Iâ€™ve written before (e.g. here and here) about understanding the importance of selection bias before attributing significant behavioural influences to the physical environment. More often than not, itâ€™s the characteristics of the people that explain more about their behaviour than the type of neighbourhood or housing they live in.
The Australian Conservation Foundationâ€™s (ACF) well known Consumption Atlas illustrates this point well (report here). The ACF estimated the per capita environmental impacts of household consumption at the Statistical Local Area level by matching household expenditure patterns with an input-output analysis for various categories of goods and services (technical report here).
The research turned up some surprising results for the city centre and the inner city. Thereâ€™re many reasons to suppose inner city populations would have a smaller negative impact on the environment than other Australians, especially compared to suburbanites living in large detached houses with two car garages.
After all, the residents of inner city Paddington, Northbridge and Fitzroy tend to occupy small apartments, town houses and terraces and have tiny gardens. They live in relatively walkable, mixed-use neighbourhoods and have ready access to public transport. On average, they also have lower rates of car-ownership than middle and outer suburban residents.
Yet the ACFâ€™s research shows inner city populations have the largest adverse impact on the environment â€“ and by a considerable margin â€“ of any group in the country. For example, per capita GHG emissions average 20-22 tonnes in metropolitan areas in Qld and 15-17 tonnes in rural areas. Yet in inner city Brisbane they average 28-32 tonnes per capita.
In NSW, the areas with the highest per capita ecological footprint are in the inner city, especially around Sydney Harbour (see exhibit). In Victoria, the highest per capita water consumption is in the inner city and inner suburbs â€“ the biggest water wallys live in Prahran and on the edge of the CBD in Docklands and Southbank.
The fact is the green benefits bestowed by the physical characteristics of the inner city are nullified â€“ the ACF actually says â€śoverwhelmedâ€ť â€“ by two key attributes of the population that chooses to live there.
The first attribute is wealth â€“ inner city residents are richer on average than other Australians. Income is very strongly correlated with environmental impact. Wealthier people buy more â€śstuffâ€ť like food, furniture, electronics and clothes that has a high direct and indirect negative impact on the environment. They fly a lot more than others too, both for work and leisure.
While high income households spend more on high cost, low impact activities such as entertainment and other services, they also spend more on electricity and most other categories of goods. Some activities with high greenhouse impacts, such as air travel and construction and renovation, tend to be concentrated in high income groups.
The second attribute is household size â€“ inner city residents live on average in smaller households, mostly of one and two persons. Their per capita environmental impact is consequently large because they donâ€™t take advantage of economies of scale:
In larger households, people tend to share common living areas, which will lower the per-person heating and electricity bills. In addition, larger households can share items such as furniture and appliances, whereas a person living alone must own a full suite of such items. It is also reasonable to think that larger households are more likely to cook together, resulting in more efficient purchasing patterns and lower levels of food waste.
The higher education level of inner city households should – and probably does – give them a greater commitment to protecting the environment. But high human capital is surely one reason why theyâ€™re richer. And wealth results in more spending, more consumption, greater waste, and higher environmental impact. As the ACF notes: â€śfar from enabling a sustainable lifestyle, increases in wealth appear to go hand-in-hand with greater environmental stressâ€ť.
So the poor environmental performance of inner city residents isn’t a consequence of physical characteristics like density. Rather, it’s explained by the characteristics of the people who choose to live there. Those who accept this conclusion but think other behaviours like obesity (or absence of obesity) are primarily the result of the physical environment rather than selection effects should ask themselves if they’re being….well, selective when it’s convenient.
Itâ€™s probably true that inner city residents would have an even larger negative environmental impact if they lived in outer suburban McMansions. However the ACFâ€™s research indicates the locational increment would probably still be modest relative to the sorts of non-physical factors discussed above. Iâ€™ll return to the ACF’s report next time (see here) because it has a number of other interesting things to say.