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Kayla Robinson
3.8 Environmental Demands of Human Populations
Ecological Footprints
 An ecological footprint is the hypothetical area of land required by a society, group, or
individual to fulfill all their resource needs and assimilate all wastes
 A country described as having an ecological footprint 2.4 times its own geographical area
is consuming resources and assimilating its wastes on a scale that would require a land
area 2.4 times larger than the actual size of the country
 Ecological footprint can act as a model for monitoring environmental impact, highlight
sustainable and unsustainable lifestyles, and allows for direct comparisons between
groups and individuals (LEDCs and MEDCs).
 It can be increased by:
o Greater reliance on fossil fuels
o Increased use of technology and energy
o High levels of imported resources
o Large per capita production of carbon waste
o Large per capita consumption of food
o A meat-rich diet
 It can be reduced by:
o Reducing amounts of resources used
o Recycling resources
o Reusing resources
o Improving efficiency of resource use
o Reducing amount of pollution produced
o Transporting waste to other countries to deal with
o Improving technology to increase carrying capacity
o Importing more resources from other countries
o Reducing population to reduce resource use
o Using technology to increase carrying capacity
o Using technology to intensify land use
Calculating Ecological Footprint
 Ideally, all resource consumption and land uses are included in an ecological footprint
calculation. However, they are usually simplified and an approximation is achieved by
using only net carbon dioxide emissions and food production.
 Ecological Footprint = (per capita food consumption kg yr-1 / mean food production of
local arable land kg ha-1yr-1) + (per capita carbon dioxide emission kg C yr-1 / net carbon
fixation of local natural vegetation kg C ha-1 yr-1)
 Factors used in a full ecological footprint calculation would include:
o Bioproductive (currently used) land - land used for food and materials
o Bioproductive sea – sea area used for human consumption
o Energy land – equivalent amount of land required to support renewable energy
o Built (consumed) land – land used for development
o Biodiversity land – land required to support all non-human species
o Non-productive land – land such as deserts
Ecological Footprints – MEDCs and LEDCs
 LEDCs tend to have a lower ecological footprint than MEDCs
 MEDCs generally have higher rates of resource consumption than LEDCs because
people have more disposable income, which means demands for resources are high.
Consumption is also high because resource use is often wasteful. MEDCs produce more
waste and pollution as by-products of production. A meat eating diet, prevalent in
MEDCs, requires more land than a vegetarian diet (because animals do not use up to 90%
of available energy from crops)
 LEDCs are characterized by lower consumption as people have less to spend, and the
informal economy is responsible for recycling many resources. More of energy from
crops goes to humans if eaten directly (prevalent in LEDCs)
 Populations more dependent on fosil fuels have higher carbon dioxide emissions.
Fixation of carbon dioxide is dependent on climatic region and vegetation type, with
countries near the equator containing vegetation with higher rates of net primary
production
 Lower rates of carbon dioxide uptake in MEDCs compared to LEDCs, and higher rates of
emissions, contribute to higher ecological footprint in MEDCs
 Case Study: Peru versus Canada
 the per capita ecological footprint of Canada is 5.4, for Peru it is 0.9
 Peru, and LEDC, has an energy component of 16% within its ecological
footprint, whereas Canada has an energy component of 53.7%
 Canada has a larger consumer driven economy, a greater car culture, uses
more energy for heating, and has higher consumer spending per capita
than Peru, all of which contribute to the high percentage of energy within
the Canadian ecological footprint
 The use of fossil fuels in Canada adds to the carbon dioxide emission
component of the ecological footprint
 The higher rates of photosynthesis and NPP in Peruvian vegetation, due to
its location near the equator, contribute to Peru’s lower net contributions
to atmospheric carbon dioxide levels
Population Policies – National and International – and Population Dynamics and Growth
 Population policies refer to official government actions to control the population in some
way
 Pronatalist: policies in favor of increasing the birth rate
 Anti-natalist: policies that attempt to limit the birth rate
 Case Study: National Level Anti-Natalist Policies: China
 China facing problems with feeding, clothing, and housing their vast
population, leading to the government thinking about family planning and
reducing the amount of children being born
 China induced its one child policy in 1979, which rewarded families that
had only one child and penalized those who had more than one (by paying
higher taxes and preventing parents from reaching high level positions in
jobs)
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Other measures included forced sterilizations and abortions so that
families were limited to one child
 Policy has been relaxed since October 1999; in rural areas, couples can
have two children without penalties
 One of the results of the policy has been gender imbalance (in 2003, 117
boys were born for every 100 girls), especially in rural areas
 There is a resurgence of female infanticide. Girls are hidden from the
authorities or die at a young age from neglect. China is offering to pay
couples a premium for producing baby girls to counter the imbalance
 There is still a preference for boys, especially in urban areas, because boys
are regarded as being more able to provide for their families
 China now offers welfare incentives to couples with two daughters and
has tightened the prohibition of sex-selective abortions
 Statistically, the one child policy was a success, preventing over 300
millions births since it was introduced
 It is predicted that there will be a shortage of potential marriage mates
which will lead to some social instability
 Case Study: Fertility in the Arab World
 Improving women’s health
 Life expectancy in women up from 52 years in 1970 to more than 70 years
and 2004
 Average number of children born to Arab women has fallen by half in the
past 20 years to a level scarcely higher than the world average
 A main cause of this is a dramatic rise in age at which girls marry
 In large Arab cities, the cost of housing, added to the need for women to
pursue degrees or start careers, is prompting many to delay marriage until
their 30s.
 International Development Policy – Millennium Development Goals
 Development goals:
o Eradicate extreme poverty and hunger
o Achieve universal primary education
o Promote gender equality and empower women
o Reduce child mortality
o Improve maternal health
o Combat HIV/AIDS, malaria, and other diseases
o Ensure environmental sustainability
o Develop global partnership for development
National development policies  declining birth rates in east Asia
o East Asia has seen a collapse in birth rates far more sudden than the west. China
continues to pursue its one child policy, despite fertility rate of 1.7 and danger of
a gender imbalance
o Low birth rate may be attributable to rising job opportunities and earning power
for women. There is a reluctance to marry and preference for few, if any, children.
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How does this differ from the west?
o Immigrants add to population and tend to have more children
o Demographic transition
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Impact of urbanization on the demographic transition is mainly through decline in
mortality. As a country continues to move into the demographic transition, the natural
increase of the urban population overtakes rural to urban migration and becomes the main
driver of urban population growth
 Case Study: Pro-natalist Policies in Romania
 Long range planning was a cornerstone of economic growth
 In the 1960s, the country was approaching zero population growth which
carried alarming implications for future labor supplies and
industrialization
 In 1966, government responded with prohibition of abortion on demand
and introduced pro-natalist policies
 The decree stipulated that abortion would only be allowed when:
 Pregnancy endangered the life of the woman
 Pregnancy was the result of rape or incest
 The child was likely to have a congenital disease or deformity
 The woman was over 45 or had given birth to at least 4 children
who remained under her care
 People who remained childless after the age of 25 were liable for a special
tax amounting to 10-20% of their income
 Government made divorce more difficult
 Family allowances were raised
 Monetary awards were given to mothers with the birth of their 3rd child
 The income tax rate for parents of three or more children was reduced by
30%
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Contraceptives were not manufactured or imported to Romania, making
birth control difficult, leading to a rise in population
Population increase was short lived when people worked around the law
The population problem returned to its original state, causing more laws to
be passed. For example, the legal age for marriage was lowered to 15
years for women, and addition taxes were levied on childless individuals
over 25. Monthly gynecological examinations for all women of
childbearing age were instituted
Romanian demographic policies continued to be unsuccessful largely
because they ignored the relationship of socio-economic development and
demographics.
Romania’s birth rate is 10.3 per 1000 and its total fertility rate is 1.39
children per woman
The Relationship between Population, Resource Consumption, and Technological Development
 Regions of the world can be classified according to population – resource ratios
 There are four main types of regions: USA type, India-China type, Brazil type, and
European type
 Ackerman’s Classification of Population, Resource, and Technology
Type
Characteristics
Examples
USA type
 Technically innovative
 USA
 Low population-resource ratio
 Parts of Canada
 Parts of Russia
 Parts of S. Africa
 Parts of Australia
India-China
 Technologically deficient
 India
type
 High population-resource ratio
 China
 N. Africa
 Central America
European type  Technologically innovative
 NW Europe
 High population-resource ratio
Brazil type
 Technologically deficient
 Brazil
 Low population – resource ratio
 Sub-Sahara Africa
4.1 Biodiversity in Ecosystems
Biodiversity
 Biodiversity refers to the amount of biological or living diversity per unit area. It
includes the concepts of species diversity, habitat diversity, and genetic diversity. It was
first made popular by ecologist E.O. Wilson in the 1980s.
 Conservation of habitat diversity usually leads to the conservation of species and genetic
diversity
 Species diversity  refers to the variety of species per unit area; it includes both the
number of species present and their relative abundance. The higher the species diversity
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of a community or ecosystem, the greater the complexity. Areas of high species diversity
are more likely to be undisturbed (primary rainforest)
Habitat diversity  the range of different habitats in an ecosystem, often associated
with the variety of ecological niches
Genetic diversity  the range of genetic material present in a gene pool or population of
a species; gene pool is all different types of genes found within every individual of a
species
The term biodiversity usually refers to the heterogeneity (variability) of a community,
ecosystem, or biome at the species, habitat, or genetic level.
Of the three types of diversity, an increase in habitat diversity is the most likely to lead to
an increase in the other two because different habitats tend to have different species, so
greater habitat diversity means greater species diversity. Different species tend to have
different genes, so more species means a greater variety of genes.
Species with low genetic diversity (like cheetahs) are more prone to extinction.
Mechanisms of Natural Selection (Evolution) and Speciation
 A species is defined as a group of organisms that interbreed and produce fertile offspring
 Speciation is the process by which new species form
 Evolution, or the development of new species over very long periods of geological time,
has been accepted by scientists for many years. Evidence is found by examination of the
fossil record: older rocks contain simpler forms of life, more recent rocks contain
 Evolution is the cumulative, gradual change in the genetic characteristics of successive
generations of a species or race of an organism, ultimately giving rise to species or races
different from the common ancestor. It reflects changes in the genetic composition of a
population over time.
 On Darwin’s trip to the Galapagos Islands, he produced his theory of evolution, noting
that:
o all species tend to over-reproduce
o this leads to competition for limited resources (struggle for existence)
o species show variation (all individuals are not alike, they have subtle differences
in appearance or behavior
 From this Darwin concluded that:
o those best adapted to their surroundings survive
o these can then go on to reproduce
 Variation is caused by genetic diversity, and survival has a genetic basis – nature selects
individuals with what it takes to survive, so successful genes are selected and passed on
to the next generation. Over time, a change in the species gene pool takes place and leads
to a new species
The Role of Isolation in Forming a New Species
Geographical Isolation:
 Isolation is the process by which two
populations become separated by geographical,
behavioral, genetic, or reproductive factors. If
gene flow between the two sub-populations is
prevented, new species may evolve.
 Geographical isolation is essential in the
formation of a new species. Without it,
interbreeding would cause the genes from two
populations to continue to mix and
characteristics of the ancestral species to remain
 Two populations of one species can interbreed
and mix genes  populations separated by
geographical barrier cannot interbreed; each
develops its own variations  eventually two
separate species develop in response to different
selection pressures  even without a
geographical barrier, two species remain
genetically distinct
Reproductive Isolation:
 Evolutionary changes in the appearance or behavior of populations may result in
males or females of those populations no longer being attracted to one another and
therefore not breeding together. This may cause the exchange of genes through
reproduction to slow, eventually stop, and different species may arise
Speciation in Progress
 Before different species are formed from ancestral populations, sub-species (or
varieties) occur; these can still interbreed but show physical, behavioral, and genetic
differences
Plate Tectonics:
 Plate tectonics refers to the movement of the eight major and several minor internally
rigid plates of the Earth’s lithosphere in relation to each other and to the partially
mobile asthenosphere below
 Movement of the tectonic plates can produce barriers such as mountain ranges,
oceans, and rift valleys that can lead to isolation of gene pools and then speciation.
Movement apart of the plates can also lead to isolation and the development or
preservation of unique species
 Formation of land bridges between previously separated plates can provide
opportunities for species to spread from one area to another
 The movement of plates through different climatic zones allows new habitats to
present themselves.
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Plate movement can generate new and diverse habitats, thus promoting biodiversity
Types of plate movement:
o Subduction of heavier oceanic crust beneath the lighter continental crust. This
can lead to new island arcs and mountain areas where magma rises up from
under the subduction area causing volcanic action and thickening of the crust
o Oceanic crust is subducted beneath oceanic crust – as both are the same
density, resulting in volcanic activity from rising magma that causes new
islands to form with new habitats forming providing new possibilities for
speciation
o Continental plates colliding, leading to an increase in continental plate
thickness and eventually to new mountain ranges
o Continental plates moving apart cause rift valleys, which may allow deep
lakes to form and potentially new seas, driving speciation into these rift areas
o In some areas, hot rock rises from deep in the mantle and breaks through the
oceanic crust. These hot spots are not actually caused by plate tectonics, but
by the movement of the plates over the hot spots can create chains of islands