Reflections

I'll take this opportunity of the final blog post (unless I decide to continue it, of course!) to go over what I've discussed on here, and to see whether the original question of whether population growth contributes to environmental degradation has been answered.

 I used evidence from the past to show how humans have had effects on their environment even thousands of years ago and significant effects at that. I would definitely call altering greenhouse gas concentrations in the atmosphere and contributing to mass megafaunal extinction significant, especially for such a small number. Logically it's clear that if that long ago we managed to alter the Earth system, then now – with so many more of us and so much more energy-intense and polluting activity – we must still be affecting our environment, if not a lot more. Still, I looked at some more recent empirical evidence about water use and biodiversity loss and there's no doubt that the data back up the logic.

source: http://kkt004.wordpress.com/tag/overpopulation/

A lot of people still challenge the idea that population growth is bad for the environment so I wanted to investigate the arguments against it and look at some of the more interesting ones (i.e. not just the ones plainly refuting the idea, not that I think you'd find that many serious ones from the environmental science community).

Firstly the argument that we can't blame population growth when really it is consumers who are the problem: too many consumers, not too many people. While this may be true, I argued that many of the population growth over the next decades is set to take place in the 'developing' world and so is most of the economic growth. Putting two and two together means a lot more consumers. However, then I found literature on the Environmental Kuznets Curve (EKC) which says that actually as societies get wealthier it is actually better for the environment! BUT, there is a catch: only past a certain level of income. Up to that 'threshold' getting wealthier is actually worse for the environment (as you pollute more than before but haven't started developing clean energy). Sadly, most of the world lives in 'poverty' and so would be going through the stage of polluting a lot until one day (maybe, far into the future) we would reach that stage where the entire world is past that income threshold. (Climate change is a global phenomenon remember so it doesn't help if only half of the population is wealthy enough to pollute less.) Who knows what damage might have taken place by then?

That same question could also be asked about the fact that population growth is slowing and population should peak before 2100, although I do think this is a fair argument against panicking and is the one I most agree with. It makes the situation less worse knowing that we're not still on the exponential trajectory, but like I said who knows what could happen before then. The world was a very different place 100 years ago and could be in 100 years time. (I realise 100 years isn't massive in terms of the Earth's existence but never before has there been such pollution and alteration of the wilderness.)

Finally there was the interesting point that when population growth slows, there is an ageing of the population which could in fact be worse for energy consumption due to the sorts of lives that elderly people live. I hadn't thought about it like that before so I was glad to have found that literature. However, the alternative really isn't an option is it? Telling people to keep having more children to avoid the population ageing while in the meantime the population is growing and growing.

source: http://www.123rf.com/photo_4424545_city-vs-nature-vector-art.html

I also introduced some examples of policies aimed at population management. This was just to show how dealing with population growth's effect is not straightforward. Even if you've established that it's bad for the environment (which is hard enough), how do you go about dealing with it?  Lots of people refuse to talk about it precisely because of some sinister past attempts at controlling population. I think not having a dialogue is even more dangerous though.

Many say the solution isn't population growth management but that our lifestyles need to change. I completely agree, but I just can't see how we are going to change our capitalist, consumerist society. It is engrained in generations. It is a lot harder to ask people to give up driving cars, or buy less 'stuff' than to improve women's education, make contraception available for those who do not wish to have children. Things like this improve people's lives, even regardless as to whether or not it is better for the environment.

The purpose of this blog was to investigate whether excess population growth is an issue. I think it is clear that it is; that is does cause environmental degradation. However, I have discovered it is definitely not a clear-cut relationship, and there are many factors affecting the Earth system. I want to stress that I am not predicting that famines, and world wars, and the end of the human race will come of it. I am sure that we could survive with many more people without destroying the Earth or ourselves (although maybe if I continue the blog this is something I could look into more closely), it just depends on what one thinks qualifies as 'destroying the Earth'. It depends on whether we should have the right as human beings to alter the planet beyond recognition just to satisfy our own needs and desires. I suppose really it goes back to the question of whether nature is there for our use and our control, or whether we are simply part of it.

Policy Series – IV

For the last policy series post, I want to do India, because it's so notorious I feel I couldn't not mention it.

I also want to post this link to an article on the BBC which talks about the dangers when man tries to control population. 

The following about India is an excerpt from the article (as is the photo):

Indira Gandhi and her son Sanjay (above) presided over a mass sterilisation campaign. From the mid-1970s, Indian officials were set sterilisation quotas, and sought to ingratiate themselves with superiors by exceeding them. Stories abounded of men being accosted in the street and taken away for the operation. The head of the World Bank, Robert McNamara, congratulated the Indian government on "moving effectively" to deal with high birth rates. Funding was increased, and the sterilising went on.

In Delhi, some 700,000 slum dwellers were forcibly evicted, and given replacement housing plots far from the city centre, frequently on condition that they were either sterilised or produced someone else for the operation. In poorer agricultural areas, whole villages were rounded up for sterilisation. When residents of one village protested, an official is said to have threatened air strikes in retaliation.

"There was a certain madness," recalls Nina Puri of the Family Planning Association of India. "All rationality was lost."

From the Media

An interesting article from the NY times archive:

Breaking a long silence on Population Control

Monica Drake volunteered to hand out condoms last month in Portland, Ore., as part of a campaign by the Center for Biological Diversity.

Policy Series – III

Today we're going to look at UZBEKISTAN.

This is a tricky one because a lot information is from rumours and 'reports' so I'm not publishing it here as hard facts. Anyhow, Uzbekistan is supposedly carrying out programs of forced sterilisation as a way of controlling population. A 2007 report by the UN Committee Against Torture reported of such practices being done to those women would had had more than two or three pregnancies already.

Here is a BBC news article with a bit more information.

Surely this is a shining example of how not to manage population growth. It brings out all sorts of human rights issues and questions of freedom and choice. We have seen in the past that there are simple schemes that have proved successful, like family planning, women empowerment and education that improve people's lives even regardless of any connection with population growth.

Population Structure, not Growth

I stumbled upon an interesting body of literature that discusses the role of population structure and dynamics in affecting climate change. Rather than simply looking at the size and growth of populations, Jiang and Hardee (2011) (along with various others) study how population composition affects carbon emissions and climate systems. The idea is whether different energy consumption levels exist among population groups with different characteristics and whether (and how) these groups' behaviour will change in the future. They find that population size; ageing; urbanisation and household size are all important factors.

Urbanisation

If we look at the case of urbanisation, on the one hand cities provide economies of scale, technical innovation, efficient land use and lower fertility rates. On the other, as people go from living in rural areas to urban ones, their behaviour changes: their consumption patterns, and their lifestyle. Conclusions are mixed and it depends on the regions studied and whether it's the long-run or the short-run impacts being considered.

Ageing

For ageing, there is also a shift in consumption behaviour and income structure. Like urbanisation it is difficult to determine whether there is a rise in energy use or a decline. An ageing population may reduce public transport demand but use cars more and increase energy demand for heating/cooling; it may also reduce overall labour productivity and so energy consumption. However, as York (2007) points out, the elderly tend to have smaller household sizes which means energy consumption per capita increases. (Imagine heating a house that 3 people live in vs 1 person living in it.)

York makes an historical analysis of demographic trends and energy consumption in 14 EU countries. He runs a regression and finds a positive relationship between an 'elderly' population and energy use. The interaction between population growth, size and ageing is complex. Low fertility leads to a decrease in population growth and eventually size which decreases energy consumption but then this leads to an ageing of said population which increases energy consumption! 

This certainly challenges the idea of less population growth being a good thing for the environment. However, the solution definitely isn't to keep growing and growing for fear of having too large a portion of the population over the age of 65. Surely that would eventually be even worse for the environment? It sort of goes back to the social and economic problems that arise when a population stops growing and starts ageing. The solution can't be to just tell everyone to have more children, because all that will do is delay the issue for a couple of generations until those children are pensioners and living on their own in heated houses. 

It seems to me like there might be some sort of 'Environmental Kuznets Curve' for ageing, whereby there will be environmental pressure for years to come as the population ages, but once it stabilises again (i.e. once the bulge of pensioners are 'no longer there' – sorry!) environmental pressures will subside and so will those on social services. Once again though, a substantial portion of the world's populations have yet to begin this ageing process and are only in the stage where death rates are falling but birth rates remain the same, so it will be a long time before that happens. The only thing I will say is that better education and family planning will perhaps mean people in countries where death rates are falling will be able to choose the number of children they'd like to have, which may result in less of a bulge in population growth.

In any case I've rambled on. The topic is such a complex one it's hard not to explore all the different avenues. The main point from this post is that the relationship between population growth and environmental degradation is not as simple as it seems. The type of population is important: whether it is urban, for example. It is not simply that smaller populations are better for the environment as this can be coupled by ageing which may (there is debate in the literature) lead to increased energy use.  

HAPPY NEW YEAR!

Happy New Year!

Now is a time for relaxation, so here are a couple of films that take their inspiration from 'overpopulation':

Soylent Green (1973)

Blade Runner (1982)

Elysium (2013)

Policy Series – II

Continuing our little series looking at some examples of 'population management' policies, today's one is SOUTH KOREA.

Like in Europe and the West previously, South Korea and a lot of developing countries experienced a rapid fall in death rates but no fall in births, resulting in massive population growth after WWII. So in 1962 they began a family planning campaign which focussed on education, maternal and child health services, and the provision of family planning supplies (e.g. contraception) and services. This was all in order to achieve 'modernisation' and of course economic growth.

top image: from 1974: "sons or daughter, let's have two children and raise them well";
bottom image: from 1981: "even two children per family are too crowded for our tiny country"

In fact, it worked so well that by the 1980s the total fertility rate had fallen below replacement level (below 2.1). So, the population began to age significantly and this put pressure on social services like the pension scheme. By 2005, the government had turned pro-natalist, with incentives like tax incentives, child care and assistance to infertile couples.

Once again, this makes you think of the different and sometimes conflicting consequences of population size and structure. What might be better for the environment – to have smaller populations – often causes stress to social and economic systems put in place for the human population. The question is really do we have the right to manipulate human activity and populations for our own, medium-term gain when this might be causing long-term damage to the global ecosystem?

Environmental Kuznets Curve

Something which I came across recently, which I have to say I hadn't heard of before, is the Environmental Kuznets Curve. The idea is quite straightforward: as income increases, environmental quality deteriorates as there is industrialisation until it reaches some income level or 'turning point', After this environmental pressures begin to lift. This creates an inverted U-shaped relationship between pollutants and per capita income (see below). This (according to Dinda, 2004) is for 2 reasons:

1. After the shift from a clean, agrarian economy to a polluting, industrial one, there is a further move to a clean service economy;
2. People with higher incomes tend to (and are able to) have higher preferences for environmental quality

source: Google images

This challenges the assumption (that I have made in previous posts) that as societies get richer and more people become consumers, environmental degradation worsens. Cropper and Griffiths (1994) examine the effect of population pressures on deforestation in developing countries and find that for example demand for fuelwood initially rises with income but then falls as more 'modern' sources of energy are used. They also find that the denser the population, the higher the income needed to 'offset' its effect on deforestation.

There are some issues I found with it and some that in fact Dinda (2004) does address towards the end of her article. Firstly, for this to work at a global scale – to combat climate change – we'd have to get the entire Earth's population past this 'threshold' (the value of which incidentally no one can agree on) over to the high income end of the spectrum. Even if this were miraculously to happen, what if in the process of doing so, we cause irreversible damage; even if no one were polluting much by that point, that wouldn't help if our atmosphere were already clogged with CO2. Actually Dinda makes the point that most of the world's population would be going from the poor 'pre-industrial economies' to the middle-income 'industrial economies' section, which is when income growth will cause the most environmental damage. Also, Dinda points out that an inverted U-shaped curve is not found for all pollutants, and certainly only ones with short-terms costs, as opposed to stocks of waste or pollutants with long-term, more dispersed costs (like I mentioned above).

So even though it's a comforting idea, especially coupled with the fact that population growth is slowing down, in practice it's not that simple. I definitely wouldn't place all my eggs in that basket.

Policy Series - I

Even though this blog isn't necessarily about the policy side of the population growth 'issue', I still think it's important to take at least a brief look at it. It's all well discussing 'overpopulation' and deciding it is an issue (or conversely that there aren't enough births) , but what about the next steps? How does one (or the government that is) go about managing it?

So over the next few weeks I'm going to introduce a series of different examples of 'population management' policies from the past and present; the good, the bad and the ugly. This will hopefully convey some of the challenges that exist when dealing with such a sensitive issue, and how if handled the wrong way, what other social and economic problems can arise.

I'm going to jump right in with the most obvious: CHINA!

In 1979, the Chinese government introduced the 'family planning policy', more commonly known as the 'one child policy' to alleviate social, economic and environmental problems. If families had more than one child, they were heavily fined. According to government officials, it has prevented some 200-400million births although these figures are disputed. However, its 'success' has come with human rights concerns about its implementation (rumours of illegal forced abortion and sterilisation abound) and its social consequences (female infanticide and sex imbalance as male children are preferred). 

In November this year (2013), the policy was relaxed, allowing only child parents to have 2 children.

Read more about it here

Overpopulation is (apparently) not the Problem

Here is an article that appeared in the Opinion Pages of the NY Times, byErle C. Ellis, associate professor of geography and environmental systems at the University of Maryland:

'Overpopulation is not the Problem'

'There is no environmental reason for people to go hungry now or in the future. There is no need to use any more land to sustain humanity – increasing land productivity using existing technologies can boost global supplies and even leave more land for nature – a goal that is both more popular and more possible than ever.

The only limits to creating a planet that future generations will be proud of are our imaginations and our social systems. In moving towards a better Anthropocene, the environment will be what we make it"

source: www.environmentalgraffiti.com

My question is would it really be a better Anthropocene, one where we have altered the natural environment beyond recognition just to satisfy our own growing needs? He says we can continue without using more land, but how much more productivity can we squeeze out of the land we already currently use? We've already had the Green Revolution, we already employ spectacular technology and genetics to get that bit extra per hectare and we already dowse our crops in fertiliser and pesticide. I don't understand how, in the context of a growing population and a growing number of consumers, one could think we wouldn't need more resources and more land.

The End of Population Growth

"There has been enormous concern about the consequences of human population growth for the environment and for social and economic development. But this growth is likely to come to and end in the foreseeable future"

This is taken from the first line of Lutz, Sanderson and Sherbov's 2001 'letter to Nature'. They used UN and US Census Bureau to create thousands of simulations in order to find trends in population growth and size and to determine about when our population will stop growing.

source: Lutz, Sanderson and Sherbov (2001)

What the graph above shows is the probability that the population will stop growing before a given date. So for example there's a 90% chance that population growth in the European former USSR will stop before 2050, whereas only less than 10% chance that will happen in Sub-Saharan Africa. In any case what this tells us is that there is an 85% chance that the world population will stop growing by the end of the century. 

The figure below shows when (and at what value) they project the world population size to peak, along with UN projections. They find that the median peak would be at 2070, with 9 billion people, after which it would begin to decline.

source: Lutz, Sanderson and Sherbov (2001)

So the main idea here is: why is everyone worrying so much about population growth when in less than 100 years our population won't even be growing anymore? The natural trend is for our population to peak and then stablise and even decline, ergo, population growth won't really be contributing anymore to environmental issues.

I suppose technically if our population stops growing by 2100, we will no longer be able to say 'right now' population growth is having negative effects on our environment, but that doesn't mean that it's not an issue in 2013 or that having a population of 9 billion doesn't have dangerous repercussions for the Earth systems. A lot can happen in 86 years and we already know (and I've already mentioned) that a lot of the current population that is 'poor' is expected to become a lot wealthier and we know what that means: more consumption. 

Something they did talk about which is worth mentioning here is the social and economic challenges that a stabilising and declining population has, the main issue being aging of course. I'll return to this topic though, it's a really important one because it brings up questions of how much the health of the environment matters, vs the social welfare of the human population, which is a tricky subject and not really the topic of this blog but everything is interlinked so I will no doubt write a post about it.

The Skeptical Environmentalist

I thought I would introduce a man who has quite infamously controversial views on the whole climate change (and thus population) debate: Bjørn Lomborg. He is not an environmental scientist and many are in turn skeptical about his statistical claims about human impact on the environment as being little more than 'manipulating the data'. This is why I'm just presenting him here with a few links to his work and the criticism that surrounds it.

His main argument is a cornucopist one: that as societies grow and become wealthier, technology will become more advanced and sophisticated – enough so as to meet our resource needs. He uses such examples as the green revolution to show how we were able to sustain a growing population and still are. He believes that economic growth is the answer and we should be focussing our resources on more pressing issues such as HIV/AIDS and poverty.

While I don't disagree that solving health and poverty issues that affect people today is extremely important too, I don't think we can just stop all efforts to keep the Earth systems healthy and 'hope for the best'. I cant help thinking that without a massively inflated population we wouldn't need new technologies that enable oil extraction in the most difficult and remote locations for example, and for that matter the ecosystems in those locations would be better off without them!

Here is his website and the trailer for his documentary 'Cool It': 

www.lomborg.com/

Links to articles (one relatively recent) he has written, summarising his arguments: 

'The Economist' article

'The Limits to Panic'

Link to the article published in the journal 'Nature', criticising his work; it's a book review of The Skeptical Environmentalist:

'Nature' article

Having dinner with Bjørn Lomborg when he came to speak for the UCL Economics and Finance Society (I'm on the right)

Consumers, not Population Growth

A paper I came across by David Satterthwaite makes the interesting point that it is consumers, and not people per se that are the cause of global warming. In other words we shouldn't blame population growth for rising greenhouse gas (GHG) emissions. Although I didn't agree with everything he wrote (I'll keep my comments until the end though), I want to present his argument here because it's a fair one, and use it as a sort of bridge between showing that high population growth is a problem for the environment and finding out the arguments denying 'overpopulation'.

Satterthwaite starts off by pointing out that the lifetime contribution to GHG emissions of each person varies by a factor of more than 1,000 (depending on their circumstances etc.) and so it is misleading to see population growth as driving environmental change. He reviews CO2 emissions and their evolution from 1950 to 1980, then 1980 to 2005 and finds little association between nations with rapid population growth and growth in their emissions. He finds plenty of examples of countries where CO2 emissions are high but population growth rates low and vice versa (see table below). 

He puts this down to the fact that many households in countries with high population growth (often low- and middle- income) don't have access to electricity for example, or do not consume the goods and services that generate GHG emissions. He analyses data on cooking fuel and access to electricity for 43 countries and finds that for 20 of them, more than half the urban population rely on non-fossil fuel cooking fuels like wood or straw and that even when they do switch, consumption remains low. He takes the stance that this will remain that way as a large portion of the world's population lives in extreme poverty and this is unlikely to change, looking at the failure of the last 50 years of development  practices (his words).

Source: Satterthwaite (2009)

All this leads him to conclude that:

"Human-induced GHG emissions are not cause by 'people' in general but by specific human activities by specific people or groups of people" (p.546)

So that rather than simply looking to population growth, we should focus on rapidly changing the consumption patterns of present and future generations. In the context of development policies, he thinks that too much investment is towards contraception awareness campaigns and not enough that challenges the 'over-consumption logic of global capitalism'; when ensuring adequate sexual and reproductive health services wouldn't even necessarily reduce emissions.

I completely understand his points about needed to alter society's obsession with consumption but my answer would be that dealing with high population growth is one (perhaps easier) place to start. It is no silver bullet but humans (consumers or not) clearly have an impact on their environment (which doesn't necessarily have to be through GHG emissions). This impact is obviously much more significant depending on e.g. their economic wealth as Satterthwaite points out, using the case of an Indian household with an income of 150,000 rupees (US$ 3, 125) contributing to emissions 10 times more than a household earning less than 3,000 rupees. 

Now the problem I have with his analysis is that yes, developed countries contribute massively to GHG emissions despite the fact they have low population growth, but they had large population growth in the past and these now large populations contribute to emissions. They have already completed the demographic transition and are economically wealthy and industrialised. His argument cruxes on his belief that most of the world's population will remain poor and so won't become consumers, but I disagree. Just in the last few decades East Asian countries have developed rapidly (and have had massive population growth) and are beginning to contribute more and more to GHG emissions, and other countries and parts of the world will follow. Incidentally these countries are also the ones where most of the world's population growth is taking place. So I'm not saying the population growth will directly increase emissions but rather that not only are these populations growing, but they are becoming consumers and it is this new, larger generation of consumers that will pose a problem for the environment.

source: World Bank

note: apologies for the presentation of the table, I wanted to make sure I could include his data but still make it legible!

Overpopulation is a Myth

So far I have only been focussing on one side of the overpopulation debate so here's a video from the other side.

I'll try to let you be the judge but I can't help making a few criticisms. It says we could all have a house and a yard and still fit into the state of Texas, but the point is not how many humans we can fit on the Earth's surface but the quality of life that would ensue and the consequences for the environment. Sure, the human population could continue to survive with massive population growth, we would still be able to exploit enough resources, but the world would look a very different place. Secondly, the video points out the low birth rates in Europe and Japan where they are the lowest in the world, but ignores the African continent and other Asian countries like India and China completely! These are not only the places with either massive or growing populations, but the places where growth in resource demands will be the highest! I'll stop myself here and let you make up your mind.

I'd be interested to know what people think about this and I will be exploring more of the academic literature fighting for the other side.

Source: http://overpopulationisamyth.com/

Water Vulnerability

So we've looked at how the human population affects (and has in the past affected) green house gas concentrations and biodiversity (animals and plants). Now I want to take a quick look at our effect on water, so here's a brief summary of Vörösmarty et al.'s (2000) article where they look at how climate change and population growth affect water stress.

They point out that a lot of focus has been on how global warming contributes to water vulnerability whereas actually direct human impact (i.e. consumption) is a lot more important than we think. They emphasise that future water demand will be based on population growth, economic development and projected changes in water use efficiency and what they find, which I think is interesting, is that water use per capita is expected to decline. So although there will be increased water stress that won't be due to an intensification of use, it will be down to population growth, migration, and development. Couple this with the fact that most of the world's population growth will now take place in cities, and you get all the issues around pollution and water-borne diseases. 

What they also determine (which you can see in the maps below) is that not only is a large portion of the world under water stress (I don't think it's the first time we've heard that though), but rising water demands are more important than greenhouse warming in "defining the state of the global water system until 2025" (p.1). You can see below: (without getting into too much complication), the fact that there is more red colour in the middle diagram than in the first means that population change has more of an effect than simply climate change on water demand and use. Obviously when the two are combined they have the biggest effect. And as climate change gets more significant as time goes on, this effect on water stress will get worse and worse and (judging by what the authors said) I'm assuming climate change may even overtake population change as having the most significant effect (as either population growth is slowing, or the lag between human activities and climate change comes into effect).

Anyhow, it is clear that humans and the growth of the human population are having effects on water vulnerability – directly through use and demand; and indirectly through causing environmental change.

  

source: Vörösmarty et al. (2000)

Biodiversity & Extinction

I would like to focus on some of the impacts the growing human population has had on the environment other than greenhouse gas emissions, or nitrogen addition. This week I want to take a look at how humans have in the past, and are now more than ever, affecting the other living things on our planet. This is important not only because species loss is bad in itself but because biodiversity is crucial to the productivity and sustainability of the Earth's systems (see Hooper et al. 2012 for more info). I don't want to make this post too long and boring so I'm going to concentrate on the role humans played in the past megafaunal extinctions and the evidence for an imminent 6th mass extinction in the Anthropocene as a result of human population growth and resource demands.

We know that humans have played a part in extinctions in the past. Barnosky et al. (2004) examine the evidence for the respective roles of climate and humans in the Pleistocene megafaunal extinctions and find that although there is a strong case backing climate variability, the effects were coupled with, and amplified by human action such as hunting. For example, many of the surviving animals were nocturnal, lived in dense, hight forest or even in the sea, so if climate was the only culprit, why did these habitat-specific species survive?

The authors find while comparing the timelines of the late Quaternary extinctions, human arrivals and climate change, that human arrival coincided with many extinction events and played a very significant role in the extinctions that occurred on the American and Australian continents (see below). Humans don't take all the blame of course, and they conclude that:

"A significant implication for conservation biology is that the coupling of marked climatic change with direct human impacts on fauna is especially pernicious. Both effects are under way today at unprecedented rates."

So I see this as a warning of what humans are capable of, and at that time there weren't very many of us! Think about today, with 7 billion of us! In fact this is exactly the line of reasoning many take to lead to the idea that in the Anthropocene, we could be very well moving towards a 6th mass extinction.







Source: Barnosky et al. (2004)

So given all that we know about the massive growth in human poopulation and activity, and that human populations clearly have an effect on extinction rates - through co-opting resources; fragmenting habitats; introducing non-native species; spreading pathogens; hunting; and changing the global climate - could we be heading towards the Earth's sixth mass extinction? We seem to hear about endangered species every day on the news and there is a general perception that our activities are causing more extinctions than is 'normal' - but what is the evidence? A paper published in 2011 by Barnosky et al. concludes that we aren't currently in a mass extinction (as compared to the previous five) but warns that if no measures are taken to protect endangered species, we could well end up in one.

The study compares the rate and magnitude of current extinctions with those of the past five mass extinctions, using the metric 'extinction per million species years' (E/MSY). They take two approaches: firstly if we assume the 'Big 5' all happened suddenly - say, over 500 years - what extinction rate would have been needed and how does that compare to the present rate? They find that that current rates are slower, but if we were to consider 'threatened' species as inevitably extinct then the rates would be comparable. For the second approach, they ask how long it would take to produce species loss equivalent to 'Big 5' magnitudes at current extinction rates. In fact if all 'threatened' species became extinct within a century and the rate remained constant, such magnitudes would be reached in 240-540 years.

This seems like a long time, but who is to say that extinction rates won't increase? The human population is growing, but also becoming wealthier. The rapid development of many Asian countries, especially China, means that there are way more people demanding the kind of lifestyle that requires activities that are harmful to biodiversity. Of course, you could argue the other way, that there is a lot of uncertainty about what 'normal' rates are and whether the results for the particular taxa they studied (due to better fossil records) can be extrapolated to other species in other places. 
Nevertheless, the authors stress that fossil records show that species richness and evenness today are low compared to pre-Anthropogenic conditions, and I stress that one of the principal differences between present day and the pre-Anthropocene era is the size of the human population. Gaston (2005) writes that:

"The most important agent of change in the spatial patterns of much of biodiversity at present is ultimately the size, growth and resource demands of the human population. This is giving rise to [...] levels of species extinction largely unprecedented outside periods of mass extinction" 

Source: http://www.biologicaldiversity.org/campaigns/overpopulation/index.html

I obviously only touched on the issues of extinction and biodiversity as the main focus of this blog is overpopulation, but if you'd like the read more about them, here are some links to blogs on the topics:

http://at-the-edge-of-extinction.blogspot.co.uk/

http://holoextinction.blogspot.co.uk/

http://bdchanges.blogspot.co.uk/2013/10/invasive-species-not-all-that-bad.html

http://anthropocenebiodiversity.blogspot.co.uk/

http://thefinalcountdown-biodiversity.blogspot.co.uk/



From the Media

Here are a few links to news stories from the past week and a 'Kal's cartoon' from The Economist archives:

• China decides to relax its one-child policy in the future

• Hans Rosling appears on BBC2 and tells us not to panic about population explosion and that measured approaches are doing the trick

• French study parallels the UN by predicting world population will rise to 9.7 billion by 2050

Source: www.economist.com

The Early Anthropogenic Hypothesis

Before I continue any further, I feel I have to mention Ruddiman's 2003 paper in which he argues that the Anthropocene began much earlier than the Industrial Revolution: about 8000 years ago. I know it's not directly about population growth, but in my eyes his hypothesis shows what impact even a tiny, 'non-consumer' human population can have (and possibly did have) on the environment and its systems.

He compares the Holocene with previous interglacials and forms three main arguments:

1. That Earth-orbital-driven cyclic variations (phew!) in CO2 and CH4 (methane) during the past 350,000 years would predict a decline in those gas concentrations throughout the Holocene but they began anomalous increases, 8000 years ago for CO2 and 5000 years ago for CH4
2. Possible explanations for those rises based on natural forcing can be refuted by paleoclimatic evidence
3. Archaeological, cultural, historical and geological evidence leads to anthropogenic explanations linked to early agriculture in Eurasia (forest clearance 8000 years ago; rice irrigation 5000 years ago)

source: Ruddiman (2007)

He looks at CH4 concentrations in Vostok ice, which show that they followed the 23,000 year orbital insolation cycle. This supports the orbital-monsoon theory that higher CH4 concentrations had their root cause in orbital precession-dominated summer insolation changes which meant monsoons were more extreme and there was more flooding. However, 5000 years ago, the CH4 signal started to increase, departing from the continued decrease expected from orbital monsoon theory (see figure A above). This risks getting very dry and technical so I'm just going to say that by the industrial era the methane concentration 'should' have been 250 ppb lower than it actually was.

As for CO2 concentration, he compares with previous interglacials and finds that in the last 3, CO2 increase reached a maximum and then dropped steadily for around 10,000 years, whereas in the Holocene CO2 concentrations did peak and start to decline around 10,000 years ago, but then started to rise 8000 years ago (see figure B above). He goes on to prove his point through examining trends at each of the 3 major orbital cycles but I'm not going to go into all of that otherwise this will turn into an essay! If you fancy reading the article (which I recommend), just click on the link above.

He continues by refuting other possible explanations: that natural loss of terrestrial biomass or changes in ocean carbonate chemistry could explain the CO2 rises. They could explain part of the rise, but not nearly enough.

He then proposes his 'famous' idea: that pre-industrial land clearance and rice irrigation are responsible. He points to the domestication of horses and the invention of the ox-drawn plow 6000 years ago, and shows that the pollen sequences in central Europe younger than 6-5000 years are altered enough that pollen analysts view them as unrepresentative of 'natural vegetation'. There was also rapid sediment accumulation in central European lakes between 5000 and 3000 years ago – backing up the claim of forest clearance. Finally the brief periods of CO2 decline could be matched with periods of human pandemics like the bubonic plague. This also backs up the deforestation idea as killing off vast portions of the human population would have meant a halt (or at least significant slowing!) to human activities such as deforestation and as many 'infected' areas were abandoned – a regrowth of forests!

Ruddiman published a response article in 2007, where he addresses the (many) challenges his work has faced. However, he still finds the CO2 and CH4 gas trends anomalous, despite having reviewed the ice timescale used. He still finds that extreme biomass burning (forest clearing) and rice irrigation can explain the anomaly. However, only about 25% of the 'excess' CO2 could come from carbon from deforestation but he proposes that the climate system feedback is responsible e.g. the ocean remained warm because of anthropogenic intervention. Finally pandemics can explain only half the CO2 decreases, but they obviously still had some effect.

Although being precise about these claims is very difficult, there is no doubt that humans did have some effect on their environment, even when they did not possess the technology (or demand) for resource exploitation. It is clear then that humans today have an even greater impact on their environment, and there are many many more of them.

UCL Lunch Hour Lecture

Last month, UCL's Judith Stephenson gave a lunch hour lecture titled 'Global Growth vs Human Health: Finding the Balance'. She is from the Institute for Women's Health so not an environmentalist but the talk was interesting as it explored some of the policy side (e.g. family planning) of the population debate. Here is the video (Blogger wouldn't let me embed the video in the post for some reason so you'll have to do with the link!):

YouTube Video

Are Humans Overwhelming the Great Forces of Nature?

The above title is taken from an article by Steffen et al. (2007) where they discuss the existence of the Anthropocene as a new epoch characterised by human-driven changes to the Earth System. The authors of the study use atmospheric CO2 concentrations to track the ‘Anthropocene’ and determine whether humans have indeed had enough impact to “overwhelm the great forces of nature”.

What they found is that concentrations of CO2 in the atmosphere have risen from 279ppm (during the pre-industrial era) to 379ppm in 2005 (now the value is estimated to be 393ppm - co2now.org). This is significant due to the fact that concentrations had only been between 260 and 285ppm throughout the Holocene. Thus, they take the beginning of the Anthropocene to be the beginning of the 1800s. Others disagree, which we will look at another time, but anyhow the results show that humans have indeed had a significant impact on the Earth System. What we want to know now is the story behind it and how it links to the notion of overpopulation.

The story that is told is that we have always affected our surroundings, but this has evolved from localised impacts as hunter-gatherers (for example with the use of fire) to having impact on a global scale after the industrial revolution. During the late Pleistocene megafaunal extinction, although there are debates about the effect of climate, it is clear that humans had a role to play, through predation. When humans began domesticating, this was affecting their environment on a larger scale, although Steffen et al. maintain it wasn’t on a large-enough scale to alter the ‘great forces of nature’. The turning point, though, was the onset of industrialisation in the post-Enlightenment era.

Previously, economic and population growth were constrained by energy limitations. This was because wind and water power are only available in certain locations and under certain conditions; the energy from plants was limited by land area and also the inefficient conversion of light energy into chemical energy through photosynthesis (less than 1%). However, the invention of the steam engine in the 1770s and 1780s by Watt, coupled with the increased usage of fossil fuels shattered this bottleneck. The Haber-Bosch synthesis – which allowed for the synthesis of fertiliser out of atmospheric nitrogen) along with improved medical care meant that the population began to grow exponentially and along with it all the activities that increased CO2 production (refer to the graphs above). This trend has continued, unabated except for the Great Depression and the World Wars, until present day.

The main point I wanted to take from this article was that humans do have an impact on the environment; there is no doubt that, and the larger the human population, the larger the impact. Although Steffen et al. are implying that it is energy consumption, and economic growth that cause CO2 concentrations to rise, it follows logically that with less humans around, there would simply be less of the activities that impact the Earth System.

Sources: first and last set of diagrams; Haber-Bosch diagram