Download Earth`s Population Growth

Earth’s Population Growth
Limits to growth and consumption
•Resource consumption at an all-time
all time high
and continuing to rise
•Population growth at an unprecedented
high
Questions
•How many people can the Earth hold?
•Are
A there
th
a fi
finite
it amountt off resources?
?
•Do we have enough land to support
agriculture?
•What
What is the FATE of our resource dependent
society?
Population Growth Rate
Average population growth rate
~0.02%/yr
Toba Caldera
Super Eruption
Evolution Bottleneck
•We have a lack of diversity
y in our mitochondrial DNA
•There is more genetic diversity in an average band of chimpanzees than
in the entire human race.
•Humanity went through a rather slim bottleneck about 74,000 years ago.
Environmental affects on population
Population Growth Rate
Demographic Transition
Doubling Times =
70
%g
growth rate/year
y
Growth Rate (%/yr)
Doubling Time
0.02
3,500
0.5
140
1
70
1.4
50
2
35
5
14
7
10
10
7
17
4
A
Average
population
l ti growth
th rate
t
~0.02%/yr
Population Growth Rate
6,261,118,623
6
261 118 623 - 2004
6,361,827,322 – 2005
6,776,311,884
Growth today ~ 1.2%
Doubling
g time 58 y
years
http://blue.census.gov/cgi-bin/ipc/popclockw
Demographic Transition
Population percentage by region
Land Surface Area ~1.5x1014 m2
Population threshold ~ 529 trillion people
shoulder to shoulder
@1
1.3%/yr
3%/yr it would take
900 years to reach this population
Environmental Impact
I = PAT
P = Population size
per-capita
p consumption
p
A = Affluence – p
T = Environmental Damage inflicted by the
g
to supply
pp y consumption
p
technologiesused
Earth’s Carrying Capacity
The carrying capacity of an ecosystem is the "maximum population size
of a species that an area can support without reducing its ability to
support the same species in the future
future"
•Estimates range from ~ 1 billion to 1 trillion people
•Range of medians from 7
7.7
7 to 12 billion people
Complicated by:
-differences in type and quantity of resources
-rapid cultural evolution of resources usage
Earth’s Carrying Capacity
The carrying capacity of an ecosystem is the "maximum population size
of a species that an area can support without reducing its ability to
support the same species in the future
future"
# of Births p
per woman
World p
population
p
in 2150
1.6 children
3.6 billion
2.0 children
10.8 billion
2.6
2
6 children
hild
Present average
27 billi
billion
Earth’s Carrying Capacity
The carrying capacity of an ecosystem is the "maximum population size
of a species that an area can support without reducing its ability to
support the same species in the future
future"
A sustainable population of humans on Earth implies:
--renewable energy sources combined with
--socially sustainable standards of living.
What is relationship between Standard of living and carrying capacity?
The current global population exceeds the median range of socially and
biophysically sustainable carrying capacity estimates.
Exceedance of Earth's carrying capacity is made possible by
consumption of nonrenewable energy sources, such as fossil fuels as
well as inequities in global distribution of food and energy
consumption.
Earth’s Carrying Capacity
Resource Consumption
Earth’s Carrying Capacity
Earth’s Carrying Capacity
Human impact on the environment.
· Six million acres of prime farmland – an area the size of Vermont – were lost in the U.S.
alone between 1982 and 1992. Four of those six million acres were lost to urban and
suburban expansion. The other 2 million acres were lost through erosion caused by
deforestation, unsustainable farming practices, and animal over-grazing.
· Fresh water is essential to health, economic development, and life itself. With increasing
numbers of people,
people the amount of fresh water available to each person decreases
decreases. Only
0.3% of the water on the planet is available for human use. Due to mismanagement, over
40% of the groundwater in the U.S. is contaminated by industrial, agricultural, and
household pollution, making it extremely difficult and costly to purify.
· As human population increases, the diversity and number of plants and animals
decreases. We lose one or more entire species of animal or plant life every 20 minutes –
some 27,000 species a year. This is a rate and scale of extinction that has not occurred in
65 million years.
· The global emission of carbon dioxide has quadrupled since 1950, largely from
deforestation and the burning of fossil fuels. Researchers say this greenhouse gas causes
global warming and disruption in weather patterns. Five storms over the span of five years
have cost the insurance industry in the United States $25
$25.7
7 billion
billion.
· 1.8 billion people live in 40 countries with critically low levels of forest cover. By 2025, this
number could nearly triple to 4.6 billion. Women often bear the burden of forest scarcity,
walking farther for wood, carrying loads long distances, or suffering a variety of ills
associated with cooking where wood is scarce.
Case study – Easter Island
Effects of overuse of natural resources
~165 km2
Effects of overuse of natural resources