The effects of global warming are already bringing harm to human communities and the natural world. Further temperature rises will have a devastating impact and more action on greenhouse gas emissions is urgently required. Multiple factors contribute to climate change, and multiple actions are needed to address it. The number of people on our planet is one of those factors. Every additional person increases carbon emissions — the rich far more than the poor — and increases the number of climate change victims – the poor far more than the rich.
Population growth is also important because it affects the Earth's ability to withstand climate change and absorb emissions, such as through deforestation as land is converted for agricultural use to feed a growing human population.
We are currently adding more than 80 million people a year to our global population. The UN projects that without further action to address population growth, there will be two billion more people by 2050, and three-and-a-half billion more by 2100.
"All options need to be exercised... We can make choices about how much of each option we use... but the idea you can leave anything out is impossible."
– Intergovernmental Panel on Climate Change, 2018
Further warming of our atmosphere is now impossible to avoid. The effects of that warming will depend on how high and how fast the temperature rises. Global warming changes weather patterns, causing severe weather events, heatwaves, droughts and floods.
Climate change is already shrinking glaciers and ice caps, altering the availability of fresh water. It contributes to ocean acidification, destroying coral reefs and other aquatic ecosystems. It makes places uninhabitable for some plants and animals, leading to extinctions and redistribution of species, threatening food production with alien pests and diseases.
For many people in the world, the impacts of climate change are already here: extreme weather events like the Australian bush fires and floods in Kenya devastate lives, while critical impacts on agriculture such as through soil degradation and unseasonal weather lead to unpredictable and unstable crop yields - especially dangerous for the poorest.
Its potential human cost is catastrophic. A rise in sea levels threatens hundreds of millions of people in coastal communities and cities across the globe. Food and water shortages and conflict over productive land will arise, while progress in global health could be rolled back by communicable diseases such as malaria reaching places they never existed before. Hundreds of millions of people are likely to be forced to migrate from their homes by 2050.
“Globally, economic and population growth continued to be the most important drivers of increases in CO2 emissions from fossil fuel combustion.”
Intergovernmental Panel on Climate Change, 2014
There are multiple drivers of the climate crisis, amongst which population is only one. Overwhelmingly, emissions are produced by people in the richest countries, and industrial development and consumption patterns in the Global North are primarily responsible for the crisis we are in today. Technological solutions, personal lifestyle changes, policies to end fossil fuel use and develop alternative energy and potentially fundamental changes to our economic sytems are all vital, especially as the timescale for preventing catastrophic climate change is so short - now less than a decade, according to the IPCC.
Whatever other changes we make, however, their positive impacts will be reduced and may even be completely cancelled out by adding emissions from hundreds of millions of new people as our population increases. According to 2020 research evaluating 44 countries, emissions arising as a result of population growth wiped out two-thirds of the reduction in emissions arising from greater energy efficiency between 1990 and 2019. Meanwhile, solutions such as reforestation may be more difficult to implement with more people needing food and land.
Reducing the number of people being born is not a panacea for climate change, but it cuts future carbon emissions, effectively, simply and permanently, and it boosts the effectiveness of other solutions.
Most importantly, it can be achieved through positive actions which empower people and improve lives.
A study published in 2017 by the Universities of Lund and British Columbia suggested that the single most effective measure an individual in the developed world could take to cut their carbon emissions over the long term could be to have one fewer child. The study relied on estimates of future per capita climate emissions which are likely to change significantly, so it must be treated with caution. Illustrative figures produced by the authors suggested, however, that it could be significantly more effective than any other method in saving climate emissions. (For more information on the study and its methodology, click here.)
All the benefits of this action are not immediate and it does not mean that we should not take other actions to cut our individual carbon footprints, of course.
The 2019 Scientists' Warning of a Climate Emergency, signed by more than 13,000 scientists from around the world, explicitly calls for "bold and drastic transformations" regarding both economic and population policies, including making family planning services available to all and achieving full gender equity.
Another major international study in 2017 identified practical policy measures that could be taken to minimise greenhouse gas emissions as quickly as possible. Project Drawdown analysed more than eighty policy options, such as plant-based diets, solar farms and electric vehicles. They identified family planning and educating girls as among the top 10 workable solutions to combat climate change available today. It found that together, they would reduce CO2 emissions by 103 gigatons by 2050 — more than onshore and offshore wind power combined. The 2020 Drawdown update revised this figure down to 85 gigatons, but it remains one of the most powerful climate solutions.
"Education lays a foundation for vibrant lives for girls and women, their families, and their communities. It also is one of the most powerful levers available for avoiding emissions by curbing population growth.”
- Project Drawdown
Because individuals in the developed world have by far the greatest impact each, people choosing to have smaller families in the richest parts of the world will have the greatest and most immediate positive effect – a vital choice given the urgency to address which climate change. Furthermore, reduced emissions as a result of fewer people being born in richer countries allows more economic development in poorer countries without adding to total emissions.
However, that doesn't mean the number of people in poor countries who currently have a negligible effect on climate change doesn't matter too. In poorer countries, including those where population growth is highest, economic development is increasing individual carbon footprints and rapidly growing populations push emissions still higher. The emissions of low-middle income countries increased by 43.2% between 2000 and 2013, due in part to increased industrialization and economic output. People living in poverty have an absolute right to economic development and we must not tackle climate change by keeping people poor. That makes it all the more important to empower people to reduce population growth through ethical means.
The world's most populous nations, India and China, are among the top contributors to climate change overall, despite lower impacts from each individual than in wealthier countries. While population growth in India and China is now relatively low, people born today in countries whose populations are still expanding rapidly will have a climate impact for generations to come. Unless we want people to stay poor, we can't ignore population growth where emissions are currently low.
In its landmark 2018 report, the International Panel on Climate Change specifically identified high population growth as a "key impediment" to hitting the critical target of limiting global warming to 1.5°C.
The ethical, effective means of achieving a sustainable population empower people and improve lives. Family planning, girls’ education and other measures to empower women are not just essential for individuals' wellbeing, but help communities and nations. Tackling poverty through greater global justice frees people from the conditions which often drive large family size, as well as helping to provide lives of dignity and security.
In the Global North in particular, choosing smaller families can be a vital part of the steps we take to reduce our emissions and impact. All these measures will help reduce family size and bring population growth to an end as soon as possible - giving us all the best chance of limiting climate change and protecting the next generation.
If we are to succeed in preventing the worst effects of climate change, we must take action to address population size.
Read our fully referenced four-page briefing
In 2018, Population Matters hosted a conference, More feet, more heat: climate change and us, which brought together an international panel to examine the relationship between climate change and population. Watch our director's presentation.
You can find all the latest updates on this topic at the link below.
Sign up to our newsletter to keep up to date with our work.