Population growth, environmental degradation and climate change

More than a third of 50 recently surveyed Nobel laureates cited “population rise / environmental degradation” as the biggest threat to humankind. Second on the list was “nuclear war”, cited by 23 per cent of the laureates, while no other issue was selected by more than 10 per cent of respondents.

Are the survey responses of the Nobelists an accurate assessment of the relative importance of the threats facing humanity? And why were population increase and environmental damage bundled together in the survey, rather than being treated as separate issues?

A new report on population growth and sustainable development from the Population Division of UN DESA revisits the complex relationships linking population increase to social and economic development and environmental change.

The human population has experienced a period of unprecedented growth, more than tripling in size since 1950. It reached almost 7.8 billion in 2020 and is projected to grow to over 8.5 billion in 2030, the target date for achievement of the Sustainable Development Goals (SDGs). 

This growth is the result of two trends: on the one hand, the gradual increase in average human longevity due to widespread improvements in public health, nutrition, personal hygiene and medicine, and on the other hand, the persistence of high levels of fertility in many countries. But is growth of the human population responsible for the environmental catastrophe our planet is facing?

The data tell a different story. For example, although high-income and upper-middle-income countries contain around 50 per cent of the global population, they contribute around 85 per cent of global emissions of carbon dioxide. Such emissions from upper-middle-income countries have more than doubled since 2000, even though the population growth rate was falling throughout this period. Most high-income countries are growing slowly if at all, and for some the population has been decreasing.

Could measures to limit future population growth make a substantial contribution to mitigating climate change? A fundamental challenge is the slow pace at which population trends change. The Intergovernmental Panel on Climate Change (IPCC) underlines that limiting global warming to 1.5°C would require rapid, far-reaching and unprecedented changes in all aspects of society to reach net-zero emissions by 2050. 

Globally, population growth is slowing down and may come to a halt by around 2100, thanks to the smaller family sizes associated with social and economic development. However, given the intrinsic momentum of population growth, the range of plausible trajectories of global population over the next few decades is quite narrow. For this reason, further actions by Governments to limit the growth of populations would do little to mitigate the forces of climate change between now and 2050. 

Instead of looking for solutions in demographic trends, achieving sustainability will depend critically on humanity’s capacity and willingness to increase resource efficiency in consumption and production and to decouple economic growth from damage to the environment. High-income and upper-middle-income countries should acknowledge their disproportionate contributions to global environmental damage and take the lead in building a more sustainable economic system for the benefit of future generations.

At the same time, in many low-income and lower-middle-income countries today, rapid population growth remains a matter of concern, because it adds to the challenges of achieving social and economic development and of ensuring that no one is left behind. The continuing high levels of fertility that drive such growth are both a symptom and a cause of slow progress in development, often linked to a lack of choice and empowerment among women and girls.

Rapid population growth makes it more difficult for low-income and lower-middle-income countries to commit sufficient resources to improving the health and education of their populations. Rapid growth and the associated slow progress in development also diminish their capacity to respond and adapt to emerging environmental threats, including those caused by climate change.

Achieving the SDG targets related to reproductive health, education and gender equality will require empowering individuals, particularly women, to make choices about the number and timing of their children. The experience of countries from all regions suggests that such changes will facilitate, and could potentially accelerate, the anticipated slowdown in global population growth over the coming decades.

Learn more on the website of UN DESA's Population Division.