Why a shrinking human population is a good thing

30 06 2022

The other day I was asked to do an interview for a South Korean radio station about the declining-population “crisis”.

Therein lies the rub — there is no crisis.

While I think the interview went well (you can listen to it here), I didn’t have ample time to flesh out my arguments; I’ve decided to put them down in more detail here.

Probably the most important aspect that I didn’t even get a chance to cover is that globally, our economic system is essentially broken because we are forced to exist inside a paradigm that erroneously assumes Earth’s resources are infinite. They are not, as the global ecological footprint clearly shows.

To slow and perhaps even reverse climate change, as well as mitigate the extinction crisis underway, we are obliged to reduce consumption globally. Shrinking human populations will contribute to that goal (provided we simultaneously reduce per-capita consumption).

But that argument, no matter how defensible, is still not even remotely appreciated by most people. It is the aim of only a minority, most of whom have very little political power to engender change.

The oft-touted ‘crisis‘ of ageing populations is founded on the erroneous notion that it will lead to economic crises for the affected countries. Indeed, countries like South Korea and Japan have declining populations, others like Italy are stable and will be declining soon, and others like Australia are only growing because of net immigration.

The reason for the hyped-up panic generally comes down to the overly simplistic ‘dependency ratio‘, which has several different forms but generally compares the number of people in the labour force against those who have retired from it. The idea here is that once the number of people no longer in the labour force exceeds the number of those in the labour force, the latter can no longer support the entirety of the former.

This simplistic 1:1 relationship essentially assumes that you need one person working to support one retired person. Errrh. Right. Let’s look at this in more detail.

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The sixth mass extinction is happening now, and it doesn’t look good for us

2 03 2022

Mounting evidence is pointing to the world having entered a sixth mass extinction. If the current rate of extinction continues we could lose most species by 2200. The implication for human health and wellbeing is dire, but not inevitable.

In the timeline of fossil evidence going right back to the first inkling of any life on Earth — over 3.5 billion years ago — almost 99 percent of all species that have ever existed are now extinct. That means that as species evolve over time — a process known as ‘speciation’ — they replace other species that go extinct.

Extinctions and speciations do not happen at uniform rates through time; instead, they tend to occur in large pulses interspersed by long periods of relative stability. These extinction pulses are what scientists refer to as mass extinction events.

The Cambrian explosion was a burst of speciation some 540 million years ago. Since then, at least five mass extinction events have been identified in the fossil record (and probably scores of smaller ones). Arguably the most infamous of these was when a giant asteroid smashed into Earth about 66 million years ago in what is now the Gulf of Mexico. The collision vapourised species immediately within the blast zone. Later, species were killed off by climate change arising from pulverised particulates suspended in the atmosphere, as well as intense volcano activity stimulated by the buckling of the Earth’s crust from the asteroid’s impact. Together, about 76 percent of all species around at the time went extinct, of which the disappearance of the dinosaurs is most well-known. But dinosaurs didn’t disappear altogether — the survivors just evolved into birds.

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Need human census data for any of your analyses? Follow these simple steps

25 02 2022

As someone who regularly delves into human demography — often from a conservation perspective — I’m always on the lookout for quick and easy ways to get the latest and greatest datasets. Whether it’s for projection human populations, or just getting country-specific population densities, I’ve found a really nice way to interface great human data with R.

In this particular example, I’m using a api (application programming interface) key to access live data on the US Census Bureau server (don’t worry — they have global data, not just those specific to the US). What’s an ‘api key’? It’s just a code that gives you permission to access the server directly from an application via an internet link.

Step 1. Apply for an api key

This is a straightforward process and just needs to be done via this URL. The approval process doesn’t take long.

Step 2: Install the idbr package in R

This stands for the ‘(US Census Bureau) International Data Base (R)’, and grants access to and queries demographic data, including contemporary, historical, and future projections to 2100 for countries with ≥ 5000 people.


Step 3: Set api key

You need to set your user api using the following commands:


Step 4. Get data

Using the get_idb() command, you can specify all sorts of queries to get various levels of data complexity. All the variable combinations for the international database are described well here.

Example 1. Life expectancy

Let’s say you wanted to plot a map of the world with the shading of a country related to its average life expectancy at birth. First we get the necessary data:

lex.dat <- idbr::get_idb(
country = “all”,
year = 2022,
variables = c(“name”, “e0”),
geometry = T)

The ensuing lex.dat object looks like this:

Simple feature collection with 6 features and 4 fields
Geometry type: MULTIPOLYGON
Dimension: XY
Bounding box: xmin: -73.41544 ymin: -55.25 xmax: 75.15803 ymax: 42.68825
code year name e0 geometry
1 AF 2022 Afghanistan 53.65 MULTIPOLYGON (((61.21082 35…
2 AO 2022 Angola 62.11 MULTIPOLYGON (((16.32653 -5…
3 AL 2022 Albania 79.47 MULTIPOLYGON (((20.59025 41…
4 AE 2022 United Arab Emirates 79.56 MULTIPOLYGON (((51.57952 24…
5 AR 2022 Argentina 78.31 MULTIPOLYGON (((-65.5 -55.2…
6 AM 2022 Armenia 76.13 MULTIPOLYGON (((43.58275 41

Read the rest of this entry »

Avoiding a ghastly future — The Science Show

1 10 2021

Just thought I’d share the audio of an interview I did with the famous Robyn Williams of ABC Radio National‘s The Science Show.

I’d be surprised if any Australians with even a passing interest in science could claim not to have listened to the Science Show before, and I suspect a fair mob of people overseas would be in the same boat.

It was a real privilege to talk with Robyn about our work on the ghastly future, and as always, the production value is outstanding.

Thank you, Robyn and the ABC.

Listen below, or link to the interview directly.

The very worn slur of “neo-Malthusian”

7 09 2021

After 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.

A Malthusian slur

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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Climate change will also make us more stupid

31 08 2021

Most people are at least vaguely aware that climate change isn’t good for us.

Let’s consider the obvious direct health effects, like heat exhaustion and stroke, dehydration, increased inhalation of particulate matter from bushfires and other pollutant sources, greater expression of allergies, higher incidence of cardiovascular and respiratory diseases, greater injury rates, and higher probability of disease transmission from flooding events (see review here).

Let’s not forget the rising incidence of mental illness either.

Then there are the climatic events that increase the probability of dying violently like in a bushfire or a flood, getting caned in a major storm by debris, personal injury from storm surges exacerbated by rising sea levels, or dying slowly due to undernutrition from crop failures.

Some of the more indirect, yet just-as-insidious repercussions are those climate-driven events that worsen all of the above, such as increasing poverty, rising violent interactions (both individual-level and full-on warfare), loss of healthcare capability (less infrastructure, fewer doctors), and increased likelihood of becoming a refugee.

So, when someone says increased warming at the pace we’re witnessing now isn’t a problem, tell them they’re full of shit.

But wait! There’s more!

Yes, climate change will also make us more stupid. Perhaps one of the lesser-appreciated byproducts of an increasingly warmer world driven by rising greenhouse-gas concentrations is the direct effects of carbon dioxide on a variety of physiological functions.

Read the rest of this entry »

It’s a tough time for young conservation scientists

24 08 2021

Sure, it’s a tough time for everyone, isn’t it? But it’s a lot worse for the already disadvantaged, and it’s only going to go downhill from here. I suppose that most people who read this blog can certainly think of myriad ways they are, in fact, still privileged and very fortunate (I know that I am).

Nonetheless, quite a few of us I suspect are rather ground down by the onslaught of bad news, some of which I’ve been responsible for perpetuating myself. Add lock downs, dwindling job security, and the prospect of dying tragically due to lung infection, many have become exasperated.

I once wrote that being a conservation scientist is a particularly depressing job, because in our case, knowledge is a source of despair. But as I’ve shifted my focus from ‘preventing disaster’ to trying to lessen the degree of future shittyness, I find it easier to get out of bed in the morning.

What can we do in addition to shifting our focus to making the future a little less shitty than it could otherwise be? I have a few tips that you might find useful:

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Cartoon guide to biodiversity loss LXVI

29 05 2021

Here is the third set of biodiversity cartoons for 2021. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.

Read the rest of this entry »

A perfect storm of global ineptitude

18 03 2021

Given the ‘success’ (i.e., a lot of people seem to be reading it) of our recent Ghastly Future paper, I thought it would be interesting to go back and have a look at what we wrote in our 2015 book Killing the Koala on the subject. I think you’ll find that if anything we were probably overly optimistic.

An updated digest of that material follows.

When your accountant tells you to reduce expenditure, you do it or risk bankruptcy; when your electrician tells you the wiring in your house is dodgy, you replace it or risk your family dying in an avoidable fire; when your doctor tells you your cholesterol is too high, you cut back fat intake (and/or take cholesterol-reducing drugs) or risk a heart attack.

Yet few with any real political or financial power heed the warnings of environmental scientists. It is not just a few of us either — globally, ecologists, conservation biologists and environmental scientists are united in telling the world (for decades now) that growth in population and consumption cannot go on forever. They have been united in telling us if we do not clean up our planet, our life-support systems could ultimately fail.

There are now nearly eight billion people on Earth, and median projections suggest that the population will grow to ten billion or more by the end of the century. Some analyses indicate that with present technologies, Earth could only sustainably support indefinitely some 5 billion people under best-case scenarios, but assuming similar proportions of poverty and suffering as we have today. Others imply that 5 billion could be many too many.

As a result, humanity is entering that near-perfect storm of problems driven by overpopulation, overconsumption, gross inequalities, and the use of needlessly environmentally damaging technologies. The problems include the intertwined dilemmas of loss of the biodiversity that runs human life-support systems, climate disruption, energy shortages, global toxification, alteration of critical biogeochemical cycles, shortages of water, soil, mineral resources and farmland, and increasing probability of vast epidemics (as COVID-19 poignantly exemplifies).

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Worried about Earth’s future? Well, the outlook is worse than even scientists can grasp

14 01 2021

Daniel Mariuz/AAP

Corey J. A. Bradshaw, Flinders University; Daniel T. Blumstein, University of California, Los Angeles, and Paul Ehrlich, Stanford University

Anyone with even a passing interest in the global environment knows all is not well. But just how bad is the situation? Our new paper shows the outlook for life on Earth is more dire than is generally understood.

The research published today reviews more than 150 studies to produce a stark summary of the state of the natural world. We outline the likely future trends in biodiversity decline, mass extinction, climate disruption and planetary toxification. We clarify the gravity of the human predicament and provide a timely snapshot of the crises that must be addressed now.

The problems, all tied to human consumption and population growth, will almost certainly worsen over coming decades. The damage will be felt for centuries and threatens the survival of all species, including our own.

Our paper was authored by 17 leading scientists, including those from Flinders University, Stanford University and the University of California, Los Angeles. Our message might not be popular, and indeed is frightening. But scientists must be candid and accurate if humanity is to understand the enormity of the challenges we face.

Girl in breathing mask attached ot plant in container

Humanity must come to terms with the future we and future generations face. Shutterstock

Getting to grips with the problem

First, we reviewed the extent to which experts grasp the scale of the threats to the biosphere and its lifeforms, including humanity. Alarmingly, the research shows future environmental conditions will be far more dangerous than experts currently believe. Read the rest of this entry »

Time for a ‘cold shower’ about our ability to avoid a ghastly future

13 01 2021

I wish it need not have happened in my time,” said Frodo. “So do I,’ said Gandalf, “and so do all who live to see such times. But that is not for them to decide. All we have to decide is what to do with the time that is given us.”

Frodo Baggins and Gandalf, The Fellowship of the Ring

Today, 16 high-profile scientists and I published what I describe as a ‘cold shower’ about society’s capacity to avoid a ghastly future of warfare, disease, inequality, persecution, extinction, and suffering.

And it goes way beyond just the plight of biodiversity.

No one who knows me well would mistake me for an optimist, try as I might to use my colleagues’ and my research for good. Instead, I like to describe myself as a ‘realist’. However, this latest paper has made even my gloomier past outputs look downright hopeful.

And before being accused of sensationalism, let me make one thing abundantly clear — I sincerely hope that what we describe in this paper does not come to pass. Not even I am that masochistic.

I am also supportive of every attempt to make the world a better place, to sing about our successes, regroup effectively from our failures, and maintain hope in spite of evidence to the contrary.

But failing to acknowledge the magnitude and the gravity of the problems facing us is not just naïve, it is positively dangerous and potentially fatal.

It is this reason alone that prompted us to write our new paper “Underestimating the challenges of
avoiding a ghastly future
” just published in the new journal, Frontiers in Conservation Science.

Read the rest of this entry »

Cartoon guide to biodiversity loss LXIII

26 10 2020

The sixth set of biodiversity cartoons for 2020. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.

Read the rest of this entry »

Grand Challenges in Global Biodiversity Threats

8 10 2020

Last week I mentioned that the new journal Frontiers in Conservation Science is now open for business. As promised, I wrote a short article outlining our vision for the Global Biodiversity Threats section of the journal. It’s open-access, of course, so I’m also copying here on ConservationBytes.com.

Most conservation research and its applications tend to happen most frequently at reasonably fine spatial and temporal scales — for example, mesocosm experiments, single-species population viability analyses, recovery plans, patch-level restoration approaches, site-specific biodiversity surveys, et cetera. Yet, at the other end of the scale spectrum, there have been many overviews of biodiversity loss and degradation, accompanied by the development of multinational policy recommendations to encourage more sustainable decision making at lower levels of sovereign governance (e.g., national, subnational).

Yet truly global research in conservation science is fact comparatively rare, as poignantly demonstrated by the debates surrounding the evidence for and measurement of planetary tipping points (Barnosky et al., 2012; Brook et al., 2013; Lenton, 2013). Apart from the planetary scale of human-driven disruption to Earth’s climate system (Lenton, 2011), both scientific evidence and policy levers tend to be applied most often at finer, more tractable research and administrative scales. But as the massive ecological footprint of humanity has grown exponentially over the last century (footprintnetwork.org), robust, truly global-scale evidence of our damage to the biosphere is now starting to emerge (Díaz et al., 2019). Consequently, our responses to these planet-wide phenomena must also become more global in scope.

Conservation scientists are adept at chronicling patterns and trends — from the thousands of vertebrate surveys indicating an average reduction of 68% in the numbers of individuals in populations since the 1970s (WWF, 2020), to global estimates of modern extinction rates (Ceballos and Ehrlich, 2002; Pimm et al., 2014; Ceballos et al., 2015; Ceballos et al., 2017), future models of co-extinction cascades (Strona and Bradshaw, 2018), the negative consequences of invasive species across the planet (Simberloff et al., 2013; Diagne et al., 2020), discussions surrounding the evidence for the collapse of insect populations (Goulson, 2019; Komonen et al., 2019; Sánchez-Bayo and Wyckhuys, 2019; Cardoso et al., 2020; Crossley et al., 2020), the threats to soil biodiversity (Orgiazzi et al., 2016), and the ubiquity of plastic pollution (Beaumont et al., 2019) and other toxic substances (Cribb, 2014), to name only some of the major themes in global conservation. 

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New journal: Frontiers in Conservation Science

29 09 2020

Several months ago, Daniel Blumstein of UCLA approached me with an offer — fancy leading a Special Section in a new Frontiers journal dedicated to conservation science?

I admit that my gut reaction was a visceral ‘no’, both in terms of the extra time it would require, as well as my autonomous reflex of ‘not another journal, please‘.

I had, for example, spent a good deal of blood, sweat, and tears helping to launch Conservation Letters when I acted as Senior Editor for the first 3.5 years of its existence (I can’t believe that it has been nearly a decade since I left the journal). While certainly an educational and reputational boost, I can’t claim that the experience was always a pleasant one — as has been said many times before, the fastest way to make enemies is to become an editor.

But then Dan explained what he had in mind for Frontiers in Conservation Science, and the more I spoke with him, the more I started to think that it wasn’t a bad idea after all for me to join.

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Extinction Anxiety

21 05 2020

Earlier this week, the SBS show The Feed did a short segment called ‘Extinction Anxiety’ where I talked with host Alice Matthews about biodiversity extinctions. Given that it has so far only been available in Australia, I made a copy here for others to view.

For more information on the state of global biodiversity, see this previous post.



CJA Bradshaw

Never let a good crisis go to waste

11 05 2020


First published in the Millennium Alliance for Humanity and the Biosphere Blog on 5 May 2020.

by Professor Dan Blumstein (University of California at Los Angeles), Professor Paul Ehrlich (Stanford University), and Corey Bradshaw (Flinders University)

Winston Churchill’s words have never been more important than today as we experience the society- and life-changing consequences of the COVID-19 pandemic.

The extent and severity of the disease is a result of ignoring decades of warnings by scientists about the general deterioration of humanity’s epidemiological environment, and specific warnings about confining live, wild animals in markets. The situation was made even more lethal by ignoring the warnings from epidemiologists and disease ecologists once it became clear that an imminent pandemic most likely arose from this practice. Many countries, including the United States, are still ignoring those warnings and the required actions to lessen the impact.

Accordingly, we should ask ourselves, “what else are we missing?” What other huge problems are hiding in plain sight where science could guide policy to avoid catastrophic future failures? For instance, there are two principal health threats that must be addressed immediately, and we must strike while the iron is hot.

The overuse of antibiotics in agriculture will cause widespread deaths from formerly treatable bacterial diseases because of the evolution of antibiotic resistance in microbes. The evolution of resistance is well-known, predictable, and obvious — not in retrospect, but now. By feeding antibiotics to otherwise healthy livestock, animals can be housed in higher densities and they grow faster. Read the rest of this entry »

Shifting from prevention to damage control

5 05 2020

timeBack in March this year before much of the world morphed into the weirdness that now dictates all facets of life, I wrote an update for the Is This How You Feel project led by Joe Duggan.

It was an exercise in emotional expression not necessarily grounded in empiricism. But in that particular piece, I had written the following line:

Few scientists in my field are still seriously considering avoidance of environmental collapse; instead, the dominant discourse is centred on damage control.

But is this correct? Is this how most scientists in conservation feel today? In a way, this post serves both as a rationale for my expectation, and as a question for the wider community.

My rationale for that contention is that it is undeniable that biodiversity is going down the toilet faster than even some of the most pessimistic of us could have predicted. We are without doubt within the sixth mass extinction event every experienced on the Earth for at least the last 600 million years.

Yet, there have never been more conservation biologists and practitioners. There have never been more international treaties and accords that expressly aim to protect biodiversity.

To assert that we have failed is unhelpful fatalism, yet it cannot be ignored that biodiversity’s predicament and those charged with turning around its fate are not exactly replete with successes. Read the rest of this entry »

Cartoon guide to biodiversity loss LX

8 04 2020

The third set of biodiversity cartoons for 2020 (plus a video treat). See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.

Read the rest of this entry »

Projecting global deaths from covid19

18 03 2020


I know that it’s not the best way to project expected deaths from a pandemic disease, but being something of a demographer, I just couldn’t help myself.

I therefore took the liberty of punching in some basic probabilities into our world population model to see how many people could potentially die from covid19. But this is not an epidemiological model, so I’m probably vastly over-estimating the total death rates.

Nonetheless, the results were revealing.

I first took the expected mortality by age class based on the Chinese data so far. I then assumed a worst-case scenario of a 60% infection rate (i.e., 3 out of 5 of us will eventually catch the virus). I assumed these values across the entire globe (not taking into account greater or lesser susceptibility or probability of death among countries or regions).

I also considered two more scenarios: (i) double the mortality rate (in each age class), and (ii) the disease outbreak lasting two years instead of just one.

The graph below shows the four different outcomes based on these scenarios relative to the baseline (no covid): Read the rest of this entry »

How I feel now about climate change

10 03 2020


‘Bleak No. 2’ by David Vogler

Five years ago I was asked by a researcher at the Australia National University, Joe Duggan, how I ‘felt’ about climate change.

This was part of an original initiative that put a human face on the scientists working on elements of one of society’s greatest existential threats.

Thus, Is This How You Feel? became a massive success in terms of bringing to the world the idea that scientists are also deeply affected by what they see happening around them.

Five years later, Joe asked me and all the other scientists who participated to provide an update on how we feel.

Here’s what I wrote: Read the rest of this entry »

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