In 1854 (the year the cause of cholera was found) the world population was 1.25 billion. Almost 200 years on, in 2020 there are 7.7 billion alive in November 2020.
Climate change, biodiversity loss, degradation of the biosphere and now the coronavirus pandemic - each is linked to human population. With fewer people, there would be fewer greenhouse gas emissions, less pollution and waste, and more space for ourselves and the rest of the natural world to survive and thrive.
In 1854, more than half the deaths in England were caused by infectious diseases. One in four children died before they were five, but now that figure in four children in one hundred. The average life expectancy was 40, but is now about 80 in Western Europe and over 60 in sub-Saharan Africa.
Demographic transition. Better healthcare and living conditions, and fewer living in poverty, results initially in lower death rates. As people are confident that children will live to be adults, birth rates fall but this lags behind the change in death rates. The result is that population rises over time. The global population of 1 billion in 1800 doubled by the late 1920s. By the mid-1970s it had doubled again to nearly 4 billion, and now it is approaching 7.7 billion. In 2020, more than twice as many people will be born than will die. by 2100, it is projected that there will be 10.9 billion humans alive.
Researchers estimate that having one fewer child would save 120 tonnes of carbon dioxide a year for the average US citizen. Living car-free would save 3 tonnes for the average person in the US, with avoiding flying, using green energy and eating a plant-based diet gave even smaller savings.
Starting in the 1960s, the worldwide fall in birth rates were down to rising levels of education, especially for women, increasing urbanisation and rises in living standards and healthcare. The availability of contraception and abortion also helped. Currently fertility rates in many countries are at, or close to, the replacement rate of 2.1 children per women. It is thought that developing countries are transitioning at a faster rate than the developed world. However, the world population is still rising.
Economic growth models (based on more people creating more demand for goods and services) often suggest that lower fertility levels are worrying. Nations which have already low fertility levels find that economic growth, stable finances and a cohesive society are more difficult to maintain with a large, ageing, economically inactive populations supported by tax income from an increasingly smaller group of working people.
Advocating population growth is on the increase, with limited access to abortion and defining women as mothers and caretakers rather than as individuals with rights. Those taking this viewpoint include nationalists and social and religious conservatives. The decision to have or not have a child is a deeply personal one, but people react very strongly and emotionally if they feel their decisions are being threatened or attacked. The eugenics movement to 'cleanse' populations of supposed undesirable traits still dogs rational discussion today. Sterilization programmes in the US disproportionately targeted minority communities and China's one child policy led to selective abortions of female foetuses.
While it is suggested that half of the predicted global population increase would come from eight developing economies plus the US, poor people in Africa where the population is growing most rapidly are not contributing at all to greenhouse gas emissions.
So what should we be doing? People in advanced economies should be re-thinking consumption-fuelled economic models, while helping people elsewhere to develop more sustainably, by focusing on education and support for family planning and gender equality, and there should be stronger measures against polygamy and forced marriage (which often takes place when the girl is still very young).
Source: Various, including feature in New Scientist, 14 Nov. 2020.