How Many People Can the World Hold?

How Many People Can the World Hold?

No one knows how many people the world can support, but most scientists agree that there is a limit. A 2011 report from the United Nations’ Convention on Biological Diversity states that the population’s demand for resources already exceeds the earth’s capacity by 20%. The primary factors that may eventually put a cap on human population are the following:

• Food: Enough food is currently produced to feed the world’s entire population, but economic and sociopolitical factors have led to food shortages and famine. Food production can be expanded in the future, but better distribution of food will be needed to prevent even more widespread famine as the world’s population keeps growing. For all people to receive adequate nutrition, the makeup of the world’s diet may also need to change.

• Available land and water: Rural populations rely on local trees, soil, and water for their direct sustenance, and a growing population puts a strain on these resources. Forests are cut for wood, soil is depleted, and water is withdrawn at

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Checking Your Environmental “Footprint”

Environmental health may seem like a global challenge, but each person has a unique impact on our planet’s health. In fact, there are ways to measure the environmental impact of your individual lifestyle.

For an estimate of how much land and water your lifestyle requires, take the Ecological Footprint quiz at You can also determine your “carbon footprint” at the Global Footprint Network website ( page/calculators) or at the Nature Conservancy website (

Go online and take one or all of these quizzes, and compare your results with the results of your classmates. Then identify ways you can reduce the size of your ecological and carbon footprints, both as an individual and as a class. ever-increasing rates. These trends contribute to local hardships and to many global environmental problems, including habitat destruction and species extinction.

• Energy: Currently, most of the world’s energy comes from nonrenewable sources: oil, coal, natural gas, and nuclear power. As these sources are depleted, the world will have to shift to renewable (sustainable) energy sources, such as hydropower and solar, geothermal, wind, biomass, and ocean power. Supporting a growing population, maintaining economic productivity, and stemming environmental degradation will require both greater energy efficiency and an increased use of renewable energy sources.

• Minimum acceptable standard of living: The mass media have exposed the entire world to the American lifestyle and raised people’s expectations of living at a comparable level. But such a lifestyle is supported by levels of energy consumption that the earth cannot support indefinitely. The United States has about 5% of the world’s population but uses 25% of the world’s energy. In contrast, India has 16% of the population but uses only 3% of the energy. China’s energy consumption is rapidly increasing, and that nation accounts for 20% of the world’s population. If all people are to enjoy a minimally acceptable standard of living, the population must be limited to a number that available resources can support.

Air Quality Index (AQI) A measure of local air TERMS quality and what it means for health.

Fossil fuels Buried deposits of decayed animals and plants that are converted into carbon-rich fuels by exposure to heat and pressure over millions of years; oil, coal, and natural gas are fossil fuels.

Smog Hazy atmospheric conditions resulting from increased concentrations of ground-level ozone and other pollutants.

Greenhouse gas A gas (such as carbon dioxide) or vapor that traps infrared radiation instead of allowing it to escape through the atmosphere, resulting in a warming of the earth (the greenhouse effect).

Greenhouse effect A warming of the earth due to a buildup of greenhouse gases in the atmosphere.

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