This article was originally published by The Journalism of Population and Sustainability and has been lightly edited for style.

In a special report published in Bioscience almost 4 years ago (“World Scientists’ Warning of a Climate Emergency 2022”), leading climate scientists issued an unambiguous call to action: “The very future of humanity depends on the creativity, moral fibre, and perseverance of the 8 billion of us on the planet now.”  These researchers emphasized both the need to equitably reduce ecological overshoot, as well as pursue massive-scale climate mitigation and adaptation. A key recommendation in the report was to stabilize the human population and allow it to gradually decrease in size by strengthening education and reproductive rights for girls and women.

A resurgent global wave of pronatalist policies runs counter to this idea. Pronatalist ideologies advocate increasing birth rates as a rational response to the shift from high to low fertility associated with the fertility transition. Such policies aim to maintain fertility at or above replacement level to avoid the social and economic challenges that may arise from ageing populations.

The notion of planetary boundaries, the limits to what the Earth can sustain, is conspicuously absent from these discussions. It is an omission that reflects a broader reluctance to acknowledge the role of the unprecedented scale of human population growth as a driver of environmental degradation. Human population growth already has imparted a significant ecological cost by contributing to the depletion of natural resources, warming the planet, fomenting widespread biodiversity loss and creating a mounting ecological debt that will be passed on to future generations.

Proposing to boost birth rates in response to declining fertility may seem like a reasonable strategy from an economic perspective, to avoid the short-term burden of a proportionally higher ratio of retirees to working age people. Yet it requires its advocates to ignore the scale and urgency of the environmental crisis and its associated long-term negative impacts.

Recent environmental assessments such as the 2026 Water Bankruptcy report highlight that we have moved beyond an era of temporary, reversible and isolated environmental crises. Reliance on technological solutions alone is no longer sufficient to address the issue. The scale and interconnectedness of these pressures point to the need to change our whole development models.

This perspective is echoed in the call to move beyond GDP as the dominant measure of progress in order to more fully recognize the value of environmental systems. In this context, reducing aggregate demand emerges as a central lever for safeguarding basic human needs while preserving ecological integrity.

Science unequivocally tells us that population size is a key variable in driving environmental degradation. Every human has an impact on nature, whether their footprint is large or small, and the aggregate impacts are currently overwhelming ecosystems. Moreover, individual footprints are not static; they evolve as wealth grows and consumption increases, and also with the conditions of our lives.

Investing in reproductive rights and voluntary family planning—across all settings— supports both human wellbeing and environmental sustainability. When women have the agency to make informed choices, they tend to opt for smaller families. Yet when demographic objectives are prioritized over individual reproductive choice, pronatalist policies often pave the way for restrictive or coercive measures that undermine women’s agency and limit their ability to reproductive self-determination.

While family planning plays a role not only in advancing reproductive self-determination, gender equity and justice, it also, indirectly, shapes population trends. Since peaking at a 2.3 per cent annual growth in 1963, global population growth has slowed to under one per cent today—a shift that could hardly have occurred without increased access to voluntary contraception and reproductive agency.

Hundreds of millions around the world remain unable to make free and informed reproductive choices. Yet despite the immense need for family planning, support for these services is dwindling. The US has long been the largest donor to these efforts, providing forty per cent of global family planning aid in 2023. Yet an abrupt cut to funding for family planning initiatives in 2025 ended the US role as the world’s leading source of support.

The fact that pronatalist discourse is largely misconceived is also a key issue. Perceptions of fertility decline often conflate lower birth rates with a shrinking population. In reality, while global fertility is declining, the number of women of reproductive age is projected to rise from 2 to 2.2 billion in coming decades. The global population is projected to expand from 8.2 billion in 2024 to a peak near 10.3 billion in the mid-2080s, adding over 2 billion people.

To put these numbers into perspective, the global population in 1950 was just 2.5 billion. Fears of ‘population collapse’ are thus largely bogus; while certain countries will experience shrinking populations, the world as a whole faces continued growth – with profound implications for planetary health. It is with all these dimensions in mind that we must examine the ideological shift toward pronatalism.

Recent setbacks in both environmental efforts and reproductive rights are not isolated events. They are intertwined, and both are symptoms of the same phenomenon: the belief that human ingenuity can endlessly outrun planetary limits.

Population growth and decline pose different challenges, and they are not reciprocal problems. We are better equipped to manage low fertility’s social and economic consequences than the cascading effects of growing environmental destruction. As Vegard Skirbekk suggests in his book, Decline and Prosper (2022), the challenges associated with ageing societies are manageable and can represent opportunities to develop good policy interventions. Efforts such as implementing progressive tax policies, strengthening intergenerational social safety nets,  easing  labor  migration  and integrating seniors into meaningful roles in society are rights-based and effective approaches. They should receive our full investment to support an ageing population and stay within ecological boundaries.

Taking a planetary health and evidence-based assessment of both demographic trends and ecological trajectories supports the view that encouraging the human population to stabilize and gradually decrease in size—by advancing reproductive rights and ensuring universal access to education and healthcare – remains a valid policy objective.

The views expressed in the paper are solely those of the authors and do not necessarily reflect the positions of their respective institutions.

Céline Delacroix is an Adjunct Professor at the University of Ottawa’s Interdisciplinary School of Health Sciences and Senior Fellow, Population Institute.

Marleen Temmerman is the Director of Aga Khan University’s Centre of Excellence Women and Child Health Aga Khan University, and Ghent University’s International Centre for Reproductive Health.

Nandita Bajaj is the Executive Director of Population Balance, and a Senior Lecturer at Antioch University’s Institute for Humane Education.

Ann M. Moore is the Principal Research Scientist at the Guttmacher Institute New York.

Phoebe Barnard is a Professor at the University of Washington’s Center for Environmental Politics, and Research Affiliate at the University of Cape Town’s African Climate and Development Initiative.

William J. Ripple is a Professor in Oregon State University’s Department of Forest Ecosystems and Society, and Associate at the Conservation Biology Institute.

William E. Rees is a Professor Emeritus at the University of British Columbia School of Community and Regional Planning.

Michael B. Gerrard is an Andrew Sabin Professor of Professional Practice at Columbia Law School.

Diana Coole is a Professor of Political and Social Theory in the School of Politics and Sociology, Birkbeck, University of London.

Robert Engelman is a Senior Fellow at the Population Institute.

Helen Kopnina is an Assistant Professor at  Northumbria University, Newcastle Business School.

Nkechi S. Owoo is a Professor in the University of Ghana’s Department of Economics.

Peter Lindsey is a Policy Coordinator of the Lion Programme in the University of Pretoria’s Mammal Research Institute, and Director of the Lion Recovery Fund at the Wildlife Conservation Network.

Sources: BioScience; Cambridge University Press; Data for Health, The Guardian; The Lancet; Palgrave Macmillan; Sustainable Development; UN; United Nations University Institute for Water, Environment and Health; United Nations Population Fund

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