Fundamentals

Discussion

Malthusian doomsayers claim:1. Natural resources are running out2. Population is growing, having less and less to eat3. Species are becoming extinct in vast numbers,

forests are disappearing, fish stocks are collapsing4. 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. That part of a planet where

life exists2. 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 BiomesBiomes: 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

DecomposersFungi, BacteriaAnimals

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 ResourcesPopulation growth

• Focus on G• Exponential growth• Characterizes anything

that can grow without limit

• Pt = Pt-1*(1+r)• Absolute increase

increases over time

Renewable ResourcesPopulation growth

• Logistic or density dependent growth

• Upper limit to the ultimate size

• Determined by carrying capacity– What defines CC?

• Growth curve inverted u-shaped

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. Feedback loops - coupled or single2. Exponential growth

• The consequences of exponential growth and its accompanying positive feedback can be dramatic

3. Lag time• 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.4. 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