A central issue of the human predicament then as now was the prospect of feeding a growing population. In 2016 Earth is carrying some 7.4 billion people instead of the ~3.5 billion it had in 1968. Some 200–300 million people have died of starvation or hunger-related disease in the 48 years since then,Footnote 1 but not the greater numbers within a decade we anticipated based on the work of agricultural specialists such as Brown (1963), Paddock and Paddock (1967), and Hopcraft (1968) in the 1960s.

Farmers in developing countries, especially richer farmers, adopted “green-revolution” technologies, based on improved grain strains and heavy use of fossil fuels, much more rapidly than most analysts had expected in the 1960s. As a result, grain production surged ahead of population growth. In addition, international actions created a global system of food storage and transfer that could avert famine when crops failed in developing countries. And with the spread of family planning programs, birth rates in many nations began declining significantly in the 1970s, thus easing the growth in demand for food.

But the long-term consequences of the green revolution are still in doubt, and chronic food shortage is still a problem in many developing countries. Today, primarily because of the maldistribution of food, just under 800 million people are seriously underfed,Footnote 2 and according to the FAO as many as two billion people are micronutrient malnourished (Ramakrishnan 2002). Thus, it remains to be seen whether our much-maligned 1968 statement that “the battle to feed all of humanity is over” will be disproven.

Some, of course, suggest the battle can still end in victory (e.g., Foley 2011), and we hope they are correct. But we have severe doubts in the face of the potentially disastrous (Mann 2009), already evident, and intensifying effects of climate disruption and resultant water shortages (e.g., Aarhus University 2014; Liu and Yang 2012; Mankin et al. 2015; Mehra et al. 2001). Food production is also threatened by overdrafting of fossil groundwater (e.g., Barringer 2011; Brauman et al. 2016), increasing losses of biodiversity—especially of pollinators (Koh et al. 2015) and enemies of crop pests (Boyles et al. 2011), which can have serious nutritional impacts (Smith et al. 2015)—the degradation of soils,Footnote 3 (Montgomery 2012) ocean acidification, pollution, and overfishing (e.g., Britten et al. 2015), and the projected addition of some four billion people by the end of the century.

The controversial original green revolution (Singh 2000) certainly was a medium-term rescue for many hungry people after the Population Bomb, but the revolution’s lead scientist Norman Borlaug was deeply concerned about population growth. He featured the population issue in his 1980 Nobel Prize address, saying:

“There can be no permanent progress in the battle against hunger until the agencies that fight for increased food production and those that fight for population control unite in a common effort. Fighting alone, they may win temporary skirmishes, but united they can win a decisive and lasting victory to provide food and other amenities of a progressive civilization for the benefit of all mankind.”Footnote 4

The needed union unfortunately has not occurred, and serious maldistribution of food supplies explains overall levels of hunger today (Ehrlich and Harte 2015b).

With no prospect that the maldistribution is likely to be corrected soon, it is surely no accident that “ag investment” is spreading. Nations like China, India, South Korea, and Saudi Arabia are buying land in Africa, Brazil, and other overseas nations (Klare 2012) in an attempt to ensure that their own populations will be fed as the food situation tightens. Like many other investors, they are anticipating a time, sometimes described as “peak soil,”Footnote 5 when population size and growth make fertile land a premier resource for investment,Footnote 6 including environmental consequences that likely will increase the value of that investment.

An array of factors makes the human predicament today much more precarious than it was in 1968. Of course, the most important is that more than twice as many people are now living on Earth as there were then. Whatever population size could, together with tightening resource constraints and increasing environmental degradation, cause widespread societal collapse, humanity is a lot closer to it now. Humanity is rapidly approaching the end of being able to exploit the fossil fuel bonanza that powered the vast expansion of civilization over the past century and a half (Holdren 2008). That alone makes collapse much more likely and initiating steps toward population shrinkage much more imperative.

Empirically, the most effective way to move toward population shrinkage involves providing women everywhere with rights, opportunities, and education equal to those provided to men (today these rights are not truly equal in any nation and are severely lacking in many) and providing all sexually active people with access to modern contraception and safe backup abortion (Dasgupta and Ehrlich 2013; Ehrlich and Ehrlich 2012). Dealing with overconsumption is more complex in theory (Ehrlich 2014), but transforming consumptive behavior has been shown to be achievable, as demonstrated by mobilizations and demobilizations at the start and end of World War II (Ehrlich and Ehrlich 2010, 2012). Of course the war posed an immediate, existential threat, which induced affected populations to change their consumptive habits, if only temporarily. We might hope that the existential threats posed today by climate disruption, faltering agriculture, rising seas, widespread toxification, and resource depletion would also change behavior, but the danger is not yet perceived widely or clearly enough to produce the desired effect.