Human Population and The Environment

1
Human Population and The Environment
2
Lecture 2 Outline

• Introduction Why are we discussing human
  population in an Environmental Biology class?
• Population growth
• Human population change over time
• Developed and Less Developed nations
• Population Parameters
• Crude birth/death rate
• Infant mortality rate
• Life expectancy
• Total fertility rate
• Population pyramids
• Demographic Transition
• Perspectives on population
• Malthus
• Ehrlic
• Marx
• Cornucopians

3
Introduction Human Population and the
Environment

• Paul Ehrlichs published The Population Bomb in
  1968. This work was one of the original
  accusations that any environmental issue is
  really just a human overpopulation issue. That
  is, every environmental problem is directly
  related to there being too many people.
  Continuing with this argument, the way to help
  the environment, then, is to control over
  population.
• Some of Ehrlichs ideas sparked a lot of
  controversy. Indeed as we shall read later in
  the lecture, some of Ehrlichs ideas are very
  draconian, and he is often heavily criticized.
• But important questions remain
• Do we have a human population problem?
• If so, is overpopulation at the root of all
  environmental problems?
• Can the population be controlled?
• What strategies exist to keep population in
  check, and will these measures help the
  environment?

4
Population Ecology

• Before discussing human population, it would be
  prudent to review general ecological population
  models.
• How does a species population changes?
• Birth (add more individuals)
• Death (remove individuals)
• Migration (immigration/emigration)

www.geocities.jp
http//tdi.uregina.ca/maguirer/rip.gif
http//www.latinamericanstudies.org/ellis-island/e
llis-island.jpg
5
Basic Population Dynamics

• Assuming no migration
• If Births gt Deaths, the population grows
• If Births lt Deaths, the population declines
• For most natural populations, whether it be
  humming birds, oak trees, slime molds, or
  whatever, there will be good years when
  populations expand and bad years when populations
  decline. Over the course of many years,
  population changes oscillate around a dynamic
  equilibrium

http//www.nature.ca/NOTEBOOKS/images/ruby.gif
Higher population
Time
Lower population
6
When populations increase, they often do so
exponentially

• First, though, lets look at linear growth
• Constant rate of growth whereby two new
  individuals are added each generation

7
When populations increase, they often do so
exponentially

• Exponential growth, whereby the population
  doubles each generation
• Compare 5th generations
• Linear 12
• Exponential 64

• Which would you rather have over 10 week period
• One cent, doubles every day
• One dollar one additional dollar every day?

8
Exponential Population Growth

• Standard exponential growth curve

R intrinsic growth curve - based on
individual species growth potential
Population (N)
Time (T)
9
Exponential Curve (continued)

• Growth is very slow at first, but as the
  population increases over time the growth rate
  becomes enormous
• Question mathematically, where does this curve
  go to?
• Infinity!
• Is this possible? Of course not. Usually there
  is some restriction on population growth, whether
  it be reduced resources, diseases, etc. In the
  real world, populations level off around a
  carrying capacity.
• Carrying Capacity the maximum number of
  individuals that the environment can support
  (Barbour et al., 1999), Terrestrial Plant
  Ecology, pg. 66.
• Usually set by the amount of available resources

10
Carrying Capacity

• The carrying capacity has a dampening function
  that limits a population once numbers grow to a
  certain value.
• As N approaches K, growth declines to zero (K-N)

K carrying capacity
Dampening function
Population (N)
Time (T)
11
Dynamic Population

• In many real world populations, the number of
  individuals vary around the carrying capacity (K)
  in a dynamic equilibrium. Sometimes populations
  crash when they reach or exceed K (they may
  exhaust all available resources or diseases may
  spread rampantly with high densities). This is
  called a population crash after a crash
  population builds slowly again.

crash
k
population
time
12
So what does all this have to do with
Environmental Biology?

• In the following slides we will be examining
  human population and relating human population to
  environmental problems.
• Human populations may be constrained by forces
  similar to those previously described
• Springboard human population growth.

13
History of Human Populations

• Prior to ca. 10,000 years ago (kya), human
  population growth was very slow (similar to the
  hummingbird example given earlier).

Then about 10 8 kya, human population
growth increased
Note the last 100 years have witnessed
the greatest increase in human populations
(Chiras, 2001. Environmental Science Creating a
sustainable future, 6th Edition, Jones and
Bartlett, Sudbury, MD, pg 150.
14
Early Human Population

• Mostly hunter/gather populations existed before
  10 KYA. These populations were very small and
  had very little population growth.
• Death rates and birth rates were both very high.
  Catastrophic population crashes were also
  possible.
• At about 10 kya 8 kya, the population growth
  rate increased, why?

15
Agricultural Revolution

• Technically, the Neolithic Revolution, term
  coined by Childe (1920).
• Transition from hunter/gather to agrarian
  societies
• Occurred through the development of cultivation
  of animals and plants
• Occurred in many different regions of the World
• Asia, Africa, North America, Melanesia, etc.

http//earthobservatory.nasa.gov/Study/HarranPlain
s/Images/fertile_crescent_350.jpg
http//www.oznet.ksu.edu/fieldday/kids/pictures/ki
dsfield600/cg_wheat_closeup.jpg
16
Why would the Agricultural Revolution result in
greater rate of population change?

• Could be from the improved living conditions and
  more abundant food supply. These events would
  lower the death rate (traditional view)
• In contrast, it could be that living in closer
  proximity to one another actually increased the
  death rate from the spread of infectious diseases
  and through poor sanitation. The increase in
  population, then, would be related to an increase
  in the fertility rate (average of offspring
  born to a female over the course of her
  reproductive lifetime), which may be related to
  the abundance of food (archeological view).
• Nonetheless, human populations started to climb

17
Human PopulationAg. Revolution to ca. 1800

• This time period is characterized by slow growth.
  You textbook mentions population increased
  slowly and variably, with periodic setbacks (pg
  124).
• The population was doubling about every 1200 years

(Chiras, 2001. Environmental Science Creating a
sustainable future, 6th Edition, Jones and
Bartlett, Sudbury, MD, pg 150.
18
Human Population 1750 - 1830

• Estimates for human population at 1750 are around
  800 million people.
• World population reached 1 billion for the first
  time in 1830. What happened around the mid
  Eighteen century to explain dramatic rise in
  population?
• Industrial Revolution
• The Industrial Revolution was another
  technological advancement that had an effect on
  human population. Why? Some possible answers
• Decrease in the death rate
• Increased birth rate
• Economists suggest that with the Industrial
  Revolution came a greater need for labor. This
  demand for labor may have contributed to the
  increase in population the increase was
  market-driven.
• The Worlds population reached 2 billion in 1930,
  only 100 years since 1830. See the following
  graph (from textbook).

19
Human Population 1000 AD present (Figure 5-1)
K 10 billion?
Note the rapid increase in the growth rate. It
is taking less time to add an additional 1
billion persons.
20
Human Population Values
Note the growth rate is slowing down
21
Human Population overall trend

• Most of the Worlds population growth has
  occurred in the last 100 years or so. From 1930
  1999, for example, population went from 2
  billion to 6 billion. This is unprecedented in
  human history.
• The dramatic rise in population is a result of
  several factors
• Better healthcare and medicine
• Better nutrition and sanitation practices
• Increase in food production (see the Green
  Revolution, pg 236 238)
• In short, technological advances in just about
  every field has contributed
• In recent years, though, population growth has
  slowed. The time to add 1 billion people is
  decreasing, but the amount of the decrease is
  becoming less and less. For example, the human
  population went from 2 billion to 3 billion in 30
  years (1930-1960). Population went from 3
  billion to 4 billion in 15 years (1960-1975).
  Population increased from 4 billion to 5 billion
  in 12 years (1975 1987). Population increased
  from 5 billion to 6 billion in 12 years this is
  the same rate of increase as the 4 5 billion.
  The rate of increase is slowing.
• Even though the rate of population increase is
  lessening, be cognizant that the overall number
  of people is still expanding.

22
World Population growth, rate and absolute growth
(Fig 5-2)

• Human population numbers are increasing, but the
  growth rate is declining. Are we reaching
  carrying capacity? See the dampening factor in
  the equation on slide 10.

23
Human Population Growth and The Environment

• The increase in human populations is an
  environmental concern for several reasons Below
  are just a few
• 1) more waste
• 2) use more resources
• 3) increased land development for both
  agriculture and habitation
• 4) more energy demands
• 5) greater pressure on wildlife and greater
  pressure on marine life
• It is suggested, then, that human population
  growth is the biggest threat to the environment
• Human population growth may possibly be the
  greatest threat to humans as well. Keep in mind
  the concept of the carrying capacity. Once
  populations numbers k, the growth rate drops.
  Sometimes if the population increases too fast
  and the numbers exceed K, the amount of available
  resources plummet and the population crashes.
  Again, what is the human carrying capacity? How
  many people will the World support? Have we
  already exceeded K, and if so, are we susceptible
  to a major population crash? We will address
  some of these issues in just a bit.

24
Different Worlds Section 5.2

• Human population growth is not the same globally.
  One of the greatest factors influencing
  population is the economic status of a nation or
  region.
• Your textbook defines three types of countries
  based on their economic status. NOTE the
  following discussion is based on economic status
  and NOT cultural values.
• High-income, industrialized countries (e.g. US,
  Canada, Japan, UK, France).
• Middle-income/ moderately developed (e.g.
  Russia, eastern Europe, Mexico, Costa Rica)
• Low-income, developing countries (e.g. Nicaragua,
  Angola, Ethiopia).
• Note the terms Developed and Developing are
  used to represent the economic status of nations.
  Developed nations include the US, western
  Europe, Scandinavia, UK, Australia, New Zealand,
  Canada, Japan, Taiwan, and several Arab states.
  Developing nations are everyone else.
• See Figure 5-4 to see the distribution of these
  three economic groups. (The file size of this
  image was too large to include in the
  PowerPoint).
• There are many disparities between the
  high-income (HI) and low-income (LI).
• HI make up 16 of the Worlds population but
  control about 81 of the wealth (GNP pg. 127)
• LI make up 41 of the Worlds population but
  control only 3.4 of the wealth (GNP pg 127)

25
Comparison of Populations Between Developed and
Developing Nations

• In order to discuss global variations in human
  population, we must first define certain
  population parameters (see Table 5-1, pg 126)
• Growth Rate the rate of growth of a population
  as a percentage. Multiplied by the existing
  population, this rate gives the net yearly
  increase.
• Total Fertility Rate the average number of
  children each woman has over her lifetime. This
  is the most widely used measure of fertility, and
  is seen as being superior to the crude birth
  rate. One advantage is that the TFR focuses on
  women that are fertile, i.e.. the members of the
  population that are actually birthing babies.
• Replacement-level Fertility a fertility rate
  that will replace just the mom and dad,
  theoretically 2.0. Mom has 2 kids, so when mom
  and dad both die 2 additional people (the
  offspring) will take their place the population
  is stable. Less than 2.0 the population
  declines greater than 2.0 the population
  increases
• Infant Mortality number of infant deaths per
  1000 live births. Infant mortality is a more
  reflective death rate statistic than crude death
  rate (below) because it focuses on a more
  sensitive age group and because it doesnt
  include persons that would die from old age.
• Crude Birth Rate number of births per
  thousand people. Not an accurate statistic
  because the thousand people include both males
  and females. As far as I am aware, males cant
  have kids. The CBR is somewhat skewed by
  including in the calculations members of the
  population that cant reproduce.
• Crude Death Rate number of deaths per thousand.
  Not a very reflective statistic because it
  incorporates the people who would be dying of old
  age, even after a long and healthy life.
• Doubling Time The time it takes for a
  population increasing at a give growth rate to
  double in size. In the human population history,
  the doubling time from 1 billion to 2 billion was
  100 years.
• The next slide compares some of these population
  parameters between developed and developing
  nations. This information is derived from Table
  5 - 3

26
Table 5-3 Population Data for Selected Countries

• Note the relationship between development status
  and total fertility rate.
• Note the US is the only developed country that
  has a TFR capable of increasing (maintaining) the
  population. Actually, some estimates for US TFR
  are closer to 3

27
Population increase in Developed and Developing
Countries (Figure 5-6)

• The higher TFR means that the developing
  countries are experiencing the greater population
  increase.

28
Ecological Footprint (Figure 5-7)

• Ehrlich and Holdren propose that the
  environmental impact is related to human
  population and the varying degrees of pressure
  different people put on the environment (see pg
  130).
• Their premise is that the more affluent
  countries, even though they are smaller in
  population, have more of an affect on the
  environment because they use substantially more
  resources. Thus, in this case, human population
  differences between developed and developing
  nations may not be the sole reason for
  environmental degradation. As mentioned in the
  textbook it is hypocritical to criticize
  developing countries for continuing to grow their
  populations. Those who live in wealthy, but
  population-stable, developed countries are
  equally guilty of environmental misuse (pg 130).
  
• The US for example has 5 of the population but
  is currently responsible for 24 of the total
  global emissions of CO2.
• The US, then, has a lager Ecological footprint
  than other developing countries.

Personally I question the source of this graph
especially regarding China and Indias
contribution. I agree with the overall concept,
but disagree with the details. This is my own
personal opinion.
29
(new section) Population Profiles

• In predicting future population trends, it is
  important to look at population growth by age
  group. For example, looking at the age structure
  of a population, whether the bulk of the
  population is older or younger, can provide
  insight into future population numbers. This
  relationship is displayed in population
  profiles, which is a bar graph showing the
  number or proportion of people at each age for a
  given population, pg 138).

30
Population Profiles US Fig 5-12)
1990
2000
Baby Boom
Age group (cohort) is on the y-axis and
population is on the x-axis. Males and females
are separated. Note with a TFR gt 2, the SU
population is expected to increase.
2050
31
Population Profile Developed Country (Fig. 5-
14)

• Italy is a developed country with a TFR 1.2.
  Note how the population is expected to decline.
• The characteristic shape of a developed country
  profile is usually top-heavy (more people in the
  older generations, TFR lt 2) or uniform (all
  generations have about the same numbers, TFR 2.

2025
32
Population Profile Developing Countries (fig
5-16)

• Iraqs population profile is characteristic of a
  developing country. The bulk of the population
  is within the youngest generations. This
  indicates several things a higher TFR and a
  higher IMR.
• In the Iraq case, TFR is expected to drop (from
  5.4 to 2.7), but IMR is also supposed to decline
  with the import of new technology.
• Developing nations have a population profile
  characterized by a pyramid-shape, bottom heavy.
  In this case the TFR much greater than 2, and the
  population will increase.

33
Comparison of Population ProfilesDeveloped v.
Developing Countries (fig 5-17)
34
Population Trends Developing Countries and the
DT

• According to the population profiles developing
  countries will continuously expand. Is there any
  hope for decreasing the population growth?
  Perhaps through the Demographic Transition (DT).
• The Demographic Transition model that shows a
  country's population trends (fertility and death
  rate) over the course of industrialization, from
  developing to developed.
• The DT occurs in 4 phases
• Phase 1 primitive stability resulting from high
  CBR and high CDR. Similar to hummingbird
  population on slide 10.
• Phase 2 with the advent of industrialization
  and better technology/health care the CDR drops
  but the fertility rate stays the same. The
  population begins to grow rapidly
• Phase 3 cultural shift during the latter stages
  of development. Social and cultural pressures
  tend to decrease the fertility rate as a
  countries progresses through industrialization.
  The CDR continues to drop. In this phase, the
  population still increases, but the rate of
  increase slows down.
• Phase 4 a county is now developed, and it is
  marked by having a stable population with low
  fertility and low CDR

35
Demographic TransitionFig. 5-18
36
Notes about the DT

• Developed by Warren Thompson (1929) and is based
  on the population transition of European nations
  through the course of industrialization, several
  centuries. The timeline for transition has been
  much faster for some nations, such as the Asian
  Economic Tigers (e.g. South Korea), but many
  developing nations seem to be stuck in phase 2.
• Some criticizes of the DT include
• Based on only European demographics, and not
  inclusive of all nations
• The supposed cultural shift in phase 3 would have
  to be applied to every socio-economic class. If
  during industrialization the upper and middle
  income groups would be the first to experience
  an increase in resources, the lower socioeconomic
  classes may not reap the benefits of
  industrialization. In this case, the drop in
  fertility would only occur within select group
  not all groups of people would simultaneously
  lower their fertility.
• Countries with a large population of subsistence
  farmers would have difficulties transitioning
  into phase 4 simply because they do not have the
  capitol needed to become industrialized. Many of
  the Developing countries would remain in phase 2
  with lowered death rate but stable fertility.
  Populations in this case would continue to rise,
  perhaps acting in a negative feedback loop.
  Figure 5 -1 9 shows several of these countries.

37
Real World Data, Figure 5-19
Nations to the left of the dividing line have
been trapped in that position for several
decades. Why?
38
Poverty, Fertility, and Environmental Degradation
(fig. 6-7)

• Negative feedback, aka Vicious Cycle (pg 156)
• From your textbook, pg 157
• A fifth of the worlds population (1.2 billion)
  live on less than 1/day
• 1 billion lack access to clean water
• 2.4 billion lack access to sanitary facilities
• 800 million are malnourished
• ..the poor suffer higher rates of disease, lower
  life expectancy, higher infant morality, higher
  illiteracy, poor living conditions, social
  exclusion, and powerlessness. In short, the
  vicious cycle of high fertility, poverty, and
  environmental degradation persists, presenting
  the international community with an enormous
  challenge.

39
(new section) Perspectives on Populations

• What can be done about the overpopulation
  problem? Several arguments have been put forth
  to explain the consequences of overpopulation.
  We wont get to every academic camp on
  population. Instead, in the interest of time, I
  am going to focus on the Neo-Malthusians and
  Cornucopians. You may wish to add other
  population perspectives during your bulletin
  board discussion, and I encourage you to go
  beyond these two camps and research others. For
  an excellent review of population perspectives
  (FYI only, not required reading) see Dr. Keith
  Montgomerys website, which has multiple links
  for classical population literature
  http//www.uwmc.uwc.edu/geography/malthus/malthus.
  htm
• Thomas Malthus (1766 1834)
• Mathematician and Anglican minister
• Wrote An Essay on the Principle of Population as
  it Affects the Future Improvement of Society
• Malthusian view on population is that if 1)
  humans need food and 2) humans have sexual
  desires, then the power of population is
  indefinitely greater than the power in the earth
  to produce subsistence, and therefore, population
  will increase exponentially.

40
Malthus

• Human population growth is exponential but
  agricultural growth is arithmetic.
• Eventually population would outstrip the
  available resources.
• Eventually the power of humans to reproduce would
  be more powerful than the ability of the Earth to
  sustain it

overpopulation
http//www.appstate.edu/neufeldhs/Bio1102/Lecture
s/MalthusGrowthCurves.JPG
41
Malthus (continued)

• Consequences of population growth poverty
• Population growth leads to poverty when the
  population increases faster than the food supply.
• Overpopulation leads to lower wages and a labor
  surplus, further exasperating poverty
• Malthus believed that the Poor should incorporate
  moral restraint to curve their high
  reproductive habits. Poverty is to be blamed on
  the Poor. Its the Poor's own fault that they are
  poor.
• The Poor should adopt middle-class values to
  avoid the consequences of overpopulation
• Malthus was skeptical that the Poor where capable
  of doing this (Social Darwinism), and thus the
  Poor would remain poor. He was opposed to
  welfare because it might encourage more poverty.

42
Critique of Malthus

• Malthusian ideas have been criticized by other
  scholars.
• One of the biggest criticisms, his interpretation
  about the arithmetic increase in the food supply
  was incorrect. Food production has skyrocketed
  in the last several decades, partly due to
  increase in technological advances (e.g.
  precision agriculture, development of new
  resistant crops, embryonic cyclogenesis, etc.).
  Food supply has kept pace (and may have possibly
  exceeded) human population.

43
Neo-Malthusians

• Two of the more outspoken, and controversial
  Neo-Malthusians are
• Paul Ehrlich The Population Bomb
• Seen as a Doomsdayer , proposes that unless
  immediate action is taken to control
  overpopulation, series crisis's will ensue.
• We can no longer afford merely to treat the
  symptoms of the cancer of population growth the
  cancer itself must be cut out. Population
  control is the only answer. The operation will
  demand many apparently brutal and heartless
  decisions. The pain may be intense. But the
  disease is so far advanced that only with radical
  surgery does the patient have a chance of
  survival, quote in Schmidtz and Willott (2002),
  Environmental Ethics What Really Matters, What
  Really Works, Oxford University Press, New York,
  pg 265.
• Garrett Hardin The Tragedy of the Commons
• Author of the Lifeboat Ethics. Quoting Goldfarb
  (2000) in his book Notable Selections in
  Environmental Studies, Second Edition,
  Dushkin-McGraw Hill, Guilford, CN,) Lifeboat
  ethics is a world model in which the develop,
  affluent nations that control and use most of the
  worlds resources are in a lifeboat while the
  struggling developed nations are floundering in
  the surrounding ocean. He concludes that it is
  folly to try to rescue all the swimmers and
  suggests that the ethically appropriate strategy
  is one of triage, by which the haves permit the
  poorest and least developed of the have nots to
  drown in order to prevent the entire boat from
  sinking (pp. 39-40).

44
Cornucopians

• A contrasting academic camp to the
  Neo-Matlhusians are the Cornucopians.
• Technological advances (e.g. in agriculture) and
  expansion of the market economy will mitigate any
  problems presented by overpopulation. If there
  are more people, then we will discover/invent new
  ways to feed them. Technology will help us
  better utilize our resources, cure diseases, etc.
• Prominent among the Cornucopians is Bjørn
  Lomborg.