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Paul R. Ehrlich is a renowned ecologist, an Emeritus Professor of Population Studies at Stanford, and an outspoken, self-proclaimed “loudmouth” and polymath with strong opinions about topics ranging from education to nuclear weapons. He is probably best known for his controversial 1968 book “The Population Bomb,” which included a number of inaccurate and alarmist predictions. He has published research on butterflies, birds, evolution, extinction, conservation, and more over a six decade career.

At age 90 last year, he went on a speaking tour to promote his most recent book, a memoir of his life. Although Ehrlich can be intentionally provocative and even careless in his speech, he made a number of interesting points that I want to share here to see if they resonate or lead to a productive discussion. I wasn’t able to talk directly with Professor Ehrlich, so this is based on a number of interviews that he gave last year.1

What should a school of sustainability focus on?

Ehrlich is grateful to Stanford for giving him decades of academic autonomy and surrounding him with excellent colleagues to enable him to pursue his work. But he is unhappy with the structure of the new Doerr School of Sustainability. In an interview with Chris Field, director of Stanford’s Woods Institute for the Environment, he refers to it as the “Fake School of Sustainability” for the “most obvious reason … The entire school has nothing of demography… If you’re not discussing population and you’re not discussing consumption, then you’re not discussing sustainability!”

He suspects that a need for funding led the Doerr School to focus on engineering and “extractive geology”, when what is really needed is social science and the arts. “Engineers just want to plane the world flat and build electric cars to drive over it.” Ehrlich believes that humanities and the arts must help us figure out how to get people to understand and respond to the threats posed by climate change. “Telling people the science doesn’t change their behavior…. We need art… We need narrative.” While there are some social scientists in the school, he is frustrated by their department’s mission, which reads in part “The Environmental Social Sciences department will discover the causes of sustainability challenges”. His view is that the causes are clear — over-population and over-consumption — and the real question is how to reduce those.

Do we all need to be poor? Is it reasonable to expect that?

Ehrlich is known for an equation he developed with John Holdren, I=PĂ—AĂ—T that conveys that our impact on the planet is a product of population, affluence, and technology (e.g., whether you are riding a bike or driving a Hummer). He developed this equation in part because population concerns at the time were often directed at poor people and people of color. He wanted to reframe the conversation.

Field relayed a question about this from one of his students: “Does Ehrlich believe that we all need to be poor?” Ehrlich cited a large study that found that if everyone on the planet used as many resources as the average Mexican, the planet could sustain about 3 billion people. (Today it is over 8 billion.) He referenced findings that consumption is not correlated with happiness beyond a certain point.

When challenged in a separate interview by Nate Hagens about why Ehrlich and many other ecologists don’t adopt such a lifestyle, he responded: “I wish I knew the answer. We’re all creatures of our culture…. I certainly live a style that uses probably ten times more energy than I would have to to live a reasonable life.” He noted that he had only one child, then went on to express skepticism about individual action. “If you think of all the things that need to be done to give somebody reasonable health care, reasonable shelter, reasonable diet, and so on, it’s a social thing, it’s almost impossible to do individually.”2

What about controlling population instead of consumption?

“There is not the slightest question that 8 billion is too many,” asserts Ehrlich, suggesting that we should be “thinking about ways to humanely reduce that number” to around two billion. He believes that empowering women can go a long way to achieving population reduction, though misogyny in many parts of the world makes that difficult.

Another complicating factor is a continued push from countries to avoid population decline and to pursue growth. The result is that we are “living in ecological debt.” He would like to see economists pay more attention to ecology. “The idea that human beings … are utterly dependent on the ecological systems of the planet for their very existence … is just not clear enough to people.” He questions whether we can successfully push for “de-growth” when our countries have GDP as their guiding metric.

Are we having enough frank discussions about all of this? How do we make them productive?

Ehrlich believes we should be having more honest conversations about the danger that humanity is in. “There is certainly a feeling among my colleagues that we’ve got to get out there and tell the truth,” he said, referring to an article he and others wrote titled “Underestimating the Challenges of Avoiding a Ghastly Future.” He attributes our reluctance to engage openly on difficult topics to our evolution as “small-group animals”, for whom social ties take precedence over other things. “Fitting in has become much more important to us than doing what is right,” he says. “Our urge is to be with the group and to not offend others.”

As an example of a problem we are not talking about enough, Ehrlich mentions the number of people living in areas that are starting to experience wet bulb temperatures so high that human bodies cannot cool down. This is a critical issue for survivability. How can we get societies to cooperate on large issues like this? “We really do need to get together, as a species, as a civilization, and solve a lot of problems… You can’t solve the climate dilemma in one country. You can’t solve the feeding humanity dilemma in one country.”

Should we be optimistic?

On the one hand, Ehrlich has seen people quickly change their consumption. He looks to World War II, where Americans rationed fuel and beef and other items when we were incentivized to do so. He thinks it’s possible that at some point the impact of climate change will be immediate enough that people will respond in similar fashion. But ultimately he is not optimistic that will happen. “There are lots of things we could do, none of which I think we will do.”

On that happy note, what are your thoughts on some of these questions? How should we rein in our environmental debt, for the sake of our children and their children?

Current Climate Data

Global impacts (January 2024), US impacts (January 2024), CO2 metric, Climate dashboard

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Notes and References

  1. Ehrlich had a pretty amusing auto-response to my email asking for an interview: “Due to the flood of emails largely over political issues, but also because of heavy “normal” work commitments and my failing eyesight, Anne and I, retired in our early 90s, can no longer respond to every email. If you are not a close friend or colleague a response may be delayed — forever.” ↩︎
  2. As one example of this, Hagens observes that the US has 4.5% of the world’s population but 50% of the world’s medical prescriptions, and wonders: “Are we sicker? Are we babies? Are we over-prescribing?” ↩︎

Climate change, despite its outsized impact on the planet, is still an abstract concept to many of us. That needs to change. My hope is that readers of this blog will develop a better understanding of...

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13 Comments

  1. Sherry,
    Thank you for your always on-point educational blog. It is the main reason I continue to remain a Palo Alto On-line subscriber.

    Keep up the good work!

  2. In the past I have stressed that over population is an important factor in dealing with climate change, etc. You have rebutted that argument on several occasions. Has Ehrlich changed you mind at all. After all, everyone consumes and pollutes.

    1. Neal, thanks for reading and for the comment. FWIW, the post that I wrote on population a while back is here: https://www.paloaltoonline.com/blogs/2020/05/17/the-weird-thing-about-population-growth/

      My 2c: I don’t agree with everything Ehrlich says (e.g., that point about not taking personal responsibility). But I am 100% a fan of empowering women, and I am happy to see birth rates coming down in countries where consumption is highest. I also very much want to see clean energy being used in developing economies where population growth is highest — it is super important. (People were really mad that China was trying to sell/build coal plants there, but it backed off.)

      If I understand correctly, Ehrlich was primarily concerned with food and water shortages wrt population growth, and I have never looked at that. I’ve only looked at this through “climate” eyes, and since population growth is highest where emissions are minimal, it hasn’t seemed as big of an issue (as long as growth is clean). I have also thought that reducing population is a lot harder than alternatives, and my thinking was it would be harmfully divisive. But I don’t know. It’s not easy to tell people to consume less either…

    2. I am with Sherry. Overpopulation is effectively a non-issue as it’s not something we in United States can do much about. Populations in practically all wealthy countries are already declining. Empowering women and increasing income of current high-birth rate countries (hopefully with less emission) will bring down population growth. To bring down emission in United States, it’s all about politics. Carbon tax (with income-based refund) would change the economics of the energy sources, but is a non-starter in the States.

  3. You said you are looking at things through “climate” eyes and that is the problem. Look at the bigger picture. Look what 8 billion people are doing to the planet besides climate change….polluting oceans, polluting rivers and lakes, polluting the air, draining aquifers, destroying rain forests, building dams, habitat destruction, litter, acid rain, ozone holes, over fishing the oceans, over grazing wild lands, etc., etc., etc.

    The Earth has a “fever.” Fevers are caused by pathogens. Humans are the planet’s pathogens. You can’t reduce the fever while increasing the number of pathogens. Symptomatic relief by picking the low hanging fruit is not a cure.

    1. There is no doubt that people have proven to be a scourge on the planet. Global population is going to naturally decline, as it already is in developed countries, but if it’s not fast enough, what policy proposals have been put forward to quickly drive down population? Vaccine refusal seems to be effective but controversial and expensive. Birth control seems more humane but politically challenging. On the technocrat side, I can imagine some kind of trading/immigration bloc restricted to countries with a birth rate < 2.1, though China would outrank us there. Then other countries are left to just fend for themselves? Would you limit families in the US to two kids? Stop providing assistance to larger families? Mandatory vasectomies? It’s always seemed to me to be easier to get people to just eat less meat, but there are no straight-forward policies there either. What policies do population people propose that are not racist or xenophobic or misogynistic or … ?

      1. Interesting that birth decline in developed countries is causing concern as the population ages and there are not enough young taxpayers to support the system. Italy is one country that is encouraging young women to have babies, earlier and more often.

  4. There is little evidence that global population will decline naturally. The growth RATE my be decline, but not total population. At what point does one say “enough is enough? Is it 9 billion, 15 billion, 20 billion?

    There will always be people that pull the race card, xenophobic card, misogynist card, etc. to promote their victimhood status. They should be ignored.

    Start by putting pressure on foreign governments to stop encouraging people to have more babies. Then eliminate the tax deduction for children and give tax breaks to couples that are childless. Money talks.

    Endless population growth and economic growth is a fools errand.

    1. @KOhlson, thanks. I should have included a reference. If you don’t have access to the NY Times, the UN maintains a very good population dashboard here, and you can view charts here. For example, you can see projected global population here.

  5. Social science is very much a neglected part of all this. From gas prices causing the “yellow vest” protests in France, to the current farmer protests based partly on objections to new green policies, actually implementing plans for a better planet is very, very hard. Without a LOT of analysis and insight, these things might very well end up toppling the governments trying to implement them. Same thing with population declines. Too much, too fast, and things will get very ugly. There has to be deep, cultural desire to put up with what will amount to austerity–not something any culture has a history of doing. Hence, the need for a lot more work on that main component.

    1. @Tim, I really agree with what you say. I’m not sure how much is “austerity” vs “less waste”, but it’s still a massive change in culture for our society, which almost prizes its ability to waste. How to change a culture? I unfortunately think things have to get pretty bad before that happens, and that can easily mean that by then we have passed tipping points. You kind of see that starting to happen. Ugh. Just as we need to start doing geoengineering experiments, we need to start doing social science experiments. Maybe that’s what states are for?

      Anyway, thanks for taking the time to comment!

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