Will Paul Ehrlich’s prediction finally come true?

Bernard Gilland | January 3, 2019 | Leave a Comment Download as PDF


This article was originally published in Down to Earth by Bernard Gilland.

The Green Revolution may have prevented the fate that was forecasted for a world bursting at the seams and unable to feed itself. But unlimited population growth means that doomsday could be well within sight.

In the period 1975–2018, world population increased steadily at 83 million per year, and reached 7.6 billion in 2018. The increase in 2017 was the difference between approximately 145 million births and 62 million deaths. Despite population growth, the global average daily food supply per person rose from 2,440 kilocalories in 1975 to 2,940 kilocalories in 2015. However, over 800 million people are undernourished and over 600 million adults are obese.

Cereals are the most important crops for food and livestock feed; globally, 45 per cent of the cereal harvest is consumed as food for humans, and 35 percent as feed for livestock; the remainder is used for industrial purposes, including ethanol, beer, whisky and vodka. The rise in world cereal production since the 1960s is mainly due to two technological advances. The first was Haber-Bosch ammonia synthesis, in which atmospheric nitrogen is fixed as ammonia which plants utilize for protein formation. Production of Haber-Bosch ammonia began in 1913, and the consumption of nitrogen fertilizer reached 103 million metric tons in 2014-2015.  The second advance was the Green Revolution that began in the 1960s, after agronomist Norman Borlaug had bred varieties of wheat that give higher yields in response to heavier applications of nitrogen, phosphorus and potassium fertilizer. The breeding and use of high-yielding rice and maize paralleled that of wheat. The most striking achievement of chemical agriculture is the maize yield in the US, which rose from 2.5 tonnes per hectare (40 bushels per acre) in 1950 to 11.0 tonnes per hectare (175 bushels per acre)   in 2016. The global cereal yield rose from 1.16  tonnes per hectare in 1950 to 3.97 tonnes in 2016. The yield in 2050 will probably reach 5.5 tonnes per hectare, thereby raising production per person from the present 380 kilograms per year to 400 kg (assuming no change in the cereal area and that the world population will be 9.8 billion). The global average nitrogen application on cereal crops, 80 kg per hectare in 2015, would be approximately 130 kg per hectare.

The success of the Green Revolution created three major ecological problems:

  1.  Globally, less than half of the applied nitrogen is taken up by crop plants; the remainder volatilizes in the form of ammonia and nitrous oxide or leaches to groundwater, resulting in eutrophication (the formation of algae) in rivers, lakes and coastal waters; this creates “dead zones” in which fish cannot live.
  2.  Applying large amounts of fertilizer to crops changes the balance between these nutrients and those needed in small or trace amounts; the latter include calcium, sulphur, magnesium, iron, manganese, copper, zinc, cobalt, boron and selenium.
  3.  Approximately 40 per cent of global irrigation water is obtained by pumping groundwater from tube wells; this has resulted in the depletion of aquifers and the lowering of groundwater levels, thereby contributing 0.4 millimeters to the global sea level rise of 3.4 millimeters per year.

In 1950, France had a population of 42 million and 20 million hectares of arable land, i.e. 2 persons per arable hectare. The nitrogen fertilizer application on cereals was negligible, and cereal production per person was about 400 kilograms per year, slightly higher than the present world average.  If the ratio of population to arable land were 2 persons per hectare on the world’s 1.6 billion arable hectares, the world population would be 3.2 billion. Reducing world population to this size would mean reducing the global average fertility rate (currently 2.5 children per woman) to 1.5 by 2050 and holding it at that level until 2200. The proportion of the population in the 65+ age-group would rise to 35 percent. Such a drastic change in the age distribution would mean raising the pensionable age to 70 years or more. Enforcing a population limit for each country would be an insurmountable obstacle, as Charles Galton Darwin pointed out in “The next million years”(1952). Canada, Russia, Australia and Argentina would not need to reduce their populations, while China and India would each have to reduce its population to roughly 300 million, one-fifth of the present population. The relative reduction in Japan and Egypt, which have 28 inhabitants per arable hectare, would be much greater.

The population of China is projected to peak at 1.45 billion around 2030 and decline to one billion by 2100. This is partly a result of the so-called one-child policy launched in 1979 (in reality a 1.5-child policy). It was replaced by a two-child limit in 2016, but the fertility rate remains 1.6. Japan has a population of 127 million; it is projected to decline to 60 million in 2100. South Korea, Taiwan and several European countries have fertility rates even lower than Japan’s 1.4. However, the best we can hope for is a world population peak of 10 billion around 2070, which would make it necessary to increase the consumption of nitrogen fertilizer to at least 160 million tonnes per year. This is not sustainable, but there is no solution in sight.

The MAHB Blog is a venture of the Millennium Alliance for Humanity and the Biosphere. Questions should be directed to joan@mahbonline.org

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  • Jim Boyer

    I believe the human existence is in crisis mode. Humans need to escalate the action of population reduction similar to preparing for a hurricane or wildfire. The aftermath of which is wholesale destruction but this time our extinction is the prime outcome.

    The planet will survive and will adjust to the parasite called human and we WILL go extinct.

  • I’ve looked into this and the use of IPAT and think it has great value … I’m an ecologist so I fully agree with Prof. Ehrlich’s foundations. But clearly things like the Green Revolution change fundamentally the equation, in a way that I think Prof. Yuval and the book Sapiens are deconstructing – through technology we can unlock quite vast stores of resources that previously were unavailable. The problem is not so much resource limitation, but ecological balance, now at a planetary scale. So IPAT SHOULD and CAN be used, but we need to use it in ways that make the most of new technologies and approaches by looking at their footprint and impact, rather than a narrow focus on what we currently see as limitations.

    Please see my article “The Three Horses of Sustainability—Population, Affluence and Technology” at https://www.preprints.org/manuscript/201812.0176/v1 (OPEN ACCESS) and comment, and I started a thread on this here in the MAHB Forum at https://mahb.stanford.edu/topic/revisiting-sustainability-balancing-population-affluence-technology/

    • Greeley Miklashek

      So, then, you do understand the “T” in the I=PAT equation, right. The technology you seem to have so much faith in is part of the problem, not the solution. Only voluntary one-child families originating fro the free choice of women who have ready access to education beyond the 7th year (how about 16 years!), opportunity for meaningful work, and ready access to contraception, will save the planet and our species. Such a voluntary worldwide depopulation could lead to the re-establishment of the sustainable 1950 population level of 2.5B by 2,100. Otherwise, as the wise old man once said, we’re toast. As a ecologist, you must be familiar with the work of the animal crowding researchers prominent in my book on stress: John B. Calhoun, J.J. Christian, and Charles Southwick, right? If not, do some more reading. You will be amazed before you’re halfway through! ( :)) Stress R Us

  • Greeley Miklashek

    What Prof. Ehrlich did not factor into his I=PAT is human health.
    So, I would like to expand his iconic equation to: H&I=PAT, where “H”=health, “I”=environmental impact, “P”=population (density?), “A”=affluence (consumption?), and “T”= technology (industrial farming?). Here’s why, population density stress is killing us NOW through ALL of our diseases of civilization (heart, cancers, lungs, obesity/diabetes, accidents/ODs, suicide, mental illnesses, Alzheimer’s, addictions, etc.). How do I know these are caused by overpopulation? All humans on earth today have 99.9% identical genomes, so our disease loads must be environmental, right? Compare that with the total absence of our “diseases of civilization” in traditional living contemporary hunter-gatherers. When our hunter-gatherer ancestors roamed the healthy biosphere 12,000 years ago (before the agricultural revolution) they numbered only 2.6M for tens of thousands of years and lived in a balanced sustainable relationship with their environment. So, our unhealthy state must be environmental, right? QED Stress R Us

  • Max Kummerow

    I doubt human population will turn out to be food limited. But what does limit human population now that the “density dependent mortality” deaths from war, famine and disease are reduced? 80 million a year increase can’t go on forever, but it can go on until the earth is less livable. We are already well into “silent spring” where I live–birds and insects populations a tenth or less of 1950. And Illinois soils have lost over half their carbon–making them worse at nutrient cycling and water retention. Which is going to matter more as climate changes. I conclude that the limiting factor is intelligence or wisdom, and in particular the ability to act to incur costs in the short run to make the long run better. We are not good at that, but the short run is short. The long run soon arrives. We need institutions to reduce fertility rates in high fertility cultures. We know a lot about how to do that since 90 countries have transitioned to below replacement fertility (about 45% of world population). I think Rosling is foolish because in focusing on positive developments he forgot to mention that population is still increasing, carbon emissions rising, soil eroding, species going extinct and climate changing faster than predicted.

    • Greeley Miklashek

      10,000,000 humans starved to death last year and 800,000,000 eat one meal a day and go to bed hungry NOW. Stress R Us

  • Mike Hanauer

    To the extent we are feeding the overpopulation, it is because of frankenfoods — methods and chemicals that themselves threaten the planet and humanity. Technology always has side effects and these days they are virtually always in somebody’s backyard. Further, the impact of overpop threatens so much more than food. Virtually all else.

    Further, I believe we need to look more at what our overpop is doing to quality of life, not just the possibility of some kind of disaster or crash.

  • trilemmaman

    Malthus logic fails again. Why do intelligent minds still reject reality?

    According to the latest report of a former senior policy research fellow at the International Food Policy Research Institute (IFPRI) most people still see the world food problem through the old and persistently flawed food paradigm of ‘too many people, not enough food’.
    I was taught this seemingly logical paradigm in high school and college and took it into my biology classes as a teacher and continued to spread this faulty meme until a presenter spoke to my classes about “Ending hunger”. I thought she was wrong when she suggested that there was more than enough food, but people just couldn’t afford to buy it. Turns out I was wrong. And I wasn’t happy about it. Credibility was king in my mind. I was shocked that mine had been diminished by intelligent and committed educators/scientist relying on unexamined assumptions. They used ‘direct causation’ (shallow thinking) to arrive at a conclusion. It turns out that deeper mind functions are required to consider multiple factors and properly examine the data to arrive at a more credible conclusion. George Lakoff, a cognitive linguist and philosopher, calls this ‘systemic causation’ thinking.
    Fact is, there was more than enough food in the world, but the political systems then were dominated by a flawed economic system that valued profit over people. A condition that resulted in billions of people simply lacking the money to buy the food that was available. Economists and politicians alike had left food distribution up to the capitalist ‘market’ system which according to the UN’s World Health Organization 2014 report left 462 million underweight adults worldwide but more than 600 million obese – nearly two-thirds of them in developing countries. And childhood obesity continues to rise faster in poorer countries than richer ones.
    “With a depth and breadth that goes far beyond previous studies”, Gerald Nelson’s work with IFPRI assessed 158 countries using best and worst case scenarios of climate change and existing economic projections. They concluded that even with a population growth increase of 2.1 billion by the year 2050 — there will be enough food (if “enough” is defined by sufficient calories averaging 2,000 calories per day as the standard requirement) to feed the world. “Civil wars, poor roads, and income disparities” will continue to keep people hungry. But the problem remains today as a lack of political will regarding “access” to food. Mr. Nelson’s op-ed in the Washington Post (The global food problem isn’t what you think. Jan. 3, 2019) offers most of this information “even in the face of our extreme climate change scenario.” https://www.washingtonpost.com/opinions/2019/01/02/global-food-problem-isnt-what-you-think/?utm_term=.8663310843a3
    The bigger problem they offer is “micronutrient deficiencies”. Even in the richest nations. Climate change “will likely produce major and somewhat unpredictable effects on future supply… [but] we must shift our emphasis from food security to nutrient security.”
    It appears IFPRI still hasn’t learned, or has forgotten, a summary statement from the 1980 Presidential Commission on World Hunger. That unless our nation puts ending world hunger in the context of our own national security, it probably won’t happen by the year 2000, which was clearly achievable. And, according to the specifics of the content of the report, directly linked to US national security in the context of pandemics, terrorism, war, immigration, and environmental degradation.
    What Nelson’ op-ed didn’t mention (but hopefully covered in the IFPRI report) was the connections between climate change and our traditional agriculture systems which are fundamentally unsustainable for a variety of other factors. And, that most of those factors are still directly related to our own national security. Unfortunately, our comfortable ignorance, poisonous apathy, increasing gullibility, and lack of political will still prevents us from resolving this fundamental problem.
    Western thinking is even at fault. Our educational approach to traditional sciences conditioned us to separate issues in order to understand them. Plus, creative political concepts have deluded our minds into believing that things are “independent” from one another. These human factors conditioned our minds to discount the profound interconnectedness of nature and the unyielding reality that every system and structure in the known universe (human and natural) is irreversibly linked to sustaining our own freedom, security and prosperity.
    An asteroid, nuclear exchange, bioterrorist attack, pandemic, cyber event, global economic depression/recession, or solar flare could catastrophically alter the food production capacity of our earth — regardless of how well our political and economic system effectively manage humanities food quality, volume, and economic access.
    What we can’t do is waste more time ignoring the fundamental human need and human right of every person to an adequate, nutritious, affordable, and sustainable food supply. As well as adequate clean water, clean air, healthy soil, protection from the elements, income, education, and opportunities to express our faith — in action consistent with the golden rule instead of the rule of gold. But we must all acknowledge and act on the fundamental principle that every right requires purposeful responsibilities. By God’s wish and nature’s ways we are free to do as we please. But we will never be free of he consequences.
    Given the persistent evolution of weaponry and war, and the failure of our political systems to adapt to unprecedented technological change which is exacerbating a growing variety, velocity and volume of global stressors — we may not be able to change our flawed global political system fast enough. Our persistent reliance on war, sanctions (which can be deadlier than war – or start them), unfettered capitalism, and even the best diplomacy to impose ‘international law’ on nations is not working. Under our current international governance system, each nation has the ‘sovereign’ right to ignore international law, including human rights (especially if they have powerful weapons/militaries). This will not end soon– or end well. But existing governments could relatively easily tweak our global economic system to at least fund the inalienable human rights that all humanity should be entitled too.
    The best list of rights was globally agreed to after the horrors of World War II in the hopes of preventing another world war. But the Universal Declaration of Human Rights was insufficient to prevent other smaller wars. The UN was never given the power to enforce human rights. Doing so could have eradicated the most lethal conditions of poverty that are the frequent root cause of war and have been far deadlier than the wars that persisted. But now, much could be achieved, and can be done rapidly if funding and focusing achieving the 17 Sustainable Development Goals before the year 2030 were a political priority.
    There is no shortage of money. And no government would even need to increase its taxes or debt to fund them. There is an estimated $32 trillion of illicit funds stashed in off-shore accounts by corrupt kleptocrats (think Zaire’s former President, Trump’s Paul Manafort, or the Panama Papers), criminal cartels (drugs, weapons, knockoffs, slaves, antiquities, endangered species…), and tax evading capitalists and corporations (Trump?, Apple?…). Again, we just lack the political will. Or, in one word. Justice.
    Is it just a coincidence that “Justice” was 2018’s “word of the year”? Any guesses on what the word will be for 2019? Here’s my guesses. “Distractions” “Principles” “Interdependence” “Holistic” “Comprehensive” “Systems” “Resilience” “Catastrophic” “Extinction” “Suicide” “Truth” “Thoughtless” “Unwise” “Selfish” “Senseless” “Irrational” “Stupid”.

  • NP1

    humankind, as with all species, has but 2 purposes in life:


    and reproduction

    the rest is window dressing, despite political and religious protests to the contrary

    we eat and consume to the maximum, when that maxum has passed, our numbers will die back to a sustainable level, which will be around 1 billion people–roughly the population before we got our hands on fossil fuels.

    Which means that 6.5 billion of us don’t have much of a future.

    still the party was good while it lasted


    • trilemmaman

      Some humans have other purposes. Some commit to solving problems. Other just to bitching about them.

  • Valoha Prager

    Stop projecting into the future and stop doing what we shouldn’t be doing and do it NOW. Start from the position of THERE is NO FUTURE.

    • trilemmaman

      That pessimism is self fulfilling. There will be a future. Just not sure how many people will be around to record it. But we have the capacity to sustain it…IF we change our thinking. I haven’t seen many people do it…but its possible, and some do.

  • melharte

    I’m curious as to why he uses 2 persons per arable hectare in 1950 as a sustainability level by which he sets a goal of population reduction to 3.6 billion, which is well above the 1950 population level of roughly 1+ billion – and at a time when our global natural resources are plummeting. Any ideas, anyone?

  • Code Clements

    Three sites folks reading this could visit that explain some of these points very clearly are:
    A. “Www.Populationpyramid.net” which lists all world countries by population. You can see the population from 1950 to 2100 in 1 or 5 year increments and it is quite fascinating .
    B. Hans Rosling on TED TALKS or you tube. World renown statistician (now passed away) who has about 12 videos explaining and showing how the world has improved for the very poor, babies per woman, etc. Not only is it informative but also entertaining. Start with “the magic washing machine”
    C. http://Www.gapminder.org is the institute founded by Rosling and now managed by his son and daughter in law. To see how ignorant we are of what has happened in our world in the last 50 years, take the test and be amazed ! Happy reading!

  • stevenearlsalmony

    Unfortunately, the predictions do appear to be coming true.

    • trilemmaman

      Because we lack the will or the passion to organize in such a way as to influence our elected officials.

      • anotherneighborhoodactivist

        I don’t think a critical mass of people understand the systemic nature of our problems. The YVM (yellow vest movement) in France exemplifies this difficulty. The (overwhelming) best available science says we need to put a price on carbon. However, Macron tried to do it in a way that hurt mostly working people, not the wealthy. The wealthy who happen to emit far more GHG per capita than the poor. The ‘demands’ of the YVM that I have seen on line contain very little in the way of recognition of the underlying need to put a price on carbon—just “not on us.”

        Economic and ecological problems are inseparable. Until we get that and act on it, we won’t solve either problem. I don’t believe humans will solve them on our own initiative; it is far more likely that the solutions will be forced on us (exogenously?). Collapse—economic or ecological—is one way that happens. If the latter happens first, the former will follow. If the other way around, the result is more difficult to predict.