Cornucopians can select from an ideological buffet of arguments to deny that our growing human population is a serious problem. I have identified seven of them, but they are not exclusive---some overlap and could be treated as corollaries of others. Those in population-denial typically employ a coalition of them to make their case.
The Capitalist Lie:
We can grow the pie so that even the poorest among us can have a satisfactory slice. "A rising tide floats all boats". The larger the population base, the larger the market, and the longer the production runs, making per unit costs lower for everyone. Resource shortages are signalled by rising prices, which only encourage entrepreneurs to increase supply by the promise of higher profits, and tap into limitless human ingenuity by funding research to find alternatives to those resources which are exhausted or affordably accessible. In other words, we can "grow" the limits. The differences between Keynesians and free marketeers of the Austrian School are superficial---a petty dispute between those who believe that governments can create wealth by 'prime-pumping' fictional wealth into an unsustainable economy and those who believe that an unsustainable economy can best grow with less government intervention. Both schools of fiscal management assume that the human economy is not subject to bio-physical limits.
The Socialist Lie:
There is enough to go around, if only the pie was divided up "fairly and equitably". The problem is not with growth, but how the benefits of growth are shared. People are our greatest resource, the more the merrier. (Ask the Sandinistas). We need only ensure that they are properly fed and educated to exploit their potential. The root of our predicament is not over-population, but poverty, that is, capitalism. Furthermore, there is no "humane" way to control population growth, so it must be ignored. Growth can be 'sustainable'. The concept that there are limits, and that violating them might involve our extinction, and that nothing is more 'inhumane' than extinction, is beyond the pale of socialist consideration. The appalling environmental track record of command economies like those of the former Soviet bloc is ignored or forgotten, or if need be, disowned for not being examples of ‘true’ socialism, but rather, of “state capitalism”. Capitalists, however, are not to be granted similar dispensation to disown corporate debt capitalism. The “eco-socialism” that the green-left talks about is still on the drawing board. History is skeptical.
The Green Lie:
We can arrest economic growth---as we must---without reversing population growth. By reducing our personal footprint, by re-using, recycling and conserving, by making responsible consumer choices, by adopting 'green living' habits, by aspiring 'to live like Ghandi and not like Gates', by living simply, we can allow all of humanity to simply live. And by proper land use management, burgeoning human populations can be steered out of harm’s way from greenfield acreage, farmland, and sensitive wildlife habitat and concentrated in densely packed cities to minimize their energy footprint. You can't nationalize the environment. Environmental issues like climate change---which is the only important metric of environmental degradation----are global problems that demand global solutions and global cooperation. We must be 'inclusive'. We therefore cannot alienate other nations by strengthening our borders, rather, we must work to lower them and be welcoming to all who aspire to live here. We must remake our nation into a microcosm of the human family. Our mandate is not to constrain our population growth---which can be decoupled from GHG emissions, habitat and farmland loss----but to increase our 'diversity'. There is no national culture worthy of preservation, unless it is found in the developing countries. If migrants greatly increase their footprint upon settlement here, then our obligation is not to deter them, but to reduce our own footprint to responsible, third world levels. In short, let's move over, squeeze tighter, and consume and waste less to accommodate more and more newcomers. It was our profligate lifestyle that drove them from their homes, so it is our moral and legal obligation to assist them by opening our doors to them, even if it rescues only a fraction of their numbers. The Green slogan is that of Socrates. “I am not an Athenian or a Greek, but a citizen of the world.” And the Canadian version is "Canada---home to the world."
The Feminist Lie:
Population control is intrusive, it is another male attempt to control women's bodies. Population growth is not a problem but a symptom of gender inequality. If women are "empowered" by education and career opportunities, they will of their volition choose to have a number of children that is sustainable for the society at large. Procreative rights are incontestable. Sustainability is a by-product of human, women’s, workers and farmers rights, which therefore must be our primary focus.
The Technology Lie:
We can maintain or increase our extraction of renewable and non-renewable resources by developing more efficient technologies. Thus there is a confluence of socialist, green and feminist agendas into what may be termed the "environmental justice movement". The Jevons Paradox, that is, the fact that in the context of an economy premised on growth, more efficiencies, by making things cheaper, only provokes more total consumption, is not confronted.
The Religious Lie:
God or Allah will provide. Procreation is more than a right, it is a duty. And who better to enforce that duty than priests, mullahs and husbands? We are the creator's anointed species, with a mandate to grow and exercise dominion over other species. We can have our cake and eat it. We can expand without limit and push rival and subordinate species off the plate and be "good stewards" at the same time.
The Simonian Lie:
Julian Simon's assertion. The more people there are, the greater the chances that geniuses like Einstein will be born to generate the ideas that will save us. 15 billion brains are better than 10 or 7 or 2 billion brains. This belief, even if not overtly stated, runs like an undercurrent through all cornucopian lies. The notion that human brains, to function optimally, need proper nutrition, education and healthy bodies to carry them is a minor detail, as is the fact that the planet cannot indefinitely deliver those pre-requisites to the number of people who live now, never mind those billions that Simonians of all stripes want to add.
While the eco-Malthusian position offers an alternative perspective, it is often alloyed with some of the preceding impurities which confuse and compromise its central thrust: Without population stabilization and reduction, per capita reductions in consumption occasioned by frugal behaviour or efficiencies in technology or land use are ultimately futile, and that without cultural change and the force of law, unsustainable behaviours will persist even if the common people of both genders are "empowered" to make fertility choices. From speed limits to no-smoking bylaws to fish catch quotas, all laws are inherently "coercive", and all individual rights are ultimately conditional on the probability that their free exercise does not substantially restrict or infringe upon the rights of other people and other species to survive and flourish. Population reduction is not a gender issue, for over-population itself is more coercive in its influence upon women than anything the Chinese government has instituted. While the prospect of applying one-child per family laws universally is slim, the fantasy that voluntary measures alone will achieve the global population decline we need is even more remote. This is the "Malthusian Lie" that must be exposed when the cornucopian lies are finally laid to rest. The question that ‘voluntary’ family planning advocates must ask is, “Why, in the pursuit of population stabilization, with even the levers of total media control and a one-party dictatorship at its disposal, did the Chinese government find it necessary to complement moral suasion with legal sanctions?”