This is a guest post by Javier
Javier holds a PhD in Biochemistry and Molecular Biology and has been a scientist for 30 years in molecular genetics and neurobiology. He wrote a blog on macroeconomy and investments from a cyclic point of view for over two years and currently writes a blog in Spanish about the economic crisis, energy crisis and climate change at http://www.rankia.com/blog/
game-over/ . Javier goes by the name of Knownuthing on his blog.
Opinions expressed in this post are those of Javier and not necessarily those of the blog owner Ron Patterson. This post was translated from the Spanish by computer and may therefore contain some grammatical errors.
The Problem of the Human Population
The question of whether or not overpopulation in the world is clearly debatable. For starters there is no agreement on what should be the world’s population and is also clear that currently the world is able to withstand the seven billion people who live and there is little doubt that it can support more, as the number increases constantly.
However, there is concern for decades that in a finite world at some point should be the limits of the world’s population, and that may not be very smart to reach those limits. Although efforts to limit population growth in some countries like India or China, today these efforts have been abandoned or are abandoning were made in the second half of the twentieth century, mainly due to the pace of population growth is declining alone globally.
As in all matters based on the laws of nature, we can use science to analyze the problem of the human population. The science that helps us in this case is ecology, which has a specific branch of human ecology . Anyone who thinks that we do not apply the laws of biology, is that it has lost touch with the reality of human nature. For very rational to presume to be, we are still animals and not very rational forget.
1. How many and how fast we grow?
The world’s population at the time of this writing is 7,301,880,780 people on the face of the Earth. You can see the current figure on pagehttp://www.worldometers.info/world-population/
Seven 1300 million and growing at a rate of 1.1% per year, ie 80 million people each year , the equivalent of two Spains completely filled each year.
Fig 1 Growth of world population and growth rate estimates up to 2050. Source: World Population Data
Since the growth rate is declining naturally, if not intervene any new factor human population on Earth would peak slightly above the 10 billion people by 2062 according to the United Nations. This is the problem size. The odds that this issue is addressed in political form before 2062 are very low. Political campaigns to reduce the growth of the human population are decreasing, not increasing. The most effective of all, China’s policy of one child per couple is relaxing and and only a third of the population is subject to this limitation (Source: The Australian ).
Fig. 2. The population of Earth is very unevenly distributed. Population density in 2006 at national or subnational level people per km2. Source: Wikipedia
The question therefore is not to analyze whether the earth is able to support 10 billion people, it most likely is yes you can, but if you can do indefinitely. And here’s where we come in ecology. A half capacity to support a species called capacity (carrying capacity) .
2. The carrying capacity
In the context of ecology, the carrying capacity (K) is a theoretical concept, which represents the maximum number of individuals of a species that is capable of supporting ecosystem . This concept demonstrates its practical usefulness when observed that populations with capacity growth tend to occur in many species, a sigmoidal growth asymptotically approaches a value that was defined as capacity (Odum, Fundamentals of Ecology, 1953). Another more modern working definition is that the capacity of a population is the size of the population (N) when its growth rate (r) becomes zero and stops growing (Molles, Ecology: Concepts and Applications, 2012).
Fig. 3. The growth of a population (dN / dt) limited by its capacity (K) follows a sigmoid curve, which is proportional to its maximum growth rate (r) by the population size N and a factor is less the closer N to K.
The load capacity is not a static value as shown in Fig. 3, but to depend on the environment and the interaction of the species with the same, and indeed may vary varies with time. Natural areas managers measure key indicators of species and habitat to determine which populations are responsible below the carrying capacity. Experiments in natural areas under management by government agencies show that populations are limited by the medium. Essentially the availability of food, but also to a lesser extent by other factors such as water, shelter and space (see for example: Carrying Capacity – How many deer can we Have? ). Populations living therefore tend to fluctuate naturally around a certain level which is defined as its charge capacity. An animal population may be below its carrying capacity in the spring after a hard winter, or temporarily above it during the winter, a situation that usually lasts a short time and that inevitably leads to a decline in population due to multiple natural limiting factors (eg mortality, disease, migration and decrease the rate of reproduction).
The concept of carrying capacity also applies to human ecology . The study of human populations shows the recent evolution of their capacity. If we analyze the population of England and Japan over the last few centuries (Fig. 4), we can see that in both cases the population had reached the end of its sigmoidal growth, stabilizing their populations in the value of their capacity, 5 million in the case of England and 35 million in the case of Japan (K1). The Industrial Revolution began in England in the mid-eighteenth century and Japan in the second half of the nineteenth century, substantially increased the capacity (K2) to current levels, causing a rapid increase in population in both cases, to the new level (Meyer & Ausubel 1999. Carrying Capacity: A Model with Varying Logistically Limits ). Note that the shorter duration of the industrial revolution in Japan (77 years) due to be later, it corresponds to a growth in population correspondingly faster.
Fig. 4. Evolution of the population of England and Japan in recent centuries. We can see how the lifting capacity (K, inferred) results in the increase of population (P million) according to a sigmoidal curve to stabilize at the new value. Source: Meyer & Asubel 1999 .
Numerous studies can relate the increase in capacity in human populations with increased food availability . See for example Hopfenberg 2003, Human Carrying Capacity Is Determined by Food Availability .
The factors leading to an increase in human carrying capacity are essentially :
Expansion . Increased cultivated by two processes, increased land area exploited by man and change in land use (forest -> grass -> culture) surface towards higher productivity.
Increased energy expenditure . Extensive farming mechanization, irrigation, use of fertilizers, herbicides and pesticides.
Increased knowledge . Selection of seeds and species, use of improved agricultural techniques, improved fishing technologies.
Positive climatic factors . Increase in temperature and humidity. Increased rainfall Increased CO2.
Factors leading to a decrease in human carrying capacity are essentially :
Declining resources . Aquifer depletion, rising and declining fuel and energy, collapse of fish populations.
Environmental degradation . Pollution, soil loss, nutrient loss, desertification, deforestation, loss of pollinators, pest favoritism.
Adverse climatic factors . Droughts, floods, weather extremes (El Niño and La Niña), reduction of temperature and humidity.
Historically the global carrying capacity of humanity has experienced a gradual increase, although there have been local collapses because the positive factors have predominated over the negative . Especially with the industrial revolution energy costs soared and a strong increase of knowledge which subsequently led to the green revolution began, all of which produced an exponential growth of the human population. This past success leads to much of humanity to think that future increases in knowledge and technology now can not imagine allow indefinitely increase the capacity , or at least we are far from a maximum load. This theory however contains hidden errors and fallacies that completely disabled. These errors are as follows :
Technological progress is ambivalent because it also allows an increase in the rate of consumption. Is technological progress in fishing techniques which led to the collapse of fish populations.
Increased capacity is subject to the law of diminishing returns . The cost is becoming progressively higher for a progressively smaller profit. As the population increases the effect of the positive factors per person (dilution effect) is reduced, while increasing the negative factors and cost.
The decrease of non-renewable resources or overexploited renewable is a function of the rate of exploitation , which increases as a function of population growth.
Therefore we can conclude that there is a maximum load capacity for humanity . However there is no agreement on the best way to measure and both methods to measure their results are widely variables. Methods based on determinations constrained by a constant factor, be it surface, amount of food available, or other factors or combination of factors results give very variable and highly dependent on questionable assumptions.Based methods of curve fitting and extrapolation population lacking a theoretical basis. JE Cohen in 1995 in an article in Science ( Earth’s Population Growth and Human Carrying Capacity ) and a book (How Many People Can the Earth Support?) analyzed 65 different estimates of the capacity of mankind. Although most studies tended to estimates between 8 and 16 billion , the change was tremendous, about three orders of magnitude (from millions to billions). The findings appear to be carrying capacity depends on the assumptions one makes and the method used to calculate it . A very unscientific answer.
There is another independent way to calculate the maximum load for the human population, which consists in calculating the proportion of products of photosynthesis on Earth that humans are suitable for use. A 1986 study by Vitousek et al. Human Appropriation of the Products of Photosynthesis estimated that about 40% of potential photosynthetic primary production of the Earth was in the service of humanity or unused pollution, urbanization, desertification, soil loss etc. Since the population in 1986 was 5 billion people, if calculations Vitousek et al. are correct, the ceiling can not be far away from those 10 billion planned for 2062, at which essentially all of the photosynthetic capacity of the Earth will be at the service of humanity and the factors that promote a reduction in capacity they become dominant in the system. Others have made similar estimates and dispersion range of estimates is much lower than in the case of load capacity, calculated that ownership does humanity of primary production of the Earth between 25 and 50% (Day et al 2009. Ecology in times of scarcity ; Haberl et al 2013. Global human appropriation of net primary production (HANPP) ). The factor of 2 which separates these estimates is extremely small considering the short time it takes the human population to double.
Fig. 5. Global Map of the human appropriation of net primary production (HANPP) in 2000 in absolute units (gC / m2 / year). This value can be negative (green) eg on sites where the desert is irrigated, and the Nile Delta. Source: Haberl et al. 2013
We can therefore conclude that the maximum load capacity of the Earth to humanity exists and is well above the estimated maximum population of mankind in 10 billion for 2062. It should be noted that such a degree of appropriation of net primary production of the Earth is at the expense of a strong destruction of biodiversity and increasing environmental degradation, which puts into question that this capacity can be sustained indefinitely.
3. Overshoot
Analyzing the payload carries the important question of what happens when this is exceeded. We have already seen that populations above its capacity reduced its population by natural limiting factors such as mortality, disease, migration and decrease the rate of reproduction. When a stock is above its capacity is said to be in overshoot (overshooting).
The overrun is common in natural populations. For example, many animals experience high mortality during the winter at high latitudes and high mountain, to recover their numbers during the summer, indicating that during spring are below the carrying capacity and fall over.
Throughout history has often been human populations that have been found have overrun. The most common response has been emigration .The ancient history to the Maya, is packed dropout urban settlements when their environment is degraded to make unsustainable population. There are strong indications that both the invasions of the Sea Peoples in the Late Bronze Age, as the barbarian invasions which began in the Middle Ages were actually induced migration persistent drought conditions around the Black Sea and in the steppes of Central Asia respectively, which reduced the carrying capacity below the population.
But often the overrun is part of the ecological strategy of the species, which breeds explosively above its capacity regularly subsequently suffering a collapse. Equally common is that the excess is present when the capacity is altered temporarily , since every species has the potential to grow exponentially. An interesting example is the medium ground finch (Geospiza fortis) one of the famous finches of the Galapagos. The population inhabiting the small island of Daphne Major, a volcanic cone of 0.4 km2, was studied exhaustively by Peter Grant et al. for 30 years. When researchers began the study in 1976 there were 1200 individuals of G. fortis on the island, but the drought of 1977 reduced the population by the end of this year to only 180 copies, a reduction of 85% of the population in just one year . Although a few birds may have migrated to other islands, most died of starvation, because during drought plants that produce seeds which are their main food did not. In 1977 he fell through any chick on the island. Between 1977 and 1982 the population of this small bird that can live about ten years, remained at about 300 copies. In 1983 the weather conditions known as El Niño occurred and precipitation increased about ten times the average of previous years. The conditions were ideal, both for the production of seeds which are the main food of adults, and the caterpillars that feed their chicks. Consequently the medium ground finch population increased to about 1100 individuals, quadrupling in size in one year. Since finches have a set of three eggs that means essentially that year onwards all couples took all her brood of two clutches, resulting in maximum growth . In 1984 and 85 they returned to take extreme drought and population began to collapse. Even in later years one could observe that most of the copies of the island were born in 1983, given the high birthrate of that year.
Fig. 6. Top. Population of medium ground finches on Daphne Major (green) and rainfall (in blue). In years of high rainfall population of finches is triggered. Below.Distribution of the population of finches in percent by the age of individuals in years. The lack of individuals born in drought years is observed. (A) Population in 1983. The distribution is regular except for the absence of individuals born in 1977 when no nidificaron finches. (B) Population in 1987 still lacking the generation of 1977, while the population is completely dominated by the generation of 1983 with abundant rainfall. The droughts of 1984 and 1985 have not only prevented reproduction but have reduced the number of survivors of the other years. Source: Molles, Ecology: Concepts and Applications, 6th Ed 2012..
By analyzing the capacity of Geospiza fortis on Daphne Major island we find the problem and fix a value seen since in dry years the island supports a population of about 200-300 copies, while in wet years the capacity load is at least four times. Take a weighted average does not make much sense, and try to estimate the wet nor dry years. Clearly annual rainfall above average temporarily modified upward load capacity, as in other ecosystems and other species temporary modification may be lower. Populations simply adjust their number varying birth rates and mortality.
From a population standpoint finches are not interested fourfold in wet years since that exacerbates competition the following year and leads to an even higher mortality, which is distributed across the population unnecessarily reducing the total number of individuals . From an individual standpoint, every finch interested in having the largest number of offspring possible to maximize the chances that anyone survive the carnage. We can see that the conflict is resolved in favor evolutionarily exceeded the maximum possible at the cost of the worst possible subsequent mortality.
4. Overshoot and oil
Can the human species in a situation of temporary modification to increase its capacity and address a situation overrun? It is reasonable to ask whether the human species is analogous to the medium ground finch in a wet year remain Island Daphne Mayor our world.
Energy moves the Universe and the energy is the basis of life. In energy terms, a greater accumulation of solar energy in the system oscillator Southern El Niño (ENSO) transfers more energy to the surface seawater passing in greater abundance in the atmosphere increasing rainfall on Daphne Major. Water availability allows plants to take advantage of a greater amount of solar energy to grow and produce seeds. The energy stored in the chemical bonds of molecules of plants allows the multiplication of caterpillars and their predators finches. The energy flows contemplate Sol -> Water Sun -> Ground -> Seed -> Pinzón, and Sol -> Ground -> Tracks -> Chick Finch, are the essence of system operation.When the system transmits more energy There’s finches and transmits less energy when their number is reduced.
Considered worldwide human population keeps growing well below capacity during most of its history. Much of its growth comes from its expansion to other continents and increased acreage. It is however from the industrial revolution as we have seen, the capacity rises substantially and with it increases the availability of food and parallel growth of the population. Since the industrial revolution does not occur simultaneously worldwide, the global effect is shown as an increasingly rapid gradual increase in population. The increase coincides with the increasingly widespread use of energy from fossil fuels, coal first, and then oil and gas, which make possible an increase in productivity.
It is the increased availability of energy from fossil fuels which allows first release of most of the population of the tasks of primary food production , and secondly the appropriation increasingly faster a increasing share of net primary production of the Earth . It is incontestable that the availability of abundant cheap energy from fossil fuels which allows humanity to increase its capacity . The increase of knowledge is a transversal factor. On the one hand is the one that enables the collection and use of a fossil fuel that had always been there;moreover knowledge growth is due to the release of tasks primary production and increased productivity and economic development that allows the use of fossil fuels, and finally increasing knowledge requires a increasing amounts of energy. Nobody is aware that no energy from fossil fuels the current state of our knowledge would be much lower.
Fig. 7. Transition Model of human population. In the mode of operation that has taken place in the history of mankind (Mode I), increased energy has allowed a more rapid decline in the resources of the Earth (more resources for humanity) and increased knowledge with three factors potenciándose by positive feedbacks (green arrows). This leads to an increase of the available food, increased capacity and an increase in population. Economy belt acts as facilitating operation while expands. In the first mode all the feedbacks are positive, so any increases ever faster and humanity feels invincible and is not able to detect the boundaries. The model fails when resources become insufficient and enters mode II. In mode II insufficient resources and reducing external energy remains positive feedback, so that less energy and less fewer resources less energy resources, while reducing energy acts negatively on increasing knowledge. Food production decreases, and with it the capacity and population. The population continues to reduce the resources of the Earth despite its decline, but the decrease acts negatively on the increase of knowledge. As a result the knowledge stagnates or declines and does not act on reducing energy, resources and food. The economy is no longer able to act and contracts. In mode II positive feedbacks have negative effects, like negative and humanity feels powerless and unable to find solutions. Below, model representation of population transition. The end of the last glacial period (a), the implementation of basic agriculture (b), global expansion and advanced agriculture (c), and the industrial revolution (d) have expanded the capacity of mankind for about a factor of 10 each. Since mankind has not been able to exercise any self-control, mode transition occurs at the maximum population, causing a decrease in capacity due to lack of resources and energy (e). The onset of the next ice age will represent another decrease in capacity (f).
Although the rapid growth of the human population goes back centuries, when we analyze its growth rate, what we see is that this is triggered from 1910 (Fig. 8). There is the widespread use of coal which triggers the population worldwide, but the widespread use of oil, which has a direct effect on farm mechanization and the transfer of people from farm work to the secondary and tertiary sectors of the economy. The increase in the growth rate reaches its peak in the 60s of last century, when oil use is spreading worldwide, and decays since decreasing parts of the globe that are to incorporate the development induced energy from oil. Interestingly, the maximum rate of global growth is achieved by 1962, years before the green revolution to take place, so that increased food production, avoiding a humanitarian catastrophe is not actually increasing the growth rate of the population, this had taken place before.
Fig. 8. Evolution of the rate of increase in world population between 1800 and 2005. The rate soars from 1910 when it doubles once before World War II and again after. The fall in the late 50 corresponds to the Great Leap Forward Mao Zedong, which led to a population crash in China. Source: Wikipedia. Data: US Census Bureau.
Oil is therefore equivalent to increasing rainfall for Daphne Mayor Finch. It is the main channel of energy whose increase has allowed the multiplication of mankind to current levels. The expression that humanity is in the Oil Age is correct.
Caution is however before the analogy between humanity and finches too far. Finches have no control over the production of their food, while mankind has enough control over the production of his. Increasing food production has an immediate effect on the population of finches, whereas although that was true in the past of mankind, now the situation is reversed. Is population growth which leads to increased food . Nobody is aware that agricultural production in Spain could be much higher, but there is growing demand simply because the population has decided not grow. In fact the recent history of Spanish farming is a history of limitations and reductions both from the EU as due to global competition.
We can however conclude that increasing the capacity of humanity has been made possible by a steady increase in energy from fossil fuels, especially oil. Such energy may increase continues increasing counteracting capacity increasing degradation of the loss of fertile soil and resource depletion. Since fossil fuels and other resources are finite and are subject to increased exploitation due to population growth, humanity is in a situation of high load capacity temporarily . When this situation comes to an end decreased capacity will inevitably lead to the human population is in a state of overshoot and suffer reduced proportionally.
5. The case of the Soviet Union
We have several examples of overshoot in the history of mankind. One of the best known is that of the Soviet Union. Without going into the causes of its collapse, which is a matter of debate, we can stick to a number of illustrative facts:
In 1987 the Soviet Union reached its peak oil production and two years later his peak consumption. In just eight years its oil consumption falls by 50% (Fig. 9).
For the next 1987 years the country will join in a severe economic crisis characterized by shortages widespread.
Between 1988 and 1998 grain production fell by 37% (from 103 to 65 million tons per year), the production of meat, heavily subsidized in the Soviet era, fell by 56% (from 10 to 4,400,000 MT per year ). Grain imports also fell by 90% (from 21 to 2,100,000 MT per year) Source: Liefhert et al. 2010 Russia’s Transition to Major Player in World Agricultural Markets .
Since 1988 the birth rate, which was stabilized, begins a steep descent and continue down to the end of the crisis in 1999. At the same timethe mortality rate begins to grow more acute growth in 1991. As a result of Therefore, the growth rate was two decades stabilized at 0.5% plummets turning negative in 1991. The population is reduced for 20 years, and has not grown back (Fig. 10).
In 1991 the political entity divides into many smaller countries.
Without going into an analysis of causes and consequences, the Soviet case seems a textbook example of how peak oil and the severe economic crisis that accompanies it are related to a reduction in food production and population decline.
Fig. 9. Production and exports of oil consumption corresponding to the former Soviet Union until 1991 and all countries that formed since. Peak oil is observed in 1987. After more than 25 years, production has recovered, but not consumption. Although the peak, the Soviet Union never lacked oil.
Fig. 10. Evolution of the population in Russia between 1950 and 2012. Natural growth in green, blue births and deaths in red (data on annual ‰). Between 1987 and 1994 the effect of the collapse of the USSR, followed by stabilization until 2001 and slow improvement since then notes, having recovered the level of pre-crisis growth. Source: Wikipedia.
At the moment I’m interested to bring three points to the analysis of the Soviet collapse. The first is that the collapse took place amid a global prosperity . The rest of the world was perfectly able to export to the Soviet Union all goods demanded it. But that did not prevent imports were reduced. The demand is not what you want or need, but what you can afford, and the Soviet Union was able to pay less and therefore got less and less the rest of the world. His demand collapsed.
The second point is that food production suffered a sharp decline even though the fields were still fertile, agricultural workers were still available tools and knowledge was undoubtedly Russia he lacked enough oil to agriculture since remained exporters. And of course food production fell even though the Russians wanted to keep eating just as well. That is, all pieces were completely in place except the economy. Despite being a command economy whose main objective was to feed all citizens, demand plunged, because citizens had a much lower purchasing power, and supply sank because the producers had trouble paying to get the inputs necessary and to collect their products. It is a clear warning that food production depends on the economy , and the capacity can sink, triggering hunger and starvation, even though it has the capacity to produce enough food.In Spain we are well able to significantly increase our food production, yet in the wake of the 2008 crisis had to enable that school cafeterias open during the holidays to combat child malnutrition among the most disadvantaged.
The third point is that the Soviet collapse was caused by a reversible reduction of available resources . As a result, after 12 years of crisis Russia was able to correct the situation, and although today almost none of the analyzed parameters recovered from 1986 levels, recovery is remarkable. A collapse due to an irreversible reduction of essential resources is not likely to be reversed.
6. sustainable carrying capacity.
As we have seen in the case of finches, a fundamental property of all living beings is their ability to grow exponentially rapidly to reach its capacity. If birds and bees do well, it is natural for humans to have done. The novelty from a biological point of view is that we are failing to do so and there are countries that could still raise their capacity but have zero or negative growth. But load capacity achieved by mankind is based on exhaustion and dispersion of a unique heritage of natural capital which includes not only fossil fuels but also fertile soil, groundwater, minerals and biodiversity are depleted or degraded quickly to current population levels. Humanity is reducing their potential for future load by eating and degradation of this natural capital received.
If humanity is in a temporary situation of high load capacity has primarily been made possible by the energy extracted from oil and other fossil fuels, such capacity will be reduced according to the availability of these fuels is reduced. Any reduction in the carrying capacity overshoot immediately put us in causing increased mortality and decreased birth to adjust the population to the new capacity. To determine the seriousness of the problem and imagine how far he can take it down before stabilizing population indefinitely, we investigate the capacity of mankind under sustainable conditions without damaging the environment. Of course this exercise is highly unlikely, since as we have seen, is difficult enough to calculate the current carrying capacity under known circumstances.
To load capacity is sustainable indefinitely should not rely on non-renewable resources and must rely on renewable resources only way that allows maintenance. This is an astringent criterion since mankind has never given well maintained in a sustainable carrying capacity. Almost as soon as they appeared behaviorally modern humans, about 50,000 years ago, they began to cause the second worst extinction of the last 55 million years, the EQA (Late Quaternary Extinction) that eliminated the vast majority of megafauna (≥ 44 Kg ) as well as much of the wildlife slow play and all surviving members of their own gender (Koch & Barnosky 2006, Late Quaternary Extinctions: State of the Debate ). And all this before reaching the million humans. It was not a bad debut for brilliant species.
Fig. 11. Anthony Barnosky the EQA was essentially an exchange of megafauna biomass (red, right scale) for human biomass (blue, left scale). To Barnosky, the total biomass of megafauna and man before the EQA was the same as the existing megafauna biomass, man and cattle 200 years ago, but has increased since July. Barnosky concludes: “The normal basal level of biomass is exceeded only after the Industrial Revolution indicates that the abnormally high current level of biomass megafauna is supported only by fossil fuels If biodiversity is indeed a choice between human biomass. biomass of other species, as indicated by both the EQA and theoretical considerations, then the depletion of fossil fuels without replacement by alternative energy sources mean that a collapse of the biomass is imminent, this lowering human biomass and causing extinction in wide range of other species. Source: Barnosky 2008 .
In 1977 Mark N. Cohen in his book “The Food Crisis in Prehistory: Overpopulation and the Origins of Agriculture” suggested that agriculture was imposed to humanity despite entailed major work, poorer health, higher mortality and higher risk due to population pressures worldwide demanding an increase in the number of calories obtained per unit of space (see Cohen 2007 CID Rethinking the Origins of Agriculture ). This theory has been supported by multiple lines of evidence, including the evidence that agriculture could not be developed during the last glacial period because its climate was extremely hostile to the beginning of agriculture for their high variability is climate, its dryness and its low CO2 (Richerson et al. 2001 Was Impossible Agriculture During the Pleistocene but Mandatory During the Holocene? A Climate Change Hypothesis ).
Agriculture Before the man had begun to alter the landscape to make it more productive using the fire . With the development of agriculture, deforestation is accentuated , and obtaining metals, with its high consumption of charcoal, caused an even greater increase. During Roman times there is plenty of historical and scientific evidence that the increase in population and economic development led to degradation or deforestation of many forests did not subsequently recovered, especially in Italy, the Iberian Peninsula and North Africa (Harris 2013 Defining and detecting Mediterranean deforestation, 800 BCE to 700 CE .). Shipbuilding, with a high requirement of wood, especially of tall trees, was also an important factor in deforestation since fleets from ancient Greece to the maritime powers of the XV to XIX, especially Spain and England suffered an abundant deforestation.
The main conclusion is that throughout its history mankind has behaved according to their biological programming, struggling mightily to increase their capacity with no regard to their sustainability, and therefore there is no Paradise Lost man in balance with nature. The phrase “Be fruitful and multiply; fill the earth and subdue it; have dominion over the fish of the sea, the birds and all animals” (Genesis 1:28) is a particularly insightful description of humanity. We have fulfilled this mandate more biological than divine origin and this has been our most successful and simultaneously our greatest failure .
If mankind were to match the capacity conferred by the sustainable use of renewable resources, what would be the size of population? Again it is difficult to obtain and highly hypothetical answer. We can start with the calculation of the ecological footprint , the concept proposed by W. Rees of the University of British Columbia in 1992, and has led to an international NGO that promotes sustainability, Global Footprint Network . The ecological footprint is measured by determining the amount of land and sea needed to sustain biologically productive consumption and assimilate the waste of the population, comparing them with the actual area available (Rees 1996, Revisiting carrying capacity: area-based indicators of sustainability ). According to the calculations of ecological footprint, the current population of the Earth consume resources and generate waste that would require 1.7 planets to sustain . According to these calculations, the sustainable carrying capacity of the Earth at current consumption is 4,300 million. It is a chilling calculation, because it is a figure 41% lower than the current and 57% less than the 10,000 million expected in 50 years. Now we begin to understand what being a finch in Daphne Mayor at the end of a wet year.
Fig. 12. Representation of the global ecological footprint. Since 1970 the Earth is negative and is currently 70% in the red. Source: Global Footprint Network .
However, for those who want even more worrying, there are even more stringent than those of the ecological footprint, such as energy criterion criteria. The load capacity is determined by the amount of energy through the system . For humanity we can distinguish between intrasomática energy, which comes from the foods we eat and holding our population, and extrasomatic energy, which is all the energy we have been using since the domestication of fire and animals that use intrasomática to increase our energy and our population as well as for many other applications, some relevant to our capacity as warm us and defend us from disease, but most can be considered irrelevant use for the subject matter. If we remove from the equation of energy from non-renewable sources, fossil and nuclear fuels, we will be eliminating 90% of our extrasomatic energy. With the 90% base much of the increase of our intrasomática energy due to the mechanization of agriculture, fertilizers, herbicides and based on the oil and natural gas pesticides leaves. A global energy we would be in a similar situation 1870 when it had a population of 1,500 million people who used approximately 10% of the energy we use today. Of course now we have more advanced knowledge of agriculture and improved seeds, is our agriculture would be more productive than then, but at the same time have degraded much soil, groundwater and ecosystems, so that the final productivity could not be higher. Of course we still talking about hypothetical figures, and you can argue that we can greatly increase energy from renewable sources by that we do not have much of nonrenewable energy. That is true and I hope so, but also arguably remains to be demonstrated that renewables are able to self-replicate , ie wind turbines and solar panels are able to sustain their surplus energy mining operations in remote areas , transport over long distances and the manufacture and assembly of the parts needed not only to maintain but to produce new wind turbines and solar panels when their useful life is over, and remove and recycle old. So far renewables have acted only as extensions of fossil fuels and nobody has proven that it can not sustain indefinitely a society of current technological level based only on renewable .
If you want to know what sustainability means bringing our limit, and ensure that the human population is not only completely sustainable and does not cause any harm to the environment, but allows a maximum biodiversity for the rest of the planet’s species, we compare our population with other mammals of similar size . Charles Fowler conducted this analysis in 2003 and discovered that the human population is two and a half orders and more abundant magnitude as the most abundant populations of large mammals (Fowler & Hobbs 2003, Is humanity sustainable? ).That is, the maximum number that we assign the biosphere, our real place in the world is 25 million human . Although there have been large mammals over that figure on Earth, without exception were ruminants, such as bison of the American prairies. For an omnivorous species like ours, a green figure of 25 million is correct. It is estimated that mankind had that number some 4,000 years ago, toward the end of the Bronze Age.
Fig. 13. Size of the human population (dark gray bar) in logarithmic scale on the X axis, compared with 63 species of humanlike body size in mammals. The limits of 95% confidence among nonhuman species are indicated by the shaded edges in light gray area. Source: Fowler & Hobbs 2003
7. Capacity and Climate Change
Seems to be little concern about the effect of global warming on the load capacity, however after over 200 years of warming since the lows of Little Ice Age, no one has observed a negative effect of warming on human carrying capacity . Quite the contrary, agricultural productivity per unit area is still increasing, and crop growing seasons lengthen at high latitudes. Donohue et al. have shown in 2013 that satellites show a 11% increase in plant foliage arid temperate zones between 1982 and 2010, attributed to the fertilising effect of CO2 (Donohue et al. 2013,Impact of CO2 fertilization on maximum foliage cover across the globe’s warm, arid environments ).
Fig. 14. The greening of the world. The satellite images show an increase of foliage between 1982 and 2010 than in temperate arid areas reached 11% and is attributed to the fertilizing effect of CO2. Source: Donohue et al. 2013 .
The Earth has been in substantially warmer, wetter and more CO2 than today passed, and the effect has been more productive Earth. In fact fossil fuels have occurred in times like this. Based on all this evidence it is logical to think that humanity has little to fear of global warming on what their capacity is concerned. Not so with respect to a global cooling that would be extremely dangerous .
There is abundant evidence of the damage done to the human carrying capacity of the Little Ice Age , from the complete eradication of the Vikings from Greenland to the elimination of a quarter of the population of Finland in the years 1696-1697. Losing 15% of its population to Scotland for “The ill years” between 1695 and 1699 was instrumental in his decision to join England in 1707. During the Little Ice Age famines were so abundant in many countries, which organize conferences among historians dedicated exclusively to it (ZiF 2015, Famines During the Ice’Little Age’ (1300-1800) ).
Reaching the end of the exceptional situation within a glaciation of living in an interglacial period is to cause undoubtedly a brutal reduction capacity of mankind, and not just because a good portion of the northern hemisphere is buried under permafrost. The glacial periods of glaciation must also be extremely hostile to agricultural production times . A limitation posed by low temperatures on plant productivity, add the other phenomena that accompany it, lower humidity of cold air, resulting in lower rainfall and a decrease of CO2 that causes a depletion of growth. It should be added increased flooding from melting. To make matters worse, during glacial periods the millennial-scale climate variability (Dansgaard-Oeschger events) is about three times larger than that experienced during the Holocene , which by comparison has been remarkably stable. This climate variability is reflected in a corresponding variability in the ranges of vegetation (Pickarski 2013, Vegetation and climate history During the last glacial-interglacial cycle at Lake Van, eastern Anatolia ). The return of such conditions would be very difficult to establish sedentary civilizations based on agriculture lasting more than a few centuries in many parts of the globe, promoting nomadism, and significantly decreasing the capacity of the world, probably below hundred million people.
Fig. 15. Dansgaard-Oeschger events in the pollen record from Lake Van in Turkey. Scale in thousands of years before present with oldest on the right. Top red stable isotope data of oxygen in the NGRIP record are an indicator of temperature. The peaks marked (•) and numbered corresponding to the DO events that take place every 1-3 thousand years and consisting of a sudden heating followed by cooling may be abrupt or gradual. The width of the heating and cooling is 3 times that have occurred in the Holocene, including the current warming. Below, arboreal pollen (AP) expressed as a percentage of total pollen, which shows the rollover to the vegetation is subjected during the DO events. Source: Pickarski 2013 .
The end of the interglacial is not something to be concerned personally, but it is clear that unless premature extinction, is what awaits mankind. The astronomical signing of our interglacial indicates that belongs to the group of short duration , with an average of 13 ± 3000 years (Tzedakis et al. 2012, Can we predict the duration of an interglacial? ), so it could end in about 1,500 years, although this climate would have cooled considerably in the coming centuries, possibly suffering another Little Age Ice even colder beginning in about 300 years. This possibility can not be ruled out at all and for a species of mammal hairless should be a matter of more preparation than heating.
Fig. 16. The thickness of the ice cover in several places compared to the height of buildings. Source: XKCD .
8. Concepts and myths.
A. Humanity is well above its capacity.
This depends on which one wants to expand the definition of capacity up to match your vision of the problem. The concept of carrying capacity has an outside source to ecology, in shipping where denotes the maximum carrying capacity. From there it goes to the management of natural areas in the early twentieth century to define the maximum population of large mammals should be allowed before finally invade ecology, where most of the ecologists used to define the maximum achievable population. According to this definition widely used humanity can not be above its capacitysince its population is not only supported but still clearly expanding.
An alternative use of the concept of carrying capacity is to add the requirement to be “sustainable indefinitely” or “without harming the environment” or “no overexploit resources.” This automatically allows putting the human species above the capacity of the medium, but does so at the expense of loading the concept, because by definition the load capacity for any species varies constantly (can not be permanent or stable) and may not be a theoretical fixed number. Also makes the load capacity can not be calculated because as we have seen not calculate these situations lack of damage to the environment or sustainable exploitation and therefore the load capacity becomes longer arbitrary and have utility other than to scare people.
B. Humanity is in overshoot.
Again this involves expanding the definition of overshoot to serve our objectives. The overrun is by definition a situation where the population is in excess of the carrying capacity. The individuals of a population in overshoot do not get half the minimum resources for subsistence and population therefore presents negative growth during that generation . Suppose that a population that has these characteristics is in overrun supposed to know the future. Daphne Mayor finches are not in excess in a wet year. They are in overshoot the following year when the rains fail and seeds are not produced. In a wet year follow another, and then another and another, finches would not be in overshoot, but in their capacity, which manifest impropriety to say that a species is in overrun when obtaining sufficient resources.
C. The reindeer on the island of St. Matthews is a good example of overshoot and collapse due to excessive population growth and overexploitation of resources.
29 reindeer, introduced to the island of St. Matthews in the Bering Strait in 1944, had played to over 6000 in 1963, when its population collapsed in the winter of 1963-64 to less than 50 individuals in poor conditions in 1966 they had produced no offspring (Klein, DR 1968. The introduction, Increase, and crash of reindeer on St. Matthew Island ). From the beginning the case was presented as an example of the effect of uncontrolled growth and overexploitation of resources, leading to a population collapse .
The death of almost all of the reindeer on the island of St. Matthews in a single winter is suspect. Seasonal variations in the availability of food for the reindeer do when it becomes scarce high mortality occurs during several winters followed to reduce the population to more sustainable levels by the annual growth of vegetation. This is what has been observed in other cases. As stated by Miller et al. 2004 ( St. Matthew Island reindeer crash revisited: Their demise was not nigh-but then a, why did They Die ) there is evidence to suggest that the death of reindeer can be attributed to an unusually cold winter in 1963-64 could do that snow cover harden while the reindeer were unable to reach the food underneath. If so, would have the same number of reindeer, because its capacity is reduced to zero. The experience taught to distrust too good examples.
D. The natives of Easter Island are a good example of the collapse of civilization by overexploitation of resources and ecocide.
Easter Island is a small island of 163 km2 located 3,700 km off the coast of Chile, which is believed to have been colonized by Polynesians between 400 and 800 AD. Its inhabitants brought with them a culture developed in very different climatic conditions, where logging was a much more sustainable than in Easter Island practice. To make matters worse, the inhabitants soon developed indigenous cultural practices, the erection of moai (megalithic statues), requiring transfer from the quarries to their places of location. The population of the island is estimated that perhaps reached 15,000 by 1600 and entered into cultural and poblacionalmente slope to that date. At the time of first contact with Europeans in 1722, the island was completely deforested and the population was estimated at about 3000 inhabitants. A popular theory is that due to burning and indiscriminate felling of trees to clear space for agriculture, and to move the statues of Easter Islanders deforested the island and its environment degraded to the point of reducing its charge capacity below its population , so they resorted to cannibalism wars and to adjust its population to the new situation of the island. This theory has proved popular and is defended by example by Jared Diamonds success in his book “Collapse: How Societies Choose to Fail or Succeed” (2005).
However there is an alternative theory of the lack of scientific evidence to support the theory of ” The islanders committed ecocide about themselves “. The alternative theory advocates the following points:
Based on radiocarbon dating and the East Pacific Polynesian colonization, colonization took place centuries later, around 1200 AD .There was no time for human overpopulation.
Rats brought by the colonizers as food were the main cause of extinction tree to reach overpopulation and feed on seeds and tender stems of palms as in other islands (Auld et al. 2010 Disruption of recruitment in two endemic palms on Lord Howe Island by invasive rats ).The slash and burn and use of wood by the islanders were contributing factors, but the fragile ecosystem and the slow growth of palm trees against the explosive reproductive capacity of rats made the result was a foregone conclusion.
The islanders did not depend for their livelihood on the trees , feeding on crops of sweet potato, rats and chickens that get brought to the island and fish from shore, and fought successfully erosion and loss of soil nutrients with stone gardens. Its population was well fed judging from archaeological remains of skeletons.
The moai were designed to move unused wooden upright palm, which also is not dense enough to support much weight. Watch the video The statues walked .
No evidence of widespread violence and cannibalism would have been exceptional. The collapse of the population of Easter Island took place as a result of contact with Europeans due to epidemics and finally to the nineteenth century slave topped it off. Is once again the genocide and ecocide not responsible for the damage.
The new theory of ” The islanders are an example of success in adversity and challenges of a difficult environment and with serious ecological problems “with the evidence that supports it has been exposed by Hunt & Lipo 2009 ( Revisiting Rapa Nui (Easter Island ) ” Ecocide ”).
Fig. 17. The statues walked. With relatively few people and effort, a replica of a moai of 5 tons walks with surprising agility to swing it from side to side. It is not known that such is developed on the slopes. Source: National Geographic.
9. Conclusions
1. Despite dramatically increased the carrying capacity of the Earth to its species, mankind has done at the cost of ownership of a large percentage of net primary production of the planet, greatly increasing pollution, degradation the environment and biodiversity loss , indicating that we do not have much to grow.
2. Estimates indicate that in the absence of changes in the trend world population will reach its maximum in about 50 years in the vicinity of 10,000 million people before starting down .
3. The explosive growth of the human population is a recent phenomenon, primarily between 1910 and 1962 and is related to the increased availability of petroleum energy in production and distribution of food worldwide and the reduction of labor in the field it allows.
4. The high capacity of mankind is dependent on a steady increase in the use of oil and other fossil fuels which gives temporary and condemnation of