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 »





Inexorable rise of human population pressures in Africa

31 08 2016
© Nick Brandt

© Nick Brandt

I’ve been a bit mad preparing for an upcoming conference, so I haven’t had a lot of time lately to blog about interesting developments in the conservation world. However, it struck me today that my preparations provide ideal material for a post about the future of Africa’s biodiversity.

I’ve been lucky enough to be invited to the University of Pretoria Mammal Research Unit‘s 50th Anniversary Celebration conference to be held from 12-16 September this year in Kruger National Park. Not only will this be my first time to Africa (I know — it has taken me far too long), the conference will itself be in one of the world’s best-known protected areas.

While decidedly fortunate to be invited, I am a bit intimidated by the line-up of big brains that will be attending, and of the fact that I know next to bugger all about African mammals (in a conservation science sense, of course). Still, apparently my insight as an outsider and ‘global’ thinker might be useful, so I’ve been hard at it the last few weeks planning my talk and doing some rather interesting analyses. I want to share some of these with you now beforehand, although I won’t likely give away the big prize until after I return to Australia.

I’ve been asked to talk about human population pressures on (southern) African mammal species, which might seem simple enough until you start to delve into the complexities of just how human populations affect wildlife. It’s simply from the perspective that human changes to the environment (e.g., deforestation, agricultural expansion, hunting, climate change, etc.) do cause species to dwindle and become extinct faster than they otherwise would (hence the entire field of conservation science). However, it’s another thing entirely to attempt to predict what might happen decades or centuries down the track. Read the rest of this entry »





Cartoon guide to biodiversity loss XXXV

8 03 2016

Another six biodiversity cartoons for you this week (see here for why I provide six each time). See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.

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Human population size: speeding cars can’t stop quickly

28 10 2014

Stop breeding cartoon-Steve Bell 1994Here at ConservationBytes.com, I write about pretty much anything that has anything remotely to do with biodiversity’s prospects. Whether it is something to do with ancient processes, community dynamics or the wider effects of human endeavour, anything is fair game. It’s a little strange then that despite cutting my teeth in population biology, I have never before tackled human demography. Well as of today, I have.

The press embargo has just lifted on our (Barry Brook and my) new paper in PNAS where we examine various future scenarios of the human population trajectory over the coming century. Why is this important? Simple – I’ve argued before that we could essentially stop all conservation research tomorrow and still know enough to deal with most biodiversity problems. If we could only get a handle on the socio-economic components of the threats, then we might be able to make some real progress. In other words, we need to find out how to manage humans much more than we need to know about the particulars of subtle and complex ecological processes to do the most benefit for biodiversity. Ecologists tend to navel-gaze in this arena far too much.

So I called my own bluff and turned my attention to humans. Our question was simple – how quickly could the human population be reduced to a more ‘sustainable’ size (i.e., something substantially smaller than now)? The main reason we posed that simple, yet deceptively loaded question was that both of us have at various times been faced with the question by someone in the audience that we were “ignoring the elephant in the room” of human over-population.

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Cartoon guide to biodiversity loss XXV

8 09 2014

Here are 6 more biodiversity cartoons for your conservation-humour fix (see full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here).

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