The Elephant In The Room
Randolph Femmer
Friday, 04 September 2009 14:56 UTC
I couldn’t help but notice that, despite this forum’s intelligent and influential membership, out of 118 posts to date (September 4, 2009), almost none of the posts address “the elephant in the room.”
Can this simply be an oversight? Or are we displaying an avoidance?
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It is true that little has been said of climate change. I suspect that it is not because people are deliberately ignoring it. Indeed the literature is replete with examples of climate influencing populations and reports of the effects of climate change on numerous aspects of species ecology. I believe there is compelling evidence that animal and plant populations and communities, and ecosystems, respond quickly to fluctuations in climate.
In an attempt to move discussion on from the General Theory topic, which, like Alan, I believe is going in circles, I’ll outline my view of the state of play.1) There are now a large number of examples where birth and death rates, and the population growth rate, correlate with climate.
2) Temporal trends in population growth or demographic rates have then been attributed to climate trends.
3) Simulation models have been developed to explore how a changing climate could influence population dynamics.
4) Climate change, or indeed any changing environmental variable, causes challenges to existing theory – be it stage-structured or not.There are challenges relating to 1). What measures of weather should researchers use? Average temperature, rainfall, amount of snow, solar radiation etc.? And over what period should these variables collected? Annual, monthly, weekly? But when climate changes, and, for example, spring occurs earlier or the timing of resource availability changes, is there any logic in using a fixed window – i.e. weather in March or April? And should the effects of a large number of different weather variables be examined, or should variables be selected from a priori knowledge of the system?
It is my view that the choice of weather variable should be chosen through an ecological understanding of the study system. How is weather expected to impact birth and death rates, and how does this guide the choice of weather variable? Should one focus on indirect effects via food, or indirect effects operating via other processes? For example, do changing weather patterns impose novel foraging or thermoregulation constraints? This a priori choice of weather variable sapproach should help narrow the range of variables that need to be considered in analyses. Unfortunately there are often many potential ways that weather can influence ecologists and population dynamics. More research on how best to identify climatic drivers is probably warranted; this network would seem an excellent place to discuss possible directions.
B) Related to A) it is currently in vogue to attribute any population trend to a changing climate. I think that a realistic ecological mechanism is required to justify such linkages.
In relation to 4) most population dynamic theory assumes the population is at equilibrium. This is mathematically more tractable than assuming non-stationary dynamics. Climate change is non-stationary so can not easily be incorporated into existing theoretical frameworks, including the ‘general’ one championed by Alan. There have been some elegant attempts recently to examine non-stationary dynamics, but clearly this is an area requiring further attention. There is a lot of silent expertise signed up to this list who will have thought about this issue in a lot more detail than I.
I’m hoping I’ve got the right elephant, and there’s not a herd of them in the room….
Best,
Tim -
Hi, Tim – Thank you for your post. Actually, I think that you are exactly right and there may be an entire herd of them in the room (ha), with climate / population considerations being one of them. Actually, I was envisioning human population growth itself with five billions added since 1930 (circa two billion in 1930 to our seventh billion which is due in late 2011) and then two more billions after that (eight and nine) on-track to join us by mid-century.
Since a case can be made that earth’s long-term carrying capacity for an industrialized humanity is probably something a little less than two billion, and since things like climb-and-collapse actually take place in other species, to me our current avalanche (on a worldwide basis) is one of the biggest of the big elephants in the room.
So basically, I think that we are looking at a potentially-calamitous set of humanitarian, civilizational, and biospheric disasters over the four decades just ahead, including the possibility of collapse – and that we should be talking about it.
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In my opinion, the elephant in the room looks something like this:
Trying to ignore the arrival of five additional billions in the years since 1930, and then ignore additional billions number eight and nine on-track to arrive by mid-century is analogous to the crew of the Titanic avoiding the very large and prominent topic of icebergs.
Any reactions?
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The dual effects of both Elephants are quite interesting because climate and anthropogenic resource uses (land use + watershed use + marine use; caused in large part by changes in human numbers and behaviors) are both changing in non-stationary ways. This presents some interesting challenges for the theoretical and empirical study of populations.
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Hi Randolph,
Thanks for the latest post; my lack of response before now is because I am currently in California and was enjoying the Labor Day weekend.
I am no expert on human population dynamics, but I won’t let that stop me posting some thoughts. A good topic to bring up.
1) Estimating carrying capacity for populations while they’re still increasing in size is a challenge. This is because different assumptions about the part of the life cycle where density-dependence operates most strongly, and the shape of the functional form for the density-dependence, can have substantial impacts on the estimates of carrying capacity.
2) The estimation of carrying capacity in the global human population is complicated even further because various other factors need to be considered, including (a) technological advances in food production, (b) changing life history patterns in many countries due increased longevity and lower fertility rates, © continuing economic development, altering patterns of demands on resources and (d) changing climate. I do not know what the carrying capacity of the globe is, and treat all estimates with scepticism.
3) Some populations approach carrying capacity slowly, others overshoot and can then experience a rapid population decline. The behaviour of a population as it approaches carrying capacity depends to a large extent on how density-dependence operates – is it via contest or scramble competition? If it is contest competition resources are shared out between the lucky ones who all have enough to survive. The unlucky ones get few (or no) resources and die. If it is scramble competition resources are divided equitably (or nearly so). If resources are scarce, and population size large, no one (or few) have enough to survive and the population crashes. In reality, there are few cases of pure contest or pure scramble competition. I can only speculate on where humans lie on this continuum.
4) Age-structured populations, including human populations, show momentum. This means that even if fertility dropped to zero now, the decline in population size is initially slow. This is because a substantial proportion of the population are fit and well, and have a considerable lifespan ahead of them. Reductions in fertility rates consequently take time to show any noticeable affect in population size. The longer the expected lifespan of an individual, the greater the population momentum. One of mankind’s greatest achievements in the past decades has been to decrease mortality rates at all age-classes in the developed world through improved diet and healthcare and treatment of disease – this has increased population momentum. Hopefully a similar achievement can be delivered in the developing world. This should lead to a decline in fertility rates.
5) Fertility rates have dropped noticeably in many parts of the world – especially the developed world but they are also dropping in much of the developing world. The replacement fertility rate is about 2.1. In much of Europe, Asia and the Americas fertility rates are substantially below this. Although I do not have numbers to hand, they have dropped as low as 1.2 in some European countries. Reductions in fertility rates have led some demographers to predict a peak in human population size as early as the middle of this century. I find such predictions convincing, although they do not incorporate density dependence.
6) Fertility rates decline when populations become developed. One of the best predictors of fertility rate is female literacy. If a country has a high female literacy rate it tends to have low fertility. In general, female literacy rate and development are coupled – more educated people usually speeds development.
7) Given 1) to 6) it is my view that human population size will decline if development continues and living standard improve. I see no other acceptable alternative – personally I do no consider legislation limiting family size as socially acceptable.
8) Because I believe there is no obvious acceptable alternative to reducing human population size I do not see human population as the elephant in the room – it is not something that I ignore, but my knowledge does not extend to development. So now I turn to speculation:
9) Do I think the human race is close to, at, or above carrying capacity? I really do not know the answer to this, although evidence suggests we are using up non-renewable resources at an accelerating rate. Is the globe on the edge of experiencing a catastrophic decline in human population size because of a shortage of resources? Again, I do not know the answer to this, but it is apparent that food security and water availability is a growing concern in many parts of the world. It is also apparent we are changing our natural environment, on average making the globe a harder place for people to live. Can we slow the rate at which we use up non-renewable resources, increase food and water availability and reverse the changes we’re making to our natural environment while improving living conditions for the average person? I believe we have the potential to do this, and that many solutions to specific problems already exist. Will we deliver on this potential before it is too late? I’m not convinced we have the desire to do so. If we don’t, though, it will be the human race that pays the cost – the world will survive.
Anyone else out there?
Cheers,
Tim -
Thanks for posting this topic, Randolph.
Following Tim’s comprehensive discussion of the topic, I’d like to ask a couple of questions relating to the initial (human population) issue and the relation of climate change (which is currently most likely directly caused by human effects) to population dynamics theory:
Since a case can be made that earth’s long-term carrying capacity for an industrialized humanity is probably something a little less than two billion
1) Can you tell us where this carrying capacity value comes from?
2) Tim suggests that the changing climate basically has an additive impact on population growth, albeit through different (sometimes complex, interacting) mechanisms in different populations1. I’d tend to agree with this view, but I’d also be interested to hear if Randolph or others see this as a reasonable, useful representation, or do you propose another view?
I think the 2nd point relates to much of the previous discussion on this Forum, without requiring one to choose between an unstructured or structured approach to population theory. Is it possible to develop a useful theory of population dynamics in the absence of environmental variation (which can then be added ad hoc), or will the long-term changes to the environment lead to stronger directional selection in populations, which could have a strong effect on dynamics?
Recent evidence suggests that not all is doom and gloom: the BBC reports that Scotland is on route to achieving a 20% reduction in CO2 emissions by 2010 (compared to 1990 levels). While Scotland is a small country, it shows how strong political motivation can start to drag us in the right direction.
I don’t mean to use this as a political forum by any means, simply as an example that technological advances and other anthropogenic forces can hopefully return us to a more sustainable way of life.
1 Apologies if I’m not paraphrasing you correctly here, Tim.
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Thank you to all of you (above) for your multiple and thoughtful posts which are much appreciated. A lot of points raised, however. Let me post a couple of quick observations and then try to address some of the individual points a little later in the day.
First, as you can tell, my principle concern is only partially theoretical, because natural systems and climate systems care nothing about any of our external theoretical constructs, for either they will continue to function in the face of the damage, wastes, and exponentially increasing pressures that we exert upon them, or they will not.
(Quick example: If Brazil’s plans to conserve 10% of its Amazon forests are successful, somewhere during the 90% eradication that current policy envisions and may permit, one might expect multiple thresholds or tipping points to be transgressed [transpiration?-cycling?-rainfall?-pollination?] so that even the remnants of the system eventually decline and disappear.)
Thus, by focusing solely on efforts to conserve biodiversity, NGOs and public policy may be overlooking larger, and critical, “whole-systems” perspectives. Suppose, for example, that we were to collect and conserve representative samples of a person’s lung, liver, muscle, kidney, nerve, and endocrine cells and tissues (a la biodiversity). Would saving representative 10% samplings of such cells and tissues ensure that the person themselves would continue to survive or would the loss of 90% of those systems result in catastrophic systems failures and collapse? What if we were to save 50% of a person’s lung, liver, kidney, digestive, blood, and endocrine systems? Could we reasonably expect the person to even survive, or would a 50% loss of all such systems constitute a new and highly-precarious condition? Such considerations might suggest, perhaps, that we should be conserving at least 50% of earth’s natural systems – (and to the extent that the above analogy holds, that fifty percent may not be enough).
Secondly, suppose that we each set forth our own estimates of earth’s planetary carrying capacity for an industrialized humanity. Roger Revelle’s published estimates (circa 1974, 1976) proposed [IMHO mistakenly] a possible carrying capacity of 44 billion (about six times our current numbers – just imagine that). The trouble with his estimate is that it was derived based soley and entirely upon assumptions concerning food and agriculture (Not addressed? NO consideration whatsoever of the impacts of the wastes and physical damage generated by each of those billions.)
(Such “food-only” calculations appear throughout the literature of the past half-century, and the trouble with many of them is that they are often based upon a faulty and unstated assumption that food and agricultural considerations are the sole or principle limiting factors for an industrialized humanity. What if other factors such as wastes, climate, and/or physical damage to functioning systems exert their effects first? Thus, analyses that confine themselves entirely to food and agriculture alone may be guilty of an oversight that might be called “the fallacy of the agricultural maximum.”)
Thirdly, if we each devise our own estimates of earth’s carrying capacity for an industrialized humanity, and those multiple estimates turn out to be diverse, which estimate shall we accept? Should we accept the highest estimates and hope that something has not been overlooked (a la Revelle)? Or should we average all of the estimates and accept the medium value as the basis for biospheric policy and then hope again that something has not been overlooked? On the other hand, the cautious (and conscientious) among us might at least suggest that if one makes estimates of earth’s carrying capacity (e.g., at a Western European standard of living), one’s estimates had better not be too high.
Lastly, common assumptions that underlie much of today’s complacency include suppositions such as “the open-space delusion” (I have a post on this topic in the marine biology topic of this forum). (It may be, for example, that outbreaks of dinoflagellate red-tide – e.g., Karenia brevis – have more to tell us about ourselves than we currently imagine.)
As I said, I would like to address some of the other points raised perhaps a little later this afternoon. I have a lengthy manuscript on these same subjects which I may have to post in its entirety. In the meantime, the hyperlink in this post (below) offers two easy PowerPoints (intended primarily for educators, journalists, students, and policymakers) and several ancillary pdfs. (Several are also posted at www.scribd.com – search Wecskaop.)
Your thoughtful posts are important and deeply appreciated. I, for one, think this is a worthy discussion to have and am appreciative of the interest already shown and the contributions that have already been made.
p.s.- I apologize for the missing graph in my earlier post (I posted a graph of human population growth over the past 10,000 years with an obvious skyrocketing beginning circa 1830) and in the intervening day or two, it has mysteriously morphed into an icon. (I have posted a similar graph, however, and an assortment of population-climate-environment perspectives in an assortment of PowerPoint and PDF resources here.)
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Dear Randolph, Tim and Mike, I have read the post about human population dynamics. First, I think that we need another specific section to discuss this VERY interesting topic. About human population dynamic, one important tjhing to realize is that while a positive relationship between per capita growth rates and density (cooperation) can be observed between 1600-1965, after the period 1965-1970 a clear negative feedback is operating, that can be observed at global scale (using total human population) and also at continental scale. A very important issue is to decipher is what is the limiting factor for human population, as Randolph said, food had commonly used as the measure of that. However, we are producing more food per capita than ever in the planet and population per capita growth rate is decreasing since 1965, I suspect that something related with our capacity to produce and consume energy is related with this trend.
more later
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Thank you to all of you for your continuing “elephant-in-the-room” posts and observations. In post number five above, Tim raised a lot of important points, including a correlation between female literacy and reduced fertility rates, along with his point number two involving the contributions of increasing longevity and lower fertility rates.
This latter point (longevity and fertility) is certainly crucial because, given current U.N. medium projections released earlier this spring, it is possible that world population could peak above nine billion sometime after mid-century. Even if the U.N.’s medium projections should occur, however, any biospheric or environmental benefits that might be anticipated can almost certainly be expected to be wiped out by a worldwide litany of industrialization, CO2 emissions, and similar human impacts.
Soberly speaking, however, the U.N.’s medium projections may be undermined by technical and medical advances involving longevity compounded by delayed feedbacks built into our response times. As Bongaarts and Bulatao note (Beyond Six Billion, National Academy Press, 2000), there is a tendency or a statistical likelihood for demographic projections to underestimate the actual population numbers that eventually emerge. One reason for this is that anticipated reductions in birth rates, even when they occur, are quite often cancelled out or offset by even greater (but unanticipated) reductions in death rates.
(A famous example of this seems to have taken place in Sri Lanka which, in 1939 had a birth rate of 35/1000 and a death rate of 21/1000 so that its population was growing at a rate of 14 extra/1000. Forty-five years later, after nearly a half century of birth rates that generally trended lower, Sri Lanka’s birth rate had fallen to 27/1000. However, during the same period, its death rates had fallen to just 6/1000, due in considerable part to advances in the war against malaria. Notice that not only did the falling death rates cancel-out the effects of falling fertility, but due to the discrepancy between the two not only was Sri Lanka’s population larger due to a half-century of growth, but its 1984 growth rate (now equal to 21 extra/1000 as opposed to 14 extra/1000), was actually fifty percent greater than it had been forty-five years earlier.)
I took the time to cite the above because I think that a distinct possibility exists that this same sort of thing may be about to happen on a worldwide basis. For example, in a 2005 review paper addressing studies in longevity, Cynthia Kenyon – Cell 120 (25 Feb 2005): 449-460 – reports on successful six-fold extensions of lifespan in laboratory animals, commenting (approximately) that should an equivalent success ever be achieved in humans, we might see healthy, active 500-year-olds. (Think molecular genetics, genomics, cancer vaccines, organ replacements, resveratrol, and similar. My list, not hers.)
(Not our topic, however, but were the above extension ever to successfully occur, would replacement level fertility for the average woman have to fall to just four-tenths of a child – per century?) To our topic, however, no such dramatic life extensions would be necessary to toss today’s U.N. medium projections right out the window. Even more modest increases of just fifteen or twenty or twenty-five years by mid-century would be more than sufficient to wipe out the hypothetical stabilization that the most recent projections envision (think again of those cancer vaccines, anti-malarial drugs, and advances in molecular genetics).
Any realism to any of the above? I don’t claim to know. However, think what we have all seen happen in five and six decades spans of time in fields like computers, DNA technology, aeronautics, and communications. First there is an initial discovery or breakthrough, followed by rapid and accelerating advances, followed by wide proliferation.
(Think, for example, of the first powered flight of a heavier-than-air vehicle in 1903 by the Wright brothers. They flew their plane at Kitty Hawk, North Carolina for twelve seconds and a distance of 120 feet. Less than seven decades later, astronauts traveled to the moon and returned safely to earth in about one week.) All of which could, perhaps, mean that if we are at or beyond earth’s long-term carrying capacity already, our current troubles (e.g., climate as just one) may be part of a prelude to collapse.
Rather than post more right now, will leave it at that. Would like to respond to Mike who invited a comment on my own assessment of a planetary carrying capacity of something somewhat less than two billion (at a Western European standard of living, for example). Since this post is too long-winded already, will try to address Mike’s inquiry next time.
p.s. – In one of my earlier comments above, I posted an image of a graph depicting human population growth over the past ten thousand years or so, only to find that an unwelcome icon had posted itself in place of the graph. This morning I have found that the original graph actually does display (at least it does on my computer) if the post containing the icon is copied and pasted into a word document.
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Hello list,
Mauricio, why do you think that our increased ability to increase and use energy has led to a reduction in fertility rates in Europe where fertility rates have dropped over the past half century? I’m not familiar with this argument and would like to hear it expanded.
Randolph, your points are very well made. You are clearly concerned about human population size, and its continued growth. But do you have any solutions on how to stop it? My view is the only acceptable way is via development. I believe our best hope of changing the human population growth rate is to simultaneously improve living standards while reducing the negative impacts of a Western lifestyle on the environment. This won’t be easy (turning an oil tanker analogies), but I believe it is potentially achievable. Things are starting to move in the right direction in some places (but not all) as Mike pointed out. One sign of change is that in many developed countries there is a growing number of people who are concerned about their impact on the planet. If this number continues to increase, vote-chasing politicians will start to see mileage in championing policies that penalise high-impact lifestyles (as a an expert lobbyist once pointed out to me, politicians tend not to lead they respond to public opinion), and the development of technology to reduce impact will become economically more rewarding. Perhaps this is pie-in-the-sky lilly-livered liberalism, and the discussion is moving towards the political rather than population ecology, but I cannot see any alternative. The key question is can we deliver before the catastrophic increase in mortality rates, and associated breakdown in society that some are predicting, occurs? I don’t know.
So my question is do you see any alternatives?
Cheers,
Tim
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