Transcript Day 1-2013 - WordPress.com

Lecture 5
Ecosystems, Biodiversity and Human Populations
7
What country is the city in??
Delhi
Kolkata
India
Mumbai
India
Shanghai
India
Sao Paulo
China
Karachi
Brazil
Dhaka
Bangledesh
Mexico City
Mexico
Pakistan
Lagos
Nigeria
Kinshasa
Demographic Republic of the Congo
Kolkata
Delhi
India
Mumbai
India
Sao Paulo
Brazil
India
Shanghai
China
Karachi
Pakistan
Dhaka
Lagos
Bangledesh
Mexico City
Mexico
Kinshasa
Nigeria
Demographic Republic of the Congo
Living beyond the planet’s means
FIGURE 6.18
Humanity’s global ecological footprint surpassed Earth’s capacity to
support us in 1987
Natural selection
What is natural selection ?
Natural selection is the gradual, non-random, process by which
biological traits become either more or less common in a
population as a function of differential reproduction of their
bearers.
It is a key mechanism of evolution. Ecology and evolution are
tightly intertwined
Natural selection
Natural selection is the means by which beneficial variations in a
population tend to be preserved while unfavorable variations tend
to be lost.
One of the key concepts behind the theory of natural selection is
that there is variation within populations. As a result of that
variation, some individuals are better suited to their environment
while other individuals are not so well-suited. Because members of a
population must compete for finite resources, those better suited to
their environment will out-compete those that are not as well-suited.
Natural selection acts on genetic variation
• Directional selection
drives a feature in one direction
• Stabilizing selection
produces intermediate traits,
preserving the status quo
• Disruptive selection
traits diverge in two or more
directions
FIGURE 3.2
If the environment changes, a trait may no longer be adaptive
Some species are more vulnerable to
extinction than others
• Extinction occurs when the environment changes too rapidly for
natural selection to keep up
• Many other factors also cause extinction
– Severe weather
– New species
– Specialized species
Endemic species
a species only exists in a certain, specialized area.
These species:
– Are very susceptible to extinction
– Usually have small populations
http://www.mnn.com/earth-matters/animals/photos/endemic-species-top-9-lonelyanimals/sinarapan
Ecology is studied at several levels
• Biosphere
the total living things on Earth
and the areas they inhabit
• Ecosystem
communities and the nonliving
material and forces they interact
with
• Community
interacting species that live in
the same area
FIGURE 3.9
Population Ecology
Population Ecology: investigates how individuals within a species
interact with one another.
Community Ecology :
Focuses on interactions among species.
Ecosystem Ecology :
Studies living and nonliving components of systems.
http://home.comcast.net/~sharov/PopEcol/lec1/whatis.html
Population Ecology
Habitat, niche and degree of specialization are important in
organizational ecology.
Habitat:
The specific environment in which an organism lives. Each organism
has patterns of habitat use.
Niche:
A species’ niche reflects its use of resources and its functional role in
a community.
Specialists: Species with very specific requirements.
Generalists: Species with broad tolerances, able to use a wide array
of habitats or resources.
Population Ecology
Populations exhibit characteristics that help predict their dynamics.
Important Characteristics of a population are:
Population Size:
the number of individual organisms present at a given time.
Population Density:
the number of individuals in a population per unit area.
Population Distribution (dispersion):
the spatial arrangement of organisms within a particular area.
Population Ecology
(continued) Important Characteristics of a population are:
Populations sex ratio:
Proportion of males to females.
Age distribution (structure):
The relative numbers of organisms of each age within a population.
Birth and death rate:
Measure the number of births and deaths per 1000 individuals for
a given time period.
The likelihood of death varies with age; this can be graphically
shown in survivorship curves.
Population Ecology
Survivorship Curves
Type I: high survival rate of young, live most of expected life span
and die in old age (example : Humans ).
Type II: relatively constant death rate. Death could be due to
hunting or diseases (examples: squirrels, honey bees).
Type III: many young, most of which die very early in their life.
Plants, oysters and sea urchins are examples.
Population characteristics
• Population distribution
(dispersion) = spatial
arrangement of organisms
within an area
– Random – haphazardly
located individuals, with
no pattern
– Uniform – individuals are
evenly spaced due to
territoriality
– Clumped – arranged
according to availability
of resources
• Most common in
nature
FIGURE 3.11
Population Ecology
Populations are dynamic, they can:
Grow
Shrink
Remain stable
Population growth or decline is determined by :
Births
Deaths
Immigration
Emigration
Population Ecology
Growth rate =
( crude birth + immigration ) - ( crude death + emigration )
rate
rate
rate
rate
• Unregulated populations increase by exponential growth
• When a population increases by a fixed percentage each year, it
is said to undergo exponential growth.
Population Ecology
Original Population = O
Births = B
Deaths = D
Immigration = I
Emigration = E
Growth rate = G
G
=
(B + I ) - (D + E)
______________
O
X 100
Population Ecology
Researchers studied a population of 34 peregrine falcons for one
year to analyze the effect of pesticides on population growth.
In the first spring, 20 hatched and lived. During the season, 9 baby
falcons dies from severe birth defects, 11 died as a result of direct
pesticide exposure, 8 were captured and were taken to a
conservation area. During the last three months, 4 birds migrated
into the area.
Calculate the population growth of peregrine falcons in this study
(Show your work)
How would you describe the overall health of this population?
What are the consequences for the future?
Population Ecology
Extirpation :
http://dictionary.reference.com/browse/extirpation
Population Ecology
The growth rate for a population of 90 field mice in six months was
429%. If the number of birds was 342, the number of deaths was
43, and there was no emigration , calculate the number of mice that
migrated into the field.
Population Ecology
Limiting factors: factors which restrain population growth
Every population is eventually contained by limiting factors, which can
be:
Physical
Chemical
Biological characteristics of the environment.
Examples???
Water, space, food, predators, and disease
The interaction of the limiting factors determines the carrying
capacity.
Population Ecology
Carrying Capacity:
The average population density or population size of a species
below which its numbers tend to increase and above which its
numbers tend to decrease because of shortages of resources.
The carrying capacity is different for each species in a habitat
because of that species' particular food, shelter, and social
requirements.
Unregulated populations
• Steady growth rates cause
exponential population
growth
– Something increases by
a fixed percent
– Graphed as a J-shaped
curve
• Exponential growth cannot
be sustained indefinitely
– It occurs in nature with
a small population and
ideal conditions
FIGURE 3.14
Also called geometric growth
Carrying capacity
• Carrying capacity
the maximum population size of a
species that its environment can
sustain
– An S-shaped logistic growth
curve
– Limiting factors slow and
stop exponential growth
Carrying capacity changes
FIGURE 3.15
Humans have raised their carrying capacity by decreasing the
carrying capacity for other species
Population Ecology
•
•
Carrying Capacities can change
Some factors are density-dependent, others are densityindependent
Biotic potential and reproductive strategies vary amongst species
K-selected: Species that devote large amounts of energy and
resources to caring for a few offspring - their populations tend to
stabilize over time at or near their carrying capacity.
R-selected: Species that have high biotic potential and devote their
energy and resources to producing as many offspring as possible in
a relatively short time.
Changes in populations influence the composition of communities
Conclusion
• Natural selection, speciation, and extinction help determine
Earth’s biodiversity.
• Understanding how ecological processes work at the
population level is crucial to protecting biodiversity
Trying to be environmentally friendly…..
http://www.ted.com/talks/catherine_mohr_builds_green.html
Biodiversity
The conservation of Biodiversity
Social and economic factors affect species and communities.
Costa Rica took steps to protect its environment and had active
ecotourism.
Conclusion:
Speciation and extinction determine Earth’s biodiversity.
Many human activities are playing a role in biodiversty loss.
http://polarbears.wwf.ca/
http://wwf.panda.org/about_our_earth/biodiversity/threatsto_biodiversity/
http://www.cbd.int/doc/publications/cbd-ts-50-en.pdf
Biodiversity
What is it??
Svalbard Seed Bank
Located in an old copper mine on remote northern island of
Spitsbergen, Norway.
The main storage is 120m inside a sandstone mountain, on a
tectonically dead island.
Seeds are packaged in special four-ply packets and heat sealed to
exclude moisture. A local coal mine and powerplant supplies the
electricity for refrigeration control.
The remote northern location also serves as a natural fridge. In the
case of complete power failure at least several weeks will elapse
before the temperature rises to the temperature of the surrounding
sandstone bedrock.
Svalbard Seed Bank
There are many types or "cultivars" of any given fruit.
A cultivar is a cultivated plant which is chosen and given a special name
because of its desired characteristics.
Various types of cultivars (for example in apples, the Red Delicious in the
1870s) come in and out of favour over the years.
In the middle of 20th century the dominant banana cultivar exported to
North America and Europe was the Gros Michel.
Around 1950 the Gros Michel become virtually extinct due to the rapid
spread of the so called "Panama Disease," a fungal infection that attacks
the roots of the banana plant.
The Gros Michel was replaced with more resilient but notably less tasty
Cavendish cultivar
Biodiversity
Modern agriculture is generally focused on maximizing profit by
extracting maximal possible crop yield.
A small number of specially selected cultivars of any given crop are
planted throughout the world, displacing in the process numerous
other local varieties. This approach guarantees consistently high
yields under normal conditions.
Biodiversity
Essentially, every single commercially grown plant is a clone of one
of only a few specially selected strains of genetic material. Diversity
of genetic material is thus reduced to a bare minimum, leaving crop
species exposed to any disease which can exploit that single strain.
With corn, wheat, and rice being grown world wide in such a
fashion, there is a concern that a newly mutated strain of fungus
could wipe out an entire world crop in matter of months, and cause
massive food shortages.
Biodiversity
“We
can no longer see the continued loss of biodiversity as an issue
separate from the core concerns of society: to tackle poverty, to
improve the health, prosperity and security of present and future
generations, and to deal with climate change. Each of those
objectives is undermined by current trends in the state of our
ecosystems, and each will be greatly strengthened if we finally give
biodiversity the priority it deserves.”
Convention on Biological Diversity's 'Global Biodiversity Outlook 3' report
http://gbo3.cbd.int/
Biodiversity
Biodiversity has declined by more than a quarter in the last 35
years.
The Living Planet Index (LPI), which tracks nearly 4,000
populations of wildlife, shows an overall fall in population
trends of 27% between 1970 and 2005.
Population growth and our consumption are the primary
reasons.
Specifically, habitat destruction and wildlife trade are the
major causes of population decline in species.
Click me....
Human Population
Population:
Human growth, demography, education
and ecological footprint
http://perspectivesinnature.blogspot.com/2009/12/implications-of-human-population-growth.html
“As you improve health in a society, population growth goes down.
You know. I thought it was…before I learned about it, I thought it
was paradoxical.”
– Bill Gates, Microsoft Corp.
http://www.gatesfoundation.org/Pages/home.aspx
Human Population and Growth
Is population growth really a problem?
It has resulted in technological innovations, improved sanitation,
better medical care, increased agricultural output, a decline in
death rates and a drop in infant mortality.
http://www.prb.org/pdf11/2011population-data-sheet_eng.pdf
Perspectives on human population have
changed over time
• 1700s
more children meant better support in old age and more labour
for factory work
• 1766:
Thomas Malthus – growing population is eventually checked by
limits on births or increases in deaths
• 1968:
Paul Ehrlich – population is growing too fast and must be
controlled
Human Population and Growth
Cornucopian view:
Resource depletion as a consequence of greater numbers of people,
is not a problem if new resources can be found to replace the
depleted ones.
Even if resource substitution could enable indefinite population
growth, could we maintain the quality of life that we would desire,
or would our descendants have less space, less food, and less
material wealth than the average person does today?
Many governments have found it difficult to let go of the notion that
population growth increases a nation’s economic, political, and
military strength.
Human Population and Growth
IPAT model:
How humans’ total impact(I) results from the interaction among
three factors:
(P) Population
(A) Affluence
(T) Technology
I=PxAxT
A sensitivity factor (S) can be added to the equation to denote how
sensitive a given environment is to human pressures :
I = P x A x T x S.
Impact generally relates to either pollution or resource consumption.
Modern-day China shows how all elements of the IPAT formula can
combine to result in environmental impact in very little time.
Human Population and Growth
One-Child Policy
Under Mao Zedong’s leadership (1949-1976),
improved food production and distribution and
better medical care allowed China’s population to
swell, causing environmental problems
The government instituted a population-control program in the 1970’s.
• Started with education and outreach efforts encouraging late
marriage and fewer children, and increasing the accessibility of
contraceptives and abortion.
• In 1979 instituted a system of rewards and punishments, in forcing
a one-child limit per family.
• China’s growth rate is down but there have been unintended
consequences such as widespread killing of female infants and an
unbalanced sex ratio.
Demography
Demography:
The science of human population: The application of population
ecology principles to the study of statistical change in human
populations is the focus.
The principles of population ecology apply to humans
Like other organisms, humans have a carrying capacity set by
environmental limitations on our population growth.
Estimates of the human carrying capacity have ranged greatly, from
1-2 billion people living prosperously in a healthy environment to 33
billion living in extreme poverty in a degraded world without natural
areas.
Demography
People are very unevenly distributed over the globe.
This uneven distribution means that certain areas bear far
more environmental impact than others
At the same time, areas with low population density are often
vulnerable to environmental impacts. The reason they have
low populations may be that they are sensitive and cannot
support many people.
http://www.navdeep-humanpopulation.blogspot.com/
Rates of growth vary with region
• At today’s 2.1% annual growth rate, the population will double in
33 years
• If China’s rate had continued at 2.8%, it would have had 2 billion
people in 2004.
FIGURE 6.3
Demography
Age structure diagrams show the relative sizes of each age group in
a population and are especially valuable to demographers in
predicating future dynamics of a population.
• The ratio of males to females, the sex ratio can also affect
population dynamics.
• The naturally occurring sex ratio in human populations at birth
features a slight preponderance of males.
This ratio can be skewed, examples are China and Sarnia
Demography
• Live male births in the Aamjiwnaang First Nation has been
declining from the early 1990s to 2003, from an apparently stable
sex ratio.
• Likely due to environmental and occupational chemical
exposures.
• This community is located immediately adjacent to several large
petrochemical, polymer, and chemical industrial plants.
• A community health survey is currently under way to gather
more information about the health of the community.
- Mackenzie, Lockridge and Keith (2005)
http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info:doi/10.1289/ehp.8479
- Mackenzie, Lockridge and Keith (2005)
Age structure affects future population
dynamics
• Having many individuals in young age groups results in high
reproduction and rapid population growth
FIGURE 6.10
Population growth
Population growth depends on what 4 factors?
Birth, death, immigration and emigration
Immigration and emigration are increasingly important in the
modern world:
flow of refugees
transportation
Natural rate of population change: is the change due to birth and
death rates alone, excluding migration.
Since 1970s growth rates in many countries have been declining and
the global growth rate has declined partially because of a steep
drop in birth rates.
Population growth
Total Fertility Rate (TFR):
is the average number of children born per female member of a
population during her lifetime.
Replacement Fertility:
the TFR that keeps the size of a population stable, for humans it is
2.1.
Population growth
Demographic transition is a theoretical model of economic and
cultural change that explains the trend of declining death rates and
birth rates that occurs when nations become industrialized.
Pre industrial:
characterized by condition in which both death rates and birth rates
are high
Transitional stage:
death rates decline and birth rates remain high.
Industrial stage:
creates employment opportunities, particularly for women causing
birth rate to fall
Post-industrial stage:
both birth rates and death rates remain low and populations stabilize
or decline slightly.
4 stages of demographic transition
FIGURE 6.14
Population growth is seen as a temporary phenomenon
Female literacy is associated with birth
rates
Women’s empowerment greatly affects population growth rates
Drops in TFR have been most noticeable in countries where women
have gained improved access to contraceptives and education,
particularly family planning education.
Many women still lack the information and personal freedom of
choice to allow them to make their own decisions about when to
have children and how many to have.
In societies in which women are freer to make reproductive
decisions, fertility rates have fallen, and the children are better cared
for, healthier, and better educated.
Female literacy is associated with birth
rates
FIGURE 6.15
Is the demographic transition universal?
• It has occurred in Europe, U.S., Canada, Japan, and other
nations over the past 200-300 years
• But, it may or may not apply to all developing nations
• The transition could fail in cultures that
– Place greater value on childbirth
– Grant women fewer freedoms
For people to attain the material standard of living of North
Americans, we would need the natural resources of four and a
half more Earths
Is the demographic transition universal?
Population policies and family-planning programs are working around
the globe.
The government of Thailand has relied on an education–based
approach to family planning that has reduced birth rates and slowed
population growth.
India has had long-standing policies, but some think they need to be
strengthened. http://www.indexmundi.com/g/g.aspx?c=in&v=31
Brazil, Mexico, Iran, Cuba and other developing countries have
instituted active programs consisting of population reduction targets,
incentives, education, contraception and reproductive health care.
http://www.indexmundi.com/map/?v=31
Is the demographic transition universal?
• In 1994 the united Nations hosted a conference in Cairo on
population and development at which 179 nations endorsed a
platform calling for all governments to offer universal access to
reproductive health care within 20 years.
• Despite the successes of family planning internationally, the
United States has often declined to fund family –planning efforts
by the United Nations.
• Cancelling this funding was one of George W. Bush’s first acts upon
becoming a U.S. President in 2001
Is the demographic transition universal?
Poverty is strongly correlated with population growth
Consumption from affluence creates environmental impact
Individuals in affluent societies leave a larger “ecological footprint”
In 1999 the richest 20% of the world’s people:
used 86% of the world’s resources
had over 80 times the income of the poorest 20%
The wealth gap and population growth contribute to violent conflict
Other factors
HIV/AIDS is a major influence on human populations in parts of the
world
Of the 38 million people around the world infected with HIV/AIDS in
2004, 25 million lived in the nations of sub-Saharan Africa.
The AIDS epidemic is unleashing a variety of demographic changes
Premature deaths, of both infants and young adults are reducing
the average life expectancy in African nations.
Severe demographic changes have social, political, and economic
repercussions.
Other factors
Everywhere in sub-Saharan Africa, AIDS is undermining the ability of
developing countries to make the transition to modern technologies
because it is removing many of the youngest and most productive
members of society.
Is the demographic transition universal?
Although global populations are still growing, the rate of growth has
decreased nearly everywhere.
There has been progress in expanding rights for women worldwide.
In addition to the clear ethical progress of this development, it also
helps to slow population growth.
True sustainability demands that we stabilize our population size in
time to avoid destroying the natural systems that support our
economies and societies.
Low growth does not mean fewer
people
FIGURE 6.13
Conclusion
• The human population is larger than at any time in the past
• However, the rate of growth has decreased because of:
– Demographics
– Better rights for women
• How will the population stop rising?
– demographic transitions
– governmental intervention
– disease
– social conflict