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 »





Keeping India’s forests

9 08 2016

I’ve just returned from a short trip to the National Centre for Biological Sciences (NCBS) in Bangalore, Karnataka, one of India’s elite biological research institutes.

Panorama of a forested landscape (Savandurga monolith in the background) just south of Bangalore, Karnataka (photo: CJA Bradshaw)

Panorama of a forested landscape (Savandurga monolith in the background) just south of Bangalore, Karnataka (photo: CJA Bradshaw)

I was invited to give a series of seminars (you can see the titles here), and hopefully establish some new collaborations. My wonderful hosts, Deepa Agashe & Jayashree Ratnam, made sure I was busy meeting nearly everyone I could in ecology and evolution, and I’m happy to say that collaborations have begun. I also think NCBS will be a wonderful conduit for future students coming to Australia.

It was my first time visiting India1, and I admit that I had many preconceptions about the country that were probably unfounded. Don’t get me wrong — many of them were spot on, such as the glorious food (I particularly liked the southern India cuisine of dhosa, iddly & the various fruit-flavoured semolina concoctions), the insanity of urban traffic, the juxtaposition of extreme wealth and extreme poverty, and the politeness of Indian society (Indians have to be some of the politest people on the planet).

But where I probably was most at fault of making incorrect assumptions was regarding the state of India’s natural ecosystems, and in particular its native forests and grasslands. Read the rest of this entry »





Damned by nature; damned by man

26 10 2012

I am a forest officer from India. I want to narrate a story. No, my story is not about elephants or tigers or snakes. Those stories about India are commonplace. I wish to narrate a simple story about people, the least-known part of the marathon Indian fable.

Humans are said to have arrived in India very early in world civilisation. Some were raised here from the seed of their ancestors; others migrated here from all over the world. Over the centuries these people occupied every inch of soil that could support life. The population of India today is 1.2 billion. Each year, India’s population increases by a number nearly equal to the complete population of Australia. Such a prolific growth of numbers is easy to explain; the fertile soil, ample water and tropical warmth of India support the growth of all life forms.

Not all numbers are great, however, and big numbers sometimes exact the price from the wrong persons.

This is my story.

I went to work in the state of Meghalaya in north-eastern India. Pestilence, floods and dense vegetation have made north-eastern India a most inhospitable place. Population is scanty by Indian standards. Life does not extend much beyond the basic chores of finding food and hearth. In the hills, far away from the bustle of modern civilisation, primitive tribal families practice agriculture in its most basic form. Fertilisers are unknown to them, so they cultivate a parcel of land until it loses its fertility, ultimately abandoning it to find other arable land. When the original parcel has finally recovered its fertility after a few years, they move back. It is a ceaseless cycle of migrating back and forth – the so-called practice known as ‘shifting cultivation’.  Ginger, peas, pumpkin, brinjal and sweet potato can be seen growing on numerous slopes in the Garo Hills of Meghalaya beside the huts of the farmers built on stilts, with chickens roosting below.

When I reached Meghalaya and looked about at the kind of world I had never seen before, I admit that I found the tribal folk a little strange. They lived in a way that would have appeared bizarre to a modern community. The people did not seem to know how many centuries had passed them by. For me as a forest officer, what looked worst was that that these people appeared to have no comprehension of the value of forests for the planet. They built their huts with wood. They cooked on firewood. Most of their implements were made of wood. A whole tree would be cut and thrown across the banks to make a bridge over a stream. Above all, their crazy practice of shifting cultivation would ultimately remove all the remaining forest.

I decided my main job in this place was to save the forest from its own people, and we enforced Indian laws to preserve the forests.

On one occasion my staff saw a young local man running with an illegally obtained log of wood and started to chase him, waving their guns in the air to scare him. He ran barefoot amid dense bushes a long distance before we managed to apprehend him. I had bruises on my arms and a leech hanging from my armpit drinking my blood by the time the race was over. I admit that in my anger at the time, I wanted to impale the man to the earth at the spot where he had cut down the tree. It was not the leeches and the bruises that angered me. The tree he was carrying was (until quite recently) in perfect condition.

But Meghalaya isn’t populated solely by subsistence-farming villagers – there are also a few successful traders originally from big cities who have settled in this economically depressed region. They dress smartly and speak impeccable English. At the time, I remembered wondering how these more sophisticated types could be maintaining their relatively lavish lifestyles among the poor villagers who walked barefoot in the dense forests. On a couple of occasions I dropped in at the home of a prominent trader.  He hosted me graciously in his beautiful home. I admit that I enjoyed these visits because they were my only link to the civilisation I had become used to prior to moving to Meghalaya. But I never visited the home of any tribal villager, for what could I talk to them about anyway?

Read the rest of this entry »