There is a lot of advertorial prose in this article; and its tone of manic cheerfulness seems odd in an academic piece. Phrases like these are seeded throughout it: "the rise and rise of Western Australia,", "West Australia booming", "rich economic, social and physical tapestry of metropolitan life across Australia", "Such growth is impressive and reinforces WA’s role as the economic power-house of Australia".

Such phrases seem more appropriate to a developer's glossy brochure.

There is too little awareness of the crippling infrastructure costs such rapid population growth can bring. Jane O'Sullivan of University of Queensland has pointed out that each extra person costs at least $200,000 in infrastructure. See http://www.onlineopinion.com.au/view.asp?article=10137&page=0 . A recent report by Curtin University found that state development costs including infrastructure for new suburbs are $684,000 per dwelling - mostly paid by the taxpayer. At the national average of around 2.6 people per household that’s approximately $263,000 per extra person.

In South East Queensland, which had till recently the fastest population growth rates in Australia, the state government was effectively bankrupted. It was forced to let infrastructure lapse and to sell of major public assets (even in the middle of a boom) -- and suffered the worst defeat in the state's history. http://www.abc.net.au/unleashed/39930.html

It seems frivolous to ignore all these problems --not to mention the resource and environmental ones Mr Raven's comment raises -- and to concentrate merely on what wonderful "diversity" this influx of people (mostly from already well-established migration source-countries) will bring. What about the more serious issues Crispin Hull raises: http://www.crispinhull.com.au/2011/09/03/witches-hats-make-governing-too-hard/

True, changes in cultural and religious preponderance are a very legitimate concern of demographers, and (for some matters) of town planners. But the reality is that these newcomers are not going to live in Innuit fishing settlements or agrarian communes.

Their demands on housing, roads, hospitals, sewerage, water, food, and the battered environment will be very little different from that of existing population. Planning for their ethnic diversity is surely a far lesser challenge than planning for this great increase in human numbers.

So why the heavy evidence on the challenges (but "exciting" challenges) posed by their diversity? If this was a developer's brochure, the answer would be obvious: it's a standard distraction tactic. But why should a professor of urban/regional planning be wearing the same rose-tinted lenses?

Paul Maginn wrote: "... the focus of the piece was on social diversity and if there are costs attached to this then I'm interested in the "social costs" that not acknowledging and responding effectively to increased diversity might result in."

Explaining the cost of diversity on society is a little bit like explaining the cost of cancer on the body; the trick is to understand how anyone could possibly argue that diversity strengthens rather than shreds the commonalities that bind a community - and, more broadly, a nation - together.

An incontrovertible lesson from human history is that conflict - not harmony - is the general rule wherever and whenever two or more well-defined ethnic groups inhabit the same territory. Yet Australian policymakers appear to have ignored this historical reality, instead believing that they can engineer through mass diverse immigration a utopia where all groups of people from anywhere in the world, mixed together in any numbers and proportions whatsoever, will eventually settle down as a harmonious society, appreciating — nay, celebrating! — their differences... which will of course soon disappear entirely.

Some may remember Dr. Robert Putnam's study on the social effects of diversity. The eminent Harvard political scientist was so shocked by his findings that he kept them quiet for years for fear that anti-immigration activists and anti-multiculturalists would jump all over them. His conclusion? Diversity is social poison - it completely destroys trust within a community. "The effect of diversity is worse than had been imagined," Putnam concluded. This is the case even after adjusting for the factors of class, income, and urban versus rural residence.

Putnam found that “the more people of different races living in the same community, the greater the loss of trust.” He reported that the greater ethnic diversity in society the less trust people had in each other, even people of their own racial/ethnic group. “In more diverse setting, Americans distrust not merely people who do not look like them, but even people who do.” In addition, “inhabitants of diverse communities tend to withdraw from collective life, to distrust their neighbors, regardless of the color of their skin, to withdraw even from close friends, to expect the worst from their community and its leaders, to volunteer less, give less to charity and work on community projects less often, to register to vote less.” He added that “in colloquial language, people living in ethnically diverse settings appear to ‘hunker down’—that is, to pull in like a turtle.”

If you want to destroy an existing community, adding ethnic, cultural, and linguistic diversity is the way to do it.

Dr. Frank Salter, an Australian urban anthropologist and ethnologist, has done some interesting work on ethnic diversity.

According to Salter:

"Multi-ethnic societies are often confronted with the problem of discrimination and group conflict. People generally want to live among, marry, and work with their own ethnic group. This can lead to conflict, because affiliation with one group translates into rejection of others, even in the absence of ill-feeling. A business owner seeking to work with fellow ethnics must discriminate when hiring or firing or finding partners, however indirectly and surreptitiously. Due to their small numbers this low-key discrimination usually hurts minorities more than majorities. But as immigrant numbers grow members of the original majority ethnic group also suffer. They are pushed out of areas of employment and business; they suffer from the higher rates of crime often shown by immigrant communities; they become the minority is poorer suburbs; and they sense a threat to their continuity as a people belonging to a particular place. They observe that the newcomers have a different group identity, one that excludes them, and that where there were few, now there are many. They sense, sometimes with justification, that they are losing their country."

Salter asserts:

"Cross-cultural comparisons reveal the wisdom of Australia's first prime minister Edmund Barton who believed that ethnic homogeneity must be the cornerstone of Australian nation-building. More ethnically homogeneous nations are better able to build public goods, are more democratic, less corrupt, have higher productivity and less inequality, are more trusting and care more for the disadvantaged, develop social and economic capital faster, have lower crime rates, are more resistant to external shocks, and are better global citizens, for example by giving more foreign aid. Moreover, they are less prone to civil war, the greatest source of violent death in the twentieth century."

Byron M. Roth, Emeritus Professor of Psychology, Dowling College, New York, issues the following warning in his book "The Perils of Diversity: Immigration and Human Nature":

"From the perspective of inclusive fitness, unfamiliar others are potential free-riders and, out of a concern that they will be exploited by others, people reduce considerably their altruistic attitudes and behavior in a general way in more diverse communities. This loss of trust is a symptom of a breakdown in social cohesion and is surely a forerunner of the sort of ethnic conflict that is always likely to break out if allowed to do so. This is undoubtedly the reason why multicultural nation-states are forever promoting tolerance and ever more punitive sanctions for the expression of ethnic hostility, even going so far to as to discourage the expression of opinion about the reality of ethnic and racial differences. Currently these measures are directed at the host population when they express reservations about the wisdom of mass immigration, but this will surely change as it becomes ever more obvious that it is the presence of competing ethnic groups that is creating the tension and not the expressed reservations of the majority population. The real danger for modern democracies is that in their zeal to promote multicultural societies, they will be forced to resort to the means that have characterized all empires attempting to maintain their hegemony over disparate peoples."