The Overpopulation Project studies the causes of human overpopulation and the role ending population growth can play in dealing successfully with global environmental and social problems. Believing that much of this century’s projected population increase can and should be avoided, we also explore humane policies to end population growth sooner rather than later. Our interdisciplinary work, straddling the disciplines of ecology, demography, policy analysis and environmental ethics, has been made possible by generous funding from the Global Challenges Foundation (and Laszlo Szombatfalvy), the GAIA Initiative for Earth–Human Balance, private donors, and our home institutions: Colorado State University and the University of Gothenburg. Our recent scholarly reports include the following:

Procreation and Consumption in the Real World. Philip Cafaro. Environmental Ethics (2023)

Population Effects on Biodiversity and Climate Change: Evidence from Recent Scientific Literature, 2010-2022. Philip Cafaro, Pernilla Hansson, and Frank Götmark. Indian Journal of Population and Development (2023)

Advancing the Welfare of People and the Planet with a Common Agenda for Reproductive Justice, Population, and the Environment. Joseph Speidel and Jane O’Sullivan. World (2023)

Fewer people would help preserve biodiversity: A response to Hughes et al. (2023). Philip Cafaro, Pernilla Hansson, and Frank Götmark. Biological Conservation (2023)

An Analysis of Three Decades of Increasing Carbon Emissions: The Weight of the P Factor. Lucia Tamburino, Philip Cafaro, and Giangiacomo Bravo. Sustainability (2023).

Human fertility and religions in sub-Saharan Africa: A comprehensive review of publications and data, 2010-2020. Nicola Turner and Frank Götmark. African Journal of Reproductive Health (2023).

Achieving sustainable population: Fertility decline in many developing countries follows modern contraception, not economic growth. Frank Götmark & Malte Andersson. Sustainable Development (2022).

Overpopulation is a major cause of biodiversity loss and smaller human populations are necessary to preserve what is left. Philip Cafaro, Pernilla Hansson, and Frank Götmark. Biological Conservation 272 (2022)

Conserving biodiversity means limiting our numbers: A response to Green et al. 2022. Philip Cafaro, Pernilla Hansson, and Frank Götmark. Biological Conservation 273 (2022): 109701

Population Governance. Karin Kuhlemann. In The Rowman and Littlefield Handbook of Bioethics, edited by Dinucci et al. Rowman and Littlefield (2022)

Population and climate change. Ian Lowe, Jane O’Sullivan, and Peter Cook. Discussion paper. Sustainable Population Australia (2022)

Reducing human numbers and the size of our economies is necessary to avoid a mass extinction and share Earth justly with other species. Philip Cafaro. Philosophia 50 (2022): doi 10.1007/s11406-022-00497-w

Population growth, family planning and the Paris Agreement: An assessment of the nationally determined contributions (NDCs). Jenna Dodson, Patricia Dérer, Philip Cafaro, and Frank Götmark. International Environmental Agreements: Politics, Law and Economics (2022)

Just Population Policies for an Overpopulated World. Philip Cafaro. Ecological Citizen (2021) 5: epub-046-1 (1-10)

Protecting Half the Planet and Transforming Human Systems Are Complementary Goals. Eileen Crist, Helen Kopnina, Philip Cafaro, et al. Frontiers in Conservation Science (2021) 2: 781292 (1-9).

World scientists’ warnings into action, local to global. Phoebe Barnard, William Moomaw, Jane O’Sullivan et al. Science Progress (2021) 104 (4): 1-32.

Climate ethics and population policy: A review of recent philosophical work. Philip Cafaro. WIREs Climate Change (2021): e748 (1-17).

Discussing Population Concepts: Overpopulation is a Necessary Word and an Inconvenient Truth. Frank Götmark, Jane O’Sullivan, and Philip Cafaro. Indian Journal of Population and Development 1 (2021): 51-60.

Reconciling a Positive Ecological Balance with Human Development: A Quantitative Assessment. Lucia Tamburino and Giangiacomo Bravo. Ecological Indicators 129 107973 (2021):

Population Growth and Family Planning in the Nationally Determined Contributions (NDCs) made under the Paris Climate Agreement. Working Paper, The Overpopulation Project.

Population Growth and Climate Change: Addressing the Overlooked Threat Multiplier. Jenna Dodson, Patrícia Dérer, Philip Cafaro, and Frank Götmark. Science of the Total Environment 748, 141346 (2020):

Human Fertility in Relation to Education, Economy, Religion, Contraception, and Family Planning Programs. Frank Götmark and Malte Andersson. BMC Public Health 20, 265 (2020):

The Social and Environmental Influences of Population Growth Rate and Demographic Pressure Deserve Greater Attention in Ecological Economics. Jane O’Sullivan. Ecological Economics 172 (2020): 106648.

From Population to Production: 50 Years of Scientific Literature on How to Feed the World. Lucia Tamborino et al. Global Food Security 24 (2020): 10036.

The Elephant in the Room: The Role of Interest Groups in Creating and Sustaining the Population Taboo. Karin Kuhlemann. In Almiron, N and Xifra, J (eds) “Climate Change Denial and Public Relations: Strategic Communications and Interest Groups in Climate Inaction” 1st edition (2019): 74-100.

The Potential Environmental Impacts of EU Immigration Policy: Future Population Numbers, Greenhouse Gas Emissions and Biodiversity Preservation. Philip Cafaro and Frank Götmark. Journal of Population and Sustainability 4 (2019): 71-101.

How Should Ecological Citizens Think About Immigration? Philip Cafaro and Jane O’Sullivan. Ecological Citizen 3 (2019): 85-92.

Policy-based Population Projections for the European Union: A Complementary Approach. Philip Cafaro and Patricia Dérer. Comparative Population Studies 44 (2019): 171-200. Animated populated projections.

Complexity, Creeping Normalcy and Conceit: Sexy and Unsexy Catastrophic Risks. Karin Kuhlemann. Foresight 21 (2019): 35-53.

Aging Human Populations: Good for Us, Good for the Earth. Frank Götmark, Philip Cafaro and Jane O’Sullivan. Trends in Ecology and Evolution 33 (2018): 851-862.

Immigration Ethics: Creating Flourishing, Just, and Sustainable Societies in a World of Limits. Addison Phillips. Masters thesis, Department of Philosophy, Colorado State University, 2018 (directed by Philip Cafaro).

Discussing Population Growth in the Magazine Sveriges Natur 1950-1995 and 2014-2017. Ann-Marie Ljungberg. Masters thesis Department of Biological and Environmental Sciences, Gothenburg University, 2018 (directed by Frank Götmark).

‘Any Size Population Will Do?’: The Fallacy of Aiming for Stabilization of Human Numbers. Karin Kuhlemann. Ecological Citizen 1 (2018): 181-189.