physical, pertaining to the availability of land, water and other critical resources. The second being cultural, arising from, and existing in the minds of people, independently of any physical world limitation and human mental activity.
The reason for this dichotomy is because we’re looking at two distinct type of problems with two completely different classes of solutions.
The first category – physical limitations, are an objective problem. They present themselves as engineering problems, the challenge being to find a solution to achieve a particular outcome given the physical constraints of a specific system.
The second category – cultural limitations, are wholly subjective problems, dealing with the cultural biases, prejudices and unsubstantiated opinions of people, as they exist within their minds and the fruits of their thinking. These limitations are addressed by changing the way people think, whether it’s legislators, authorities or academics.
Physical or cultural limitations? The curse of the mini-farm mentality
In the academic debates suggesting that UA can’t work in cities, I’ve often seen a major logical flaw that ensures that the resultant discussions are worthless.
You would expect academics to be objective, but that’s another flawed assumption, they’re subjective humans just like everyone else, and though they may aim for objectivity, everyone has mental ’blind spots’ which elude scrutiny.
If we take a more philosophical perspective of the discussions to analyse the logic and reasoning, we see sloppy logic of untested assumptions creeping in. There is always one unspoken, unquestioned assumption, and it’s the same one every time – that UA is just scaled down rural agriculture, and therefore has the same qualities, requirements, limitations, problems and outcomes.
Nothing could be further from the truth, UA is a qualitatively different approach to food production under a completely different set of growing conditions. We UA advocates aren’t looking to clear vast areas of space in cities and recreate the social and ecological disaster that is rural agribusiness on a smaller scale.
The problem with the ‘mini-farm mentality’ is that it’s essentially a straw man argument that creates and imaginary problem to battle. It mistakenly assumes an agricultural solution which is not a UA reality and claims that it can’t be done, based on supposed sound resource arguments. The logical flaw is assuming that UA is identical to rural agribusiness, the only difference being quantitative.
Agribusiness is about destroying the environment and communities, UA is not. No person in a community setting would knowingly and willingly poison and pollute the place where they and their families live and eat. Simple enlightened self-interest.
Ecologically sound and sustainable design systems such as Permaculture utilize whatever space and resources are available to create food systems that co-exist harmoniously with the community and with Nature. There is none of the typical dominate and control, clear-fell and poison mentality in UA.
Sustainable design and working with available resources
A key point in sustainable food production is being able to create a design solution using available resources and bridging the gaps not with more money, resources or energy, but with innovation, creativity and sound knowledge of ecological systems.
A permaculture style “function over form” design which does not compromise functionality and efficiency with the dictates of vain aesthetics is well suited for UA design. First and foremost, to address the growing issue of food security in cities, we need to solve a problem, growing enough food – sustainably.
One point that critics of UA tend to bring up often is aesthetics. My question is this. Have they seen edibles growing in public spaces in other countries where UA is the norm? Or are they opposing virtual realities of “messy UA” they have dreamed up in their own minds?
Either way, window dressing and fluff such as the tediously repeated aesthetic concerns about ‘tidiness’ of the landscape architecture profession can be considered after the fact if at all, as a lack of perspective and priority is clearly evident here.
That said, if we were to do a design site analysis of a city, we would need to work out what resources were available to work with. Before anything else, we’d need to identify which resources we need to grow food.
Site analysis of a city, determining resource availability
I’ve always wondered what potential resources are available in the city of Melbourne, Australia, where I live.
To a permaculture designer the act of observation never ceases, the trained eye instinctively spots unutilised resources, areas with potential for growing food, or potential solutions waiting to be had in the surrounding landscape when going about one’s daily activities!
In this case, we’re looking at a whole city. To grow food, we primarily need land and water. We also need people, the community to support any UA efforts.
A good way to determine our resource potential is by identifying how many houses we have to work with.
Looking at the Census Statistics 2011 – Greater Melbourne VIC, we find the following statistics:
• People – 3,999,982
• All private dwellings – 1,636,167
• Occupied private dwellings 1,430,665 (91.0%)
• Unoccupied private dwellings 141,506 (9.0%)
The occupied private dwellings are comprised of:
• Separate house 1,039,342 (72.6%)
• Semi-detached, row or terrace house, townhouse etc 165,486 (11.6%)
• Flat, unit or apartment 219,111 (15.3%)
• Other dwelling 6,159 (0.4%)
Houses have rooftops, and rooftops have the potential to harvest rainwater. Now we know how many possible rooftops we have to catch rainwater from!
We also need to know how big those rooftops are, but that might be difficult. Rooftops are the same size or larger than houses, so we can use house size instead. How big area houses in Australia – big and getting bigger according to recent figures:
“We’ve never lacked for space in this wide brown land. Maybe that’s why Australians choose to live in the world’s largest houses, with an average size of 243 square metres. And, despite cries of overcrowding in our cities, research shows Australian houses are actually getting bigger. According to some data we’re also leading the world in floor space per capita. In fact, the average size of a new Australian house increased from 162.2 square metres to 227.6 square metres between 1984 and 2003, that’s a jump of 40%. The average new Australian home is now 10% bigger than even its US equivalent.” (2)
That’s plenty of roof space, and we know from our Bureau of Meteorology statistics that the Melbourne mean annual rainfall is 650mm.
Let’s see what these figures tell us.
Rainwater Harvesting Potential
If we consider only occupied dwellings, and of those we use only the categories of ‘Separate house’ and ‘Semi-detached, row or terrace house, townhouse etc’ and exclude ‘Flat, unit or apartment and other dwellings’ we have a total of 1,039,342 + 165,486 = 1,204,828 residences in Melbourne.
If the average house size is 243 square metres, and underestimating by not making any allowances for roof size being bigger than occupiable house size, we have a total roof space of 1,204,828 x 243m² = 292,773,204m².
Considering that each mm of rainfall on a square metre of roof amounts to one litre, the total rainfall that can be captured annually from Melbourne rooftops alone (as a gross underestimate) is 292,773,204m² x 650mm = 190,302,582,600 litres, or well over 190 megalitres of water.
Growing Space Potential
Assuming that occupied residences specified above (with the same exclusion of high density housing) allocate a paltry two square metres to food production as a hypothetical example, we would have a total of 1,204,828 residences x 2m² = 2,409,656 m², or just over 602 acres of growing space.
This is where a lot of academics get it wrong with UA, we don’t need large centralised farms, as distributed systems are far more resilient as they don’t have a single point of failure. One acre is 4,000 square metres, and it makes no difference in UA if that’s one single plot or 4,000 little ones, it’s the same growing space for vegetable gardening.
Food Production Potential
If Australians can produce the same amount of food as US home gardeners (3) – an average yield of 1/2 pound of fresh produce per sq. ft. of garden area.
1lb= 0.4535923kg and 1ft²= 0.09290304m²
To convert this kg/m² (0.5 x 0.4535923kg)/0.09290304m² = 2.44 kg/m²
So, 1,204,828 residences with each allocating 2m² each to food growing can produce 2,409,656m² x 2.44 kg/m² = 5,879,560kg or 5,880 metric tonnes of food.
Since nothing other than money talks for some people, if US home gardeners are achieving a $600 estimated dollar return for a 600 sq. ft. food garden, that’s US$1/ft², which translates to 1/0.09290304 = US$10.76/m².
If we calculate total value of produce, 1,204,828 residences with each allocating 2m² each to food growing can produce 2,409,656m² x US$10.76/m² = US$25,927,898, that’s almost US$26 million from 2m² of garden per residence.
Now, no reasonable person will claim that’s insignificant. If any critics still wish to maintain their position, I will gladly accept an insignificant donation of US$26 million into my bank account.
Let’s take it up a level now, beyond a paltry 2m² per household.
What would happen if our food gardens were the same size those of US gardeners – 600ft² or 55.741824m²? Total growing space becomes 1,204,828 residences x 55.741824m² = 67,159,310m² or 16,789 acres.
This will produce 67,159,310m² x 2.44 kg/m² 163,868,716kg or 163,870 metric tonnes of food which would be worth 67,159,310m² x US$10.76/m² = US$722,634,175 or roughly US$723 million which by today’s exchange rate is roughly US$723 million/0.75 = AU$963 million!
Since agriculture in Australia produces around AU$6,000 million, with the hypothetical figures of 2m² per household the city of Melbourne, Victoria could produce an additional 4.33% of the total Australian national combined peri-urban and rural produce value. If we push the figures and imagine all those households in the city of Melbourne with an average 56m² garden to match their real US counterparts, they could theoretically produce an additional 16.05% of the total Australian national rural produce value!
Now let’s not forget that the total Australian agriculture figures of AU$6,000 million include both peri-urban and rural figures, and peri-urban agriculture is usually about four times as productive as rural agriculture for the same space. Now we have a fairer comparison, which would suggest that urban agriculture figures would constitute a higher percentage of additional produce against the rural yield and monetary figures.
For those who have eyes to see
When we let go of any fixation with rural agriculture models, which are wholly inappropriate in UA applications, and think outside the square, it puts us in a better position to utilize the space and rainfall that is already available in a decentralized and distributed manner across the urban landscape to grow food in cities.
UA takes well thought out, intelligent design to work with the existing elements in a landscape, as is the practice in permaculture design. The idea of requiring clear-felled ‘blank canvasses’ is neither practical nor desirable, it’s in fact indicative of a lack of any real ecological/sustainable design skills.
Using real world data for calculations rather than speculation allows us to make more meaningful evidence-based assessments of the potential for cities to grow their own food. In this assessment, we see that the Australian coastal city of Melbourne has the potential to generate a significant quantity of food to address future food security issues.
One of the most significant conclusions that emerge from assessing the UA food production potential of a city is that the biggest obstacles to UA are not physical resource limitations, as some academics would have us believe. The biggest barriers to UA are cultural limitation, obstacles of the human mind, coming from those who choose think small, engaging in limited thinking and occupying themselves with short-term concerns, lacking the necessary foresight to consider the long-term implications of our current trajectory.
1. Urban Environment Food publication – United Nations, www.un.org/ga/Istanbul+5/72.pdf
2. “Why are our houses getting bigger?” Emma Sorensen, http://www.realestate.com.au/advice/is-bigger-better/
3. “The Impact of Home and Community Gardening In America” report, page 12 – Amount of Food Grown and the Gross Domestic Garden Product