Tag Archives: food

The backyard of Sustainable Cities

Your backyard

HOW BIG IS YOUR backyard? Is it a roof top or patio garden, a patch behind a terrace house, or the proverbial quarter acre in the suburbs. Could your backyard sustain you?

“Are you self-sufficient?” is a question often asked by visitors to Dr Richard Stirzaker’s Canberra backyard at the height of summer. At this time of year his fruit trees are laden and the backyard overflowing with vegetables, leading visitors to wonder about whether he ever visits the shops.

The reality is that Richard’s bountiful backyard falls a long way short of feeding himself for the year, let alone his wife and three kids. In his book, The Scientists Garden Richard calculates that on his 877-square-metre block, the backyard could just grow enough potatoes, fence to fence, to supply enough calories for himself only. Gone would be the fruit trees and vegetables which make the backyard so appealing during summer and provide the necessary variety in our diets.

Sustainable Cities

The notion of sustainable cities requires us to redefine our backyard. For cities are not, and never will be sustainable within their boundaries. Instead the backyard of a sustainable city extends well past what you see from your back door. The challenge is how can we contribute to the stewardship of this extended backyard?

Dome

To understand how big a backyard a sustainable city needs, let’s imagine an air and water-tight dome over our city. Such a dome would be roughly 40 kilometres across to enclose a city the size of Sydney or Melbourne and be home to around four and a half million people.

Our dome needs some farmland to produce our food as even Richards’s bountiful backyard is too small to provide a balanced diet. In fact our current diet requires around 2.8 hectares of farmland per person to grow enough food for the year (pdf). So we need to extend our dome out to 400 kilometres to include this farmland for our 4.5 million people.

But our dome needs to be much bigger to supply the water and fresh air we need. It would balloon to nearly 600 kilometres if we add a catchment area to supply water, and vegetation to absorb the carbon dioxide released by our city and stabilise the atmosphere.

A dome spanning 600 kilometres would be quite an engineering feat. When we tried running one on a small scale in the 1990’s Biosphere 2 project we could not manage it with only eight people in a dome 128 metres across. And our mega dome would become even more unmanageable if we add in space for the treatment of waste, the energy used by the city, resources for commerce, climate regulation, the national parks we like to retreat too, and room for Australia’s diverse plants and animals.

Our imaginary dome highlights the fact that the backyard which sustains you is a lot bigger than what is immediately outside the back door.

Extended backyard

So when you stand in your backyard, be it a roof top or patio garden, a patch behind a terrace house, or the quarter acre in the suburbs, look beyond the boundaries of your own backyard. Look beyond your street, your suburb and your city, for this is where the future of sustainable cities lies.

The need to connect and look after our expanded backyard is not just altruism, but enlightened self-interest: last time I looked there were no new continents to move to, so we better start looking after what we have.

This article first appeared on the ABC website

Jane Nethercote, Crikey (Australia)

So you think that your shower bucket is saving the planet. Think again. Most of your water waste is around your waist.

Through eating and drinking, the average Briton consumes about 3,400L of water a day, according to Hidden Waters [PDF], a recent report from Waterwise. Australian irrigation scientist Professor Wayne Meyer reckons it’s more like 3,000L per meal, or 10,000L of water a day in the Western world.

Everything you eat and drink contains “embedded water” – the so-called hidden water it takes to bring produce from the field to your table. But not all foods are created equal. It takes a lot of water to grow food, and then “much more water to feed and service the animals that we eat”, says Waterwise’s head of research Joanne Zygmunt.

Which means vegetarians have a right to feel smug: a leafy diet contains about half the embedded water content of a meat-lovers regime. Not that anything is ever that simple. There’s methane output too of course, and here, some might venture that vegetarians are bigger contributors.

Natural rainfall (green water) plays a large part in embedded water content – only 15% of crops produced worldwide are irrigation-fed — but 70% of global freshwater withdrawals are for irrigation (blue water). And in Australia in 2003-04, the most extensive use of irrigation in agriculture was for pasture for grazing (ABS), not for crops. Despite being the driest continent on earth, Australia is a net exporter of embedded water. Water that we don’t have.

So how do you trim your water use? The Crikey Water Diet can help. Our motto: A moment on the lips, a life of bucket trips.

To kick off, here are some general rules, with expert commentary from Kelvin Montagu of the Cooperative Research Centre for Irrigation Futures.

  • Find food close to the source. “The closer your food is to the source of all food, photosynthesis, the less hidden water you will be using. All the food we eat is originally produced by plants as they grab carbon dioxide out of the air and produce sugars via photosynthesis, losing a lot of water in the process.” 
  • Green should be seen. “If you are dead keen on reducing the amount of hidden water in your food then eat leafy vegetables. By doing this you minimise the amount of food value lost as the original sugars are changed to more complex foods – but there is a limit!”
  • Fruits and grains reduce the pain. “The next best is to eat fruits and then grains which will have more hidden water than vegetables. This is because there is a cost to the plant in transporting, making new more complex compounds and storing them in the fruits and grains.”
  • If it moves, lose it. “The real big jump in hidden water comes when another animal gets involved. A lot of the food values are lost in the conversion of the original plant into the products from animals such as cheese, eggs and finally meat.” It’s estimated that one kilogram of beef has 50,000-100,000L of embedded water, more than a backyard pool, as Des Houghton notes in the Courier-Mail.
  • Where did it come from? There are many variables in food production and embedded water can vary significantly depending on country (or even region), as well as the aridity or humidity of the atmosphere. A kilogram of tomatoes produced in the UK has an average embedded water content of eight litres, but a kilo from Indonesia contains about 340 litres.

Originally published in Crikey – 26 March 2007.