Dallas - Fort Worth, Texas
We begin with an example similar in almost all respects to Brisbane, Perth, Adelaide or any of Australia's Car Cities. It has been chosen to make the point that the phenomenon of urban sprawl engulfing its surrounds is definitely not just an Australian problem or one of the developing world. Satellite images very clearly reveal how frequently, and how extensively, Urbanisation is changing landcover in the developed world. The example chosen here is from the USA; a study of the landcover consequences of the expansion of the twin cities of Dallas-Fort Worth, Texas.
Three Landsat FCC images of Dallas-Fort Worth, Texas: March 12, 1974; March 22, 1989; and the 1974-1989 difference image.
Use your browser to open each image in a new window to compare them.
We have Landsat MSS images that permit us to look back fifteen years, from March 22, 1989 to March 12 1974. The expansion of the two cities and their peripheral urban areas between these two dates is clearly obvious to the naked eye. No specialised enhancement is really necessary to show the sprawling increase of Urbanisation - houses, roads, freeways, even airports. All this expansion has been at the expense of the surrounding agricultural land.
The absolute population increase in these twin cities was 850, 000; from 844, 000 in 1970 to 1, 700,000 in 1990. This is about the same size of increase that Sydney and Melbourne experienced over the same period, only the rate of increase was higher. The population of these twin cities doubled in 20 years.
With this small increase in the absolute number of people, why then can we observe such a large increase in the size of this urban area?
Why has it become such a sprawling city?
The apparent answer is that the urban planners and the citizens of Dallas-Fort Worth prefer a low density urban environment. As you can see from the images, and particularly using the digital data, much of the spatial patterning of the urban area is contributed by roads and freeways. These are cities built around the automobile. These are Car Cities in the national home of Car Cities. Are they very different from what we have allowed Australian cities to become? Aren't these images very similar to Melbourne, Adelaide and Perth?
I want to make two points. The first is that the expansion of these twin cities has been at the expense of high quality agricultural land. That conversion of productive agricultural landcover to asphalt and concrete is irreversible. Any irreversible change reduces options for future action.
The second point is that all Car Cities, in the USA and in Australia, can only function with cheap fossil fuels. It was the unwise and profligate use of cheap fossil fuels that spawned them in the first place. This pattern and style of Urbanisation is not sustainable.
My forecast is that the twin cities of Dallas and Fort Worth are unlikely to persist in their present form for long into the 21st century. Neither will their Australian counterparts. In perhaps 20 years time, these two satellite images will again be scrutinised by people interested in looking back to use the past as a guide to the future. You are part of the first attempt.
