|If measures are not taken, a booming population could increase global poverty, analysts say [GALLO/GETTY]
Back in 1798, clergyman and author Thomas Malthus fretted that the "power of population is indefinitely greater than the power in earth to produce subsistence for man".
When Malthus was writing in 1810, the world's population was about one billion. It will hit seven billion on October 31, according to the UN, and debates about how many people the planet can sustain only seem to be intensifying. The global population is expected to hit nine billion by 2050.
"We don't really know how to adequately feed seven billion people - we still have one billion who are not getting enough to eat - so how are we going to feed nine or ten billion?" asks John Weeks, director of the International Population Centre at San Diego State University.
"My own belief is that we don't have enough resources to sustain seven billion - much less nine or more at the standard of living that we have in the West," he told Al Jazeera.
"Malthus was obviously wrong about a lot of things." He certainly overestimated prospective population growth rates and underestimated the ability of technology to revolutionise agriculture. "But the question about how many resources we can generate sustainably remains unanswered," Weeks said.
Other early scholars came to different conclusions from Malthus, who used his dire predictions to preach chastity and religious moralism.
In the 1670s, Antoni van Leeuwenhoek, the Dutchman who invented microscopes, estimated that the world could sustain 13.385 billion people.
Population is not necessarily the problem, rather over consumption and inequality drive the worst environmental degradation, some of Malthus' critics argue.
"The consumption of the rich causes far more environmental problems per person than the modes of consumption from the vast majority of people - who have fewer claims to resources and incomes," Richard E Bilsborrow, faculty fellow at the Carolina Population Centre, told Al Jazeera. "High consumption [in the rich world] is linked to degradation in the poorer countries. Still, the latter people are degrading the environment."
More people, more geniuses?
Mao Zedong, the architect of communist China, didn't worry about over population because "every stomach is born with a pair of hands". In his view, the need to consume was balanced by the ability to produce.
Chairman Mao was not the only powerful cornucopian - someone who believes that population growth is a blessing, not a curse.
Standing on the other side of the political spectrum and sharing a similar world view, was Julian Simon, a business professor and fellow at the free-market CATO institute, who passed away in 1998.
To oversimplify his arguments, Simon contended that resources are not becoming any more scarce and population growth should be celebrated; more people means more geniuses who can solve the world's problems through technology and innovative policies.
|View our special coverage of the population milestone
Today, it looks like Mao and Simon are out of style. China's population grew from fewer than 600 million in the 1950s to nearly one billion in 1978, when reform-minded leaders imposed the one child policy, worrying there were too many idle hands and empty stomachs.
Part of Simon's fame stems from a bet he made with the ecologist Paul Ehrlich. Simon thought that prices for basic metals - a measure of scarcity - would fall through the 1980s, while Ehrlich wagered they would rise. Simon won, but prices for food, fuels and commodities have increased dramatically since then - and many hedge funds and speculators see a rising arch over the long-term for prices of basic goods - indicating that supplies are becoming scarcer.
"We don't have any more land on which to grow food," Weeks said. "All the resources we are exploiting need to be exploited more efficiently."
Inequality vs population
In early 2011, the International Monetary Fund released a paper entitled Inequality, Leverage and Crisis, warning that spiraling inequality could have "disastrous consequences" if not addressed.
And they are not alone in sounding the alarm. "The global wealth pyramid has a very wide base and a sharp point," The Economist reported in January 2011. "The richest one per cent of adults control 43 per cent of the world's assets; the wealthiest ten per cent have 83 per cent. The bottom 50 per cent have only two per cent."
This massive amount of money is often spent on private jets, multiple estates and market speculation. If the gap between the haves, have-nots and have-yachts is reduced drastically, critics say, the world has enough wealth and natural resources to provide a decent standard of living to a large population.
"There is a rough tradeoff between population and consumption ... a country's environmental resources can be stressed by either of them," said Geoffrey McNicoll, a senior associate at the Population Council, an international non-profit organisation. "More consumption is usually a better route in generating human well-being - though with diminishing returns at high levels," he told Al Jazeera.
Between 2000 and 2010, the number of adults worldwide rose from 3.6 billion to 4.4 billion, while average wealth (total wealth divided by population) rose from $30,700 to $43,800, The Economist reported. There could be plenty to go around.
"Simply redistributing wealth would greatly improve the current situation but it is not politically feasible," Bilsborrow said.
But these calculations on redistribution do not take environmental costs into account. Some critics say that humans are already taking too much from nature and increased population - especially a globe full of people who want to live like citizens of the developed world - will only make the planet more unsustainable.
The ecological footprint of humankind - the amount of natural wealth we currently take out of the world in the form of food, energy, materials and water - is 35 per cent greater than what the planet can sustain, according to the calculations of environmentalist Mathis Wackernagell, co-developer of the ecological footprint concept.
Some people consume far more than their fair share, others far less. The current model is unsustainable, Wackernagell argues, as we are taking resources out of the planet faster than they can be regenerated. You can probably guess the worst offenders.
Residents of Canada, the US and a few northern European countries are only surpassed by the consumers in Arab Gulf States - the UAE, Qatar and Bahrain - where petroleum extraction, constant air conditioning and fleets of massive SUVs contribute to the world's highest environmental impact per person, according to the Global Footprint Network, a research organisation.
"Obviously, we could sustain a larger number of people at a lower standard of living," said Weeks. "But that would mean higher death rates and more misery."
While the population continues expanding, demographers are encouraged because its growth rate has slowed down in most regions. "The world's population growth reached its peak at 1.9 per cent in the 1960s and has dropped to about 1.2 per cent," said Bilsborrow. "The fall is really extraordinary."
A rise in living standards, access to family planning and more rights for women have all played a role in slowing the rise, analysts said.
There is, however, one significant exception. "The single major world region still experiencing rapid population growth is sub-Saharan Africa," McNicoll said. "There is some population-related conflict (for instance, between farmers and herders), but most of the region's conflicts seem to have other causes - religion, ethnicity, minerals, etc."
Improving agriculture in the region is certainly possible, experts agree, as many rural farmers still lack access to basic technologies. This will help feed a growing population in the short-term, but reducing long-term population growth is trickier in a region disproportionately afflicted by conflict. "The most productive aid we [in the West] can give is education," Weeks said. "But selling weapons is what the rich countries do most easily."
Follow Chris Arsenault on Twitter: @AJEchris