Transcript Limits to Growth and Human Carrying Capacity

Limits to Growth and
Human Carrying
Capacity
Enduring Understanding:
1. Water and soil are valuable resources, which must
be used more carefully as the human population
grows.
2. Much of the current agricultural practices result in
soil degradation and water pollution. Thus our
food supply is unsustainable.
3. Nonrenewable energy resources will be consumed
at some point, making the development of
renewable resources very important.
4. Reduction in wastes through recycling, reuse and
remanufacturing will become more important as
the population increases.
5. Human populations import materials, making it
difficult to estimate the carrying capacity of an
area.
K: Carrying Capacity
The number of individuals a given
area of land or water can
sustainably support over time.
The carrying capacity for humans is
the inverse of the ecological
footprint.
Footprint vs Carrying
Capacity
 The Carrying Capacity for Humans is
the inverse of the ecological footprint.
 Review the definition of ecological
footprint to check this!
Limiting Factors
Limiting factors are factors or resources that
limit the size of a population.
The population cannot grow larger because of
too much or too little of a factor.
Example
 10 rabbits may live in a habitat that
has enough water, cover and space to
support 20 rabbits.
 if there is only enough food for ten
rabbits, the population will not grow
any larger than 10.
 Food is the limiting factor
Limiting
factors set
a limit on
population
growth
Food, water,
nesting
sites,
predation
K versus r strategists
K strategists tend to have a few offspring
that receive a lot of parental care.
Examples: birds, elephants and
humans
r Strategists tend to have many offspring
with no parental care.
Ex: spiders, fish
Compare K to r
strategists
Sigmoid curve phases
1. Lag phase
2. Exponential Growth (Rapid
Growth)
3. Stable phase
A more realistic population
growth curve
Many populations overshoot the carrying
capacity
Human Population Growth
What do you think?
 “If we fail to bring population growth
and overconsumption under control,
then we will inhabit a planet where life
becomes increasingly untenable.”
- Paul Ehrlich
Author of The Population Bomb
Food
 An estimated 1 in 6 people suffer from
hunger and malnutrition while attempts
to grow food are damaging swathes of
productive land. -BBC
Water
 By 2025, twothirds of the
world's people
are likely to be
living in areas of
acute water
stress. -BBC
Energy
 Oil production could peak and supplies
have start to decline.
Climate Change
 Possibly the world’s greatest
environmental challenge.
Pollution
 An estimated one in four people
worldwide are exposed to unhealthy
concentrations of air pollutants. - BBC
Loss of Biodiversity
 The sixth mass extinction is caused by
ONE species: Man!
Local Carrying Capacity
Lifestyles affect resource use and
requirements
Examples?
Local Carrying Capacity
Technological developments cause
changes in resource requirements and
consumption
Examples?
Local carrying capacity is hard to
predict for human populations
The range of resources used by
humans is much greater than any
other species.
When one resource becomes limiting,
humans substitute another.
Suggest examples..
Difficulties in estimating
human carrying capacity
 Human populations regularly import
resources from outside
 Cities can grow beyond the boundaries
set by their local resources
 Importing resources increases local
carrying capacity
Local Carrying
Capacity
 What is the carrying
capacity of a city such
as Tokyo?
 Can it be estimated?
What is the value of K for the
whole human population?
Human carrying capacity is determined
by:
1) the rate of energy and material
consumption
2) the level of pollution
3) the extent of human interference in
global life-support systems…
Influences in Carrying
Capacity
 Economists argue that technology can
help human carrying capacity to
expand.
 Use energy more efficiently
 Use materials more efficiently
 Lower resource use and pollution
Reuse, Recycling and
remanufacturing
 Reuse, recycling and remanufacturing
can lower human impact on the Earth
 They can also increase human
carrying capacity
Reuse – Don’t throw it away!
Reuse – Use it again!
Recycle: Turn it back into the
same item!
Remanufacture: Convert it into
something new
Ecologists warn…..
 The world population is
forecast to increase from 7
billion to 9.5 billion people
within the next 30 years.
 Efficiency will need to be
increased by a factor of 4 to 10
to remain within global
carrying capacity.
Does humanity have a
carrying capacity and, if so,
what is it?
 The human population growth curve is
currently following an exponential
curve or a "J-shape”.
 Resource limitations and/or habitat
degradation will force the human
population curves to approach an
upper limit - the carrying capacity,
often symbolized as " K" by ecologists.