In conversation with Current Conservation

30 11 2016

bradshaw-tinkering-with-warIn August I had the pleasure of visiting the National Centre for Biological Sciences in Bengaluru, India, and while there I was interviewed by Hari Sridhar of Current Conservation. I admit that I haven’t always fully appreciated the excellent conservation reporting done by Current Conservation, and now after having been interviewed by them, I’m becoming more aware of their value (and not just because I appear in their latest issue). I really encourage CB.com readers to check it out.

In a paper published in the Proceedings of the National Academy of Sciences USA in 2014, Corey Bradshaw and Barry Brook argued that, given the current momentum of human population growth, no demographic “quick fixes” will be enough to change its trajectory in the near future. Therefore, environmental policy will be served better by prioritising measures such as technological and social innovation and reductions in consumption, while treating population reduction as a long-term goal. On his recent visit to Bengaluru, I spoke to Corey Bradshaw about the genesis of this study and its implications.

Hari Sridhar: You say “our models clearly demonstrate that the current momentum of the global human population precludes any demographic “quick fixes.” If that is the case, what do you suggest should be done instead?

Corey Bradshaw: I’ll back up a little bit and give you some of the context for writing the paper, which will sort of explain the title and that particular conclusion. Often when I gave public seminars, where I would talk about some environmental problem and future predictions of its worsening, some member of the audience would stand up at the end and say: “Well, the problem is humans. There are just too many of us. So all we need to do is focus on reducing the human population and we will fix all of these other problems.” That came up so often that I began to think: “Well, how quickly could we fix the overpopulation problem?”

Being, among other things, a population dynamics modeller, I decided I could model the human population just as well to look at that question. What would it take and how long for human population to start to decline, either from interventions or catastrophes? Human demographers don’t typically consider catastrophe scenarios when they project human populations. It’s instead done under very strict policy criteria, typically under the expected status quo, with some slight variation in things like family planning and structural change, you know, things like age structure. But we decided to try out more extreme scenarios as well to address that question. So first we said “let’s just see what happens when we only adjust fertility”. We did that and the population trajectory was more or less insensitive.

Then we said “let’s see what happens if we impose mass mortality events of various types — a third world war, pandemics, nuclear warfare” — and still the population was fairly resistant, even to these big changes. What we took away from these results was this: yes, population size must be addressed and we should have started looking into this seriously, probably post World War 2 when we were just under two billion people. We need to address overpopulation, but it’s not going to be something that can be fixed suddenly or be reduced anytime in the next few decades. It’s a century-scale issue. Should we be aiming to reduce the total human population? Yes. Should we be encouraging fertility reduction and family planning? Yes. It’s just that these will have positive outcomes at the century scale. Now most of our environmental problems are not things that we can ignore for a century. They have to be dealt with now. So our argument basically was that if we can’t address the human population problem, in the sense of reducing its size quickly, then we need to turn our attention to more immediate fixes, such as addressing consumption and various environmental mitigation policies. That was our main message. But in so doing we managed to anger both sides of the ideological position on the human population debate. In saying that something must be done but it can’t be done quickly, we upset the low-growth proponents. And by saying that we should nevertheless aim for long-term population reduction, we upset the people who are utterly opposed to any sort of fertility reduction or any action on human population growth.

HS: That’s something I want to ask you about — tell us about the attention this paper got within academia and in the media.

CB: Yeah, in the academic setting it was interesting. There were only a few critiques written about the paper and they were fairly weak. As the saying goes “All models are wrong but some are useful”, but what our model said was defensible. I suppose some of the terminology and the interpretation were points of contention with some people, but by and large the scientific community was satisfied with the result. But in the media it was completely different. Almost every single journalist I talked to put a particular slant on the results. Because of those two diametrically opposite opinions, people appeared to read anything they wanted to into it. Most people in the media didn’t of course read the paper. They read the title and maybe the abstract and the odd sentence here and there, and took from that whatever their ideological position dictated. There was right-wing media, there was left-wing media, and each had its own bias. I think only a handful of interviewers seemed to grasp the concept, which I didn’t think was that difficult. It also got a lot of responses on these comment streams. I don’t read those most of the time, but there are a lot of crazy people on the internet now. I got all sorts of hate mail, and even indirect death threats. Not serious ones. Just some random person telling me I should be removed from the face of the planet, and things like that. That happens from time to time when you deal with controversial topics.

HS: In the paper, you come up with some figures for what the population will be in 2100, under different scenarios. Could you tell us how much uncertainty there was around these figures?

CB: There was probably much less uncertainty than for most other species that are modelled. Humans tend to census themselves fairly well and we have a reasonable understanding of how many of us there are right now. While demographic data like age-specific survival rates are missing from some parts of the world, generally speaking at the scale of regions it’s well-known. So in terms of measurement error, the current and even the trends in those demographic rates are robust. Some of the assumptions, such as how much longer we’ll live given future medical innovations, are somewhat uncertain. But as it turns out, we are living so long now that even slight adjustments to longevity don’t make much difference in the long-term to total population size. And even large assumptions about, say, juvenile mortality, don’t make a huge difference because for a long-lived mammal the most important parameter that modifies population growth generally is the survival of breeding females. And breeding-age woman around the world tend to have the highest survival rates, so all the other parameters have smaller effects on population size. So while environmental variability has a large effect on small populations, it has a comparatively small effect on large populations. And we are a very large population. Incorporating a lot of uncertainty didn’t really make much of a difference. But the future scenarios were uncertain – will there be a war, will there be climate change reductions in food availability that will lead to higher juvenile mortality, etc.? We know little about the probability these things will occur and how important they’ll be. Read the rest of this entry »





What immigration means for Australia’s climate-change policies

12 06 2016

After dipping my foot into the murky waters of human population demography a few years ago, I’m a little surprised that I find myself here again. But this time I’m not examining what the future of the global human population might be and what it could mean for our environment; instead, I’m focussing on Australia’s population future and its implications for our greenhouse-gas emissions trajectories.

Just published in Asia and the Pacific Policy Forum1, my paper with long-time co-author Barry Brook is entitled Implications of Australia’s population policy for future greenhouse gas emissions targets. It deals with the sticky question of just how many people Australia can ‘afford’ to house. By ‘afford’ I mean several things, but most specifically in the context of this paper is by how much we need to reduce our per capita emissions to achieve future reduction targets under various immigration-rate scenarios.

In many ways Australia’s population is typical of other developed nations in that its intrinsic fertility (1.78 children/woman) is below replacement (which is itself ~ 2.1 children/female). Yet Australia’s population grew nearly twice (1.88×) as large from 1971 to 2014. It doesn’t take a genius to figure out that most of our population growth is due to net immigration.

In fact, between 2006 and 2014, Australia welcomed a net of 215,000 new people per year (this means that of all the permanent immigrants and emigrants, a ‘net’ of approximately 215,000 stayed each year), which represents about 1% of our total population size (that latter most likely just ticked over 24 million). Read the rest of this entry »





Could we colonise another planet to save this one?

27 10 2015

© Auston Habershaw

Let’s do a little thought experiment, shall we? The late, great Douglas Adams wrote about a planet (Golgafrincham) that decided to ship all its undesirables (it was not made clear to them that they were in fact considered ‘undesirable’) to another planet to cut their population by a third. As it turns out, it wasn’t such a great idea.

This idea — shipping people to another planet — is a common theme in the sci-fi genre when there is an impending disaster, such as the planet becoming unsustainable, too many humans over-consuming, or because some great natural calamity is about to occur. Many think Mars is the most likely possible place to get the first sustainable human colony going, but it’s going to be a logistical nightmare to put together even a small colony.

Could moving to a planet like Mars stem the inexorable increase in the human population and save planet Earth? Not likely, and here’s why.

Let’s throw caution to the wind and make some outlandish assumptions just to make this point even stronger.

Read the rest of this entry »





How things have (not) changed

13 04 2015

The other night I had the pleasure of dining with the former Australian Democrats leader and senator, Dr John Coulter, at the home of Dr Paul Willis (Director of the Royal Institution of Australia). It was an enlightening evening.

While we discussed many things, the 84 year-old Dr Coulter showed me a rather amazing advert that he and several hundred other scientists, technologists and economists constructed to alert the leaders of Australia that it was heading down the wrong path. It was amazing for three reasons: (i) it was written in 1971, (ii) it was published in The Australian, and (iii) it could have, with a few modifications, been written for today’s Australia.

If you’re an Australian and have even a modicum of environmental understanding, you’ll know that The Australian is a Murdochian rag infamous for its war on science and reason. Even I have had a run-in with its outdated, consumerist and blinkered editorial board. You certainly wouldn’t find an article like Dr Coulter’s in today’s Australian.

More importantly, this 44 year-old article has a lot today that is still relevant. While the language is a little outdated (and sexist), the grammar could use a few updates, and there are some predictions that clearly never came true, it’s telling that scientists and others have been worrying about the same things for quite some time.

In reading the article (reproduced below), one could challenge the authors for being naïve about how society can survive and even prosper despite a declining ecological life-support system. As I once queried Paul Ehrlich about some of his particularly doomerist predictions from over 50 years ago, he politely pointed out that much of what he predicted did, in fact, come true. There are over 1 billion people today that are starving, and another billion or so that are malnourished; combined, this is greater than the entire world population when Paul was born.

So while we might have delayed the crises, we certainly haven’t averted them. Technology does potentially play a positive role, but it can also increase our short-term carrying capacity and buffer the system against shocks. We then tend to ignore the indirect causes of failures like wars, famines and political instability because we do not recognise the real drivers: resource scarcity and ecosystem malfunction.

Australia has yet to learn its lesson.

To Those Who Shape Australia’s Destiny

We believe that western technological society has ignored two vital facts: Read the rest of this entry »