Introduction to Ecosystem Science's homework
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human_ecology_and_societies_carrying_capacity.pptxHuman Ecology and Our Society’s Carrying Capacity
ECS 111
30 August 2016
Dr. Olson
Demography
Quantifying populations: numbers, sex ratios, wealth, health, …..
Calculating trends: birth, deaths, and migration
Understanding population transitions: Growth rates; positive and negative, trends with respect to economic development.
Demographic shifts in use of ecological services and the health of ecosystem function.
Homo sapiens populations
Demographic Transitions
From Krise Kronicle 2008
Age and gender structure in society
SHRM Foundation 2012
See futurehrtrends.eiu.com
Unequal Distributions in Demographic Trends
ibid
Population Reference Bureau data
Previous changes
Global issues and Migration:
Migration and its consequences:
Recent News
How do we really analyze these curves?
The literature suggests something rather profound, but it may be more complicated than this.
- What are the technological issues behind these curves? What has lead to the reduction in deaths?
- What are the cultural and economic issues behind these curves?
The variation in time is obvious in both curves.
The onset of changes are different.
The width of the pink area means what?
Population Transitions
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What is happening here?
Both birth and death rates are declining, but with different starting points based on the measure of economic conditions.
However, since births > deaths human populations are increasing, and at differential rates with respect to economic development.
What factors are hidden in these curves?
Malthus’s Population Dynamics
Population grow in proportion to its size: Change (dN) is related to numbers N.
The rate of change simply is the difference between birth (b) and deaths (d); i.e. (b-d).
Introducing the Newtonian idea of mass action and his calculus then:
dN/dt = (b-d) N.
(1766-1834)
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The Dilemma
Newton showed that for (b-d)> 0 the population grows to infinity in time (exponential growth) and for (b-d)< 0 the population decays to zero. If only b=d?
When does this happen: Logistic growth and the concept of Carrying Capacity (K).
Under logistic conditions: dN/dt = rN(1-N/K)
This was first derived in about 1832 by Verlhust.
Solutions to demographic challenges?
Malthus decided: war, plague or famine
The other would be to let b=d and live at the environmental Carrying Capacity (K) where N=K and dN/dt =0; i.e. steady populations.
Now all we have to do is define K.
Reading: Brown Into. and Chapter 1
-What does Brown think determines K?
Problem: Can you derive the logistic equation? Set b=bo-b₁N and d=do+d₁N and then with some algebra define r andK.
Suggested Reading:
What does Brown feel is important?
Water: We know of no life form that can live without it; or at least reproduce without.
Soil: The basis of agriculture
Climate: The temperature and water flow that allows these to be available.
These of course depend on where we are and how many organisms are part of our ecosystem.
A DETERIORATING FOUNDATION
Falling Water Tables and Shrinking Harvests
Eroding Soils and Expanding Deserts
Rising Temperatures, Melting Ice, and Food Security
Brown (2011)
What really sets Carrying Capacity?
Water: 3 liters per day +
Food: What is a balanced diet.
Nutrients: The supplements.
Is culture part of the equation?
How are these supplied by our ecosystems (ecosystem services)?
Uses of Water
Drinking water.
Irrigation.
Recreation.
Hydro power
Navigation.
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What does Brown feel is important?
Water: We know of no life form that can live without it; or at least reproduce without.
Soil: The basis of agriculture
Climate: The temperature and water flow that allows these to be available.
These of course depend on where we are and how many organisms are part of our ecosystem.
Plant–Soil–Water Relationships
Soil cross sections.
Brady and Weil (1999)
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Brown’s third:
Climate change
Where are we at on these issues?
Human society is part of the earth’s ecosystems.
Our current system is stressing these.
Specific issues within these stresses are a concern for our future well being.
Why are we at this state of affairs and what can be done?
(4) The Commons: Our Tendency to Overuse Ecosystem Services
Lobstering in Maine
Community Garden in Mozambique
Monte Alban Archaeological Park,
Oaxaca, Mexico
Deforestation in Uganda
Whale Watching in
Massachusetts
Aral Sea
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Others: broadcasting bandwidth, Interstate Highway 95, climate change, biodiversity loss, ozone layer depletion, persistent pollutants
Tragedy of the Commons
Garrett Hardin made a big impact with his 1968 article, Tragedy of the Commons.
Hardin called a tragedy "the solemnity of the remorseless working of things."
A commons was a pasture that belonged collectively to a village.
A villager could buy one more cow and gain the full income that a cow provided.
Damage from another cow grazing the pasture seems small compared to the gain.
The entire community would suffer from the damage.
Each member of the village was motivated to keep adding cows.
To preserve the commons, the personal freedom of the villagers had to be curtailed.
Hardin is most concerned with overpopulation.
Conscience is self-eliminating: If we rely on conscience to control population, the result will be the Darwinian extinction of families that exercise restraint.
The solution? Mutual Coercion Mutually Agreed Upon.
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Prior to Hardin’s article, keywords in titles such as “commons”, “common property”, “common pool resource” occurred only 17 times in the entire English language academic literature. Some 2300 such papers would appear in the next 35 years.
In 1990, the International Association for the Study of Common Property (now known as the International Association for the Study of the Commons) formed. By 2000, attendance at its annual meeting exceeded 600.
Transitions and Change in the Commons
The impact of population changes and cultural changes in social norms (memes) effect our use of resources.
These in turn modify our use of the commons; i.e. the balance between ecosystem function and our use of ecosystem services.
An Example: The Wild West
Western Demography
Western Frontier
Massive movement of people westward: Horace Greeley (1853) “Go west, young man, Go west”
Wealth and living space: Pioneers, soldiers, Indians, the African American cowboy, the Chinese Railroad worker.
Economics and reality: Gold, farm land (water), cattle, ….
Means of travel: Horse, wagon, stage coach, train…
Natural losses: The buffalo, the great forests, rivers lost to silt and dams.
Environmental indicators and income
Can wealth per capita solve economic issues: Kuznets curves
These are recent data:
What did these look like in the wild west?
The Renaissance Europe?
Your home town?
Examples with real data:
Simon Kuznets
The Concept of Carrying Capacity
What governs development?
- Micro-view: individual behaviors
Game theory.
- Macro-view: Whole systems
Defining Carrying Capacity.
dN/dt = r N (1 – N/K)
Time rate of change of N
Maximum growth rate
Carrying capacity
Logistic Equation
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The Logistic Equation
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Logistic Growth and Populations
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Births versus Deaths
Birth rates change with population size, medical conditions, nutrition, and social norms.
Deaths also depend on population size, medical and nutrition issues, but
What about social norms and death?
World Population Growth
China and India
China Demographics
Troubles in Japan
Migration and Population Change
People per km²
European pop.
Africa and Middle East
Migration: Emigration/Immigration
Emigration = Leaving an area
Immigration = Entering one
Refugees in Europe
Human Violence
How has human conflict evolved?
Are humans basically violent to each other and to the rest of nature?
Are human violent interactions grown or decreased with the level of civilization?
How do our violent periods impact the global environment?
Has the per capita mortality increased with time?
(1618-1648)
Can we stop wars and violence?
Pax Britannia and an arms race
America and Russia: Pax Nuclear
How to think about logistics?
The basic equation: dN/dt =rN(1-N/K) has two equilibrium solutions.
Set dN/dt = 0 and solve the equation: N=K.
The other is N=0.
The next issue is are these stable?
Starting at N=0 will the system go to K?
Two issues involving real ecosystems:
How do we define K?
The processes controlling the ultimate population are large.
The simple logistic analysis does not include any interactions between ecosystem components.
Ecosystems consist of biomes and spatial components and these move.
How do things move in ecosystems?
So far the contents of ecosystems have been described; i.e. number of animals and plants or say carbon stocks
How do materials and energy move within and between ecosystems?
Here typically the cycling of materials are considered in terms of natural cycles.
Carbon Cycles
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Processes Disrupting Nutrient Cycles
Natural processes that modify nutrient cycles:
- Changes in vegetation cover
- Variations in rates of grazing, …
Anthropogenic changes in nutrient availability:
- Onset of agriculture
- Fertilization of land systems
What are the factors the set our carrying capacity?
Brown defines three factors and argues that we are pushing them.
What about Paul Ehrlich and his Population Bomb?
Can technology overcome these problems?
What happens if we can not cope?
