It took 200,000 years for human numbers to reach one billion, in about 1800. By 1930 it has reached 2 billion and since then we have seen growth at an astonishingly fast rate. By 1975 it had doubled to 4 billion and in 2022 it had doubled again to 8 billion. As of January 2025 it stands at about 8.2 billion.
The global population is increasing at an unprecedentedly fast rate -- about 1 billion every decade. The latest UN forecasts are that it will reach 9.7 billion by 2050 and around reach 10.4 billion by 2100, after which it may gradually start falling off. But in the meantime, where should all these people live?
This article (skip the ads!) explains the latest UN forecasts of when population may be expected to peak in each continent. See also the graph here.
This useful document by QCOP convenor Martin Schweiger explains some of the technical terms you may come across in connection with discussion about population.
The number of children a woman has (fertility) is decreasing in many parts of the world. So why is the number of humans still going up?
It is because there are so many people. In 1967, there were around 3.4 billion people but the average growth rate was 2.11%. This gives an annual increase of around 72 million. By 2018, the growth rate had dropped to 1.10%, but with a population of 7.5 billion, that gave an annual increase of more than 80 million people. So despite the rapid fall in birth rates in many parts of the world, the global population is still increasing by more than the entire population of the UK each year.
Growth rate measures the increase in size of a population, allowing for births, deaths, migration etc. Fertility measures the average number of children per woman; these two numbers are not quite the same.
Fertility rates vary widely over the world. Here is a 2024 map of countries by fertility rates according to the Population Reference Bureau.
Peak population
Because fertility rates and other factors vary so much country by country, projections of population increase and when it may start to peak and then decline vary dramatically between different countries and regions. This article (skip the ads!) explains the latest UK projections of when population may be expected to peak in different continents.
These estimates take current fertility, mortality and migration assumptions into account. They can change, and therefore these projections are not set in stone.
We are currently using up earth's renewable resources at an unsustainable rate, about 1.75 earths' worth per year. But as recently as 1970, humans were only using one year's worth of resources. ‘Overshoot Day’, the day on which the year’s supply of renewable resources for that year are exhausted, has been steadily advancing. In 2024 it was on August 1st.
It has been calculated that the earth could support a population of two to three billion living at the standard of the present developed world.
Suggested solutions to the food problem include eating insects and protein extracted from sewage.
Population growth is one of the main drivers of climate change. The graphs show how increased population and increased carbon dioxide in the atmosphere go hand in hand.
It has been calculated that since 1990, more that three quarters of the global reduction in carbon emissions through improved efficient and carbon cuts to energy generation has been cancelled out due to the increasing population.
Humans and their animals now account for about 99% by mass of land vertebrates: only about 1% by mass are wild. The number of wild animals has more than halved since 1970: in the same period, human numbers have more than doubled. Current species extinction rates are between 1000 and 10,000 times the natural background rate.
About 50% of land surface is already modified to meet human need. Most of the remainder is icecap, taiga, desert, mountain or rain forest. In short, we have nearly run out of space.
To deal with the increased population, we will need to increase food production by at least 70% by 2050. This, however, will be in the face of desertification and degradation of agricultural land, rising sea levels, over-fished oceans, acidification of seawater and unpredictable weather as the result of climate change. Agriculture is heavily dependent on oil, a fossil fuel, the use of which must be restrained if we are to have a chance. There is already widespread water scarcity: this will increase dramatically.
The level of pollution resulting from our numbers and our consumption is already a danger to life, both to us and to such of wildlife as survives.
Population pressure can lead to civil unrest, wars over resources, migration on a large scale and famine. Conflict over land and water is already occurring.