The Overpopulation Project is pleased to announce its most recent publication, “Population growth and climate change: Addressing the overlooked threat multiplier” published in Science of the Total Environment. Through a review of national and global studies, the paper describes the emission reduction and vulnerability reduction benefits of slowing population growth, and outlines policies that can help achieve low population pathways. We hope that this publication stimulates further discussion and inclusion of sustainable population policies in nations’ official climate responses.

By The Overpopulation Project

Population growth and climate change are threat multipliers: they both threaten people’s health and well-being, now and in the future. Continued population increase creates new risks partly by increasing climate-altering emissions, leading to more severe climate impacts. Population growth also amplifies existing risks by increasing population pressure on climate-sensitive resources such as food and water. Despite these feedbacks, population policies are usually overlooked when examining policies to reduce risks from global warming.

In a new article, “Population growth and climate change: Addressing the overlooked threat multiplier,” lead author Jenna Dodson and colleagues describe the interaction between population growth and climate change, and argue that slowing population growth can contribute to emission reductions and limit the harms caused by climate change. For these reasons, appropriate population policies should be included in humanity’s response to climate disruption.

Mitigation refers to actions that result in the prevention or reduction of climate-altering greenhouse gas emissions. Slowing population growth is a means to reduce emissions, broadly comparable to more commonly discussed mitigation strategies, such as mass conversion to renewable-based electricity or significant decreases in consumption through lifestyle changes (see figure below). Because the challenge and the threat are so immense, researchers find that gains in one area alone are unlikely to limit global warming sufficiently to protect humanity; efforts across all areas are needed to effectively limit climate disruption.

For example, Van Vuuren et al. (2018) found that combining lifestyle change, energy and material efficiency, rapid renewable electrification, agricultural intensification, non-CO2 emission reduction and a low population scenario resulted in the greatest cumulative net emission reduction, reducing emissions 50% by 2100 compared to the baseline. This clearly shows the strong role of integrated efforts across multiple areas, including efforts that achieve low population pathways.

Adaptation refers to actions that aim to reduce human societies’ vulnerability to climate change impacts. As one would expect, the larger the future population, the more people will be exposed to harmful impacts as climate disruption continues to worsen. The dangers are multiplied because most future population growth is projected for poor countries that would likely struggle to adapt to climate change even at their current numbers.

A review of global and national studies that examine human exposure to extreme heat, one increasingly important climate impact, shows that the interaction between climate and population is often the largest driver of future exposure, more important than changes in climate or population alone. This is illustrated in the graph below for six countries, and for the world as a whole; the grey bars show the marked interaction effects.

Furthermore, depending on the socioeconomic circumstances, addressing population growth can be more effective than climate mitigation itself in minimizing climate-driven risks. For example, according to Ahmadalipour et al. (2019), addressing population growth would be more effective than reducing emissions to minimize drought risk in certain African countries, since lower population paths reduce both socioeconomic vulnerability and exposure to drought. Given such evidence, researchers and policymakers have good reasons to emphasize population growth as a component of climate risk and to develop rights-based strategies to reduce the risks and harms that are coming.

So how can nations and the global community develop strategies that reduce population-related risks and achieve low population pathways? We suggest increased support for the full range of rights-based policy interventions that lower fertility and in turn slow population growth. These include indirect actions such as investments in girls’ education, opportunities for women to join the work force, and the promotion of small family sizes.

They also include direct actions such as family planning programs that include affordable access to all types of safe, effective contraception for men and women. Voluntary family planning programs have repeatedly been proven effective in reducing fertility rates. The paper details important elements from successful past family planning programs, as well as other population-related policies that provide climate change mitigation and adaptation benefits.

The ongoing climate crisis demands a multifaceted response. In concert with technological advancements and policies that end fossil fuel use, we recommend rights-based policies that accelerate fertility reduction as part of this response. These policies will contribute to emission reductions and increase adaptive capacity, thereby limiting climate disruption and reducing vulnerability and exposure to climate risk. We hope that this paper will encourage scientists, policy analysts and politicians to give proper attention to reducing population growth in the global climate response.

References

Ahmadalipour, A., Moradkhani, H., Castelletti, A., Magliocca, N., 2019. Future drought risk in Africa: integrating vulnerability, climate change, and population growth. Sci. Total Environ. 662, 672–686. https://doi.org/10.1016/j.scitotenv.2019.01.278.

Dodson, J., Dérer, P., Cafaro, P., Götmark, F., 2020. Population growth and climate change: Addressing the overlooked threat multiplier. Sci. Total Environ. 748, 141346. https://doi.org/10.1016/j.scitotenv.2020.141346.

Mora, C.,Dousset, B., Caldwell, I.R., Powell, F.E., Geronimo, R.C., Bielecki, C.R., Counsell, C.W.W., Dietrich, B.S., Johnston, E.T., Louis, L.V., Lucas, M.P.,Mckenzie, M.M., Shea, A.G., Tseng, H., Giambelluca, T.W., Leon, L.R., Hawkins, E., Trauernicht, C., 2017. Global risk of deadly heat. Nat. Clim. Chang. 7, 501–507. https://doi.org/10.1038/NCLIMATE3322.

Van Vuuren, D.P., Stehfest, E., Gernaat, D.E.H.J., Van Den Berg, M., Bijl, D.L., De Boer, H.S., Daioglou, V., Doelman, J.C., Edelenbosch, O.Y., Harmsen, M., Hof, A.F., Van Sluisveld, M.A.E., 2018. Alternative pathways to the 1.5 °C target reduce the need for negative emission technologies. Nat. Clim. Chang. 8, 391–397. https://doi.org/10.1038/s41558-018-0119-8.