Thanos was right? Scientists say Earth's population may need to be halved to save the planet

In the Marvel film Avengers: Endgame, the villain Thanos believes wiping out half the universe's population is the only way to save it. While scientists are not advocating anything remotely similar, a new study has sparked debate by proposing that the global population should gradually decline to around 4 billion by the year 2200 to reduce pressure on Earth's ecosystems and natural resources.

The proposal, published in the journal Sustainable Development, calls for a voluntary reduction in population growth through greater access to family planning, education and reproductive healthcare—not through coercive population control.

The researchers stress that the idea is not about preventing people from having children or forcing population reductions. Instead, they argue for slowing long-term population growth so future generations can enjoy a more sustainable planet.

Why do the researchers want a smaller global population?

According to the study, humanity's environmental impact is driven by two factors: how much each person consumes and the total number of people on Earth. While reducing per-capita consumption is important, the researchers argue that continued population growth makes it increasingly difficult to remain within the planet's ecological limits.

They point to major environmental changes over the past 50 years. During a period when the global population roughly doubled, carbon dioxide emissions more than doubled, global energy consumption tripled, biodiversity declined sharply, and mineral extraction and pesticide use increased more than fourfold.

The researchers write: "It will ease pressure on natural resources, lessen poverty in high-fertility regions by way of smaller family sizes, reduce pollution, reduce resource and immigration conflicts, and improve quality of life in densely populated areas. A more modest population (e.g., gently easing population to 4 billion by 2200) would protect Earth's natural heritage, including its wild habitats, wild species, and its climate."

They argue that these trends demonstrate how environmental pressures have intensified alongside population growth.

What does the study propose?

Rather than advocating compulsory population control, the researchers propose a gradual decline in the global population over the next two centuries.

The study recommends expanding voluntary family planning services, education and reproductive healthcare, particularly in lower-income countries where millions of women still lack access to contraception and reproductive health services.

According to the researchers, when women are empowered to make informed decisions about family size, fertility rates tend to decline naturally without government mandates.

The paper argues that a gradual reduction in population growth could help conserve natural resources, reduce pollution, ease competition for resources and improve living standards in densely populated regions.

Countries cited in the study

The researchers point to countries where fertility rates declined rapidly after family planning programmes became widely available.

In Iran, fertility reportedly fell from more than four children per woman in the early 1990s to below the replacement rate within about a decade. The study also cites South Korea, where fertility rates declined significantly following nationwide family planning initiatives.

The researchers argue that expanding similar voluntary programmes worldwide could contribute to a long-term decline in global population growth.

Environmental concerns

Current projections suggest the global population could continue growing during this century before eventually stabilising. The study warns that continued population growth could place increasing pressure on food, water, energy and other finite resources while driving higher greenhouse gas emissions and waste generation.

The researchers argue that addressing population growth should complement efforts to reduce consumption and improve sustainability.

Critics warn of economic consequences

The proposal is expected to remain controversial.

Economists have long argued that declining birth rates create new challenges, including ageing populations, shrinking workforces and slower economic growth. Countries such as South Korea and Japan are already facing labour shortages and rising social welfare costs linked to low fertility.

Critics say that while slower population growth may reduce environmental pressures, it could also create long-term demographic and economic challenges that governments would need to manage.

The study has reignited debate over how the world should balance environmental sustainability with economic growth as global population trends continue to evolve.

Source: This report is based on information published by the Daily Mail and findings from the study published in the journal Sustainable Development.