Troubles will come sooner. This week's government white paper proposes a 5 per cent cut in emissions, but this, like Ross Garnaut's report, assumes large per capita cuts can outpace population growth, like a swimmer prevailing against the tide. But this planning is based on the dubious assumption we are heading for 28 million people living in Australia by 2051, rather than 42 million. If the Rudd Government does not change course, even painful per capita cuts will deliver no overall cuts, but an increase. Much the same goes for water consumption. El Nino droughts come two or three times a decade, yet state and federal governments are, in effect. gambling it won't happen on their watch. Several of Rudd's ministers, most notably Penny Wong and Peter Garrett, are "population deniers". Even Rudd has been heard repeating the nonsensical claim that "numbers are not the issue". They are.

Some claim Australia is a big country, "boundless plains to share", etc. Yet the geographer George Seddon has remarked Australia is more truly "a small country with big distances". Even our agricultural areas are not so large, or fertile, as population boosters pretend. Wheat is our main crop, yet France, for instance, grows twice as much wheat (and far more of most other crops). The human as well as the natural environment deteriorates as population grows. Two years ago, the NSW Government instructed Sydney's councils to accommodate an extra 1.1 million people within 25 years. Bankstown, for instance, was told to build 26,000 extra homes. Most councils protested it was impossible to reconcile this with conserving the amenity of the suburbs. Even these draconian plans will be overwhelmed by additional people. In the Hawke-Keating days, the knee-jerk reaction to any suggestion that population growth, and therefore perhaps immigration, should be reduced was to accuse the critic of "racism". Yet polls show most immigrants think immigration is too high.

But the Government seems asleep at the wheel. The Minister for Immigration, Chris Evans, claims to foresee only "a continuing modest increase in our population levels over coming years". Others continue to claim that births are not keeping up with deaths. Bureau of Statistics figures show that births each year in Australia are twice the number of deaths, have been so for decades and look like being so for several years more. Baby bonuses are the last thing we need.

Tim Flannery has suggested that, granted the rate at which we are losing soil, Australia's safe carrying capacity in the long term may be as low as 8 to 12 million people. As he points out, humans are extremely long-lived mammals. Population growth, like herpes, is easily acquired but very hard to lose. In 1994, the Australian Academy of Science held a conference to publicise its findings on population: 23 million people should be our limit. Today, with peak oil and climate change now realities rather than theories, that might have to come down. Over the years, Australians have been promised a series of points at which population growth would supposedly be capped: Bob Hawke spoke of 25 million, which the Fitzgerald report had suggested might be the limit set by water resources. Within the last decade, Philip Ruddock, as minister for immigration, spoke soothingly of our population naturally peaking at some 23 million (later he said 25 million). Peter Costello's Intergenerational Report claimed that population would be only 28 million in 2051. Our current trajectory is to break 100 million by 2100.

Just as every fat person was once a normal child, so every bloated behemoth nation of 100 million-plus was once a nation of 5 or 10 million, with intact ecosystems and abundant water. Even Java, as late as the early 19th century, had fewer than 5 million people. Population increase suits governments wanting to please the business community now, by doing something the full cost of which will only emerge over the next 20, 30, 40 or 50 years - far beyond the attention span of three-year governments. There is still a way out and it is not economically naive to think population growth can be slowed.

Much of politics is repetitive and unproductive, but sometimes a logjam breaks. In the past two years, most politicians have ceased being in denial about climate change, greenhouse emissions, limits to water, and peak oil. All these crises reflect the deeper underlying problem: our population growth is out of control. Waiting for the population debate to begin is like waiting for the other shoe to drop. Mark O'Connor is co-author of Overloading Australia : How Governments And Media Dither And Deny On Population, published by Envirobook.