Download Fundamentals Science and the environment

Fundamentals
Discussion
Malthusian doomsayers claim:
1. Natural resources are running out
2. Population is growing, having less and less to eat
3. Species are becoming extinct in vast numbers, forests
are disappearing, fish stocks are collapsing
4. Planets air and water is becoming more polluted
Do you believe those statements? Is this something to
worry about? Why/why not?
Systems
• System
– A set of components that interact with one
another
– A system must be distinguishable from its
environment
– Systems analysis: concerned with the nature of
interactions as well as the components
– Interested in patterns, behaviors
Earth as a Living System
Earth itself a system of
biological communities
•
Biota:
–
•
All the organisms of all
species living in an area or
region up to and including
the biosphere
Biosphere:
1.
2.
That part of a planet where
life exists
The planetary system that
includes and sustains life
4 Main Systems
•
•
•
•
Lithosphere
Hydrosphere
Atmosphere
Biosphere
The Lithosphere
• Consists of the upper part of the
mantle and the crust
• Crust, less than 1% of the earth’s
mass
• Thickness varies from 5-35 km.
• Made from rocks, 2000 minerals 8 elements account for 99% of
mass
–
–
–
–
Oxygen 47%
Silicon 28%
Aluminum 8%
Iron 5%
The Lithosphere
• Igneous rocks (granite)
– Solidification of molten
materials
• Sedimentary rocks
(sandstone, limestone)
– Erosion, dissolved material,
biological activity
• Metamorphic rocks (marble
from limestone)
– Alteration of parent rock
• Constantly change but over
long time-scales
The Hydrosphere
• Includes all water on Earth.
• Lakes, rivers, ocean, water
vapor in the atmosphere
• 70 % covered with water;
97% in oceans, 2% in
glaciers ice caps, 0,0001
vapor, 0,009 in rivers etc.
• Hydrological cycle
– Precipitation, evaporation
– Changes occur much faster
than in lithosphere BUT
– Residence time varies,
depending on the reservoir
The Atmosphere
• 3 main layers
– Troposphere (weather, >0
degrees), stratosphere,
mesosphere
• Mostly composed of gasses
–
–
–
–
Nitrogen 78%
Oxygen 21%
CO2 0.04%
Methane 0.0002%
• More rapid timescales of
change, residence time
– 10 yrs methane
– 100 yrs CO2
The Biosphere
• The biosphere is the life
zone of the Earth and
includes all living organisms,
including man, and all
organic matter that has not
yet decomposed.
• Extends from top of
troposphere to 10km below
sea level
• Supports life
– Water, usable energy, air,
suitable temperature,
essential nutrients, trace
elements
Thermodynamics
• Study of energy transformations.
Fundamentals to understanding
environmental and economic systems
• Energy: the potential to do work
• Work: when something is moved
• Power: work per unit of time
Thermodynamics
• First law: Law of Conservation of Matter,
matter can neither be created nor destroyed,
only converted
– Implications, In = Out
• Second law: Entropy Law
– conversions means losses, increase in entropy or disorder in an
isolated system
– Never reaches 100% efficiency
– Require energy for all transformations
– Diminishing return to technological change
Best First Principle
• Extract best resources first
• Best:
– Most concentrated
– Least entropy
– Most distinguishable from the surrounding
environment
– Require least energy to extract
• E.g. iron ore, copper
Systems
• System:
– A set of components or parts that function together to act as one
whole.
• Isolated System
– No matter in or out of the system
• Closed System:
– No material movement into or out of the system
– The earth
• Open System:
– Not generally contained within boundaries
– Some energy or material moves into or out of the system
– Plants
Systems
• Plants as open systems
– Exchange energy and matter with environment
– Highly ordered system, takes from environment to maintain
order (life). Death deacay and disorder begins
– Autotrophs (producers), make organic matter from inorganic
matter using energy via photosynthesis
– Primary productivity: rate at which plants produce plant tissue
– GPP: Total amount of solar energy fixed by photosynthesis
– NPP: GPP – maintenance respiration
Photosynthesis
Energy and nutrient flows
• Plants and animals open systems
• Linked through feeding chains; foodwebs
• Trophic pyramids: ecosystem structured based
on the chemical energy stored at various
levels in the foodweb
Ecosystem
• Ecosystem:
– A community of organisms and its local nonliving
environment in which matter (chemical elements)
cycles and energy flows.
– Life sustained by interactions of many different
organisms, functioning together, and interacting
through their physical and chemical environment
– Inherently complex
Basic Characteristics of Ecosystems
• Structure
– Living (Ecological Communities) – Hierarchical interactions
– Non-living (physical/chemical environment)
• Processes
– Growth
– Cycling of chemical elements – important and complex
• Inflows, recycling, no waste in nature, interactions
• Food webs
– Flow of energy
• Between trophic levels
• Change
– Evolution
– Succession
Structure
• Ecosystems
– A set of interacting species that occur in the same
place and functioning together
• Food chains, food webs, trophic levels (autotrophs,
heterotrophs)
– From a small pond to Biomes
Biomes: Areas with similar climate and plant life
Different productivity of Biomes
Organization
• Food webs
• Food chains
• Trophic levels
– Autotrophs
– Heterotrophs
• Herbivores
• Carnivores
• Omnivores
The trophic pyramid – Trophic level
Energy Flows in Ecosystems
10% efficiency between levels
Decomposers
Fungi, Bacteria
Animals
Resease nutrients
Origin of fossil fuels
• All organic originally
• Coal; compressed peat, converts to coal under
pressure and heat as layers accumulate on top
• Oil; animal tissue, incomplete decomposition
under high heat and pressure
• Natural gas: methane, byproduct to oil
production
Populations and population
dynamics
• Population; a set of individuals that belong to
the same species which live in the same area
• Species: set of individuals that are capable to
reproducing
Renewable Resources
Population growth
• Focus on G
• Exponential growth
• Characterizes anything
that can grow without
limit
• Pt = Pt-1*(1+r)
• Absolute increase
increases over time
Renewable Resources
Population growth
• Logistic or density
dependent growth
• Upper limit to the ultimate
size
• Determined by carrying
capacity
– What defines CC?
• Growth curve inverted ushaped
Growth determined by:
Pt = Pt-1 + r*(CC - Pt-1)/CC
Species types
• r selected, non
specialist, high growth
rates
• K selected, specialists,
low growth rates
• Keystone species; carry
out essential roles in an
ecosystem
Systems features
• Have Components
– State variables – stocks
• Sources, sinks
– Interactions – flows
• Energy, materials, information
• Static behavior, comparative static
• Dynamic behavior
– Interactions
• Relational
• Physical
Dynamic behavior
• Feedback
– Occurs when the output of the system also serves as an
input, leading to further changes in the system
• Negative Feedback
– Occurs when the system’s response is in the opposite
direction of the output
– Self-regulating
– Stabilizing
• Positive Feedback
– Occurs when an increase in output leads to a further
increase in output
– Destabilizing
Dynamic behavior
• Exponential growth:
– Growth occurs at a constant rate per time period
– Exemplifies positive feedback
– Equation to describe exponential growth is:
• Destabilizing
Exponential growth
• Exponential growth
• Characterizes anything
that can grow without
limit
• Pt = Pt-1*(1+r)
• Realistic?
Density dependent growth
• S-shaped growth curves
• Carrying capacity
• Growth rate r
Logistic or density dependent
growth
• Upper limit to the ultimate
size
• Determined by carrying
capacity
– What defines CC?
• Growth curve u-shaped
• Stabilizing
Growth determined by:
Pt = Pt-1 + r*(CC - Pt-1)/CC
Feedback climate change
Fig 3.8
© 2005 John Wiley and Sons Publishers
Dynamic behavior
• Lags
– Separation between cause and effect in:
• Time
• Space
– Results in oscillations
Dynamic behavior
• Negative loops with delayed feedback
– Impact of overshoot not immediately realized.
– Creates oscillations.
• Coupled negative and positive feedback loops
– E.g. logistic growth.
Equilibrium and Stability
• Equilibrium
– More than one?
– Will the variable remain at
this level?
• Stability
– Will the variable return to
equilibrium after a shock?
• Resilience
– Returns to equilibrium
– Maintains functional
integrity
Environmental Unity
• Environmental unity:
– It is impossible to change
only one thing;
everything affects
everything else.
– Example: a food web
Changes and Equilibrium in Systems
• Uniformitarianism suggests changes in natural
systems are predictable and based on the past
• But how do systems change? Is this true?
• Steady/Stable state:
– A dynamic equilibrium
– Material or energy is entering and leaving the
system in equal amounts
– Opposing processes occur at equal rates
– E.g. climax state in mature ecosystems
Fig 3.12
© 2005 John Wiley and Sons Publishers
Changes and Equilibrium in Systems
• Relationships between variables e.g. cause (inflow)
and effect (outflow)
–
–
–
–
–
–
–
–
Linear
Nonlinear
Deterministic
Stochastic
Continuous
Discrete
Thresholds
Delayed
• Wonderfully complex!
Changes and Equilibrium in Systems
• Multiple Dynamic Equilibria
– Resiliency
• How quickly a system returns to its equilibrium
– Resistance
• How unyielding a system is to a disturbance
– Most are metastable – can go through rapid
transitions
Why Solving Environmental Problems Is
Often Difficult
1.
2.
Feedback loops - coupled or single
Exponential growth
•
3.
The consequences of exponential growth and its accompanying
positive feedback can be dramatic
Lag time
•
•
4.
The time between a stimulus and the response of a system
If there is a long delay between stimulus and response, then the
resulting changes are much more difficult to recognize.
Irreversible consequences
•
•
Consequences that may not be easily rectified on a human scale of
decades or a few hundred years.
When are activities irreversible?
Why Solving Environmental Problems Is
Often Difficult
5. Everything is interlinked
– Makes it difficult to manage one species at a time
6. Synergy
– Pollutants often interact to create something worse
7. Never static - always changing, always dynamic
– E.g. succession - never constant.
8. Chaos
– Chaotic behavior very common - difficult to predict
movement