Abul Rizvi rightly argues that “ we desperately need a population plan to enable better planning for our future by governments at all levels, and businesses”.

He suggests, however, that it be the immigration minister who formulates the plan. This would be a classic example of putting the cart before the horse. Immigration is merely a subset of population growth, the other subset being natural increase. A population plan thus needs to extend beyond immigration.

A population plan needs to encompass a broad range of issues, not just as Rizvi suggests, ageing and the interests of business or the economy. It must address the environment as well. Ecological sustainability has to be the bottom line. As the late, great economist Herman Daly famously said, “The economy is a wholly owned subsidiary of the environment, not the reverse.”

This is not to say it should then be the environment minister who takes responsibility for formulating a population plan. It needs a panel of experts, chaired by an ecologist to emphasise the central role of the environment. It should also include demographers to advise on the dependency ratio, scientists to advise on climate and energy, and agronomists to provide input on food production. It could include social scientists. We might add economists to advise on the provision of infrastructure. However, we don’t need conventional economists hell-bent on a growth economy. What we do want are ecological economists who understand the limits to growth on a finite planet.

Once this panel of experts has drawn up a population plan, one which recommends immigration numbers for that year, the immigration minister would then implement its recommendations. That would be the minister’s role, not drawing up the plan in the first place.

For a population plan to be genuinely sustainable, it must incorporate a phase-out of population growth. A recent paper in the academic journal Encyclopedia, cites population growth as a direct cause of deforestation, climate change, biodiversity loss, fisheries depletion, water scarcity, and desertification. As its author, Alon Tal, writes in an associated article, “ global deforestation remains staggering, especially in tropical regions. Between 2001 and 2023, Brazil lost nearly 69 million hectares of forest, while Indonesia lost more than 30 million. Most of this destruction wasn’t for lumber exports or furniture – it was simply to make room for 34 million and 59 million more people respectively”.

Climate change? “Every person is born with a carbon footprint,” Tal writes. “That means more people equals more greenhouse gas emissions. Even in countries with low per capita emissions, the cumulative impact of rising populations is massive.”

And who is to blame for the 73% decline in the earth’s monitored vertebrate populations between 1970 and 2020? “While habitat fragmentation, overhunting, and pollution are often cited as culprits, each of these ultimately is associated with population growth,” says Tal.

At some point, preferably before the last forest is cut down, before too many species have gone extinct, before the last fish is pulled from the sea, before we get to “ hothouse Earth”, and before the rivers run dry, we have to stop population growth. We may well then need to reduce our numbers slowly and voluntarily until ecological sustainability is achieved.

Were there no immigration to Australia, we would be on that path to zero population growth already. In the year ending September 2024, natural increase was 104,200, a decline of 3200 (3.0%) people over the previous year. Were that rate to continue it would take 23 years to reach zero population growth, though if fertility continues to fall further from the current record low of 1.5 (children per woman), zero growth would be reached sooner.

All that, however, assumes no net overseas migration. No government is going to cut it completely, nor should it, because of the need to retain the humanitarian program, some family reunion and to import those highly skilled workers we cannot train here. We can, however, stabilise population numbers in Australia below 30 million by reducing NOM to between 70,000 and 80,000. That’s about half what Opposition Leader Dutton is proposing (160,000), less than a third of what Labor is advocating (260,000), a fifth of what it was in the year to September 2024 (379,800) and a seventh of what it was the year before that (548,800).

Of course, in times of climate change, ideal figures for NOM may be thrown into disarray. Millions of environmental refugees may come knocking on the door; irrigated agriculture may largely disappear from the mainland, leaving us with less food to feed even our current population; parts of the country may become uninhabitable; and damage to infrastructure from repeated and worsening extreme weather may bankrupt the economy.

A precautionary approach is needed. A population plan needs to take into account not just our current resource limits, but likely future ones as well. The aim should be to achieve numbers of people where humans, wildlife, and natural systems can thrive.

I fear we have already passed that point.