3 Population growth and distribution

Human population growth is a potential cause of environmental change worldwide, including Australia, even without considering the impact of changes on living standards or resource use per capita. Historically, a higher population has generally translated into an amplified demand for resources, a larger physical footprint for our settlements and more waste going back into the environment. At the global scale, the Millennium Ecosystem report¹⁶ states that over the past 50 years, humanity has changed ecosystems more rapidly and extensively than any comparable time in human history, largely to meet increased demands for resources.

However, it is not appropriate to attribute all past Australian environmental degradation to the direct or indirect effects of population growth. Many of our historical environmental impacts are related to poor land and water practices, poor development policies or phenomena such as introduced pests.¹⁷ None of these are directly related to population growth, nor would they be immediately remedied if Australia had fewer people. Nevertheless, many of the pressures on the Australian environment do scale to some degree with:

• how many of us there are or will be
• where most of us live or are likely to live in the future (i.e. near the coast and in the suburbs of large metropolitan centres)
• the material demands that our lifestyles place on the environment
• the technologies and practices used in interacting with the environment.

Australia’s population is growing. The factors that determine this growth are mortality, fertility and net migration. The largest factor influencing population growth over the past decade has been net overseas migration rather than natural increase, although less so than over previous decades. Scenarios of future growth developed by the Australian Bureau of Statistics and by the Australian Government Treasury use plausible ranges of each of these factors in combination to generate population projections, although to some degree these are constrained by historical trends. The best recent synthesis of these analyses for both population and associated economic projections is the 2010 intergenerational report (IGR) by the Treasury.⁵ The population projections in the IGR build on those published by the Australian Bureau of Statistics in 2008.¹⁸

Australian mortality rates have fallen significantly over the past century; these falls have added to population growth and the proportion of older people in the Australian population. Australia’s crude mortality rate has fallen from 9.1 deaths per 1000 people per year in 1968 to 6.7 deaths per 1000 people per year in 2008. Mortality rates have fallen for both sexes, particularly for those aged 50 or more, since 1970. The life expectancy for Australians remains among the highest in the world. The 2006–08 life tables indicated that life expectancy at birth for men had risen to 79.2 years and for women to 83.7 years (an increase of 24.0 and 24.9 years, respectively, since 1901–10).

The total fertility rate is the average number of children a woman gives birth to in her lifetime; 2.1 is considered to be the fertility rate needed to keep the long-term population stable in the absence of changes in mortality rates and if there is no net migration. The 2008 estimate of the world total fertility rate is 2.5, ranging from 1.2 to 7.1. Most developed countries have fertility rates below the replacement rate.

Australian fertility peaked at 3.5 births per woman in 1961 (the end of the post–World War 2 baby boom). Subsequently, the total fertility rate of Australian women declined rapidly during the 1960s and 1970s, stabilised during the 1980s, then declined further until 2001. Since that time, fertility has been generally increasing to reach almost two births per woman in 2008, the highest since 1977 (Figure 2.4). The IGR base scenario projects fertility to fall slightly to 1.9 by 2013, and stay at that level for the remainder of the projection period. Although the fertility projection is below the natural replacement rate, natural increase remains positive throughout the projection period because relatively more women are currently in the younger rather than older age groups.

Australia’s current fertility rate is higher than many Organisation for Economic Co-operation and Development (OECD) countries, including Italy, Germany, Japan and Canada, and is well above the OECD average of 1.68 (2007 data). It remains below those of New Zealand (2.18 in 2008) and the United States (OECD estimate of 2.12 in 2007).

Of the three basic factors determining population (fertility, mortality and migration), the net migration rate is most subject to policy intervention, and thus the most uncertain in projections. Again, the most current scenario is provided by the IGR, which assumes in the base scenario that net migration will fall relatively sharply from an average of around 244 000 people per year from June 2006 to June 2009, to 180 000 people per year from 2012 and beyond, with an unchanged age–gender profile. To illustrate the long-term historical trends and future projections in migration, it is useful to express migration relative to the resident population (Figure 2.5). The average rate of net overseas migration assumed over the IGR projection period is around the average observed over the past 40 years; to project population growth this far into the future naturally has its uncertainties, but is nevertheless useful for anticipating potential implications for our environment.

Note: Population as at 30 June

Sources: Australian Government Treasury,⁵Australian Bureau of Statistics,¹⁹ Treasury projections

Taking these three factors together, Australia’s population in all age groups is projected to increase (Table 2.1). Over the next 40 years, the rate of growth is projected to slow slightly to 1.2% annually, compared with the 1.4% experienced over the previous 40 years. At the same time, the population will continue to age.

The low population growth scenario is based on net overseas migration of 100 000 per year, which is lower than the 30-year historical average to 2008 of 109 000, and total fertility of 1.7 births per woman, which reflects the historical minimum reached in 2001. This gives an annual growth rate of 0.8%, lower than the 1.2% annual population growth that is projected under the base scenario (Table 2.2).

Note: Population as at 30 June

Sources: Australian Government Treasury,⁵ Treasury projections

It is not just the size of the Australian population that determines the impact on the environment. The geographical distribution and composition of the population may also be important factors. For example, the population may be growing more rapidly in areas of particular environmental sensitivity, such as the coasts, than in other areas. Changes in the age structure of the population or household sizes may have implications for the consumption of particular natural resources as a result of ‘lifecycle’ effects, where different age groups have different demand profiles (e.g. an ageing population is likely to increase demands for health services).

The Australian population is highly urbanised, tends to live close to the coast and is concentrated in metropolitan urban areas (Figure 2.6). In 2006, 88% of Australians lived in metropolitan urban areas compared with 58% in 1911.²⁰ Some rural areas, and some small urban areas, have experienced and continue to experience population declines. Australia’s biggest cities are mostly located near the coast, meaning that the vast majority of the Australian population (85%) lives within 50 kilometres of the coast.

According to the most recent Australian Bureau of Statistics population projections,¹⁸ under the ‘middle case’ assumptions, the proportion of people living in the capital cities will increase from 64% in 2006 to 67% in 2056. Population projections are not available for other geographical dissections, but it is logical to assume that much of the remaining population growth will also continue to occur within coastal regions.

Where in Australia this population growth is likely to occur and its implications for the built environment of our cities and regions, heritage and natural environment is considered throughout this report.