Introduction

Although the world has seen exponential human population growth in the last few centuries, given the Earth’s finite size and resources, this growth is not sustainable. The rate of population growth is currently declining, impacted by falling birth rates, and some pockets of increasing death rates (particularly sub-Saharan Africa due to HIV). Current modelling predicts that the Earth’s population will peak at around 9.2 billion in 2075[i], based on present birth and death rate trends. However, human population growth has never been purely linear, and with forecasts of a peak population total, the less asked question is ‘what will population decline look like?’ This report will cover the scenarios for population decline in the future, and consider some of their possible impacts.

Population decline can be the result of many different influences, and can greatly vary in scale. All population growth is the product of demographics, and is simply the product of differences between birth rates and death rate. Migration impacts local population levels (either positively or negatively), and is the third variable considered in localised population modelling.

Localised population decline is an ongoing phenomenon, and may be as modest as movement between cities based on economic circumstances (such as differing levels of job vacancies), having no impact on the overall regional population, to larger scale localised events, such as natural disasters and famines, that drop the population regionally, although not significantly impacting global population growth. Whilst this report is focused on global population decline, the occurrence of multiple local population declines will potentially lead to global population decline.

Demography

Although the causes are varied, complex and interrelated, at its essence, population growth and decline result from two key demographic variables[ii]:

Birth rate – the rate at which newly born babies are added to a population

and

Death rate – the rate at which death occurs in a population

When death rate exceeds birth rate, a population begins to decline. For most of human history, birth rate has exceeded death rate, leading to a growing population.

For a population to grow, in broad terms, every female in the population needs to produce 2 offspring (or more technically, one female offspring surviving to reproductive age). This average of babies per female is termed Net Fertility Rate (NFR) and for a population to grow, needs to be greater than 2. When the rate falls below 2, technically the population is declining. However, because actual decline requires death and ageing related factors are the most common cause of death, there is a delay in the fall. The length of this delay is driven by Average Life Expectancy – the average life span of members of a population – and the higher this age, the longer the period of time before deaths exceeds birth.

External events that reduce life expectancy will also increase the pace of population decline.

World Population History

Modern humans (Homo Sapiens Sapiens) are believed to have evolved roughly 200,000 years ago[iii], however their ancestors can be traced back almost 4 million years. In that time, population growth was very limited, and indeed, may have suffered significant setbacks due to external influences, to which their limited technology offered little protection. It is speculated that the Toba volcanic eruption 75,000 years ago reduced the world’s population to 20,000 individuals[iv].

Rapid (and sustained) population growth emerged as a human phenomenon only since the start of the agricultural age, starting 11,000 years ago in Mesopotamia[v], and more recently in other regions, such as East Asia and Central America. The food surpluses that agriculture could generate powered the development of civilisation, and with it, the means to grow populations far more rapidly than in the past. It also provided the seeds of many of the forms of population decline.

Despite the boost given to population growth by the emergence of civilisation, population growth still remained constrained for the majority of the history of civilisation. Technological advances, such as medicines and machines reducing the labour input into agriculture, provided boosts to population growth, whilst increasingly deadly warfare (through technical advances in weaponry and metallurgy), incubation and spread of diseases through increasingly urban living, and the impacts of crop failure on a much larger dependant population, offset these rises.

The advent of the Industrial Revolution marked a inflexion point in the history of population growth, as the harnessing of fossil fuels and the industrialisation of manufacturing and agriculture. The European colonisation taking place within this period, despite its horrific impacts on local populations, spread these advances around the globe, creating conditions for significant population growth in these colonial centres, which would eventually become what we refer to today as the ‘developing world’ – a source of the most significant areas of population growth[vi].

Although fuel use and mechanisation offered some significant benefits to populations, allowing them to grow further (by supporting larger birth rates), the most significant impact on the population explosion witnessed over the last century, has been the decline in death rates, driven by medicines, modern sanitation, and advances in the fields of pathology and epidemiology. 100 years ago, a minor cut could be fatal, and far more soldiers died in hospitals from infections than on the field of battle. Antiseptic, penicillin and antibiotics all had the effect of massively reducing the death rate in a very short period of time, whilst birth rates tended to move more slowly, being tied to more closely to cultural factors. Although there is a correlation between standard of living and reproduction rate, a time lag exists.

Population theory

Although demographics lie at the heart of society, it has received surprisingly little attention in history (compared to other areas of intellectual pursuit prior to the 20^th century). With religion dominating much thinking, there was an emphasis on treating reproduction as a fulfilment of ‘God’s plan’, as well as stoically accepting death and hardship.

One man stands supreme in the area of population thinking – Thomas Malthus. An English clergyman by training, Malthus was the first person to provide an academic treatise on the subject population growth. In his massively influential book “Essay on the Population Problem”, he described the geometric progression of population growth, compared to the linear growth of food supply.

Although steeped in moral connotations – the discussion of excessive reproduction focused almost exclusively on the lower classes – Malthus’s arguments were more firmly grounded in economics, although limited to the narrow model of farm output and agricultural labour, despite the Industrial Revolutions emergence in the 50 years prior to the book’s publication.

Although Malthus motives can be questioned, his analysis remains influential to this day, coining such terms as the ‘Malthusian equation’ to describe his predications of cyclical population decline, and ‘neo-Malthusians’ for modern day advocates of impending population crises.

Malthus’s modern day contemporary is Paul Ehrlich, a scientist who brought demography and population issues back into mainstream thought with the publication of his 1962 book “The Population Bomb”. Like Malthus, Ehrlich also predicted large scale population decline as a growing population exceeded the resources of the earth to support it. “The Club of Rome”, an organisation founded in 1968 to raise awareness of issues facing humanity, published as similarly stark commentary on population growth in 1972, entitled “Limits to Growth”.

Like Malthus, Ehrlich and The Club of Rome’s predictions have not yet come to pass, which has earned him much scorn from supporters of growth, and opponents of population control and environmental causes. However, the premise that output and resource growth is linear, whilst population growth is exponential, remains sound, and although technologies have altered the gradient of the resource curve, its linear nature implies that a short fall of resources over population is inevitable.

Decline drivers

The routes taken by population decline can take many forms, but can be divided into three main categories:

·         Gradual demographic decline – this is simply the result of death rate exceeding birth rate

·         Event based decline – this is a decline that exceed natural decline, due to one or more events, such as war or localised famine. These declines tend to be geographically specific, and may target particular age or social groups (such as young men in wars, and the elderly and children in famine).

·         Broad global declines – historically, there are two main causes – warfare and disease (famine being a more localised effect). These lead to a net decline in global population that may take many decades to repopulate.

Historically, there have been very few instances of global population decline. Given historical birth rates have averaged above 40 births per 1000 population – or 4%, even allowing for high historical infant mortality rates, an event would need to remove 2% of the global population per annum to achieve any sort of noticeable outcome. High mortality rates of localised populations have been common throughout history, but on a global level, such events are rare, either being world-wide phenomenon (such as World War 2 or the Spanish Influenza epidemic of 1918-19), or localised phenomenon with an exceedingly high death rate amongst a large population. Several Chinese civil wars and the Great Plague of Europe fall into this category.

Famine

Until the advent of agriculture and civilisation, human population growth was limited like other animals by the amount of food they could gather from their surroundings. The development of agriculture created food surpluses that underwrote the development of cities and civilisation.

However, this disconnect from the environment created a vulnerability in populations to declines in food production, and such short-falls have happened regularly in human history. Famines can lead to large local population declines, particularly in isolated populations where external substitute food sources cannot be procured. War, human activities and natural disasters can all bring about circumstances of famine.

Famines do not have the global reach of pandemics, except under extreme circumstances such as volcanic winter, where the injection of ash into the upper atmosphere reduces global temperatures.

Famines can however be created and/or exacerbated by social factors, particularly the actions of governments. In the most significant famines in human history, the death toll from declining food production is far less significant than the deliberate or accidental failures in government action. The Great Chinese famine of 1959-1961, killing an estimated 15-40 million people[vii], is just the most extreme example of this common phenomenon.

Disease

Disease in humans is the result of infection by bacteria and viruses, whose origins lie billions of years in the past. Thus, there has always been disease, and humans and their pathogens have evolved side-by-side throughout evolutionary history. Disease within communities is an ongoing arms race between immunities that evolve in the human population (driven in part by natural selection as a result of infection by the microbes) and mutation by the microbes to allow them to circumvent these evolving immunities.

The impact of a disease on a population is driven primarily by two factors – its lethality (the percentage of people infected with the disease that die) and its transmissibility (how easily it is passed within a population). Additional factors, such as immunity within the population, and activities taken to reduce transmission, can control the impact of a disease.

The spread of an infectious disease is termed an epidemic, and a large scale epidemic is termed a pandemic. Historically, pandemics represent the largest impacts on human population decline.

Communicable diseases are those that can be easily passed from person to person. Non-communicable diseases are those that require a “special mode of transfer between hosts”[viii] (e.g. malaria and HIV). Historically, pandemics are primarily communicable diseases, although bubonic plague and HIV are two non-communicable diseases that have caused pandemic scenarios.

Although disease has coexisted with humanity for its entire existence, the birth of civilisation saw a new chapter in their effect on human populations, as greater population densities, and sanitary conditions that supported their spread emerged. Diseases that would have quickly died out in disperse hunter-gatherer tribes were able to survive and mutate into new strains in the larger populations of cities. This leads to greater mortality in the short-term, but greater resistance in the population in the long term. A key side effect of this resistance was when groups with developed immunities encountered populations that did not have resistance to the disease, making them highly susceptible, with large mortality rates. This effect was most evident during European colonisation of Africa, the Pacific and the New World, with the death toll amongst indigenous populations greatly exceeding that of conflict. Estimates link disease to up to 95% of deaths amongst indigenous populations[ix].

Some of the most historically significant pandemics in history are detailed below:

Name	Death toll	Region	Years	Species
Antonine Plague	5,000,000	Roman Empire	165-180	Smallpox
Plague of Justinian	25,000,000	Byzantine Empire	541– 542	Bubonic plague
Black Death	100,000,000	Europe, Asia	1338–1351	Bubonic plague
Third cholera pandemic	1,000,000	Russia	1852–1860	Cholera
1918 flu pandemic	75,000,000	Worldwide	1918–1920	Influenza
HIV/AIDS pandemic	25,000,000	Worldwide	1981–present	HIV/AIDS

Whilst the epidemics can impact populations, many diseases exist within a population at a more stable level (e.g. malaria). Implementing effecting protection against and treatment for these diseases tends to see a lowering of death rates, and is one of the key drivers of the rapid population growth over the last 200 years.

War

Territoriality and aggressiveness are common traits in the animal kingdom, and it is not surprising that they are prevalent in human society. Anthropologists speculate that human warfare was virtually non-existent amongst Homo Erectus and early homo sapiens, based on a lack of supporting archaeological evidence (e.g. no early cave paintings depict human fighting)[x]. This is not necessarily interpreted as early man being more peaceful, but rather a combination of low population densities and poorly developed weaponry which made combat far more dangerous and risky. The earliest known battle dates from about 14,000 years ago[xi], and the development of more advanced weapons, particularly bows, along with agriculture and civilisation are thought to be the catalyst of larger scale human warfare[xii].

War is primarily fought between power blocks over land and other resources. As civilisation has grown, and population sizes increased, the units engages in warfare have grown from the tribal level, through the city state, right up to the nation state. Allegiances of these units are often formed. Wars between groups within these divisions are referred to as civil wars, and although not bringing to bear the potential resources of conflicts between whole entities, they none-the-less have produced some of the bloodiest wars with the highest losses of life.

Deaths in wars have traditionally been confined to the combatants, which tends to focus loss of life in young males. From a demographic stand-point, this has less effect on population growth than the loss of reproductive age females, although the polygamy and remarriage social mores of the groups involved would impact this. Warfare, particularly in modern times, has tended to have a broader impact on the general population in the areas where fighting occurs, captured in the concept of ‘Total War’, which dates back to the early 1800′s. However, sieges of cities from ancient warfare through to medieval times caused significant impact to civilians across all demographics.

It is the broader impacts on non-combatants that can give war far greater lethality. Civilians may be caught in cross-fire (it is estimated some 2 million Vietnamese citizens were killed in the Vietnam War)[xiii], but migration to escape the fighting can lead to conditions where disease and hunger are rampant, and take many lives. African refugee camps are populated primarily with refugees fleeing conflicts, and are subject to conditions that lead to high mortality rates. Warfare also exposes combatants to conditions where they are highly susceptible to disease, and in many instances, particularly prior to modern antibiotics, death rates from disease far exceeded those of combat (for example, in the American Civil War, there were 212,000 on the field of battle, and c. 430,000 deaths due to disease and other causes).[xiv]

Instances of genocide related to warfare can produce sickeningly high death tolls, but it is the concentration of the deaths amongst the group targeted that make them so appalling, not the absolute number of deaths. The estimated 6 million Jews killed during World War 2 was only 10% of the total casualties in this conflict, although it represented two thirds of the Jews living in Europe at that time[xv].

The following conflicts were the only historical conflicts to kill more than 2% of the world’s population. Some, such as the Mongol conquests, were over such a large time period and geographical area, that the global population impact would have been greatly diminished:

Event	Lowest estimate	Location	From	To	% of the world population
World War II	40,000,000 – 72,000,000	Worldwide	1939	1945	1.7%–3.1%
An Lushan Rebellion	33,000,000 – 36,000,000	China	755	763	14.0%–15.3%
Mongol Conquests	30,000,000 – 60,000,000	Asia, Eastern Europe	1207	1472	7.5%–17.1%
Qing dynasty conquest of the Ming Dynasty	25,000,000	China	1616	1662	4.8%
Taiping Rebellion	20,000,000 – 60,000,000	China	1851	1864	1.6%–2.1%
Conquests of Timur	15,000,000 – 20,000,000	Asia, Russia	1369	1405	3.4%–4.5%

Source: http://en.wikipedia.org/wiki/War#Ten_largest_wars_.28by_death_toll.29

Disaster

In the year 2011, there have been a number of natural disasters that have resulted in significant loss of life:

·         extreme cold events in Europe and America in the winter of 2010-2011

·         flooding in Queensland and Victoria in the summer of 2010-2011

·         earthquake and tsunami in Tohoku, Japan (15-20,000 deaths)

·         flooding in Thailand

·         earthquakes in Turkey and Christchurch

·         eruption of the Grímsvötn volcano in Iceland

·         drought in China and East Africa

A review of most years would find a similar number of events such as these, although the locations may shift. Although ‘mother nature’s fury’ still manages to enthral us, the impact of such natural disasters is fairly inconsequential in terms of population impact. Flooding in Queensland, which attracted great media attention, saw the loss of 35 lives. This is only one tenth of the number of Australians that die on average each day (141,000 people in 2009 – 386 per day).

Although natural disasters have the potential to claim large numbers of lives, only four natural disasters in history have claimed more than 500,000 lives, the largest being the 1931 China floods that claimed 1-2.5 million lives. Thus, as a historical contributor to population decline, disasters make only a minor contribution, that is almost exclusively localised. Further, by their nature, disasters are difficult to predict, and thus do not lend themselves easily to projection.

Man-made disasters of any significant magnitude are even rarer. The Bhopal chemical disaster claimed 16,000 lives[xvi]xvii, while the Chernobyl nuclear power plant explosion is blamed for 4,000 deaths[xvii] – inconsequential figures in the scheme of human population, although highly damaging to the communities affected.

The one potential exception here are volcanic eruptions, where sufficiently large eruptions, such as the Mount Tambora eruption in 1815, throw large quantities of ash into the atmosphere that have an impact on global temperatures and agricultural production. Were such an event to occur today, the greatly increased world population would likely see significant famine, potentially leading to population decline in some areas.

Emerging Issues

Climate Change

Although there are a broad number of impacts from anthropocentric global warming, the most serious impacts on global population levels will be disruption of agriculture, as changed climate patterns disrupt rainfall patterns and overall growing conditions. Although a general warming will see some areas unsuitable to permanents agriculture, such as sub-arctic tundra, become more capable, modelling shows that there will be a net reduction in arable land, particularly as output is a product of other factors, such as soil composition, which will not change as rapidly as climate.

In Australia, modelling[xviii] predicts that rainfalls driven by the interaction of arctic air masses in the Southern Ocean that deliver large rainfalls over southern Western Australia, will shift more southerly, causing such rainfall to not reach land. As this region is one of the key grain production areas of Australia, this would cause a significant impact in food output, possibly pushing Australia from being a net exporter to a net importer of grain. Such patterns are predicted in other areas of Australia and other key food production regions in the world.

A contemporary example that demonstrates potential future situations are the recent high rainfalls in South East Asia, particularly Thailand, Laos and Vietnam. The flooding has wiped out rice crops and the terraces on which they have grown, leaving many farmers without crops to sell. Without this revenue they are unable to purchase seeds and other materials to grow next season’s crops, and an underdeveloped financing system creates difficulties in rebuilding. This is a localised example of the impact of changing climate, and the predicted growth in extreme weather events.

Additional impacts will be a potential rise in epidemics, such as mosquito borne diseases like malaria, Ross River fever and Dengue fever, as currently temperate areas become more tropical.

Peak Oil

Although often derided by critics for their predictions of large scale famine, the Club of Rome and Paul Ehrlich’s predictions are mostly undermined by their underestimation of the use of artificial fertilizers to boost crop yields, and feed the growing population numbers. Although a marvelous human achievement, fertilizers are dependent on oil, which is a finite and diminishing resource.

Whilst a world without access to oil will be a very different one from the one we know now (not only is it the key transport fuel worldwide, but it is also an essential ingredient in many manufacturing processes, such as plastics and other synthetics), the most likely global impact of peak oil will be the economic disruption caused by rising prices as output falls in the face of ever growing global demand. It has been stated that the growth and prosperity of developed nations is primarily attributable to cheap energy, and serious questions exist to the viability of modern economies in their present form in the face of rising oil prices (and because of their substitutability, other energy forms, such as LPG). Given the US dependence on cars and trucks for transport, and a chronic underinvestment in public transport infrastructure, a doubling or tripling of world oil prices (predicted within the decade by most models)[xix] could reduce the mobility of US society, with knock-on effects for productivity and political stability.

Such a scenario in the US could have several global implications. Although subject to a broad range of interpretation, the US can generally be seen as a force for military stability in the world. Military exercises by the US are driven more by seeking to stabilise situations (albeit in a way that aligns with US best interests), rather than outright conquest. Most regional conflicts, and particularly the Middle-East, stay at a simmering level, rather than escalating into large scale conflict that would force the US to intervene. A destabilised or weakened US could remove such restraints, leading to large scale regional conflicts, and resultant population declines. A weakened US could also lack the direct military intervention capabilities it currently possesses, and have to resort to nuclear weapons to intervene, leading to a possible nuclear escalation.

An alternate scenario may see the US seek to act more aggressively in its self interest, and acquire foreign oil assets by force. As history has shown, in times of great economic stress, what were once far-right politics can become mainstream orthodoxy, and politicians willing to exploit these sentiments may soon have large amounts of power[xx]. The bidding war in the 2024 Republican primary on the question of “what are you willing to do to lower oil prices?” is a scary thought to contemplate. This would have a global destabilising force, and again raise the prospect of nuclear exchange.

Oil is one of the key drivers of industrialisation, and as more developing nations seek to become more industrialised, underlying global demand for oil will rise. However, such demand will probably never be realised, as rising prices for oil will prevent poorer nations from affording it, and condemning them to lower levels of development. With development a key lever to reduced fertility, this could potentially lead to short term population rises, which would exacerbate those downward population pressure factors that are driven by population size.

A critical issue in the issues of peak oil is the fairly extreme geographical concentration of supplies (the Middle-East region contains 56% of known oil reserves[xxi]), and the dependency of the United States on imported oil. This drives a number of geo-political situations that could have global impacts.

Epidemiology

Although the world has more than enough deadly diseases, that in the face of social and economic collapse would reassert themselves as strong contributors to death rates, the natural ability of viruses and other disease pathogens to mutate and ‘interbreed’ with other pathogens creates a permanently evolving pool of potential disease vectors. Added to this, human society creates conditions where viruses that would normally remain independent of each other (because they host in different species) can interact, potentially moving from one host to another. This is particularly dangerous, as immune systems have much lower defences against viruses from other species. This means that diseases can be far more fatal and spread far more easily, which can lead to a global pandemic.

HIV

The HIV virus presents some almost unique implications in the area of disease and its impact.  Unlike all previous large scale epidemics, HIV, and the AIDS illness it contributes to, take a long period of time to develop, and death may follow up to 10 or 20 years after infection.  Without an effective cure, death still results (between 80-100%[xxii] of cases), and in several areas of the world, particularly sub-Saharan Africa, AIDS is a major contributor to death rates.  The key difference for HIV/AIDS is the demographic impacts of the delay between infection and death, as well as the impact on infant mortality (17% of babies infected with HIV die before reaching 2 years of age[xxiii]).  The significance of HIV to population decline scenarios is that it presents a model for future fatal sexually transmitted diseases with long mortality periods.  Further,  as it is strongly supposed that AIDS is a mutation of an animal-borne disease into human transmissible form, it sets a precedent for this source of infection.

Nuclear Proliferation

Although the likelihood of the human race being wiped out in a global nuclear war is fairly low, short of a cosmic event, this scenario represents the biggest threat to population levels and the general continuation of civilisation. Modelling of a large scale exchange between the United States and the Soviet Union at the height of the Cold War forecast between 1 and 2 billion short term deaths[xxiv], and the high likelihood of ongoing population decline due to the destruction of infrastructure and social structures. The collapse of the Soviet Union since then, and Russia’s decline as a global presence, has reduced this threat significantly, coupled with the reduction of nuclear arsenals and altered nuclear strategies (targeting military rather than civilian targets). Indeed Russia is currently experiencing population decline, resulting from a combination of low fertility rates, shorter life expectancy than Western nations, and negative net migration.

With China replacing Russia as the second super power, and likely to supersede the United States as the dominant economic power in the middle of the current century, the potential for a major nuclear exchange could emerge. However, China’s nuclear arsenal is a fraction of the size of Russia’s, and given the Chinese economy’s dependence on international trade, the likelihood of an arms race on par with the Cold War is far less likely, with a resultant reduction in the likelihood of a large scale nuclear exchange. Sovereignty tensions, with Taiwan being the most prominent, always have the potential to flare up into major confrontations, but these would most likely be conventional military exchanges.

Aging Population

When Total Fertility Rates drop below death rates, then a population is said to have reached structural population decline. Japan is the nation that most vividly represents this situation, although the aging of the population from the brie f post-WW2 ‘baby boom’ means that actual decline is yet to occur. Once this group starts to exceed mean life expectancy at birth (currently 82.6 years in Japan), then the mortality rate will begin to rise (as people begin to die of old age), and overtake the birth rate. Once this occurs, and without offsetting migration (currently not an option being utilised by Japan for a variety of cultural reasons), population decline is a rapid process, and very hard to correct, particularly if the factors behind low fertility rates are culturally entrenched (such as marriage customs), or tied to population aging (financial pressures of raising children being exacerbated by the taxation burden or cultural traditions of supporting an aging population).

Currently, there are 65 countries with net fertility rates below replacement rate (being 2 children, or more technically, one daughter reaching reproductive age per mother). This is currently hugely offset by 71 countries with TFRs over 3[xxv]. For low fertility to become a global phenomenon, the global TFR would need to fall and stay below 2. The factors most greatly impacting low fertility are increased levels of female education and general levels of development. TFRs below replacement rate are almost exclusively developed or industrialised nations. Such a scenario has 2 requirements: that the majority of nations reach a higher level of development, and that female rights are lifted, primarily through the avenue of education.

Many population control advocates a support a rapid transition to a global TFR slightly below population replacement levels as the most humane way to address the issue of population growth. Some of the obstacles to this include:

·         Cultural barriers, with cultural preferences for large families

·         The strong influence of the Catholic Church and other religious dogmas that influence reproductive actions

·         Barriers to family planning and the use of contraception

·         High child mortality rates, which entrench the compulsion to have many children, as an insurance policy

Although every humanist’s preference is for managed and humane population decline to more sustainable numbers, there are a number of barriers to this being achieved via structural global demographics alone. These include:

·         Long lead times – as Japan demonstrates, even severe conditions of low fertility take a long time to manifest, particularly in developed countries with long life expectancies. Japan’s birth rate has only just fallen below its death rate, despite 40 years of declining fertility[xxvi]. On a global level, even moving to a global TFR of 1.8 would not see populations decline until 2075[xxvii]. Significant population declines (say to a level of 6 billion people) would take even longer to achieve. This leaves a significant time window for other population pressures to exert their influence.

·         Impacts of resource depletion with a growing population – the present consumption levels of finite resources (particularly oil and fresh water, but also top soil and marine agriculture)are not sustainable, and a growing population, and increase in consumption through economic development and urbanisation

Scenarios

Getting Old

With the global birth rate’s declining, it seems that even without hitting any resource constraints, the earth’s population will at some point begin to decline, as the death rate of an ageing population finally passes the declining birth rate. When that occurs, and what the state of the planet will be at that time drive the two scenarios considered here, when natural death from old age becomes the driver of population decline.

Good old

In this scenario, technology delivers solutions in the areas of peak oil (allowing agricultural output and distribution systems to be maintained) and clean energy (limiting climate change to levels that can be successfully adapted to). Genetically modified crops successfully deliver increased yields to support a growing human population, whilst global agreements limit conflict to localised skirmishes. Clean energy drives desalination technology, delivering adequate water to a large percentage of the population. Political stability and moderateness becomes the norm, allowing greater gender equality, which causes fertility rates to decline in the developing world. Greater migration allows for aging population issues in existing developed countries to be alleviated.

As a result, human population continues to rise, but at a declining rate, and eventually reaches a point where fertility drops below net replacement rate. Due to demographic lags, and increased life spans due to advances in medical technology, the point at which population decline begins does not begin until 2100, when the population peaks at 9.3 billion. However, from this point onwards, population decline begins its relentless path. Developments in robotics limit the impact of this decline, and global population consensus decrees that a long-term target of 4 billion people be reached. When such a point is reached (in about 2500), the earth will face a potentially new population challenge, but will have dodged the overpopulation bullet is well as could possibly be hoped.

Bad old

As the world reaches and passes peak oil, it is not so much the reduced availability of oil that becomes the issue, but rather the massive disruption to local and global economies that sky rocketing prices cause. $200 a barrel for oil becomes the norm, and this has price impacts throughout the economy. The growing evidence of the severe impact of climate change sees similar rises in other energy costs, but renewables fail to live up to their promise, and energy costs become a significant social cost.

The age of cheap consumable goods disappears, and goods that had been treats in times past, revert to their luxury status. Standard of living declines, as rising prices for staples such as food (particularly meat, and bulky food that has to be transported considerable distances, such as tropical fruit) and energy lead to declining discretionary expenditure.

Government, faced with increased costs to maintain vital infrastructure (and reduced revenues as tax revenues fall as company’s expense growth exceeds their revenue growth), have less revenue to spend across all sectors, and scaling back in health care, education, welfare services and other social spending further reduces the standard of living. Services formerly delivered almost exclusively by the government (health and education) become far more privatised, and much stronger social division emerges between the haves and have nots – particularly those groups previously highly dependent on government support. This social dislocation leads to increased crime, and decreased contentment in life.

Wars begin to break out in hot spots around the world, centred on resource disputes, and defence requirements stretch already strained government budgets.

The stresses on starting and maintaining families increases, driving birth rates still lower, and terminal population decline spreads throughout the world.

Hunger, disease and warfare become more prevalent, but as in the Great Depression, society manages to limp along. Life expectancy falls, but only marginally, and people still tend to live long lives, but they sometimes question the benefits of doing so.

Getting Hungry

One of the prerequisites for a growing population is the ability to feed the additional mouths added. A number of factors, such as peak oil and climate change, cast doubts about our ability to achieve increased food production to meet growing demand. This section explores two scenarios that examine these downward pressures.

Bad hungry

Peak oil causes oil prices to rise, impacting the price of fertiliser and the general costs of agricultural production and distribution. Farms are forced to adopt more organic methods as the cost of oil-based inputs becomes uneconomical. Through a combination of natural sciences and ingenuity, crop yield declines are kept at manageable levels, and mass starvation is mostly averted. Developments in other fuel substitutes, such as Gas to Liquid, prevents large scale conversion of agricultural land to the production of bio-diesel, and avoids grain prices spiralling out of control as crops such as sugar and corn are diverted to the fuel market.

Grain crop are diverted from meat production to general consumption as human food stuff, leading to a massive reduction in the output of meat, and a commensurate increase in price.

Some genetic engineering advances deliver crops that are suited to more marginal farming land, but yield gains are stymied by the increased demand for water and fertiliser these strains require.

The world is able to feed less people, and famines are unavoidable in some areas. Costs of feeding families in the face of high fuel and food prices reduce family size, and hasten the shift to natural population decline.

Very bad hungry

Peak oil leads to a quadrupling of oil price by 2050. Crop yields plunge as fertilizers become prohibitively expensive, whilst food prices soar on the back of reduced yields and steep rises in the distribution costs. Arable land close to urban centres is in short supply, having been converted to buildings through the urbanisation process. Climate change is leading to more severe weather episodes, such a drought in marginal farming regions, and floods in more tropical climates. This impacts both seasonal agricultural output, leading to localised famines through a combination of reduced output, and the unaffordability of food, as well as exporting of food to world markets chasing increased prices leaving insufficient quantities to feed local populations (driven by the ownership model of agriculture – a key factor in the great potato famine).

Countries such as Australia that were previously net food exporters find that changing weather patterns limit agricultural output of previously key regions (such as the southern Western Australian wheat belts), whilst offsetting gains are limited. Combined with rising oil import costs, and declining economic activity in trading partners reducing resources export income, leading to significant current account deficits and falling government revenues. As cost of living sky rockets, whilst income falls off the back of declining economic condition, social institutions begin to decay, and food distribution systems fail, leading to widespread malnutrition and potentially urban famine. A combination of malnutrition and outright death (if not from starvation, then greater susceptibility to diseases), particularly among the elderly that are most highly dependent on government programs and general community charity (the savings incomes of independent retirees will be severely eroded a share prices and dividend payments tumble in a declining economy, and fixed income investments become less reliable due to greater default risk). This triggers early population decline in developed countries where generational lag postponed the age differential effect.

Getting Sick

Climate change drives changes to localised climate, which in some parts of the world causes temperate climates to take on sub-tropical characteristics. This leads to the mutation of previously low impact diseases, causing first world epidemics of previously tropical diseases. Rising energy prices and declining crop yields due to climate change severely impact developing economies, particularly in Africa, and reduce health and sanitation, causing previously controlled diseases such as cholera to re-emerge. Intensive agriculture, driven by commercial interests and the need to feed an overgrowing urban population, see more mutated animal diseases entering human populations, until eventually a ‘perfect storm’ of transmissibility and fatality emerges, delivering a disease that spreads rapidly, and added and abetted by globalisation and frequent international travel, spreads around the globe. Despite advances in medical technology, mutation pressures within the population produce waves of fatal epidemics that severally effect population, and lead to spikes in death rates that cause net population decline. Because of the susceptibility of children, these epidemics also cause demographic impacts, with the next generation of breeding age reduced in number, leading to aging of local populations and eventually population declines.

Bad sick

Climate change drives changes to localised climate, which in some parts of the world causes temperate climates to take on sub-tropical characteristics. This leads to the mutation of previously low impact diseases, causing first world epidemics of previously tropical diseases, such as malaria and dengue fever. Rising energy prices and declining crop yields due to climate change severely impact developing economies, particularly in Africa, and reduce health and sanitation, causing previously controlled diseases such as cholera to re-emerge.

Because of the susceptibility of children, these epidemics also cause demographic impacts, with the next generation of breeding age reduced in number, leading to aging of local populations and eventually population declines.

Very bad sick

Intensive agriculture, driven by commercial interests and the need to feed an overgrowing urban population, see more mutated animal diseases entering human populations, until eventually a ‘perfect storm’ of transmissibility and fatality emerges, delivering a disease that spreads rapidly, and aided and abetted by globalisation and frequent international travel, spreads around the globe. Despite advances in medical technology, mutation pressures within the population produce waves of fatal epidemics that severally effect population, and lead to spikes in death rates that cause net population decline.

Good sick?

The misery inflicted by wars and famine tends to have a long tail, with long-term impacts that can take years or decades to recover from, it at all. The failed state of Somalia, driven by both famine and war, shows the difficulty of recovery. Disease, on the other hand, primarily impacts human life, leaving infrastructure and environment untouched.

Accordingly, it is possible to envisage a scenario where a worldwide plague would actually provide long-term benefits to humanity. As previously discussed, the Spanish Influenza of 1918-19 killed 10 times as many people as World War 1 in 4 years. The characteristics of the Spanish Flu that made it so deadly were its high mortality rates (up to 50% of sufferers died, compared with less then 0.1% with normal influenza) and its high rate of transmission (infecting up to 50% of exposed populations).

Were a contagious disease with these characteristics to emerge, it could potentially kill half the population of the planet (offsetting strongly improved treatment procedures with a much more rapid global spread due to frequent air travel).

The short term shock would be dramatic, but long-term, a vast number of resource constraints would be lifted, such as energy and food output. Further, the resulting global society is probably more likely to adopt developed country practices, including lower reproduction rates, meaning further possible population decline. If the disease targeted the very old and very young, these demographic impacts would be further strengthened.

Getting Shot

It is almost ironic that despite our technological advances in weaponry and hard wired aggressiveness, human efforts at killing one and other pale in comparison with natures twin arsenals of hunger and illness. World War I had a massive death toll (10.5 million direct deaths over 4 years), however in the 18 months following the war, Spanish Influenza killed between 50 and 100 million people. Likewise, of the 620,000 casualties in the American Civil War, only 212,000 were determined to have died in battle, with the majority of the 400,000 additional deaths being attributable to disease and starvation.

Populations recover very quickly following warfare, and only the largest of military conflicts (World War 2, the Mongol conquests and several Chinese civil wars) have made meaningful dents in the world population (> 3%). The An Lushan Rebellion in China between 755 and 763 may have claimed 15% of the world’s population at that time.

However, the advent of nuclear weapons has enhanced our destructive power by many orders of magnitude, allowing the potential to rival or even exceed nature in destructive power.

Two scenarios where warfare could lead to population decline are considered:

Bad shot

Even a regional nuclear exchange (such as India/Pakistan, Israel/Iran or North Korea) if targeted at population centres would be unlikely to have a significant impact on global population. Scenario estimates of an India/Pakistan exchange put fatalities at c. 10 million. Although a horrific scenario, it would not even cause global population to decline for a 12 month period.

However, as well as immediate casualties, there would be a number of flow-on effects. Fall-out could potentially make vast tracts of land both uninhabitable and unusable for agriculture. This would lead to mass migration, overwhelming services, and drops in agricultural output, leading to potential famines. The destruction of infrastructure, particularly transport infrastructure, is likely to lead to significant declines in output, as well as distracting significant resources to rebuilding and alternative operations. This would take resources away from health care and general sanitation, leading to increased death rates from disease, particularly among young people. This would have demographic implications for the impacted countries, as well as their neighbours.

Depending on the nature of the exchange, large amounts of particulate matter may be thrown into the upper atmosphere, with the potential to reduce global temperatures. Modelling shows that a 2 degree fall in global temperature could occur, possibly for several years, which would significantly reduce agricultural output, and lead to large scale famine[xxviii]. Such an event (for which an India/Pakistan exchange is the only likely candidate) could lead to overall global population decline, with the potential for political destabilisation that could have large scale flow on effects.

Very very bad shot

With peak oil and climate change driving reduced agricultural output, a larger number of people will chase a smaller pool of resources, and rather than sitting around waiting to go hungry, groups ranging in size from local militias to whole nations, will seek to secure the feeding of their populations and access to oil. Despite a shortage of food, there is no shortage of weapons, and localised and regional conflicts occur on a scale unseen since World War II.

Initially, Civil wars are the dominant conflict type, as groups within countries seek to control food and energy sources, as well as other resources that provide wealth. Although casualties from conflicts are high, the major impact is starvation as food resources are no longer evenly distributed. Large scale migration to escape fighting sees the emergence of refugee mega-camps, with resultant disease tolls. Developed nations, struggling under their own oil and agriculture issues no longer have the capacity to offer assistance in anywhere near the scale required, and starvation of refugees becomes the dominant cause of death.

Russia’s significant, but inequitably distributed resources may well become a flashpoint for internal conflict, as may the lure of former Soviet resource rich territories, such as Ukraine and Kazakhstan, prompting a new period of Russian expansionism.

Key to agriculture, particularly in arid areas, is the control of water. Nowhere is this more significant that in the Middle-East and with Israel and Iran both fielding nuclear arsenals, a localised nuclear exchange is almost inevitable. As well as the local loss of life (likely to be proportionally high, as the Middle East climate leads to denser urban populations that would be impacted nuclear strikes), oil infrastructure is likely to be targeted, further exacerbating the world’s oil issues.

Likewise, dwindling resources and collapsing infrastructure push India and Pakistan towards more extremist forms of government, and armed border conflicts quickly escalate into a medium scale nuclear exchange. The flow-on effects of this exchange are far more significant.

As China takes the mantle of most powerful nation from the US, it may seek to use it new found position to address unresolved territorial issues, particularly Taiwan. Depending, on the degree of isolationism the US adopts to deal with its internal economic decline, it may or may not seek to intervene, and with limitations on its ability to project into China’s home turf, may resort to nuclear weapons in any regional conflict. Retaliatory impacts would place not only the United States, but potentially Japan at risk.

The nature of modern combat sees smaller armies with greater reliance on technology focused on targeting enemy combat infrastructure, seeing smaller casualties for both troops and civilians. However, such combat techniques can only by maintained by a handful of nations, and only for short periods. Any protracted conflicts would most likely resort to World War II tactics, with resultant casualty rates. Likewise, respect for civilians and other innocent bystanders would quickly evaporate, especially amongst the sides losing ground.

Putting numbers on casualty rates in future wars is difficult, particularly as the casualties are more likely to come from hunger and disease than bullets. Although the death tool from any nuclear exchange would be horrific (estimates of a large scale exchange between India and Pakistan range from 5-20 million immediate deaths), it is the destruction of infrastructure and its impact on death rates that would be the truly horrific number. Any significant nuclear exchange would leave the target country with an instant negative population growth scenario, and again, with the rest of the world fighting resource constraints, assistance in rebuilding (such as the Marshall Plan) would be limited, meaning the diversion of large amounts of resources to rebuilding infrastructure.

Any nuclear exchange would also likely through up large amounts of dirt and ash into the atmosphere (nuclear strikes at hardened military targets need to be ground bursts, which throw up far more fallout and particulate matter). As this matter enters the stratosphere, it takes a long time to fall back to earth, and can be dispersed around the world. This has global climate implications, which in turn affects crop growth, and may lead to worldwide crop failure and resultant famine, potentially killing billions. Modelling has predicted that a large scale nuclear exchange would lead to a world-wide temperature drop of 15 degrees[xxix]. Such an occurrence would be a species extinction event to rival those of previous epoch ending disasters.

Conclusion

With the reality of Malthus’s battle between exponential population growth and linear resource growth, future human population decline will be inevitable. Emerging issues such as climate change, energy costs and nuclear proliferation up the ante on the risks humans face of population decline being driven by external forces, rather than demographic shifts over time.

To help us envisage how population decline might manifest itself, we have made use of future studies and scenario planning, and utilised a four scenario model, summarised neatly (if crudely) as:

·         Getting old

·         Getting hungry

·         Getting sick

·         Getting shot

The scenarios that emerge from applying this model drive home an important message. The only scenario that envisages a desirable future is the “Good Old” scenario. Closer consideration of this scenario shows a raft of pre-requisites that map closely to the solutions needed to address many of the ‘wicked problems’ facing contemporary society. As we have seen, unless these problems are addressed, the alternate scenarios range from pessimistic to down-right abhorrent.

Examining the negative scenarios surely provides significant incentive to society to face and tackle the problems that dog our future progress, as it is in our personal and collective interests to ensure that the alternatives envisaged do not come to pass.