8th and 15th May 2000

Allaby Reading:  Sections 26, 28, 53, 54

(If you had an unexcused absence on either ocassion write a 2 page summary of sections 54 and 54).

In the first section of this course we concerned ourselves primarily with the physical, chemical, and biological context in which we live.   Details about the 4 subsystems of Earth: hydrosphere, lithosphere, atmosphere and biosphere were studied.  We examined the general environmental constraints imposed on living things. In addition, we explored the origins of the human species, emerging from tropical Africa -- a species that extended the repertoire of primate characteristics into new habitats. 

In the second section of the course we examine in some details the human transformation of Earth.  For the most part of human history (98%) we had a mode of life referred to a hunter-gatherer which was characterized by consuming a wide variety of plants and animals.  For the most part humans would have lived in small bands and would have had a nomadic mode of life.   It is worth considering this primitive human condition in order to allow us contrast our current achievements and mistakes in the light of a life-style that was sustainable over a very long period (200,000 year compared with post-agriculture human existence 10,000).  With the discovery of agriculture this changed.  We explored the three modes of human existence and contrasted them in terms of food security and the structure of society.  The story of the last 10,000 year is one of progressive modification of 4 subsystems of Earth.  This is a theme that we began to explore by viewing the movie Cadillac Desert and one that we will conclude next week.

Easter Island is often cited as an example of a community, living in a relatively closed system (a mere 150sq. miles in area), that overshot the limits of their environment resulting in environmental degradation and decline of their civilization.   Evidence of an advanced culture having been once present on the Island was apparent to the first European visitors in the 1700's, despite the squalor that the remaining inhabitants were then living in.  Massive stone monuments, totaling almost 600 in number, were dispersed throughout the island.  Why had the technologically skilled, socially advanced culture of Easter Island disappeared?

Easter Island had never been richly endowed with natural resources.   Soil drainage was poor and there were no permanent streams on the island.   There island was isolated and therefore quite impoverished biologically.  Even the coastal waters had few fish. The island was colonized by people in the fifth century.   Perhaps there were no more than 20 or 30 original inhabitants.  Using the easily cultivated sweet potato as their main crop the original islanders had plenty of free-time to pursue other activities.  A crucial cultural activity was the creation of large stone platforms known as Ahu.  To transport the stones to their final location the islanders used logs to roll the stones into position.  When first colonized the amount of forest was extensive.  However putting timber to use in transporting the stones into position as well uses resulted in a denuded island by the 1600.  There were no trees left for canoe building, for fishing equipment; soil was degraded and eroded and soil fertility declined.  Crop yield declined.  The size of the population started to dwindle.  The population regressed into more primitive modes of existence.

        Easter Island Link

I spent a little time at the beginning of one class on the cataloging of collapsed civilizations.  There are a few general theories advance as to why so many civilization disappear.  The reasons include:

1. Depletion of resources

2. Occurrence of a catastrophe

3. Insufficient response to circumstances

4. Intruders

5. Class conflict

6. Social Dysfunction

7. Mystical factors (included in this would be that the vigor of societies is determined by their moral fervor and that societies that indulge in excesses of the flesh will decay and wither - the death through orgy theory that I dismissed in class).

8. Chance concatenation of events

A more general theory of collapse suggests that when the cost of complexity outweigh the benefits a society will collapse.  Although I think this is an area of historical analysis that will be useful in thinking about some of our modern predicaments we would need a separate class to cover it.  If you are interested in the topic a good book to start with is:

Tainter, Joseph 1988 The Collapse of complex societies.Cambridge University Press.

There was a link between available natural resources and the welfare of the Easter Islanders.  In thinking about the implications of this for our industrial societies population is seen as a vital link - growing populations need more resources.

It should be pointed out that population by itself is not the only factor to be considered.  Clearly as shown in the diagram factors such as consumption level have a very predictable impact on natural resources. When viewed on a global scale there is a large disparity in resource consumption levels in different regions.

Resources we defined variously:

1. That to which one resorts or on which one depends for supply or support; means of overcoming a difficulty
2. available source of wealth; a new or reserve supply that can be drawn upon when needed
3. the ability to deal resourcefully with unusual problems; "a man of resource" [syn: resourcefulness, imagination]

Resources can be classified as

renewable (potentially)

non-renewable

potential

Since population is such a pivotal factor in considering resource issues it is the topic we turn to next:

Human Population Growth

2 World Population Profile 1998 http://www.census.gov/ipc/www/wp98.html

3 United Nations Population Division 1998 http://www.popin.org/pop/1998/2.htm

When graphed over a long period of time the growth in human population can be seen as a remarkable and unprecedented phenomenon.  Below I first drew the shape of the graph starting at ~200,000 years ago.  Viewed through this very broad lens the recent surge in population (post-1800) appears as wall emerging from the preceding long period of negligible growth.  Even when viewed over the past   10,000 year one can see most of the growth occurring rather suddenly.

Year	World Population	Time interval
1804	1 billion	100,000 years +
1927	2 billion	123 years later
1960	3 billion	33 years later
1974	4 billion	14 years later
1987	5 billion	13 years later
1999	6 billion	12 years later

Although it is often convenient to state the human population grows in conformity with a particular model (e.g. exponentially) it is important to remember that population growth is subject to the contingency of history - although as long as the number of children being produced is greater than the replacement level (2.1) the population grows historical events can plan a large role in sculpting a population's history - example Egypt:

That being stated there are some overall trend in population.  The encouraging news in recent times is that the percent growth has dropped in since the late 1960's.

World Population estimates

• 6 billion people and growing at 1.33%, net addition of 78 million per year
• Medium-fertility projection indicates the most like population size at 2050 to be 8.9 billion
• Global average fertility stands at 2.7 births per woman (contrast with fertility of 5 in 1950)
• There is a fertility drop in all parts of the world (6.6 to 5.1 in Africa; 5.1 to 2.6 in Asia, 5 to 2.7 in Latin America and the Caribbean)
• HIV/AIDS is having a devastating effect on many countries. In the hardest hit African countries, the average life expectancy has dropped 7 years.
• Pronounced aging of the world's populations as longevity increased

US Population Projections

Since fertility rate in the US average around the replacement level (2.1 child per woman) two things: immigration (the immigration assumption in the medium projection is 820,000 per year), and population momentum (the progression of the younger population into their reproductive years), and the increasing longevity will fuel the growth.

There is clear differences emerging in the distribution of world population. Much of the growth is occurring in areas of the world with the highest levels of biotic diversity and with globally important ecosystems.

---

Demographic Transition: Applying the Breaks

The above diagram summarizes the demographic transition model. The demographic transition is the term used for that idealized set of changes in mortality and fertility rates through which countries have gone or are expect to go. Starting with both high mortality and fertility rate, the mortality rate drops. The birth rate remains relatively high for some time after this producing a period of rapid population growth. When fertility rates drop the population growth rate (Natural rate of increase) drops and the expansion of the population is once again at a low level. It is very important to remember that the population size differs greatly at either side of the transition, going from relatively low at the beginning to relatively high at the end. If a country has gone through the demographic transition the population growth is low (though the increase in population stated in absolute terms can be high -- a small percentage of a large number can be more substantial than a large percentage of a small population).

References and Figures:

Abernethy, Virginia D. Population politics - the choices that shape our future.Plenum Press 1993.

Cohen, Joel E. How many people can the earth support? Norton 1995

Hardin, Garrett. Living within limits. Ecology, Economics and Population Taboos. Oxford University Press, 1993.

Livi-Bacci, Massimo. A concise history of world population. 2nd Edition. Blackwell Publishers. 1997.

Countries can Be classified as :

Early-Transition (e.g. Europe)

Late-Transition (e.g. China, India, Brazil, Egypt)

Pre-Transition (e.g. Many African Nations)

---

Early Transitional Countries (e.g. Europe)

• Some types of family limitation always practiced.
• However French nobility of the 17th Century provide first written documentation of an entire social class practicing family limitation.
• By the end of the 19th Century family limitation spread to Germany, Sweden, Hungary, and New England.

Some general points:

Fertility declined at different times and rates in different places

Timing of the declines in mortality and fertility not simple

Families must be ready, willing, and able to reduce family size for fertility to fall

Only with the birth rates fall of South American and southeast Asian countries did growth rates peak and fall.  Again no simple patterns are found in an examination of the fertility transition in these countries.

Six Commandments of exporting the fertility transition (Cohen 1995)

"Ready, willing, and able"

• Promote contraception Informational programs, through mass media (there are 1.9 billion radio sets around the world). Voluntary or coerced.
• Develop economies
• Promotion of family planning seen by some as neo-colonialism, and insist that wealth-transfer is the key to stabilizing populations in pre-transition countries. "Development is the best contraceptive."
• Save children Approach favored by UNICEF and many demographers. In short term improving infant mortality appeared to increase rather than decrease population growth.
• Empower women More opportunities for girls to stay in school resulted in delayed marriage and postpones onset of fertility. Increased education results in greater opportunities of work outside home and consequently greater exposure to modern views on family size.
• Educate men A survey in Nigeria in 1994 showed that 97% of men and 91% of women agreed that men wanted more children than women. A majority agreed that a woman would be reluctant to practice family planning if she feared that her husband would object.
• Do all the above!

---

99% of Human Life: Hunting and gathering

Three Main Ecologies have been explored by humans during their time on Earth.  For most of the time we were nomadic hunter-gatherers and clearly as a species we were shaped by this longest period of our history.  Agriculture was "invented" 10,000 years ago.  This transition has often been portrayed as a fine moment in human history.  However although we reap the benefit of this today in terms of material comforts many now view the origins of agriculture as a crisis in human history and suggest that health may have dis-improved as a result (see books by Jared Diamond on this topic).  I must confess that I have a hankering after the distant past of human history (although as a weak-eyed, feeble-limbed specimen I would not have lasted long!).  The third ecology we have adopted is an urban oriented, industrial ecology.

Survey

1. Assuming that your daily requirements for food and shelter were taken care of in all the
   given options, how many hours would you choose to work?
   
   60+ hours
   12-19 hours
   40 - 50 hours
   Typically hunter-gathers spend between 12-19 hours per week "working" (searching for food),
   compared to the work-load of the average industrial worker (40-50 hours) or a farmer on a small
   holding (60+ hours). 12-19 hours work has been reported for one group of Bushmen, 14 hours for the
   Hadza nomads of Tanzania.

2. From which option below do you think that you would get the most adequate nutrition?
   a mixture of plant and animals of at least 75 species
   a mixture of chemically treated, packaged foodstuffs of indeterminate origins
   a mixture of 5 plant and 3 animal species, with little need for food additives
   
   Hunter-gatherers typically exploit a vast range of plant and animal species for subsistence and do not
   rely heavily on a few refined and domesticated species as is the norm for agricultural and industrial
   societies. With the advent of the city the problems of storage, and transportation (which are minimal
   for hunter-gatherers) become paramount.

3. Which of the following forms of social organization would you favor?
   -highly hierarchical based upon wealth or descent, where slavery and war are common
   -egalitarian, without ultimate social power invested in a single individual, absence of
   slavery, warfare rare
   -hierarchical social organization based upon elite political class, where slavery is
   common or covert, and war is constant

   It has long been recognized that the mobility, lack of specialization, low population densities, broad dietary
   range, and need for co-operation in the hunt produce societies which are highly egalitarian, with a
   infrequent incidence of slavery and war. There are some hunter-gathering societies which could be called
   non-egalitarian are these are characterized as having high population densities, sedentary (as opposed to
   mobile), having occupation specialization, and being engaging in focal exploitation of a single resource
   (often fish).Cooperation can be harshly imposed however. For instance Turnbull gives us the following account: "Ekianga leaped to his feet and brandished his hairy fist across the fire. He said he hoped Cephu would fall on his spear and kill himself like the animal he was. Who but an animal would steal meat from others? ....[Cephu had broken away from the hunting circle and set his nets up ahead of his companions]...Cephu tried very weakly to say that he had lost touch with the others and was still waiting when he heard the beating [to flush the prey animals into the circle]. Manyalibo ... said... [of Cephu] "let him go and hunt elsewhere and be a chief elsewhere". Cephu knew he was defeated and humiliated. Alone his band of four or five families was too small to make an efficient hunting unit. He apologized profusely,
   reiterating that he really did not know he had set up his nets in front of the others, and said that in any
   case he would hand over all the meat".
   
   From: Turnbull, Colin 1962 The Forest People. A Study of the Pygmies of the Congo. A
   Touchstone Book, Simon Schuster.

4. Which option below would seem to represent a more secure society?
   
   -Large settlement size, high population size relative to food resources, medium to high
   dependence of food storage, common specialization, perimeter defense needed, tightly
   controlled resource ownership
   -Permanent settlement, high population size relative to food resources, food transport
   and storage obligatory, specialization obligatory, perimeter defense and constant
   expansion needed, tightly controlled resource ownership
   -Small settlement size, low population size relative to food resources, little dependence
   on food storage, little occupational specialization, no requirement for social boundary
   defense, no competition tolerated, diffuse ownership

5. Which form of environmental impact do you think that you could live with
   
   -modification of small portions of habitat through fire, reduction of prey numbers
   through hunting
   -permanent changes in energy flows, disrupted nutrient cycles, depletion of soil fertility,
   fouling of inland and coastal waters
   -all of (b) plus, destruction of natural biomes, changes in atmospheric chemistry,
   modification of global temperatures, depletion of atmospheres ability to shield cancer
   forming UV rays.
   
   The earliest assaults on the environment at the hands of man came from hunter-gathers and are
   discussed below. However, because of their very low population density (number of people per unit
   area) the extent of the habitat modification was not large. Two types of damage can be distinguished,
   intentional and non-intentional. Intentional damage is the deliberate modification of habitat to
   encourage a change of vegetation or to make the habitat more favorable to preferred prey items.
   Non-intentional damage includes local extirpation (extinction) due to over-hunting, and setting of fire
   which spread to areas outside of the zone of interest.
   
   Important Note: The literature on hunter-gatherers is extensive and technical. The observations that I have made here and in class serve the purpose of introducing the notion that for much of human pre-history this form of social organization was prevalent. It would be a mistake though to assume that the indigenous human condition can be inferred by studying their modern analogues (those people still living a hunter-gatherer mode of life). These extant hunter-gatherer groups have followed their own individual trajectories over the millennia. Modern studies emphasize the diversity of these groups and not their similarities.
   
   See: Lee, R.B. and I. DeVore Man the Hunter, Chicago: Aldine 1968.
   Kelly, R.L. The Foraging Spectrum. Smithsonian Institution Press 1995.

   Diamond, J. The Worst Mistake in Human History. Discover 1987.

   Livi-Bacci, M. A concise history of world population. Blackwell Publisher, 2nd Edition 1997

Ecological Impact of Hunter-gatherers

Localized use of fire: for communication, hunting, and land clearing

The use of fire in ecosystems to change habitat is an ancient practice. For instance, in the early 19th
century up to 5000 bush fires per year were reported in Australia. Fires were used to create an
environmental mosaic that encourages wallabies, bandicoots and possums, all of which were hunted.

Forest clearings expanded

Forest clearing which open naturally (from natural tree fall to hurricane damage) were scrupulously
maintained as favorable hunting areas.

Pleistocene overkill: between 12,000 and 10,000BC 200 genera of large mammal went extinct

N. America: 75% of large mammals
S. America: 80%
Australia: 86%
Africa: 14%
Europe: 9 species

The hunter-gatherer responsibility for the loss of large mammal species (>55 lbs) is
controversial. The coincidence of mammalian extinctions and the arrival of man to different
geographical regions has convinced many scholars that the two events are causally linked. Others
argue that man arrived at a time when the Ice Age was receding and this increase in temperature
represented a stress to many mammalian species (the sorts of species that went instinct in North
America include Wooly Mammoth, armadillos, pangolins, sloths, some deer species, large rodents
and some carnivores). An explanation that falls somewhere in the middle of these two extremes is
that man the hunter provided the coup-de-grace to a stressed and dwindling population of these large
mammals.

The original hypothesis came from Paul Martin from the University of Arizona.

A very recent discussion of the topic can be found in:

Shepard Kreech III (1999) The Ecological Indian: Myth and History.   Norton

"The relevance of climate to these events has at times been too casually dismissed.  Climate changes were pervasive at the end of the Pleistocene.   Temperatures warmed by roughly thirteen degrees Fahrenheit, and the climate became drier overall.... Entire habitats changed rapidly at the end of the Pleistocene."

In contrast to the extinctions in the Americas is the very low number of extinctions that occurred in
Africa and Eurasia where man had the longest tenancy.

---

When are many people TOO many people?

I mentioned that there is a debate over whether population growth made the invention of agriculture a necessity or whether the agriculture allowed for an expansion of population.  One, still fairly controversial notion, is that agriculture destroyed the well established patterns of hunter-gatherer communities, resulted in an erosion of habits (long period of nursing, synchronized female cycles, periodic absence of men from the community) that lowered fertility.  If this notion is valid it argues that population growth increased with agriculture.  This increase in population required a greater agricultural productivity to support it.  A positive feedback cycle ensued, more people leading to more agriculture, leading to more people and so on.

Although we know that human population growth over the past 200 hundred years is without precedence we still need to answer the question of whether human population growth is a cause for concern.  Most policy makers have concluded that it is.  As is always the case in debates of world policy there is some dissenting voices.  To answer the question posed above "When are many people TOO many people?" policy makers have employed the concept of carrying-capacity - the maximum number of people that can be supported in perpetuity on an area, with a given technology and set of consumptive habits, without causing environmental degradation (Fernside 1986) Carrying capacity is determined by the amount of energy, land, water, food and other resources available to humans.  Obviously carrying capacity is a very plastic concept.  Since humans are master at manipulation of the environment we can obviously support more people than would be supported in a global landscape that had not been modified by human ingenuity (for agriculture, energy extraction).  Having an environment that merely sustains existence is probably not sufficient for anyone.   Most will want to include quality of life in their consideration of how many people can be sustained.  Factors included here may encompass the ability to breathe clean non-polluted air, having fresh food (rather than dehydrogenated astronaut food!), having place of beauty for repose, having access to wild habitats, etc.  When these considerations are include (the term used is cultural capacity) the number of people that represents an overload is very much smaller than an estimate that uses survival as a criterion.

Here are some of the estimate that have been made of human carrying capacity - notice how vastly it varies:

10¹⁶ - 10¹⁸ people

"If heat removal were the sole limitation, then we could manage about 120 persons per square metre for an outer skin temperature [of structures that cover the Earth] of 1000^oC - which represents .. a world population of 60,000 million million in 890 years time. 1000 ^oC may be a modest figure for the technology of AD 2854 and the population could, as far as heat is concerned, be able to rise again for each rise of absolute skin temperature of .. 26%. The difficulty in rising it much further while keeping all thermodynamic efficiencies high would, however, seem to be formidable. We seem to have found one possible absolute limit to human population, due to the heat problem, which at present be reached 800 -1000 years from now."

J.H. Fremlin 1964

< 4.5 billion people

"The real dreamers are those who assert that we can create a sustainable economy, with a high average standard of living for all, in a healthy environment - with the present world population of 4.5 thousand millions, or even more"

D.W. Mann 1964

10-11 billion people

"Cautious estimates presented in this essay uncover a resource slack equivalent to feeding adequately another 2.5-3 billion. And equally conservative appraisals of new productive inputs needed to feed yet another 2 - 2.5 billion people show that we could do so without recourse to revolutionary bioengineering advances"

V Smil 1994

---

Feeding the World

One of the main concerns regarding the population has been that growth of population will result in catastrophic loss of life because of food shortage.  This possibility was pointed out in the late 1700s by the Rev T R Malthus. His argument was that population grows exponentially (i.e. by multiplying the number originally there by a fixed rate, eg 2, 4, 8, 16 ....) whereas increased food production proceeds arithmetically, by addition of fixed amounts (e.g. 1,2,3,4,5).   Something growing exponentially will always outstrip something growing in a geometric fashion.

Soil

Ultimately the The production of food is ultimately dependent upon the health of the soil. Below is a typical soil horizon showing where the different "horizon" of the soil are.  The vigor of crops will depend upon the nutrient content of the organic layer.

Soil development is a product of

1. Climate

2. Relief (the contours of the land)

3. Organisms

4. Parent Material

5. Time  (for instance the soils of Illinois are very young dating back only 10,000 years or so, and are consequently very fertile)

As we saw in the movie on agriculture in class modern agriculture has certain characteristics:

• Simplification:  there are relatively few crops grown (major ones below).  Notice that many of our stables are grasses.

• Farms, in contrast to natural ecosystems, are species poor. We concentrate on maximizing the
  production of a few plant and animal species.

• Hi-inputs of fertilizer and pesticides

To maintain high output we supplement natural fertility with fertilizers (usually adding critical
ingredients that are in short supply such as nitrogen and phosphorus, and sometimes other
mineral such as potassium etc.)

• Residue removal
  After crops are produced, the remain plant debris is removed from the surface (though not
  always, sometimes the residue is plowed back in, to reduce nutrient loss.

• Cycles disrupted
  When crops are taken from the system they are consumed in place that can often be very remote
  from the place where they were produced. Any residue and waste end up far away from the
  farm. This necessarily disrupts the cycling of these nutrients (this is true, to a greater or lesser
  extent for all consumption in the natural or man-dominated world; but the efforts to minimize
  the negative repercussions of this are minimal in modern agriculture).

• Soil eroded
  The advances in production upon which we are so dependent are sustained by an exhaustion of
  this natural capital.
  Alternatives Most of the attempts to remedy the disadvantages of modern techniques in
  agriculture try to take advantage of natural features of ecosystems. For instance "no-till"
  agriculture minimized disruption to the soil surface, no plowing is involved and loss of
  nutrients from the soil is minimized by allowing a large build up of crop residue to remain on
  the surface of the field (it attracts a big diversity of small critters and microbes).

• One feature in common with all the agricultural alternatives is that they mimic natural ecosystems by
  Closing cycles
  Soil conservation
  High diversity
  Longer food chains
  

We can now ask the question:

Has this outstripping of food resources by the human population occurred?

On a global scale food production has greatly increased.  This has been facilitated by the "green revolution", that is, use of better fertilizers, new crop breeds, and better irrigation.  Look at the increases in the production of different food type in the chart below (1965 vs 1995).

However another way to view this data is to look at regional differences in the per capita food production.  That is, the food produced for every member of the population.  Although the grain production has increased dramatically since the 50's there has been a gradual reduction in the per capita production worldwide.  Looking at this for different region there is some very clear patterns.   In some regions (e.g. Africa) there have been very dramatic decline.

The amount of grain in stock has decline in recent years.  The number of days of carryover consumption has also declined.  It has recently dipped below the line considered necessary for food security (i.e. the amount needed to feed the world in the event of an anomalous bad harvest).  One of the reason for this is that with increasing affluence people use excess grain to feed cattle.  This decreases the surplus.

Because we have always managed on a global scale to keep production of crops high (through technological improvements) one viewpoint is that we will continue to do so.  Very often these technological advance come at a price - as seen in the example of Indonesia (seen in the video).

Others would see the picture as being more bleak noting that a major catastrophe would result in a large scale collapse of industrial economies.