According to the United Nations, the world’s population reached 8 billion people on 15 November 2022. What are the implications of adding one billion people into the world in just twelve years?

Population and Development Review marked the occasion with this collection of essays and reflections from the demographic science community on this population peak, including emphasizing issues of population aging, sustainable development, climate change, as well as investments in universal education and health. An introduction to the collection is reprinted here.

All places are now accessible, all are well known, all open to commerce; most pleasant farms have obliterated all traces of what were once dreary and dangerous wastes; cultivated fields have subdued forests; flocks and herds have expelled wild beasts; sandy deserts are sown; rocks are planted; marshes are drained; and where once were hardly solitary cottages, there are now large cities… What most frequently meets our view (and occasions complaint), is our teeming population: our numbers are burdensome to the world, which can hardly supply us from its natural elements; our wants grow more and more keen, and our complaints more bitter in all mouths, whilst Nature fails in affording us her usual sustenance… Tertullian, A Treatise on the Soul, Chapter 29, about 200 AD.

When Tertullian considered the overpopulated state of the world over 1800 years ago, the global population was around 200 million. Today, November 15, 2022, marks the day the UN has estimated the world will officially reach 8 billion inhabitants, approximately forty times what it was in Tertullian’s day. Despite centuries of population pessimists from Tertullian to Malthus to Ehrlich and beyond, world population continues to march ahead. Often this march has been more of a crawl but sometimes it is a sprint—enabled by historical milestones like the twin Industrial and Green revolutions and the epidemiological transition. While overpopulation alarmism is still alive and well, these fears have eased substantially since the 1970s, when concerns over “the population bomb” and mass starvation transformed into more nuanced consternation over climate change and economic well-being. However, this easing of tensions may not be from détente between population optimists and pessimists, but rather because concerns regarding global overpopulation may soon become moot: population growth is slowing to the point that world population is projected to peak in the 2070s–2080s, and then begin a long, slow decline. This does not mean the world is any less anxious regarding demographics than before: on the contrary, fear of population growth is giving way to the looming specter of population ageing and decline, and the economic stagnation many believe must inevitably follow.

We at Population and Development Review decided to solicit a collection of brief reflections from the demographic science community on the meaning of this population peak. What are the implications of adding one billion people into the world in just twelve years? It is a highly relevant question for PDR and its readers. These commentaries emphasize issues of population ageing, sustainable development, and climate change mitigation and adaptation, as well as investments in universal education and health, and addressing inequalities within and across countries. Demographic science has much to contribute to our understanding of current and future population composition and distribution and how this shapes future economies, cities, ecosystems, climate, and human population itself. Thanks to our contributors for offering us much demography-related food for thought as we mark this important milestone.