Population, consumption and resources

Seen from orbit at night, the Nile draws a line of light through the desert: tens of millions of people living along one river, as people have for seven thousand years. Humanity passed 8 billion people in 2022 and the United Nations expects the population to peak at about 10.3 billion in the mid-2080s before slowly declining. How that many people can live well on one planet, with room, clean air, gardens and wild places left over, is one of the defining questions of the century. This explainer is educational. We respect every family’s choices; what we argue for is education, health and real choice for everyone.

One simple equation

Scientists often summarise human impact with a simple identity: Impact = Population x Affluence x Technology, or IPAT. Population is how many of us there are. Affluence is how much each person consumes. Technology is how much impact each unit of consumption causes: the emissions per kilowatt-hour, the land per tonne of food, the waste per product. It is not a law of nature, but it shows where the levers are, and that all three matter.

P: how many of us

Population growth is slowing almost everywhere, because families are choosing to have fewer children as child survival, education (particularly for girls), and incomes improve. More than half of all countries now have fertility below the replacement level of about 2.1 children per woman. Future growth is concentrated in parts of Africa and Asia; elsewhere populations are ageing and, in many countries, already shrinking.

A: how much each of us uses

Numbers alone do not tell the story, because a person in a rich country uses far more of the planet than a person in a poor one. If everyone lived like the average resident of the United States, humanity would need about five Earths; like the average resident of India, about three quarters of one (Global Footprint Network). The richest tenth of humanity is responsible for roughly half of consumption-based emissions, while the poorest half accounts for about a tenth (Chancel, 2022).

This is why growth in developed countries weighs so heavily on nature. Each new suburb, road and holiday home in a wealthy region brings a large footprint with it, and the land is taken from somewhere. The UN’s global biodiversity assessment ranks changes in land and sea use as the biggest direct driver of nature’s decline: three quarters of the land surface has been significantly altered by people, and around one million species are threatened with extinction (IPBES, 2019). Much of this damage cannot be undone on any timescale that matters to us: a species that is gone does not come back, and an ancient forest or a wetland takes centuries to recover, if it ever does.

The world extracts more than 100 billion tonnes of materials every year, three times as much as in 1970 (UNEP International Resource Panel, 2024).

What islands teach

An island is a small planet: its soil, forests, water and minerals are all there is, and there is nowhere else to go. That makes islands the clearest laboratories we have for what happens when demand outruns what the land can renew. They also teach humility, because the most famous story is not quite what it seemed.

Rapa Nui (Easter Island) is often told as a warning: islanders cut down every tree to move their great statues, and their society destroyed itself. Jared Diamond’s Collapse (2005) made this account famous. The forest really did disappear. But the research since then paints a more complicated picture. People seem to have arrived later than once thought, around 1200 (Hunt and Lipo, 2006). Polynesian rats that came with them ate palm seeds and stopped the forest regrowing (Hunt and Lipo, 2009). Radiocarbon modelling suggests the population grew steadily until Europeans arrived in 1722 rather than collapsing before them (DiNapoli et al., 2021), and the island’s stone gardens could feed a population of a few thousand (Davis et al., 2024). Some researchers still see climate and resource stress in the record (Lima et al., 2020). What is not in doubt is what came after contact: in 1862 and 1863 slave raiders took more than 1,400 people to Peru, disease followed, and by the late 1870s only about 111 islanders remained.

Other islands give clearer evidence of people exhausting their own land. On Mangareva, forest clearance on the hills led to erosion, the loss of tree crops and of timber for voyaging canoes, and a long period of hardship (Kirch, 1997). Its neighbour Henderson Island lost several bird species to hunting and was abandoned once the trade that sustained it failed (Weisler, 1995). On Nauru, a century of phosphate mining for farms abroad has left the central plateau, about four fifths of the island, largely mined out and uninhabitable (Republic of Nauru, NBSAP). And Norse Greenland shows how pressure on fragile pastures combined with a drying climate (Zhao et al., 2022) and a collapsing ivory trade to end five centuries of settlement.

Islands rarely die of one cause. But where the land was already overused, every other shock was harder to survive.

A balance, not a race

None of this means people are the problem. It means balance matters: a population that the land, water and ecosystems of a region can support well, with room for nature and a high standard of living for everyone. Around the world, as societies become healthier, better educated and more secure, families choose to have fewer children, and populations stabilise on their own.

That future raises a question worth planning for: a stable population with fewer births will be an older one. We want those extra years to be healthy, active and creative, so that a smaller, better-educated population keeps learning and contributing for longer. That is why the Local Solar System Foundation also follows the science of slowing and reversing ageing, and explains openly and carefully what research on ageing has confirmed and what it has not. Today, people worldwide spend about ten years of their lives in poor health: in 2021 global life expectancy was 71.4 years, and healthy life expectancy 61.9 (WHO, 2024). No therapy today stops or reverses ageing; narrowing that gap through prevention and research is a goal worth working towards.

Education is the key

The most powerful and humane way to reach a balance is education, above all where schooling is still out of reach. Girls who stay in school tend to marry later, have children later, and have fewer and healthier children, by their own choice. The World Bank estimates that limited education for girls costs countries between $15 and $30 trillion in lost lifetime earnings, and that universal secondary education for girls could reduce fertility and slow population growth (Wodon et al., 2018).

The cost of a larger family

Raising a child takes money, time and attention, and parents have a limited supply of all three. Economists call this the quantity-quality trade-off: with more children, each child tends to receive a smaller share of the family’s resources (Becker and Lewis, 1973). For families living on little, a larger family can be a heavy economic load, and it is often older siblings, especially girls, who leave school early to help.

The evidence is real but depends on the place. In rural China, studies of twins found that an additional child reduced the schooling of the other children (Li, Zhang and Zhu, 2008; Rosenzweig and Zhang, 2009). In wealthier countries with free schools and health care, such as Norway and Israel, researchers found little or no effect of family size on children’s education (Black, Devereux and Salvanes, 2005; Angrist, Lavy and Schlosser, 2010). The lesson is not that large families are wrong, but that where public support is thin, every additional child stretches the family further, and good public schools and health care make the biggest difference.

Family planning is a right

Family planning means that people decide freely whether, when and how many children to have, with the information and means to do it. It must always be voluntary and based on rights: coercive population policies have caused great harm and have no place in any solution. Access still falls short. About 164 million women worldwide had an unmet need for family planning in 2021 (UN DESA, 2022), and in low- and middle-income countries tens of millions of women who want to avoid pregnancy lack modern contraception (Guttmacher Institute, 2024). Closing that gap saves the lives of mothers and babies and gives families the freedom to invest more in each child.

Education is how humanity grows: not in numbers, but in what each person can know and do.

Mars is the exception

Everything above is about Earth, a crowded planet with a fragile living layer. A settlement on Mars would face the opposite problem. A small colony of a few hundred or a few thousand people would need to grow, both to have enough people for the many skills a society needs and to stay genetically healthy. There, larger families might be part of the plan. That is a different world with different rules, and only there.

T: where engineering helps most

The T is where invention pays off. Electricity from wind and solar, efficient buildings and vehicles, precision farming, recycling and circular design all cut the impact of each unit of consumption. History shows this lever can be enormous: the energy needed to produce a unit of economic output has fallen steadily for decades, and in many rich countries emissions have fallen while incomes kept rising. It is also why we invite people to bring energy ideas.

Food: meat without the harm

Humans are omnivores. Our ancestors have eaten meat for millions of years: stone tools and cut-marked animal bones go back at least 2.6 million years, and possibly 3.4 million (Semaw et al., 1997; McPherron et al., 2010). Meat and animal foods helped fuel the growth of our large brains (Aiello and Wheeler, 1995; Pobiner, 2013). We are not carnivores in the biological sense, like cats, which must eat meat; we are adaptable eaters, and meat has been part of human diets and cultures throughout our history. No one should be made to feel guilty for eating it.

The challenge is how it is produced. Livestock supply chains account for about 12 percent of human-caused greenhouse gas emissions (FAO, 2023), need a large share of the world’s farmland, and industrial farming raises serious questions about animal welfare. The answer we are interested in is not giving meat up, but producing it better: with far less land and without animals suffering.

• Cultivated meat is real meat grown from animal cells in a bioreactor, without raising and slaughtering an animal. Singapore was the first country to approve it, in December 2020. The United States followed in 2023 with cultivated chicken from UPSIDE Foods and GOOD Meat, and later cultivated salmon and pork fat; Israel approved cultivated beef from Aleph Farms in January 2024, and Australia and New Zealand approved cultivated quail from Vow in 2025 (FSANZ, 2025). Some places, including Italy, Florida and Alabama, have banned it.
• It is not yet cheap. Growing cells at food scale needs sterile bioreactors, nutrient media and energy, and an influential analysis concluded that, without major advances, costs would stay too high for everyday food (Humbird, 2021). Investment has fallen sharply since 2021 (GFI, State of the Industry). This is exactly where open research can help: cheaper growth media without animal serum, larger and simpler bioreactors, edible scaffolds for whole cuts, and honest lifecycle studies.
• Precision fermentation uses microbes to make specific animal proteins, such as the whey protein in milk or the haem that gives meat its flavour; several such ingredients are already sold.
• Better livestock farming matters now, for the billions of animals raised today: higher welfare standards, better feed and breeding, feed additives that cut methane from cattle, rotational grazing, and less waste from farm to fork.

If you are a biologist, engineer or student, cultivated meat is one of the most open research frontiers in food. We would like to hear from you.

Room to live: space, gardens and open air

More than half of humanity lives in cities, and the UN expects about two thirds to by 2050. Dense, well-planned cities can be remarkably efficient: shorter trips, shared walls, public transport and shared services. But density has a limit, and in many cities people are being squeezed into ever smaller homes.

In Hong Kong, where the median home offers 16 square metres per person, about 215,700 people lived in 2021 in subdivided units, flats split into several tiny rooms, often with a shared kitchen or bathroom and little daylight. The median subdivided unit measured 11 square metres, giving each resident about 6 square metres, about half the size of a parking space (Hong Kong Census and Statistics Department, 2021). As housing costs rise, ever smaller homes are becoming normal in many cities.

This matters for health. The World Health Organization makes a strong recommendation that governments prevent and reduce household crowding, because crowded homes spread infectious diseases and are linked to poorer mental health (WHO Housing and Health Guidelines, 2018). Crowding is associated with psychological distress, feeling depressed, family conflict and poorer sleep, and in a survey of 1,194 subdivided-unit residents in Hong Kong, those with stronger social support reported less loneliness, depression, anxiety and stress, a reminder that shared space and community matter when private space is scarce (Chan et al., 2026). Children suffer most: they have nowhere quiet to study, and crowded homes are linked to lower school achievement and behavioural problems (Evans, 2006; Solari and Mare, 2012).

Why gardens and open air matter

Green space is not a luxury. In a study of nearly one million Danes, children who grew up with the least green space around their homes had up to 55 percent higher risk of developing a psychiatric disorder later in life (Engemann et al., 2019). People who spend at least two hours a week in nature report better health and wellbeing (White et al., 2019). During the COVID-19 lockdowns, people in Britain with a private garden or a park within easy reach reported better wellbeing and health (Poortinga et al., 2021). A review of more than 140 studies links green space to lower stress hormones, heart rate and blood pressure, though the authors warn that many studies are weak (Twohig-Bennett and Jones, 2018). Hospital patients with a view of trees recovered faster than those facing a brick wall (Ulrich, 1984). The WHO’s review of the evidence links urban green space to lower stress, more physical activity, better mental health and cooler, cleaner air (WHO Europe, 2016).

A good standard of living for humans includes daylight, enough room for a family to live and study, and access to gardens, parks, trees and open air. That is part of why balance matters: a planet where every person can have a decent home with green nearby is a planet where population, consumption and land are in proportion.

Proven solutions

None of this is hopeless. Countries, cities and farmers around the world have already measurably eased the pressure on land and resources, some of them within a single generation. Here is what they did, and what changed.

Girls’ education and voluntary family planning

• Bangladesh. In the early 1970s a woman in Bangladesh had almost seven children on average; today it is about two (World Bank). In the Matlab programme, started in 1977, health workers visited women at home with maternal and child health care and contraception. Fertility in the programme villages fell by about 17 percent compared with similar villages nearby, and women and children there were healthier two decades later (Joshi and Schultz, 2013). From 1994 a national stipend paid for girls to stay in secondary school. Girls’ enrolment grew by about 13 percent a year and overtook boys’, and the programme delayed marriage, raised contraceptive use and lowered fertility, with benefits that the study estimates far outweigh its cost (Khandker et al., 2021).
• Iran. Fertility fell from more than six children per woman in the mid-1980s to about two by 2000: by two thirds in fifteen years (World Bank). A network of rural health houses brought primary health care, including voluntary family planning, to the villages. Child deaths fell, and the share of married women using contraception rose from 55 percent in 1990 to 81 percent in 2021 (Corker et al., 2024; Abbasi-Shavazi, McDonald and Hosseini-Chavoshi, 2009).
• Thailand. Thailand launched a voluntary family planning programme in 1970. Fertility fell from about six children per woman to below replacement level around 1990, driven by better basic health, girls’ education and the programme itself (Yeung and Abalos, 2025; World Bank).
• Kerala. This Indian state reached below-replacement fertility in the 1990s, while most of India still had large families. Researchers credit progress in health and social development, and a long history of widespread education and empowerment for women (Nair, 2010).

In every case families chose to have fewer children once children survived, girls went to school and women could get health care and contraception freely. No coercion was needed.

Wasting less food

• United Kingdom. The charity WRAP works with supermarkets, food companies, councils and households, and runs the Love Food Hate Waste campaign. Household food waste per person, measured in council bins, fell by about a quarter between 2007 and 2018, from 91 to 67 kilograms a year, and total UK food waste per person was 22 percent lower in 2021 and 2022 than in 2007. Household waste has crept up again since 2018, which shows that the work never finishes (WRAP, 2025).
• South Korea. Food waste was banned from landfill in 2005, and since 2013 households pay for the food waste they throw away, using special bags or, in Seoul, bins that weigh each deposit and charge it to the resident’s card. The share of food waste recycled into fertiliser and animal feed rose from 2 percent in 1995 to about 95 percent, and Seoul’s weighing bins cut the city’s food waste by 47,000 tonnes in six years (Broom, 2019).

Healing the sky and the land

• The ozone layer. Under the Montreal Protocol, agreed in 1987, the world phased out nearly 99 percent of the chemicals that were destroying the ozone layer. The layer is now on track to recover to its 1980 state by around 2040 over most of the world, 2045 over the Arctic and 2066 over Antarctica (WMO and UNEP, 2023). It is proof that a global resource problem can be solved when every country acts.
• Costa Rica’s forests. In 1997 Costa Rica became the first country to pay landowners, nationwide, to protect and regrow forest (Pagiola, 2008). Forest now covers 60 percent of the country, up from 56 percent in 2000 (FAO, via World Bank), and recordings from sites paid under the programme show the sounds of forest wildlife returning (Delgado et al., 2026).
• Niger’s regrown farmland. Instead of clearing every shoot from their fields, farmers in the Maradi and Zinder regions began protecting and pruning the trees that regrow from old roots. Over two decades from the mid-1980s, about 200 million trees returned on 5 million hectares of land, and they now help secure the livelihoods of about 4.5 million people (Sendzimir et al., 2011).

Organisations doing this work

These non-profit organisations work on the problems described above and publish their results. Have a look at what they do and, if their work convinces you, consider giving to them directly. The Local Solar System Foundation has no affiliation with any of them and receives nothing from them. Before you give, read each organisation’s own reports and accounts and check how it measures its results. The figures below are the organisations’ own.

• CAMFED (Campaign for Female Education, UK registered charity 1029161) pays school costs and supports girls through secondary school in Ghana, Kenya, Malawi, Tanzania, Zambia and Zimbabwe. It reports that it helped 9.3 million children go to school between 1993 and 2025. Its network of former students, the CAMFED Association, has more than 355,000 members who in turn support girls in their own communities.
• Room to Read (US non-profit) runs literacy and girls’ education programmes in Asia and Africa. Its Girls’ Education Program, which helps girls stay in school, has supported more than 4.5 million girls in 14 countries, including Bangladesh, India and Nepal.
• MSI Reproductive Choices (UK registered charity 265543) provides contraception and reproductive health care, working in 36 countries. It reports supporting more than 100,000 women and girls every day.
• Population Services International (PSI) (US non-profit, founded 1970) works with local organisations on family planning, sexual and reproductive health, malaria, HIV and other health services.
• WRAP (UK registered charity) works with governments, businesses and households to cut waste of food, plastics and clothing, and measures UK food waste against its 2007 baseline, as described above.
• Project Drawdown (US non-profit) publishes free, science-based analysis of which climate solutions, from cutting food waste to restoring land, do the most good, so that people and funders can put their effort where it counts.

How you can help

• Support education, especially for girls and in places where schooling is hardest to reach; it improves lives and gives families real choices. The organisations above are a place to start.
• Support voluntary family planning and reproductive health services, always based on rights and free choice.
• Protect green space where you live: join local planning consultations, defend parks and gardens, and ask for trees and open space in new housing.
• Use things longer. Repair, buy second hand, borrow and share tools; the materials already in circulation are the cheapest resource of all.
• Waste less food. Roughly a fifth of food available to consumers is wasted; plan meals, store food well and use leftovers.
• Back better food research. Follow and support work on cultivated meat, precision fermentation and higher-welfare farming; researchers can bring their ideas.
• Ask for circular rules: right to repair, longer warranties, deposit schemes and recycled content standards.
• Join the conversation and help translate this explainer via the contribution board.

Sources and further reading

• United Nations (2024), World Population Prospects 2024
• United Nations, World Urbanization Prospects
• UNEP International Resource Panel (2024), Global Resources Outlook 2024
• Global Footprint Network, Earth Overshoot Day and Country Overshoot Days
• IPBES (2019), Global Assessment Report on Biodiversity and Ecosystem Services
• UNEP (2024), Food Waste Index Report 2024
• Ehrlich and Holdren (1971), Impact of population growth, Science 171
• Chancel (2022), Global carbon inequality over 1990 to 2019, Nature Sustainability 5
• Diamond (2005), Collapse: How Societies Choose to Fail or Succeed, Viking
• Hunt and Lipo (2006), Late colonization of Easter Island, Science 311
• Hunt and Lipo (2009), Revisiting Rapa Nui (Easter Island) “ecocide”, Pacific Science 63
• DiNapoli et al. (2021), Approximate Bayesian computation of radiocarbon and paleoenvironmental record shows population resilience on Rapa Nui, Nature Communications 12
• Lima et al. (2020), Ecology of the collapse of Rapa Nui society, Proceedings of the Royal Society B 287
• Davis et al. (2024), Island-wide characterization of agricultural production challenges the demographic collapse hypothesis for Rapa Nui, Science Advances 10
• Kirch (1997), Microcosmic histories: island perspectives on “global” change, American Anthropologist 99
• Weisler (1995), Henderson Island prehistory, Biological Journal of the Linnean Society 56
• Republic of Nauru, National Biodiversity Strategy and Action Plan
• Zhao et al. (2022), Prolonged drying trend coincident with the demise of Norse settlement in southern Greenland, Science Advances 8
• WHO (2024), COVID-19 eliminated a decade of progress in global level of life expectancy
• Wodon et al. (2018), Missed Opportunities: The High Cost of Not Educating Girls, World Bank
• Becker and Lewis (1973), On the interaction between the quantity and quality of children, Journal of Political Economy 81
• Li, Zhang and Zhu (2008), The quantity-quality trade-off of children in a developing country, Demography 45
• Rosenzweig and Zhang (2009), Do population control policies induce more human capital investment?, Review of Economic Studies 76
• Black, Devereux and Salvanes (2005), The more the merrier? The effect of family size and birth order on children’s education, Quarterly Journal of Economics 120
• Angrist, Lavy and Schlosser (2010), Multiple experiments for the causal link between the quantity and quality of children, Journal of Labor Economics 28
• UN DESA (2022), World Family Planning 2022
• Guttmacher Institute (2024), Adding It Up 2024
• Semaw et al. (1997), 2.5-million-year-old stone tools from Gona, Ethiopia, Nature 385
• McPherron et al. (2010), Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia, Nature 466
• Aiello and Wheeler (1995), The expensive-tissue hypothesis, Current Anthropology 36
• Pobiner (2013), Evidence for meat-eating by early humans, Nature Education Knowledge 4
• FAO (2023), Pathways towards lower emissions
• FSANZ (2025), Approval report A1269: cultured quail as a novel food
• Humbird (2021), Scale-up economics for cultured meat, Biotechnology and Bioengineering 118
• Kupferschmidt (2013), Lab burger adds sizzle to bid for research funds, Science 341
• Good Food Institute, Cultivated meat, seafood and ingredients: State of the Industry
• Hong Kong Census and Statistics Department (2021), Persons living in subdivided units
• Chan et al. (2026), Housing precarity and mental health among shoebox house residents in Hong Kong, BMJ Public Health
• Poortinga et al. (2021), The role of perceived public and private green space in subjective health and wellbeing during and after the first peak of the COVID-19 outbreak, Landscape and Urban Planning 211
• Twohig-Bennett and Jones (2018), The health benefits of the great outdoors, Environmental Research 166
• WHO (2018), Housing and Health Guidelines
• Evans (2006), Child development and the physical environment, Annual Review of Psychology 57
• Solari and Mare (2012), Housing crowding effects on children’s wellbeing, Social Science Research 41
• Engemann et al. (2019), Residential green space in childhood is associated with lower risk of psychiatric disorders from adolescence into adulthood, PNAS 116
• White et al. (2019), Spending at least 120 minutes a week in nature is associated with good health and wellbeing, Scientific Reports 9
• Ulrich (1984), View through a window may influence recovery from surgery, Science 224
• WHO Regional Office for Europe (2016), Urban green spaces and health: a review of evidence
• Our World in Data, Population growth
• World Bank, World Development Indicators: fertility rate, total, school enrolment, secondary, female and forest area
• Joshi and Schultz (2013), Family planning and women’s and children’s health: long-term consequences of an outreach program in Matlab, Bangladesh, Demography 50
• Khandker, Samad, Fuwa and Hayashi (2021), The Female Secondary Stipend and Assistance Program in Bangladesh: what did it accomplish?, Asian Development Bank South Asia Working Paper 81
• Abbasi-Shavazi, McDonald and Hosseini-Chavoshi (2009), The Fertility Transition in Iran: Revolution and Reproduction, Springer
• Corker et al. (2024), Health transitions and the rise of modern contraceptive prevalence: demand, access, and choice, Population and Development Review 50
• Yeung and Abalos (2025), Social determinants of low fertility in Asia, The Lancet Regional Health: Western Pacific 65
• Nair (2010), Understanding below-replacement fertility in Kerala, India, Journal of Health, Population and Nutrition 28
• WRAP (2025), UK Food Waste and Food Surplus: Key Facts
• Broom (2019), South Korea once recycled 2% of its food waste. Now it recycles 95%, World Economic Forum
• WMO and UNEP (2023), Ozone layer recovery is on track, helping avoid global warming by 0.5°C
• Pagiola (2008), Payments for environmental services in Costa Rica, Ecological Economics 65
• Delgado et al. (2026), Large-scale forest restoration accompanied by biodiversity recovery in Costa Rica’s redistributive payment for ecosystem service program, Global Change Biology
• Sendzimir, Reij and Magnuszewski (2011), Rebuilding resilience in the Sahel: regreening in the Maradi and Zinder regions of Niger, Ecology and Society 16