Despite the global birth rate falling to 2.5 children per woman, population growth will continue for decades, to 8.1 billion people by 2025 and 9.6 billion in 2050, according to the UN.

More infants are surviving, people are living longer and we have the largest ever population – 1.8 billion – of young people aged 10 to 24 years. Barring a cataclysm, population growth is inevitable.

Which prompts people to ask: Are we too many? Answers generally fall into one of two camps.

Yes: We face a crisis of overpopulation

No: Overconsumption not overpopulation is the real crisis

We consider both sides of the debate in turn.

Every day a billion people go hungry and as many as 2.7 billion people face water scarcity for at least one month every year, points out the WWF. Moreover, the fastest population growth is in areas least capable of managing it. Population growth “poses a bigger threat to poverty reduction in most African countries than HIV/AIDS,” declared the UN Population Fund (UNFPA) back in 2008.

“As aquifers are drained of water for agriculture, and as glaciers shrink due to climate change we will see agricultural productivity decline just as more people move to meat-based diets,” argues Simon Ross, CEO of UK-based campaign group Population Matters. He believes that expanding populations will force food prices beyond the reach of the poorest, leading to more hunger and conflict.

Many argue that failing to tackle high birth rates perpetuates suffering. If all the women in the poorest countries who wanted to avoid pregnancy could get family planning advice and contraception safely, it would mean millions fewer unwanted pregnancies, infant deaths, and pregnancy-related deaths, says a 2012 report by the UNFPA and the Guttmacher Institute.

Reduced population growth also historically delivers a “demographic dividend” — fewer dependent children and elderly people but large numbers of working-age people. “The first countries that went through this were the East Asian ‘tiger’ economies," explains UN demographer Ralph Hakkert. “Economists estimate that a third of their economic growth can be attributed to this demographic bonus.”

Even though humanity struggles to sustain its most vulnerable people, we are still consuming about 25% more renewable natural resources than the planet can reproduce. If population reaches 9 billion people by 2050, we will be using the biological capacity of two Earths, warns WWF.

More people will mean expanding farming and deforestation, which also increases the already colossal carbon footprint of agriculture, the biggest contributor to climate change.

Scaling up the food system will be challenging due to denuded soils and climate change but also because agricultural land is being swallowed by expanding cities.

“With smaller populations we can have increasing living standards per head but less consumption, more space, better lives, smaller impacts on the planet, and more room for wildlife,” concludes Simon Ross.

Fixating on population growth numbers is misleading, contends statistician Hans Rosling in a recent lecture ‘Don’t Panic: The truth about world population’.

We have already reached “peak child” and so demanding a halt to population growth is senseless because “most of the remaining population growth is an inevitable fill-up of remaining adults” living longer lives.

As US economist Nicholas Eberstadt observes, population growth “was not because people suddenly started breeding like rabbits – rather, it was because they finally stopped dying like flies”.

During the 20th century, the number of people jumped from 1.6 to over 6 billion. Yet despite dire warnings the health and wealth of the majority improved dramatically. “Fifty years ago, some people said people in Asia will never get out of extreme poverty just as people say about Africa today,” noted Rosling.

Moreover, the benefits of reducing population growth are exaggerated, argues Matthew Connelly, author of ‘Fatal Misconception’, a history of population control programs. He contends that good governance, education, and infrastructure are far more effective weapons against poverty. Famine and conflict are less about the numbers of people than about bad decisions, culture and glaring inequalities.

When it comes to resource depletion, the extra billions will barely make a difference, because they will be amongst the poorest 40% of people who consume less than 5% of natural resources, writes Fred Magdoff, professor emeritus of plant and soil science at the University of Vermont. “However, resource use and pollution could be cut in half if the richest 700 million lived at an average global standard of living,” he notes.

The new billions also have a negligible effect on climate change. “Almost all the fossil fuels are used by the three richest billions, more than 85%,” says Hans Rosling, “and in the next decades it is economic growth by the next 2 billion which will increase fossil fuel use.”

There will be an estimated 2.2 billion new middle-class consumers in Asia alone by 2030, according to global consultants McKinsey.It is not a “population explosion” that we should worry about but a “consumption explosion”.

Current patterns of consumption are arguably robbing the poor and future generations of natural resources. If we ate less red meat, for example, or turned fewer food crops into vehicle fuel, feeding 9 billion people would be less problematic.

In this world view, the real question is not “are we too many?” but “are we too greedy?”