On 31st October 2011 the world population is projected to reach a landmark 7 billion people, according to UN estimates. A great deal of debate has surrounded the importance of this figure and what it means for the planet and its many inhabitants. The Royal Society is conducting a study which will address this, entitled ‘People and the Planet’, to be published in early 2012.

One point of discussion is the exact date of 7 billion people. This latest UN projection uses a new and more complex method than ever before. Hania Zlotnik, Director of the UN Population Division, has described how 100,000 future fertility paths have been calculated for each country. From these, a central value was taken to generate the ‘medium variant’ projection. It is from this that the 31st October 2011 is inferred.

Critics have rightly pointed out the challenges of making such a prediction. Because censuses are infrequent and incomplete, it is impossible to determine a precise date; even Ms. Zlotnik herself has said that “an interval of a few months or even a year would be a reasonable range of uncertainty”.

So what is the significance of this special date and the number 7 billion? It is not the number that is important, but the trend that it signifies. Demographers have calculated that global population first reached 1 billion in around 1804; by 1927, it had risen to 2 billion; 1959 saw 3 billion people; 4 billion arrived by 1974 and 5 billion by 1987; in 1998 the world surpassed 6 billion, and it has since taken around 12 years to reach 7 billion.

Given this continued increase, it is unsurprising that many have voiced their concerns and raised questions on the subject. What are the implications of the continued population increase for humanity? How many is ‘too many people’? What are the planetary limits? Will we have to change how we live, and how much we consume?

Sir John Sulston, Chairman of the Royal Society’s report on population, recently addressed these population issues in The Times: “It’s not simply a case of ‘more people’. While in some countries fertility remains high, in others it is very low. For example, because of plummeting birth rates, increasing life expectancy and little immigration, Japan’s greying population is set to shrink. The same is true in Western Europe”.

The UN’s medium variant projection is dependent on the past trends in fertility reductions and interventions continuing into the future. Whilst this projects that there will be 9.3 billion people by 2050, the numbers could range from 8.1 to 10.6 billion, the UN’s low and high variants. We have some ability to determine which path we follow.

And there are wider dimensions to population: people cannot be thought of as simple, collective statistics. Gross inequalities exist in the well-being and consumption patterns of people around the world; each person should flourish and live sustainably.

Professor Joel Cohen of the Laboratory of Populations at Rockefeller and Columbia Universities, and member of the ‘People and the Planet’ working group, demonstrates this by bringing together a set of striking numbers: “Some 850 million to 925 million people experience food insecurity or chronic undernourishment. In much of Africa and South Asia, more than half the children are of low height for their age as a result of chronic hunger. While the world produced 2.3 billion metric tons of cereal grains in 2009-10 — enough calories to sustain 9 to 11 billion people — only 46 percent of the grain went into human mouths. Domestic animals got 34 percent of the crop, and 19 percent went to industrial uses like biofuels, starches and plastics.” By dissecting the statistics and examining the ways in which they are linked, a clearer picture emerges of the challenges and opportunities that 7 billion people face.

The Royal Society’s report will focus on the relationship between population, consumption and the environment, and the implications for human wellbeing. It will consider the unprecedented size and growth of global population; but it will also consider a much wider range of statistics and facts. In so doing, it will address the dynamics and trends of which 7 billion people are a part, the broader implications of this, and what may be done about it. Only by consulting the evidence can we hope to understand the impacts of 7 billion people and more.


  1. Ms. Hania Zlotnik, UN Press Conference
  2. Sir John Sulston FRS ‘Overpopulation is too big a problem to ignore’ The Times 10 October 2011
  3. Professor Joel Cohen ‘Seven Billion’ New York Times 24 October 2011

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