Animation – the evolution of Washington DC’s Metrorail from 1976 to 2010 (click to view)

If we could significantly increase population densities and get many more people out of their cars and into public transport, we’d go a long way toward making our cities sustainable. We’d almost be there if we could generate most electricity from renewable resources.

Or so you might think. Yet the Australian Conservation Foundation (ACF) disagrees. In its Consuming Australia report (here and here), it reckons that even if every single Australian household switched to solar energy, and every household member caught public transport, cycled or walked instead of driving, total household greenhouse emissions would only fall by about 18%.

Given that public transport accounts for just 10% of passenger trips across the country at present and renewable sources contribute only 8-10% of national energy supply, the scale of effort and pain required to eliminate cars and coal would be extraordinary.  A one fifth fall in emissions seems a modest pay-off for that sort of investment.

The explanation, according to the ACF, is we wouldn’t be tackling the main problem. It isn’t the energy, water and land we consume directly that matters most (although they’re still important) – it’s the indirect energy, water and food embodied in the goods and food we consume that’s the real issue.

The largest environmental impact comes from the resources and contamination involved in making/manufacturing the things we buy. They account for more than four times the emissions generated directly from uses liking cooling homes and powering appliances.

Similarly, six times as much water is embodied in the goods and food we buy, as we use directly within our homes. For example, the “dairy sector alone accounts for one of every ten litres of total household water use”.

The ACF sounds a dire warning:

Even drastic measures to reduce direct personal water and energy use may not have the desired effects, unless they are complemented by strong action to reduce the environmental impacts associated with the food we eat, the clothes we wear, and all of the other products we buy…..Even though it is vital to reduce use of energy and water in our own homes, if we really want to tackle our impact on the environment we must as a society begin to address the indirect impacts of our consumption patterns.

It’s not that the sorts of principles implicit in ideas like Smart Growth, New Urbanism and Transport Oriented Design don’t matter, it’s that they’re not enough. In fact according to the ACF they’re not even the main game:

For households to make a serious dent in greenhouse emissions, they must go well beyond merely reducing energy and petrol use….consumption of food and other consumer goods far outweighs the direct impacts of energy and water use in the average Australian home.

As I read it, the ACF is concerned  we’re not giving priority to fighting global warming and other environmental issues on the fronts with the highest likely pay-offs. For example, on the finding that inner city populations have the highest environment impact (see my post of 10 April 2012), the ACF says:

Any benefits from urbanisation, such as higher population densities in the inner cities leading to increased use of public transport, are completely over-ridden by the negative impacts of the additional consumption of the (affluent) inner city areas.

The ACF has its own agenda for action. Sounding a lot like the voluntary simplicity movement, it proposes the best way to reduce our environmental impact is by:

Shifting consumption from high impact goods to lower impact services

Consuming sensibly rather than carelessly…

Cutting down on waste and unnecessary expenditure

Purchasing efficient and environmentally sound products.

Now I think the idea that a war should be fought with equal intensity on all fronts is unwise. It’s much smarter to focus most effort on those battles that give the best bang for the buck.

Some environmentally friendly actions will give a bigger pay-off than others for the same effort or “cost”. Some will  be too hard politically and others will involve so much sacrifice that people who otherwise have the best of intentions will simply ignore them – our propensity to holiday in Rome if we can afford it rather than Rosebud or Redcliffe comes to mind.

The ACF’s key message is we’re not doing enough. Beyond that though, the ACF also reminds us to think carefully about what the most important battles are.

A lot of discussion about cities assumes implicitly that anything and everything that can be shown to improve sustainability should be tackled simultaneously. A smarter course would be to give greater thought to the relative pay-off to cost ratio of different urban policies.

In fact it would be even smarter to do what the ACF suggests. That is, recognise that urban policies are only one way of encouraging much-needed changes in human behaviour toward greater sustainability. And recognise that urban policies might not be the smartest way in all circumstances.