​The beginning (1798) of thinking about future growth of the human population

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The power of population is indefinitely greater than the power in the earth to produce subsistence for man. Population, when unchecked, increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio. A slight acquaintance with numbers will shew the immensity of the first power in comparison to the second. By that law of our nature which makes food necessary to the life of man, the effects of these two unequal powers must be kept equal. This implies a strong and constantly operating check on population from the difficulty of subsistence. This difficulty must fall somewhere, and must necessarily be felt by a large portion of mankind. ‐Thomas Malthus

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Change in views on the subject of human population growth

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​Paul Ehrlich: 1968: “...the underdeveloped countries of the world face an inevitable food‐population crisis. Each year food production in underdeveloped countries falls a bit further behind burgeoning population growth. ...it now seems inevitable that it will continue to its logical conclusion: mass starvation”

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Malcolm Potts, 2007: “In the 1950s and 1960s, when the global population was projected to grow by 3 billion in 50 years, the term ‘‘population explosion’’ captured the attention of scientists as well as the general public. Now, when another 3 billion people may be added to the world’s population, the response is a collective yawn.”

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“The rapid growth in the world’s population over the past 200 years ... has been largely driven by the increased survival of the children who were born and not by higher fertility. More babies, small children and adults as well survived because of improved nutrition, better water, better hygiene and vaccines.” ‐Martha Campbell, U.C.Berkeley School of Public Health 2007

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Impact of coming changes in human population ecology on human society

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​Three factors set the stage for further major changes in families: fertility falling to very low levels; increasing longevity; and changing mores of marriage, cohabitation, and divorce. In a population with one child per family, no children have siblings. In the next generation, the children of those children have no cousins, aunts, or uncles. If adults live 80 years and bear children between age 20 and 30 on average, then the parents will have decades of life after their children have reached adulthood and their children will have decades of life with elderly parents. The full effects on marriage, child bearing, and child rearing of greater equality between the sexes in education; earnings; and social, legal, and political rights have yet to be felt or understood. ‐J. E. Cohen 2003. Science 302:1172‐1175. "Human population; The next half century".

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Headline of National Geographic article (Jan. 2011) by Robert Kunzig:
"By 2045 global population is projected to reach nine billion. Can the planet take the strain?" Since then the U.N. has projected that the population will ultimately exceed 10 billion this century "...resources are not material; they are socially defined. The fact is that we have only one nonrenewable resource and that is space. Otherwise mankind's basic resources are knowledge and skill...on balance our heavy use is expanding the world's resources, not diminishing them."

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Quote from Noam Chomsky in 'Growth' edited by W. L. Oltmans 1974
"..I don't think there is any doubt whatsoever that...there are limits to growth set by natural, by physical and chemical law. It would be inanely optimistic to simply assume that technology will somehow develop and overcome the finite limits of resources and the finite capacity of the ecological system to tolerate pollution and destruction. Of course that's not the case." this is now widely accepted, but what are the resources and what are the limits?

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"The consumer-resource interaction is arguably the fundamental unit of ecological communities. Virtually every species is part of a consumerresource
interactions, as a consumer of living resources, as a resource for another species, or as both...If we are to understand population regulation and its various manifestations, we therefore need to focus on consumer-resource interactions." (p. 1) Murdoch, Briggs, Nisbet. 2003. Princeton University Press.

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without courses in sociology and psychology, or special classes in sex education, [hunter/gatherers] know at least as much about human nature as most of us do...Sexual abstinence during prolonged lactation, the pruning of twins, a failure to prolong a person's life unnecessarily; these and other measures and abstentions prevent overpopulation more effectively than does the pill .... Carlton S. Coon 1971, The Hunting Peoples, 1971, p.389.

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"It is very difficult even today to say conclusively and statistically why even self‐reflective individuals actually do whatever they do, let alone to pin down reproductive psychology definitively and to separate out personal reasoning and values from social, religious, and economic factors in decision‐making. ...the difficulties of historical analysis are multiplied many times because scientists cannot go back to past generations and conduct surveys. Moreover even the basic historic demographic data are notoriously flawed and are too often simply estimated from theories and assumptions that may not even be correct." ‐Philip Regal

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"…it seems to be impossible to predict the onset of fertility decline from existing social or economic conditions." ‐Joel Cohen

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Fertility is now below replacement level in the developed world Countries that have greatest ability to support children have a fertility rate that, if continued could lead to extinction. Both quotes from Jan. 2011 National Geographic

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"Chinese women, who were bearing an average of six children each as recently as 1965, are now having around 1.5. In Iran, with the support of the Islamic regime, fertility has fallen more than 70 percent since the early ’80s. In Catholic and democratic Brazil, women have reduced their fertility rate by half over the same quarter century. “We still don’t understand why fertility has gone down so fast in so many societies, so many cultures and religions. It’s just mind‐boggling,” says Hania Zlotnik, director of the UN Population Division. "The U.N. projects that the world will reach replacement fertility by 2030."

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Closing quotes on history from Joel Cohen:
"No optimist, if that is the right word, has suggested that the Earth could support 5.7 trillion people, and with good reasons...It follows that, for the next ten millenia, the average future population growth rate cannot exceed a doubling every millenium, or an average growth rate of 0.069 % per year." (1995 growth rate would get us there in 436 years) "...the amount of time remaining to bring the numerical...growth of the human population to a halt is not extremely long. Within the next 150 years or so, and possibly much sooner than that, a drastic though not necessarily abrupt decline in global population growth rate is inevitable."

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"...we today cannot clearly foresee the final effect of an unprecedented rapid increase of population within closed frontiers. What seems to be least uncertain in a future full of uncertainty is that the demographic history of the next 400 years will not be like that of the past 400 years." Harold F. Dorn. 1962. Science 135:283‐290.

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"The earth's population must ultimately approach a long‐term average growth rate of zero. This is a simple mathematical fact." J.E. Cohen 1995

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"People who live in a stationary population must choose: they can have a long average length of life together with a low birth rate, or a high birth rate together with a short life expectancy" J.E. Cohen 1995, 'Methuselah's choice'

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W.W. Murdoch: "Poor countries, even in the worst of famines, have always produced enough food to feed their people, if the food were evenly distributed. The simple idea—too many people, too little food—is simply not tenable." (The poverty of nations. 1985)

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Poor people cannot influence international markets and may be increasingly unable to pay market prices. Income inequality is the cause of starvation (Inequality between countries is increasing). Professor Emeritus, UCSB Author of The Poverty of Nations MacArthur Award winner, first head of NCEAS.

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Foley et al. ("Solutions for a crowded planet"): There is a need to increase production and decrease impact of agriculture "...tremendous progress could be made by halting agricultural expansion, closing 'yield gaps' on underperforming lands, increasing cropping efficiency, shifting diets and reducing waste." Main gains seem to be shifting to more vegetarian diet

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Cohen:  "Humans seem to resolve these conflicts of values by personal and social processes that are poorly understood and virtually unpredictable at present. How such conflicts are resolved can materially affect human carrying capacity...." "resolve" does not mean "optimally resolve"

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Noam Chomsky – "With the environmental crisis, we’re now in a situation where we can decide whether Mayr was right or not. If nothing significant is done about it, and pretty quickly, then he will have been correct: human intelligence is indeed a lethal mutation. Maybe some humans will survive, but it will be scattered and nothing like a decent existence, and we’ll take a lot of the rest of the living world along with us."

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"a significant proportion of births in developing countries are the result of unintended pregnancies. For example, an estimate by the Global Health Council in 2002 revealed that roughly one‐quarter of the 1.2 billion pregnancies that occurred in the developing world between 1995 and 2000—some 300 million—were unintended (Daulaire et al. 2002)." "The ever rising numbers of abortions and of maternal deaths that result from abortion are additional evidence of the incidence of unwanted pregnancy around the world."

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Population 'problems' and environmental problems in general require cooperation between societies

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​"Humanity's globalizing civilization must take this enhanced opportunity to explore conscious evolution and try new ways of organizing societies to cooperate to solve its burgeoning global problems...each day that we do nothing forecloses options for creating a better future for ourselves and our fellow inhabitants of Earth." Paul & Anne Ehrlich 2008 The Dominant Animal. Island Press.

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The problem is that we live in a Global Commons, in which we bear neither the
full costs, nor the full benefits, of our actions.....Many of our environmental and other global problems can be traced to such conflicts, and to the unwillingness of individual agents to take account of the greater good. One of the great challenges in achieving sustainability will be in understanding the basis of cooperation, and in taking multicellularity to yet a higher level, finding the pathways to the level of cooperation that is the only hope for the preservation of the planet. Simon Levin, Moffett Professor of Biology, Princeton University, ‐one of 2‐3 biggest names in theoretical ecology

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Cohen's last sentence in App. 6: "...to believe that no ceiling to population size or carrying capacity is a prospect, you have to believe that nothing will stop a sufficient proportion of additional people from increasing the Earth's carrying capacity by more than or at least as much as, they consume."

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"Both sides in the arms race are...confronted by the dilemma of steadily increasing military power and steadily decreasing national security. It is our considered professional judgment that this dilemma has no technical solution. If the great powers continue to look for solutions in the area of science and technology only, the result will be to worsen the situation.''– Hardin suggest overpopulation is the same type of problem • Is a dilemma for all 'common pool resources' (CPRs)‐air, water, fish stocks...

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