Environmental degradation, food insecurity, and population growth

ENVIRONMENTAL DEGRADATION AND FOOD SECURITY
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LIVING WITH THE EARTH
CHAPTER 3
ENVIRONMENTAL DEGRADATION
AND FOOD SECURITY
Cooking a meal in Africa
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Objectives for this Chapter
A student reading this chapter will be able to:
1. Discuss the impact of population on resources and
ecosystems.
2. Define the following terms and explain their response to
population growth: retrogression, soil erosion, desertification,
deforestation, wetlands destruction, and wildlife destruction
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3. Define the term food security and discuss the reasons leading
to food insecurity among many nations worldwide.
4. List the suggested steps that might be taken to minimize
global food insecurity.
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5. Explain the most likely reasons for a growing food insecurity
in the United States.
6. List and discuss the demographics of the populations in the
United States at risk to food insecurity.
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INTRODUCTION: THE DEBATE
The ability of our planet to sustain and feed the dramatic
increases in human population growth has been an on-going
debate stretching back over 200 years.

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The Viewpoint of Malthus and Followers
Neo-Malthusians (Malthus, 1789)
Human growth is logarithmic and plants grow arithmetically.
Growth will eventually surpass the ability of the land to feed
the expanding population.
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Technology and Policy Will Save the Day
Cornucopians
The real threat to global stability is the failure of nations to
pursue economic trade and research policies that increase food
production, more evenly distribute food and resources, and limit
environmental pollution.
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Technology and Policy Will Save the Day
The Green Revolution
Strains of plants are being developed that resist diseases, pests,
drought and flooding.
So striking has been the increased production, that the
incorporation of these new variety of seeds and processes
became known as the “Green Revolution.”
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The world markets and the “Green Revolution” may promote
monocultural technology that could prove to be ecologically
unstable (Fig. 3-1).
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Fig. 3-1

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Cross-breeding (Fig. 3-2)
Induced Mutation (Fig. 3-2)
Gene Transfer (Fig. 3-3)
Precision Farming (Fig. 3-4)
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Fig. 3-2. Cross-breeding and Mutation
Hybridization- pollination or cross breeding. Corn with thin
stalk and multiple ears + corn with thick stalk and few ears—
select corn with thick stalk and multiple ears
Induced mutation- Seeds are grown to produce second
generation. Gamma or ultraviolet irradiation of seeds– select
corn with thick stalk and multiple ears

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Fig. 3-3. Gene Transfer
Adapted from Budiansky.6
“Gene gun”- recently developed “gene guns” propel gold
particles coated with DNA by bursts of helium. .22 caliber
blank cartridge is used to propel plastic bullet containing
desirable genes. The plastic bullet impacts against stopping
plate and explosively releases genes. Genes strike and pierce
plant cells at more than 1400 feet a second. Leaf cells with new
DNA are placed in agar dishes with growth hormones. New
shoots develop with many having the desired characteristics.
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Fig. 3-4 Precision Farming
Global positioning satellite (GPS) sends specific signals on
location and local soil condition to receiving systems on

tractors. Computers onboard tractor receive signal from GPS
satellite and determine field coordinates, then adjust fertilizer
dispersion.
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These advances in agricultural technologies have contributed
significantly to reducing hunger in millions of people.
However, the growth of the human population in many of the
lesser developed countries has exceeded the capacity of even
these technological wonders in agricultural production.
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Energy
Wood is being used at such a rapid pace in some LDCs that
forested regions have been decimated, and the collection of
wood for fuel may require several hours each day or as much as
25 percent of average income.
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Energy
On the other hand, the history of fuel use in the developed
nations moved from wood to more efficient fuels.
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Energy
The impact of human activity on environments can be
summarized by the following relationship:
I=P*A*T
Paul Errlich, Stanford
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Energy
I=P*A*T
Where:
I: the impact of human energy-related activity on the globe
P: is the population size
A: is the affluence in terms of per capita consumption
T: is the technologies to supply each unit of consumption

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Attitude and Behavior
Will we progress in a smooth transition to a world of global
stability and health, or will national and personal interests
prevail at the expense of the larger global community?
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What are the attitudes and behaviors that may have an impact on
this outcome?
Tragedy of the Commons
Many members of any society will likely pass on the
consequences of their destructive actions if they will benefit in
the short term and receive little or no negative consequences
from that action.
Garrett Harden

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The Pioneer
The consequences of laying waste to a land in the past were
minimized by the ability of the population to emigrate.
The pioneer mentality cannot be continued indefinitely in the
presence of massive population increases.
We must seek a sustainable development.
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Declining Investment in Technologies
Government funding for organizations which are largely
responsible for the Green Revolution has been falling.
The major gains in food crops experienced as part of the Green
Revolution are unlikely to continue in the absence of investment
in research and development.
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Family Planning Cuts
The United States reduced overall foreign assistance in 1996
with a 25 percent decrease in USAIDs funds and a 35 percent
cut in the family planning/population assistance budget.
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These cuts could result in:
220 million unintended pregnancies;
117,000 additional maternal deaths and 1.5 million women who
experience permanent impairment;
9.3 million additional deaths of infants and young children.
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IMPACTS ON THE ENVIRONMENT
As the population increases the need for food increases.
As the need for food increases, land is cleared, soil is degraded,
and desertification occurs.

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Deforestation
Biomes include tropical rainforests, temperate forests, prairies,
deserts, and arctic tundra.
The majority of tropical forest biomes occur in areas of the
world at risk from overpopulation and many are being
threatened with slash and burn techniques to make room for
croplands.
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Deforestation
Defined as the permanent decline in crown cover of trees to a
level that is less than 10 percent of the original cover.
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Deforestation
The Benefits of Rainforests are:
a major producer of oxygen for the global atmosphere;
the major carbon dioxide sink;

a potential source of new pharmaceuticals useful in the
treatment of human disease;
and an important source of species diversity.
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Deforestation
Rainforests (Fig. 3-5, 3-6)
In spite of the numerous benefits from rainforests, they are
disappearing at an alarming rate.
By 1987, tropical rainforests were disappearing at the rate of 42
million acres each year, representing a loss of 115,000 acres
each day.
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Fig. 3-5
Source from NASA..24

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Fig. 3-6
Adapted from NASA.24
Map that highlights the locations of some of the world’s major
rainforests, including Mexico, Belize, Honduras, Guatemala, El
Salvador, Nicaragua, Costa Rica, Columbia, Ecuador,
Venezuela, Brazil, Cote d Ivoire, Nigeria, Central African
Republic, Congo, Malaysia, Indonesia, Philippines and Papua
New Guinea
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Soil Degradation
What is soil?
Soil consists of small particles of rock and minerals mixed with
a major proportion of plant and animal matter in various stages
of decay.

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Soil Degradation
Plants are called autotrophic because they synthesize their own
food from inorganic substances.
Plants also derive nutrients from soil
Micronutrients
Macronutrients
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Soil Degradation
Loam
Soils best suited for agriculture consist of sand, silt, and some
clay in a homogeneous mixture referred to as loam.
Humus
Complex organic matter that has been biologically broken down
so that original plant and animal matter is unrecognizable.
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Soil Degradation

Humus serves to:
retain moisture much as a sponge;
serve as an insulator to heat and cold;
and to bind and release nutrients to plants in useable forms.
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Fig. 3-7 Major Soil Biomes
Map of major soil biomes. Tundra are in the top half of the
globe. Taiga is in the upper third of the globe under Tundra.
Temperate forest, grassland and woodland are below Taiga.
Deserts are below Temperate forest and below tropical
rainforests, which are sandwiched between the two prominent
desert regions.
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Soil Degradation
Soil Erosion
As woods are cut and fields are plowed to plant crops, soils are

lost to the effects of wind and runoff water (Fig. 3-8).
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Fig. 3-8
Adapted from Turk and Turk.7
Pie Chart of soil erosion. Woods have 0.4% moisture loss and 0
tons of topsoil loss. Grass cover has 1.9% moisture loss, 0 tons
of topsoil loss. Grain crops have 26% moisture loss, 86 tons of
topsoil loss. Freshly tilled soil has 50.4% moisture loss, 161
tons of topsoil loss. About ¼ of the chart is labeled as “other”
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Soil Degradation
Farming techniques practiced to reduce soil erosion are:
Rotation
Fallowing
Terracing

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Soil Erosion
Globally, soil erosion claims over a billion acres every year,
and 1.2 billion acres of global cropland is losing topsoil so
rapidly that these acres are expected to become unproductive in
the next few decades.
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The Process of Desertification
What is desertification?
Land degradation in arid, semi-arid and dry sub-humid areas
resulting from various factors, including climactic variations
and human activities.
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Desertification
About 15 billion acres or one third of the earth is dry land, and
2.5 billion (or 16 percent of the earth’s surface) of these
dryland acres are hyperarid deserts where there is little or no
growth.
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Poverty and the need for food is an enormous pressure that
defies a flexible land use response and leads to desertification
(Fig. 3-9).
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Fig. 3-9
Once forested land in Africa

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The Costs of Desertification
Economic losses from desertification are calculated to be $40
billion while the cost of recovering these lands worldwide is
estimated at $10 billion annually.
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Wetlands – What are they?
Wetlands are those areas of land where water saturation is the
major factor influencing the nature of soil development and the
communities of plants and animals that live in the soil and on
the surface.
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Wetlands
Types of wetlands (Fig.3-10):
Swamps
Bogs
Prairie potholes

Bottomland Hardwood Forests
Estuaries
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Fig. 3.10
Source> USEPA, Office of Wetlands, Oceans, and Watershed.
40
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Freshwater Marshes & Swamps
40

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Bogs
40
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Prairie potholes
40
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Bottomland Hardwood Forests
40

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Coastal Marshes and Estuaries
40
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Benefits of Wetlands
Wetlands purify and replenish water supplies.
Wetlands are extremely rich in biomass (the amount of plant
and animal life).
Wetlands are an important source of food.
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Benefits of Wetlands
Wetlands absorb large amounts of carbon dioxide from the air.
Wetlands control flooding in low-lying areas as they work like
sponges

Wetlands protect coastal areas from storms.
Wetlands provide recreation and beauty.
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Wetland Losses
An estimated 300,000 acres (120,000 hectares) of wetlands are
drained or filled every year in the U.S.
Wetlands were considered a nuisance to farmers and settlers and
these areas were filled in.
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The Loss of Biodiversity and Extinction of Species
Biodiversity refers to the range of animal and plant species and
the genetic variability among those species.
Why is biodiversity important?
The greater the range of genetic variation, the more likely there
will be a survivor species in the event of major catastrophies.

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Background
99% of all species that ever existed are thought to be extinct.
The Permian extinction caused 90 percent of all species in the
oceans to disappear, two thirds of reptiles and amphibian
families perished, and up to 30 percent of insect orders were
lost.
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Background
Records of fossils show that entire groups of organisms
including fish, reptiles, birds and mammals have replaced one
another over long periods of time (Fig. 3-11).
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Fig. 3-11

Graph of relative number of species in correlation with millions
of years ago from 330-recent. The majority of species have been
reptiles, with birds and mammals arriving in the last 80 million
years.
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Background
It appears that the planet is now losing more species than are
being created, and that the activities of humans are the reason
for a rapidly growing species extinction and loss in
biodiversity.
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Loss in Biodiversity
Of the 4,327 known mammal species, 1,096 are at risk, and 169
are in extremely high risk of extinction in the wild in the
immediate future (Fig. 3-12)

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Fig. 3-12
Adpated from Doyle. 51
Map showing areas of the world where more than 15% of
mammal species are threatened in gray, and countries with the
most threatened mammal species and including 43% of the
world’s population in blue. The countries are China and India
with 75 species apiece, and Indonesia with 128 species.
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Threats to Biodiversity
Loss of Habitat
Most significant threat to biodivesity today is elimination of
habitat for agriculture and housing. Half of 300 mussel species
lost in US to pollution of rivers and creation of dams.
Over-harvesting
Cod in the North Sea off New England are heavily exploited
with as much 60 percent of the fishable stock being removed
annually.

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Threats to Biodiversity
Non-native Species
Rainbow trout never encountered “whirling disease” before the
parasite was unknowingly transplanted here from Europe.
Pollution
The acidification of lakes and streams has led to juvenile
recruitment failure among fish resulting in the disappearance of
many species in a number of industrialized countries.
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Protecting Endangered and Threatened species
Legislation first aimed at protecting wildlife in the United
States was introduced as a bill in 1926.
In 1973, the Endangered Species Act (ESA) was promulgated in
the United States (Fig. 3-13). The Act currently protects 1,135
speciesof plants and animals.

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Fig. 3-13
Species being restored
Source> US Fish & Wildlife Service: Whooping Crane-Steve
Hillebrand; Grizzly bear – Don Redfern; Bald eagle – Robert
Fields; Gray wolf - USFWS
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Protecting Endangered and Threatened species
Many environmentalists praise the ESA for reducing the
extinction rate of some animal species in the United States, and
even increasing numbers in as many as 65 species.
Others have attacked the Act as interfering with livelihood and
taking away personal property rights.
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Babbitt tells Nation: Species protection Works
May 7, 1998, Secretary of the Interior Bruce Babbitt announced
29 different animals, plants and birds have recovered
sufficiently to take off the ESA list.
Paul Nickerson, head of the Endangered Species Div of the Fish
and Wildlife ‘s Northeast Regional Office, Hadley sees
continued protection of species under State law.
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FOOD SECURITY
One of the biggest debates for the 21st century concerns
whether or not the world can produce enough food to feed
another few billion people.
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FOOD SECURITY
Food security is said to occur when all people have physical and
economic access to the basic food they need to work and
function normally.

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Food Production
For nearly 40 years, the world production of grain has risen by
more than 2 percent a year, but declined to scarcely 1 percent a
year in the 1990s.
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Food Production
Countries with critical or low food security are shown in figure
3-14.
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Fig. 3-14
Adapted from Brown and Kane. 69

Countries facing critical or low food security include Peru,
Bolivia, Mali, Niger, Sudan, Chad, Somalia, Central African
Republic, Kenya, Tanzania, Mozambique, Zimbabwe, Zambia,
Angola, Cameroon, Nigeria, Benin, Togo, Ghana, Liberia,
Sierra Leone, Burkina, Mali, and Afghanistan
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Reasons for Regional Food Shortages
Food production fell behind population growth in 64 of 105
developing countries between 1985 to 1995.
The main reasons for food shortages in eastern Africa derive
mainly from recent droughts followed by floods.
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If countries are to feed the 9 billion expected by the year 2050,
Africa would have to increase production by 300 percent, Latin
America by 80 percent, Asia by 70 percent, and North America
by 30 percent (Fig. 3-15).

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Fig.3-15
Adapted from FAO. 10
Bar graphs for the world, Asia, Africa, Russia, and Latin
America showing the percent change from 1961 where per
capita food production equals 100 and the years between 1961-
1994.
Russia has had the greatest decrease, Asia has had the greatest
increase, and the others have maintained relatively stable over
time.
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Growth rates in cereal production have been declining from 2.8
percent in the 1960s, to nearly 2.1 percent in 1992 (Fig. 3-16).

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Fig. 3-16
3 graphs. The first shows world growth rate in cereal
production. From 1961-1969 it grew 4%, from 1970-1979 it
grew 3%, from 1980-1988 it grew 1.25% , and from 1990-1996
it grew 1 %.
The second graph shows world growth rate in agricultural
production. From 1961-1969, it grew 3.25%, from 1970-1979 it
grew 2.5%, from 1980-1988 it grew 2.5% , and from 1990-1996
it grew 2.25 %.
The third graph shows growth rates in yields of all cereals in 93
developing countries. From 1961-1969 it grew 3%, from 1970-
1979 it grew 2.75%, from 1980-1988 it grew 2.5% , and from
1990-1996 it grew 1 %.
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Sources – Where will the Food Come From?
Increases in food supply must come from one or more of the
following sources (Fig. 3-17):
increases in yield (tons per acre);
increases in arable land placed under cultivation;

and cropping intensity (fewer fallow periods or more than one
crop per year or field).
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Fig. 3-17
Increases in food supply pie chart. 66% comes from increased
yields (tons of crops harvested per acre), 21% from arable land
expansion, and 13% from increasing cropping intensity (fewer
fallow periods or more than one crop per year or field)
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Sources
There are scientists who believe that the ability to expand
cropland is limited, and that it is disappearing in many areas of
the world.

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Sources
The potential for increasing agricultural land is limited by:
the significant costs of developing an infrastructure in remote
areas;
the lesser productivity of these alternative areas;
and the trade-offs in environmental destruction of sensitive
ecosystems.
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Sources
Alternative strategies are being evaluated and promoted that are
more friendly to the environment.
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Sources

These strategies are:
improved irrigation systems;
structured water pricing to reduce overuse;
alternative rotation of crops;
selective pesticide use;
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Sources
These strategies are:
use of pest-resistant varieties;
improved soil testing and fertilizer application;
regional crop breeding programs;
and more education to farmers.
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Food Security
Worldwide
Chronic undernutrition is a difficult and pervasive problem
resulting in a food security crisis in many LDCs.
Net imports to LDCs are expected to increase from 90 to 160
million tons in the years from 1990 to 2010.

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Hunger in America
More than 25 million Americans, almost 50 percent of them
under 17, resort to using food distribution programs such as
soup kitchens and food pantries (Fig. 3-18).
Nearly 35 million Americans live in hungry or food-insecure
households.
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Fig. 3-18
Adapted from Roberts and Roberts. 80
4 pie charts describing the makeup of Americans using food
distribution programs. The sex distribution is 62.4% female,
37.6% male. The age distribution is 46% are between 16-64,

38% are less than 15 and 16% are more than 65. The race
distribution is 47.7% White, 2.1 % black, 14.6% Hispanic, 2.5%
Native American, 2.5% other, and 0.7% Asian.
HUMAN POPULATION - Moore
CHAPTER 2
HUMAN POPULATION
A student reading this chapter will be able to:
1. Define the attributes of populations including birth and death
rates, growth rate, density, and mobility (immigration and
emigration).
2. Calculate rate of natural increase from birth and death rates,
and mathematically demonstrate the effects of age-sex
composition on a population.

3. Define biotic potential and maximum growth rate, and list the
various limits to growth
4. Identify, list, and explain the population growth forms.
5. Recognize and explain the concept of population explosion
with respect to complete and incomplete demographic
transition. Define population implosion and discuss the
conditions that lead to this phenomena.
6. Explain the role of urbanization in influencing sustainability
of populations.
7. Explain global population projections and differentiate
between developed and lesser developed countries with respect
to those projections.
8. List and discuss the various options for fertility control
methods, while contrasting the effectiveness, risks, and benefits
of each type.
HUMAN POPULATION

INTRODUCTION
Understanding the dynamics of human populations is a first
order of business in beginning the study of environmental
health.
There is growing realization that surging populations,
environmental degradation, and ethnic conflict are strongly
intertwined.
LESSER DEVELOPED COUNTRIES
Overpopulation, infectious disease, unprovoked crime, few
resources, and the influx of more refugees, increases the erosion
of nation-states leading to the empowerment of private armies,
security firms and international drug cartels.
LESSER DEVELOPED COUNTRIES
This is a vision of the early 21st century in many parts of the
lesser developed countries (LDCs), and threatens to expand
along with the growth of human populations.

THE CHARACTERISTICS OF POPULATIONS
Species
A species is normally considered to be a group of organisms
that can breed together with the production of a viable and
fertile offspring.
Different species not only have differing physical attributes, but
they also differ in the population characteristics.
Population
A population is considered to be the breeding group for an
organism.
Each population has characteristics that help to identify it.
Some of these characteristics are birth rate, death rate, rate of
natural increase, age distribution, and sex ratio.
Birth Rate
Birth rate refers to the number of individuals added to a
population through reproduction (live births) and is normally

expressed as the number of live births per 1,000 population
(counting the population at the midpoint of the year)(Fig. 2-1).
Death Rate
Death rate is also similarly calculated using total deaths divided
by the mid-year total population (Fig. 2-1).
Rate of Natural Increase
The rate of natural increase is determined by subtracting the
death rate from the birth rate (Fig. 2-1).
The rate of natural increase reflects the growth rate in which
migration is not considered.
The growth of a population in the absence of migration must
depend on the birth rate being higher than the death rate.

Fig. 2-1
Birth rate equals the number of live children born in a year per
1 000 total population
Birth rate in year Y = Number of live children born in year Y
over the midyear population in year Y
Birth rate in year 1998= 4,345,600 (children born in 1998) over
271,600,000 (population in mid-1998)= 16/1000
Death rate in year y= 2,172,800 (deaths in 1998) over
271,600,000 (population in mid-1998) = 8/1000
Rate of natural increase in year 1998 = (Birth rate - Death rate)
= 811000 or 0.8 percent*
*These are approximate numbers for the United States used only
for example.
Living with the Earth - Gary Moore
Age Distribution
The age-sex composition of the population has a profound effect
on the birth and death rates of a country because the probability
of dying or giving birth within any given year depends upon the
age and sex of the population members Fig. 2-2.

Age Distribution (Fig. 2-2)
Graph showing the age distribution in different regions. The
reproductive ages are noted as 15-50, which has the most people
in stable and declining populations. Expanding populations have
more children under 14 than any other ages
Expanding populations: Mexico, Asia, and Africa have a bell
curve distribution between relationship of percentage of
population and age, with 7% of the population being under the
age of 14 and 2-3% over the age of 55.
The United States is a stable population with a much steeper,
more jagged bell curve with people over 55 making up 3% of
the population and children making about 3.5% of the
population
Western Europe and Japan are declining populations with an
even steeper curve, with only 3% children and 1-2% adults over
55

Total Fertility Rates
Total fertility rates(TFR) represent the number of children a
woman in a given population is likely to bear during her
reproductive lifetime providing that birth rates remain constant
for at least a generation.
Immigration
In nature, when the density of organisms becomes too great, the
intense competition for food, water, and other resources
damages the entire population. Some species have the ability to
disperse or migrate out of the area and in doing so, temporarily
relieve the overcrowding.
This process is called emigration.
Immigration
When species emigrate from an area, they must immigrate or
enter into another area.
Driven by natural disasters, war, disease, and disappearing
resources, the numbers of refugees worldwide may exceed 15
million, with about 880,000 to 1.4 million immigrants entering

the United States each year, including more than 200,000 who
enter illegally.
POPULATIONS DYNAMICS
There are periodic upsurges in many populations that lead to
overwhelming numbers.
Whether these population explosions occur in rabbits,
lemmings, soldier ants, or locusts, there is always some natural
pressures that bring the population back into balance with their
natural surroundings.
Biotic Potential
The unrestricted growth of populations resulting in the
maximum growth rate for a particular population is called its
biotic potential.

The biotic potential of species differs markedly and is
influenced by: (1) the frequency of reproduction; (2) the total
number of times the organism reproduces; (3) the number of
offspring from each reproductive cycle; and (4) the age at which
reproduction starts.
Environmental Resistance
Environmental resistance refers to those pressures that limit
population and may include such factors as disease, wars,
predatory behavior, toxic waste accumulation, or species
competition (Fig. 2-3).
Fig 2-3

Biotic potential – environmental resistance = actual rate of
resistance.
Graph with population on y axis and time on x axis
Environmental resistance is food, light, or space shortage,
climate changes, disease, predatory behavior, toxic wastes,
competition
By plating bacteria as outlined in figure 2-4, one can examine
and then plot a bacterial growth curve (Fig. 2-5).
Lag Phase
The initial part of the curve in which the organisms show no
increase in growth rate, but are preparing for the exponential
growth phase which follows.
Fig. 2-4

Original inoculum is diverted into various test tubes, one to
another, so it loses potency.
The first tube creates too many confluent colonies to count on a
nutrient agar plate, the next creates less, the third less than that,
and the final creates 2x10 to the sixth power colonies/ml
Calculation: Number of colonies on plate x reciprocal of
dilution of sample= bacteria/ml. In this example, there are 20
colonies on the plate of 1:100,000 dilution = 2 million
bacteria/ml. A growth curve can be constructed if the original
inoculum is counted by this process hourly for 24 to 48 hours.
Fig. 2-5
Graph with time up to 24 hours on the x axis and log of numbers
of bacteria on the y axis. An S curve shoes the lag phase for the
first 6 hours, the log or exponential growth phase for the next
six hours, the stationary phase for six hours after that and the
death or logarithmic decline phase for the remaining 12 hours

Fig. 2-6
If an organism grows too rapidly and the population escalates
beyond the carrying capacity of the environment in which it is
located, a “J” type growth curve may develop (Fig. 2-6).
X axis is time and y axis is log of numbers of organisms. A
short lag phase is followed by a steep log or exponential growth
phase which exceeds carrying capacity
This behavior sometimes oscillates every few years as in the
case of lemmings that inhabit the arctic tundra north of the
Canadian forest.
Every 3 to 4 years the population explodes, then crashes the
following year, followed by a 2 year cycle of slow recovery
(Fig 2-7).
Figure 2.8 shows the effects of predators on populations.

Fig. 2-7
Graphic depiction of lemming population cycles. Every 3 to 4
years the population explodes, then crashes the following year,
followed by a 2 year cycle of slow recovery.
Fig. 2-8
Population size cycles but is relatively constant. This can be
effected by the presence of predators. Graphic shows a squiggly
but relatively constant rate of population for animals’

population size, then the same population over time in the
presence of a predator, with a pronounced decline.
k-Strategy (type I”)
When large organisms with relatively long life spans have only
a few offspring, but devote their energies to protecting and
nurturing the offspring to enhance their individual survival until
they can reproduce (Fig.2-9).
Density dependent factors include such items as food supply,
which becomes more limiting as the size of the population
grows.
r-Strategy
r-strategy populations are typically small, short-lived
organisms, which produce large numbers of offspring and
receive little or no parental care (Fig. 2-9).
These organisms are limited by density-independent factors
such as a drought that dries up a pond, or sudden climactic
changes such as El nino which alters the temperature of the
water making it uninhabitable for certain species.

Fig. 2-9
Adapted from Turk & Turk. 7
Graph of r-strategy, Type II and k strategy/type I populations
with number of survivors on the y axis and age on the x axis.
R-strategy populations are Type III: insects, fungi, fish,
mollusks, plants. They produce large numbers of offspring and
receive little or no parental care. They don’t live long. K-
strategy organisms with relatively long life spans have only a
few offspring, but devote their energies to protecting and
nurturing the offspring to enhance their individual survival until
they can reproduce. Type II populations are some birds, and
humans experiencing malnutrition and disease.
POPULATION TRENDS IN THE WORLD

Demographers use the information on population size, fertility
rates, migration, birth and death rates, growth rates, infant
mortality, density, age-sex composition and other factors to
statistically characterize human populations.
Their purpose is to predict what will happen to that population
over time.
POPULATION TRENDS IN THE WORLD
Historical Trends
After earth’s temperature stabilized about 10,000 years ago,
humans began to domesticate animals and cultivate crops, this
allowed the human population to increase (Fig. 2-10).
Since then, the world growth rate has increased dramatically,
although we are currently experiencing a downward trend (Fig
2.11).
Fig. 2-10
Adapted from Turk & Turk. 7

Graph with population in billions on the y axis ranging from 0
to 6 and year on the x axis. Ranging from 2 million BC to 1998.
2 million BC to 0 BC is considered to be before the Christian
era. Once the Christian era began, population began to steadily
increase and spiked in 1998, when it reached 6 billion.
Fig. 2-11
Graph showing thesteady increase in the annual rate on natural
population increase in the world from 1700 to modern times.
There was a spike in population in 1970, with a 2.06%
increase and slow decline to a 1.4% increase in 1997.

Historical Trends
Growth Rate
The rate of births is the ratio of births to the population, and
death rates represent the ratio of deaths to the population.
Growth rate is then determined by the birth rate minus the death
rate.
The population has grown so much, that even the smaller
growth rates lead to additions of larger numbers of people to the
global population (Fig 2-12).
Fig. 2-12
Graph of population growth from 1960-2000. Year is depicted
on the x axis. Annual increase in world population from 0-90
million on the y axis. Even smaller growth rates lead to
additions of larger numbers of people to the global population,
growing 1.7% in 1960 lead to 51 million more people and a
total population of 3 billion, whereas growing 1.4% between
1998-2000 lead to 85 million more people and a total population
of 6 billion.

Historical Trends
Doubling Time
Another useful way to demonstrate growth rate is to present it
as doubling time (Fig. 2-13), or the number of years for a
human population to double its size. The doubling time can be
calculated according to the following relationship:
doubling time = 0.70 / growth rate
Fig. 2-13
Doubling time in years from 0 to 700 on the y axis, countries
and regions on the x axis. Northern Europe has taken 700 years
to double at 0.1 %- the rate of natural increase. Southern Europe
has taken 350 years to increase .2%, Western Europe has taken
233 to increase .3%, U.S, 87.5 to grow .8%, Oceania 53.8 to

grow 1.3%, Asia 50 to grow 1.4%, South America 46.6 to grow
1.5%, and Africa 26.9 years to grow 2.6%
Historical Trends
Demographic Transition
Developed countries have exhibited slowly declining birth and
death rates over the last century.
This has resulted in a diminishing difference between birth rates
and death rates and a very low rate of natural increase resulting
in a stable population with very long doubling times (Fig. 2-14).
Fig. 2-14
Adapted from United nations Population Fund. 3
DeBirth rate vs. death rate in more developed countries between
1750-2000. Slowly declining birth and death rates have resulted

in a low rate of natural increase. Birth rate = 11/1000
Death rate = 10/1000. 11-10=0.1 rate of natural increase and a
doubling time of 700 years
Historical Trends
Incomplete Demographic Transition
LDCs do not have the resources to institute social security, and
have unstable policies that fail to capture the trust of its
citizens.
The populations had remained stable with high birth rates and
high death rates.
Developed countries introduced better sanitation and nutrition
to LDCs, resulting in a decrease of the death rate (Fig. 2-15).
Fig. 2-15
Adapted from United nations Population Fund. 3

Less developed countries have high birth rates and newly lower
death rates, with a high rate of natural increase. Birth rate =
31/1000. Death rate = 10/1000. 31 – 10= 2.1 rate of natural
increase. Doubling time = 33 years.
Current Population Trends
The world’s population is growing at a rate of 1.4 percent
annually and is expected to reach six billion people by the
middle of 1999
Almost 98 percent of the annual increase in the world’s
population is occurring in the LDCs.
Population Decreases in the Developed Countries
Declines in Fertility
In 1970 there were 19 countries reporting declining fertility
rates while in 1997 over 57 countries have reported below-
replacement fertility rates.
By the year 2060, Europe will have lost almost 25 percent of its
population.

Concerns About Decline
There is a concern throughout Europe and Japan that the
declining population will result in decreasing house and land
prices as the demand declines along with the population.
In the southern island of Kyushu, Japan, officials are offering a
gift of $5,000 to parents who have a fourth or subsequent child.
Concerns About Decline
Higher education for women with new aspirations and higher
incomes, is considered to be a factor for declining fertility rates
in many countries.
In fact, as illiteracy among women decreases in a country, the
average number of children born to those women declines (Fig.
2-16).

Fig. 2-16
The greater the level of illiteracy among women, the more
children they are likely to have. The more money a woman
earns in the home, the fewer children she is likely to have.
Fertility Rates in the United States
The replacement TFR level for most countries is accepted as
being 2.1.
Subtle changes in social attitude appeared to produce rather
significant changes in fertility rates (Fig. 2-17).
Fig. 2-17
Source: U.S. Bureau of the Census

Total fertility rate on y axis between 0 and 4.0. X axis has the
years between 1920-1997. The replacement TFR is 2.1. The US
has spent more than 20 years at below replacement level.
Immigration and the Changing Racial Landscape in the United
States
Although the TFR has remained below replacement levels,
immigration adds at least another 850,000 to 1.2 million people
to the United States each year.
The expanding population of elderly white will be expecting
support from a working population of tremendous diversity and
proportionally fewer workers per retiree (Fig. 2-18).
Fig. 2-18

In 1950 there were 16.5 workers per retiree. In 1997 there were
3.3 workers per retiree/ By 2025 there will only be 2.2 workers
per retiree.
Current Population Trends in the Less Developed Countries
More than 80 percent of the world lives in the LDCs.
In the next 20 years 1.76 billion children will be born in the
LDCs (Fig. 2-19).
Fig. 2-19
Adapted from Population reference Bureau 2 and the United
Nations Population Fund.3

Population in a bar graph showing contrast between developed
and lesser developed countries from 1750 to 2100. Developed
countries have a significantly slower population growth. By
2100, 2 billion people will live in developed countries and 12
billion in lesser developed countries.
Predicted Future Trends in Populations
The median or best estimate by the United Nations is that the
world population will stabilize at 11.5 billion people around the
year 2150 if the world fertility rate drops to 2.06 and life
expectancy is 85 years (Fig.2-20).
Fig. 2-20
Adapted from Doyle18 and Motavallui.19
Projections of population growth. With a TFR of 2.5 there will
be 28 billion people in 2150. With a TFR of 2.06 there will be
11.5 billion. With a TFR of 1.7 there will be 4 billion in 2150.

Urbanization - What is it?
The mass migration of people to the cities.
Megacities
Defined as having a population of more than 10 million, will be
commonplace by the year 2015, with 9 of the 10 largest cities
being in the the developing countries. (Figs.2-21, 22).
Fig. 2-21
Adapted from the Environment.17
Bar graph of urbanization across the globe, will Tokyo being
the only city in a developed country that houses much of the
population at about 30 million, Bombay India has roughly the
same amount. Lagos Nigeria and Shanghai China have about 22
million. Jakarta Indonesia has just over 20 million, Sao Paulo
Brazil and Karachi Pakistan have about 20 million Beijing
China, Dhaka Bangladesh, and Mexico City Mexico have about

18-19 million.
Fig. 2-22. Borders of W. Africa merged by megacities
Urbanization
Facilitates the spread of disease.
Potential increase in violence
Environmental degradation
THE CONTROL OF POPULATION
Empowerment or Force

Countries attempting to bring population growth under control
without first empowering women and providing effective birth
control have often resorted to oppressive population control
policies.
Population Policies in Some Countries
India
India was the first country to introduce family planning in 1951,
with the rhythm method.
China
China continues to enforce a one-child policy in the nation’s
largest cities such as Beijing and Shanghai.
Family Planning Versus Population Control
Population Control
Government directed programs that set a policy for establishing
an optimum population size.

Family Planning Versus Population Control
Family planning
Population control is in contrast to family planning programs
that are directed at assisting couples in having the number of
children they desire regardless of how many.
METHODS OF FERTILITY CONTROL
Introduction
Methods that prevent fertilization of the egg are called
contraception.
Methods vary in their risks to health, their efficacy in
preventing pregnancies, ease of use, acceptance, and costs.
Contraceptive Methods that are Reversible
Natural Birth Control and Family Planning
Hormonal
Oral Contraceptives (Fig. 2-23)
Depo-Provera
Norplant (Fig. 2-24)

Fig. 2-23
Fig 2-24
Contraceptive Methods that are Reversible
Spermicides (Fig. 2-25)
Barrier Methods
Male Condom (Fig.2-26)
Female Condom (Fig. 2-27), Diaphragms, and Cervical Caps
(Fig. 2-28)
Intrauterine Devices (IUD’s) (Fig. 2-29)

Fig. 2-25
Fig. 2-26
Fig. 2-27

Fig. 2-28
Fig. 2-29
Contraceptive Methods that are Permanent
Sterilization has become one of the most popular methods for
contraception in the United States among married couples who
have achieved their desired level of parenthood
Vasectomy
Male sterilization by making an incision on either side of the

scrotum and snipping out a piece of the vas deferens.
Tubal Ligation
Blocks the entry of eggs into uterus, eggs released from the
ovaries dissolve and are reabsorbed into the body.
Abortion
The medical means of terminating a pregnancy.
Nearly 60 million abortions occur annually on a worldwide
basis.
Abortion can also be safely induced within the first 9 weeks of
pregnancy by administering the drug RU-486.

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