In the past 200 years, several aspects have caused on impact in global mortality rates in humans including: medical science improvements, decreased starvation risk, diminished prevalence in epidemic diseases, lower rates of war, and less severe economic depressions (Abrams, 2011). Currently, approximately 1 billion people live in extreme poverty in the world, thus, higher population makes solution to any environmental problem more difficult (Abrams, 2011).

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According to Cohen (1997), fertility will not reach or stay at exactly the replacement level needed due to increased poverty, increased inequialty both within and between countries, simultaneous declines in social security and pensions occur as life expectancy gets higher, and pro-natalist religions are increasing in numbers. Abrams (2011) also noted that fertility reduction is necessary, but not sufficient for economic growth, as it allows greater investment per capita in health and education, reduces birth rates, and increases economic development.

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If morbidity doe not become compressed, potential problems with a steady increase in population growth may include a rise in Alzheimer prevalence (possibly tripling to 13.5 million of all U.S citizens over age 65 by 2050), unmanageable geriatrician-patient ratios (1 per 5000 people over age 65 in the U.S), higher healthcare costs especially for the elderly, and fewer working age individuals supporting the economy due to lowered fertility (Abrams, 2011). Thus, longer life expectancy with a larger fraction of retired or impaired citizens would force revisions in both the health care and retirement systems during the century, greater regulation of nursing home care will be demanded, younger people may be required to devote a regulated time for elderly care, and new pressures may become inevitable such as having higher birth rates to ensure there will be enough children to care for the extended old age of parents.

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Hardin (1968) first introduced the term “The Tragedy of the Commons” (TOC) in relation to the dated arms race identifying security as being the ultimate human resource. Hardin argued that Jeremy Betham's desired “greatest good for the greatest number” is an impossibility. Wikipedia defines it as a dilemma arising from the situation in which multiple individuals, acting independently and rationally consulting their own self-interest, will ultimately deplete a shared limited resource even when it is clear that it is not in anyone's long-term interest for this to happen.

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According to Abrams (2011), TOC can be avoided by cooperation, enforced and generally accepted rules, or conversion to private property; however a problem may be the second tragedy of the commons where new members of the population inherit the  right to exploit by previous regulations. Even with continual updating or direct taxes on births, the situation for an individual gets worse with more people, because higher population size means that the best policy will involve less profit per individual, although still, any new system would reflect the preferences of all people. Furthermore, Abrams (2011) stated that unregulated capitalism makes TOC inevitable, as producers who can reduce costs at the expense of damaging a public good (air, water, wilderness) and exploiters who overuse common resources are the ones being favored. TOC situations are more difficult to solve between nations; CO2 emissions reductions harms the nation that does the reduction, but benefits are spread globally, monitoring emissions of countries is very difficult, poorer countries give up more by agreeing to reductions, and the media promote tar sands, while ignoring global warming (Abrams, 2011).

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Cohen (1997) noted that the cost to a single nation that drastically reduced fossil fuel use would be enormous due to an immediate higher cost of energy, loss of industry and wealth to countries which did not embark on large reductions, and countries which invest nothing in research would still benefit from new solar or wind technologies.

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International agreements on limiting population size will be very difficult to achieve if they are needed. Many human environmental problems arise because individual and group interests differ or country and world interests differ. Higher population density makes the negative impacts of such situations larger (and they affect more people). Higher populations mean that previous group-optimal policies will need constant adjustment. Population regulation itself can be seen as a tragedy of the commons when individually desired family sizes conflict with socially desired total population size (Abrams, 2011).

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overcrowding