State of the Environment

2001

Human Settlements Theme Report

Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Professor Peter W. Newton, CSIRO Building, Construction and Engineering, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06747 7

Urban stocks and processes

This section reports on the following environmental indicators, which are defined in Newton et al. (1998).

Environmental indicator
HS 0.1 International migration to Australia
HS 0.2 Gross domestic product (GDP)
HS 0.4 | a | b | Information Economy
HS 1.1 | a | b | Total energy use
HS 1.2 Energy use in industry
HS 1.3 Energy use in transport
HS 1.4 | a | b | Domestic energy use
HS 1.5 Commercial energy use
HS 1.7 | a | b | Renewable energy
HS 1.8 | a | b | Cost of energy
HS 2.2 | a | b | c | Municipal household water consumption patterns
HS 2.3 | a | b | Total annual water usage by sector
HS 2.11 Residential water consumption under alternative water pricing
HS 3.4 Residential density
HS 3.5 | a | b | Percentage of medium and high density residential construction
HS 4.1 Access to public transport stops
HS 4.2 | a | b | Car ownership
HS 4.5 CBD parking supply and charges
HS 5.1 | a | b | c | Population and household growth rate
HS 5.4 Visitor numbers
HS 6.1 Floor area per person
HS 6.7 Building materials used in housing/embodied energy
HS 6.8 | a | b | Operating energy efficiency

A stock is the quantity of something we can count or measure. The stock of people (the population) is the number of people. Similarly, we might be interested in the stock of houses, cars, trees or land. People, houses, cars and trees can all be counted, but sometimes we are interested in different measures of quantity. For instance, we might prefer to keep track of the housing stock in terms of the area of floor space rather than the number of houses, or we might be interested in both.

Stocks consist of similar, but not necessarily identical, things. The population is made up of males and females of different ages who live in different places. As these differences can be very important, we need to take account of the substocks which make up the main stock. So, for example, we record the size of the stock (the number) of men in New South Wales between the ages of 25 and 30. Summing over all the states, both sexes, and all age groups, we get the total population - the stock of all people. We need to disaggregate stocks in this way in order to deal with the consequences of different distributions over age or other characteristics.

If health were an issue of concern, we could disaggregate the stock of people by some measure of health status and record the numbers in the various categories (e.g. good health/poor health; or less/more than some number of days illness over some time period). Information about the stock of people classified according to health status is important in estimating the needs for (stocks of) health care infrastructure.

The age distributions of stocks are particularly important for two reasons - they determine current needs, and they put limits on the rates at which things can change. The age distribution of the population, for example, determines the mix of infrastructure required to meet the needs of young and old people, such as the relative numbers of schools and nursing homes. The age distribution of buildings or vehicles determines their maintenance and replacement needs.

Many of our stocks have been built up slowly over many decades. The economy is geared to operating and maintaining these stocks and to providing for modest growth, but it may not be able to make radical changes in a short time. The rate of introduction of new technologies is often limited by the renewal rate of the stock; that is, by its age distribution and the typical lifetime of its members. If routine maintenance and replacement are neglected, the rate of failure in ageing components can build up to unmanageable levels.

Flows are the rates of change of stocks. The stock of people - the population - changes under the influence of three flows: births, deaths and migration. As, in this case, the stock is measured as a number of persons, these flows are measured in persons per year. Like stocks, flows need to be disaggregated so that we can understand the distributions over their important characteristics. Flows are important because economic activity - the interaction of key processes of demand and supply - is measured as flows (e.g. housing starts, new car sales and GDP, all measured per year).

Thus, the most immediate and short-term policy considerations (flows) are generally determined by long-term variables (stocks) that are seldom the focus of policy deliberation. If stocks such as domestic housing and the motor vehicle fleet are built up over long periods of time, it is unlikely that their structure and function can be changed quickly. Thus, the nature of the stock can hold back or retard any attempt to quickly change the nature of the flows that are derived from the stock. The term 'infrastructure inertia' or 'policy inertia' is used to describe this attribute of a particular stock.

The challenges posed by stock inertia come in many forms. The stock of school teachers in Australia is skewed towards older ages because of a wide number of factors, some of which are related to the demographic characteristics of the 'baby boomers' generation and their attraction to teaching as a profession. As the retirement age of this group of teachers approaches, there will be a requirement to gradually increase the effort devoted to the recruitment and training of new teachers to ensure that adequate numbers and types of teachers are available for coming generations of students. The teaching stock cannot suddenly be replaced in one year. The motor car fleet is somewhat similar, being composed of a wide variety of makes, types and ages which contribute to an overall fuel efficiency which requires approximately 11 litres of petrol to travel 100 km. If, because of oil prices, greenhouse gas emissions and city air pollution, a policy goal was developed to increase the fuel efficiency of the national car fleet to 5 litres per 100 kilometres, the process could take 15-20 years because of the size of the vehicle stock and its relatively slow rate of turnover.

As the size and activity of a modern economy grows, and as the stocks of infrastructure and human capital grow also, two things happen. Firstly, as the stocks become larger, the inertia increases, and any effort to alter the flows derived from the nature of the stocks becomes more difficult. Secondly, the composition of the stocks may become more complex as new technologies are added to the mix, rather than displacing old technologies. For example, a new television set means that a household potentially has two televisions, and a new refrigerator means that the older, less efficient model might be used to keep drinks cold in the garage. Resource flows generally increase with stock increase, although this need not be so, depending on the contribution from recycling and reuse.

Within the political realities of modern economies and lifestyles, there are limited opportunities to alter the functional characteristics of national stocks, particularly when stock structure is saturated. If policy-makers wish to take account of stock inertia in developing effective environmental policies, there are three guiding ideas which may help: