A few weeks ago we published a paper that was in the works for a long time, so long in fact that one of my co-authors died before it was published online.
That co-author was none other than the legendary Paul Ehrlich of Stanford University, and of The Population Bomb fame (and infamy). More importantly, but often overlooked, Paul wrote more than 700 scientific articles and 30 books during his career.
Paul Ehrlich died on 13 March 2026 at the ripe old age of 93, exactly two weeks before our article appeared online. Paul had a good innings no doubt, but I wish he had survived long enough to see what might very well be his last co-authored paper.
I first met Paul back in the mid-2000s during a trip through San Francisco. I had organised to come chat with Professor Gretchen Daily at Stanford, and Paul came along for lunch. I remember vividly how we clicked almost immediately.
We clicked so well in fact, that we wrote a book together, co-authored several high-impact papers (e.g., ‘ghastly future‘), spent a month in Bellagio as Rockefeller Foundation writing residents, participated in various public and parliamentary presentations, and generally just got on like a house on fire. Paul and his wife Ann became like family, so much so that they were de facto grandparents to my daughter who grew up with them in near-annual contact.
This post isn’t about Paul per se, but I cannot ignore the profound influence Paul had on my career, my personality, and my life view. I miss him. I am therefore dedicating this paper and post to his memory. So long, and thanks for all the fish.
Back to the paper in question.
The paper (Global human population has surpassed Earth’s sustainable carrying capacity) has already been downloaded nearly 23,000 times since it was published less than a month ago. It has an Altmetric score of 543, and is currently the top-trending paper in Environmental Research Letters.
Nothing like writing about human population to get the punters engaged.

We show empirically that the Earth has already exceeded its ability to support the global human population sustainably, with dire implications for increasing pressure on food security, climate stability, and human wellbeing. However, slowing population growth and raising global awareness could still offer us some hope.
Our study shows that humans have pushed well beyond the planet’s long-term carrying capacity and that continued growth under current patterns of consumption will intensify environmental and social challenges for communities worldwide.
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Back in March this year before much of the world morphed into the weirdness that now dictates all facets of life, I wrote
The very worn slur of “neo-Malthusian”
7 09 2021After the rather astounding response to our Ghastly Future paper published in January this year (> 443,000 views and counting; 61 citations and counting), we received a Commentary that was rather critical of our article.
We have finally published a Response to the Commentary, which is now available online (accepted version) in Frontiers in Conservation Science. Given that it is published under a Creative Commons Attribution License (CC BY), I can repost the Response here:
In their comment on our paper Underestimating the challenges of avoiding a ghastly future, Bluwstein et al.2 attempt to contravene our exposé of the enormous challenges facing the entire human population from a rapidly degrading global environment. While we broadly agree with the need for multi-disciplinary solutions, and we worry deeply about the inequality of those who pay the costs of biodiversity loss and ecological collapse, we feel obligated to correct misconceptions and incorrect statements that Bluwstein et al.2 made about our original article.
After incorrectly assuming that our message implied the existence of “one science” and a “united scientific community”, the final paragraph of their comment contradicts their own charge by calling for the scientific community to “… stand in solidarity”. Of course, there is no “one science” — we never made such a claim. Science is by its nature necessarily untidy because it is a bottom-up process driven by different individuals, cultures, perspectives, and goals. But it is solid at the core. Scientific confluence is reached by curiosity, rigorous testing of assumptions, and search for contradictions, leading to many — sometimes counter-intuitive or even conflicting — insights about how the world works. There is no one body of scientific knowledge, even though there is good chance that disagreements are eventually resolved by updated, better evidence, although perhaps too slowly. That was, in fact, a main message of our original article — that obligatory specialisation of disparate scientific fields, embedded within a highly unequal and complex socio-cultural-economic framework, reduces the capacity of society to appreciate, measure, and potentially counter the complexity of its interacting existential challenges. We agree that scientists play a role in political struggles, but we never claimed, as Bluwstein et al.2 contended, that such struggles can be “… reduced to science-led processes of positive change”. Indeed, this is exactly the reason our paper emphasized the political impotence surrounding the required responses. We obviously recognize the essential role social scientists play in creating solutions to avoid a ghastly future. Science can only provide the best available evidence that individuals and policymakers can elect to use to inform their decisions.
We certainly recognise that there is no single policy or polity capable of addressing compounding and mounting problems, and we agree that that there is no “universal understanding of the intertwined socio-ecological challenges we face”. Bluwstein et al.2 claimed that we had suggested scientific messaging alone can “… adequately communicate to the public how socio-ecological crises should be addressed”. We did not state or imply such ideas of unilateral scientific power anywhere in our article. Indeed, the point of framing our message as pertaining to a complex adaptive system means that we cannot, and should not, work towards a single goal. Instead, humanity will be more successful tackling challenges simultaneously and from multiple perspectives, by exploiting manifold institutions, technologies, approaches, and governances to match the complexity of the predicament we are attempting to resolve.
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Tags: commentary, complex adaptive system, consumption, critique, human population, Malthusian, neo-Malthusian, over-population, overshoot, Population
Categories : agriculture, anthropocene, biodiversity, climate change, demography, economics, education, Endarkenment, environmental economics, environmental policy, extinction, food, governance, human overpopulation, poverty, science, societies, sustainability