Geosciences Australia has released a new series of satellite images comparing the extent of development in Melbourne in 1988 with 2010. Click on the image above to go to Geosciences Australia’s web site where you can do a “swipe” comparison of the two images i.e. move the cursor across the image to progressively reveal the second image underneath.
According to a report in The Age, the images show a “massive” increase in urban sprawl, with Melbourne’s urban footprint surging to the north, west and south-east. Melbourne has “marched into surrounding rural landscapes” and its “unofficial boundary is now more than 150 km east to west”.
Melbourne has certainly expanded at the fringe over the last 22 years, there’s no doubt about that. However I’ve argued before that both the extent of sprawl and its downsides are routinely exaggerated, so I want to have a closer look at these images and at The Age’s interpretation.
One thing that struck me straight up is that any comparison of the two satellite images can be misleading unless the viewer appreciates Melbourne was still suffering the effects of a long drought in 2010 (compare the size of the dams in each year). So areas that appear to have gone from green to brown between 1988 and 2010 might reflect lack of rain, rather than an increase in development.
In fact 1988 was an unusual year. There was a La Nina event in 1988-89 – the first since 1973-76 – and hence there were wetter than normal conditions. Have a look at this older CSIRO comparison of satellite images of Melbourne in 1972 and 1988, and note the CSIRO cautions that 1972 was much drier than 1988.
It should also be borne in mind that 22 years is a reasonably long period in urban development terms. We shouldn’t be surprised to see substantial change when a metropolitan area is growing. Have a look at these images to see how spectacularly some other growing cities have changed in the course of 20 years.
The level of growth also needs to be considered. Melbourne’s population grew from circa 3.1 million to around 4 million between 1988 and 2010. That’s an increase of about 30%, which is considerably more than the apparent increase in the size of the urbanised area. That’s to be expected, as a large proportion of population growth – currently approaching half – is accommodated within the existing urban fabric via redevelopment.
And then there’s The Age’s claim that Melbourne’s urban footprint spreads “more than 150 km east to west”. It doesn’t. Using GIS, I measure at most 75 km from the western edge of Wyndham to Lilydale in the east and 85 km to Pakenham in the south-east. If I measure instead from Melton (putting aside that it’s separated by 9 km of green wedge from the continuously urbanised area), I still get less than 80 km to Lilydale and less than 100 km to Pakenham. Some might think that’s still too big, but it’s a lot less than 150 km plus. Read the rest of this entry »