Introduction to Environmental Science

Chapters 1 and 2

We Cannot Create or Destroy Matter

• Law of conservation of matter – matter cannot be created nor destroyed• Matter is converted from one

form to another

Everything we think we have thrown away remains here with us in some form…

Energy Changes Are Governed by Two Scientific Laws

• First Law of Thermodynamics– Energy input always equals energy output

• Second Law of Thermodynamics– Energy always goes from a more useful to a less

useful form when it changes from one form to another• Decreased energy efficiency

The Second Law of Thermodynamics in Living Systems

Systems Respond to Change through Feedback Loops

• Positive feedback loop - causes a system to change in the same direction

Systems Respond to Change through Feedback Loops

• Negative feedback loop – causes a system to change in the opposite direction from which it is moving– Opposing process

• Can promote sustainability!– Aluminum mining can

recycling

Time Delays Can Allow a System to Reach a Tipping Point

• Time delays vary– Between the input of a

feedback stimulus and the response to it

– Example: Planting trees

• Tipping point, threshold level– Causes a shift in the

behavior of a system

System Effects Can Be Amplified through Synergy

• Synergistic interaction – two or more processes interact so that the combined effect is greater than the sum of their separate effects– Helpful• E.g., campaign vs. individual persuasion

– Harmful• E.g., Smoking and inhaling asbestos particles

Ecology

Chapters 3 and 4

Habitat vs. Niche

• Habitat – place where an organism lives– Organisms address

• Niche – role of an organism in an ecosystem (physical, chemical, and biological conditions that a species needs to live and reproduce)– Organisms occupation

• Thousands of organisms can occupy the same habitat but each organism has its own niche.

Habitat vs. Niche

Levels of Organization of Life

• Organism- a living thing

• Population- a group of organisms of the same species that live in a particular area

• Community- populations of different species that live in one particular area

Several Abiotic Factors Can Limit Population Growth

• Limiting factor principle– Too much or too little of any abiotic

factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance

Range of Tolerance for a Population

of Organisms• Range of tolerance may vary in populations

– Small differences in genetic makeup, health, and age

A Food Chain

Ecological Efficiency

• No organism EVER receives all of the energy from the organism it just ate

• 10% Law– Only 10% of the energy

from one trophic level is transferred to the next

Some Ecosystems Produce Plant Matter Faster Than Others Do

• Gross primary productivity (GPP)– Rate at which an ecosystem’s producers

convert solar energy into chemical energy stored in their tissues

• Net primary productivity (NPP)– Rate they create and store energy minus

the energy they use for homeostasis– Ecosystems and life zones differ in their

NPPNPP = GPP - R

Nutrients Cycle in the Biosphere

• Biogeochemical cycles, nutrient cycles– Nitrogen– Hydrologic– Carbon– Phosphorus– Sulfur

• Connect past, present, and future forms of life

Nitrogen Fixation

• Nitrogen gas cannot be used by living things directly– Converted by

lightening

• Bacteria in soil and ocean convert nitrogen gas into ammonium (NH4

+) and nitrates (NO3

-) – Fixation

Assimilation

• Used by plants to produce amino acids, proteins, nucleic acids, and vitamins

• When organism dies bacteria convert proteins into ammonia or ammonium– Ammonification

Returning Nitrogen

• Specialized bacteria in soil and bottom of lakes convert NH3 and NH4

+ back into nitrates – Nitrification

• Nitrates are converted to nitrogen gas and returned to the atmosphere– Denitrification– N2

– N2O

Nitrogen Cycle Summary

• Fixation – gas ammonium or nitrate

• Assimilation– Taken up by plants through roots; incorporated into

proteins• Ammonification

– Bacteria break down proteins into ammonia and ammonium

• Nitrification– Ammonia nitrates

• Denitrification– nitrates gas

Human intervention in the nitrogen cycle

– Additional NO and N2O • Burning fuels at high

temperatures

– Destruction of forest, grasslands, and wetlands

– Add excess nitrates to bodies of water• Runoff

– Remove nitrogen from topsoil• Harvesting nitrogen

rich crops and irrigation

Nitrogen Cycle in a Terrestrial Ecosystem with Major Harmful Human

Impacts

Hydrologic Cycle Including Harmful Impacts of Human Activities

Alteration of the hydrologic cycle by humans

• Withdrawal of large amounts of freshwater at rates faster than nature can replace it

• Clearing vegetation– Increases temperature

and thus evaporation

• Increased flooding when wetlands are drained

Carbon Cycle Equations

Cellular RespirationC6H12O6  +  6O2    6CO2  +  6H2O +ATP 

Photosynthesis6CO2 + 6H2O sunlight C6H12O6 + 6O2

Carbon Cycle

• Marine sediments are earth’s largest store of carbon– Carbon is trapped

between layers of sediment

– Converted to fossil fuels when heated and compressed

Natural Capital: Carbon Cycle with Major Harmful Impacts of Human Activities

Phosphorous Cycle

• Phosphorus – Helps form important molecules like

DNA, RNA, and ATP Inorganic phosphate PO4

3- is released into the soil and water as sediments wear down.

– Eventually enters the ocean, where it is used by marine organisms

– Does NOT include the atmosphere

• Organic phosphate moves through the food web and to the rest of the ecosystem.

Phosphate Cycle

Ocean

Land

Organisms

Sediments

Phosphorus Cycle with Major Harmful Human Impacts

Sulfur Cycles through the Biosphere

• Sulfur found in organisms, ocean sediments, soil, rocks, and fossil fuels

• SO2 in the atmosphere

• H2SO4 and SO4- released during

volcanic eruptions (toxic)

Sulfur Cycles through the Biosphere

• Human activities affect the sulfur cycle– Burn sulfur-containing coal and oil– Refine sulfur-containing petroleum to

make gasoline and other heating products

– Convert sulfur-containing metallic mineral ores• Copper lead and zinc

Natural Capital: Sulfur Cycle with Major Harmful Impacts of Human Activities

Evolution

Chapter 5

Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring

• When environmental conditions change, populations– Adapt– Migrate– Become extinct

• Genetic resistance – ability of one or more organisms in a population to tolerate a chemical designed to kill it

• Malaria

Most of the normal bacteria die

The genetically resistant bacteriastart multiplying

Eventually the resistant strainreplaces the strain affected bythe antibiotic

A group of bacteria, including genetically resistant ones, areexposed to an antibiotic

Normal bacterium

Resistant bacterium

Geologic Processes Affect Natural Selection

• Tectonic plates affect evolution and the location of life on earth– Location of continents and oceans– Species physically move, or adapt, or form

new species through natural selection

• Earthquakes

• Volcanic eruptions

Geographic Isolation Can Lead to Reproductive Isolation

Extinction is Forever

• Extinction

• Endemic species – Species found only

in one area– Particularly

vulnerable– Golden Toad (Costa

Rica) died out when habitat dried up

Species Diversity: Variety, Abundance of Species in a

Particular Place • Species diversity– Species richness

– number of different species in a community

– Species evenness – abundance of organisms within each type of species

Species Diversity: Variety, Abundance of Species in a

Particular Place

• Most species-rich communities– Tropical rain forests– Coral reefs– Ocean bottom zone– Large tropical lakes

Worldwide Richness?

• Diversity varies with geographical location– Richness is highest at tropics– Lowest at the poles

Question: Is productivity higher in a species-rich ecosystem?

Each Species Plays a Unique Role in Its Ecosystem

• Generalist species– Broad niche– Live in different places,

eat different food, high range of tolerance

– Examples?

• Specialist species – Narrow niche– More prone to

extinction– Examples?

Specialist Species and Generalist Species Niches

Question: Is better to be a

generalist or a

specialist?

Niches Can Be Occupied by Native and Nonnative Species

• Native species – organisms that normally live and thrive in a particular ecosystem

• Nonnative species - invasive, alien, or exotic species– May spread rapidly– Not all are villains

Indicator Species Serve as Biological Smoke Alarms

• Indicator species – species that provide early warnings of damage to a community or ecosystem– Can monitor environmental quality • Trout• Birds• Butterflies• Frogs

Coal Canaries: 1800s – 1900s

• Coal miners took caged canaries into mines to act as early warning sentinels

• If birds stopped singing and appeared to be distressed miners knew there were poisons being released

Keystone, Foundation Species Determine Structure, Function of Their

Ecosystems• Keystone species – have a large effect on

the types and abundances of other species in an ecosystem– Pollinators– Top predator

• Foundation species– Create or enhance their habitats, which benefit

others • Elephants• Beavers

Endangered Species

Chapter 9

Endangered and Threatened Species Are Ecological Smoke Alarms

• Endangered species – so few individual survivors that species could soon become extinct over its range

• Threatened species- still abundant, but numbers are declining

Loss of Habitat Is the Single Greatest Threat to Species: Remember HIPPCO

H• Habitat destruction, degradation, and

fragmentation

I• Invasive (nonnative) species

P• Population and resource use growth

P• Pollution

C• Climate change

O• Overexploitation

Ecological Succession

• Natural ecological restoration– Primary succession – gradual

establishment of biotic communities in lifeless areas where there is no soil or sediment

– Secondary succession – series of communities with different species develop in places containing only soil or bottom sediment

No Population Can Grow Indefinitely: J-Curves and S-Curves

• Biotic potential – capacity for population growth under ideal conditions– Larger organisms

tend to have low potential

Population Growth

• Exponential growth – population that increases at a fixed rate– J-Curve

• Logistic growth – rapid exponential population growth followed by a steady decrease in population growth– S-Curve

Population Growth

S-Curves

• Environmental resistance – combination of all factors that act to limit the growth of a population

• Carrying capacity (K) – maximum population of a given species that a habitat can sustain indefinitely without being degraded

S-Curves

Phases of Logistic Growth Curve1. Lag Phase – little initial growth.2. Rapid Growth Phase3. Stable Phase – stabilizing factors limit growth

Species Reproductive Patterns

• r-Selected species, opportunists – species with a capacity for a high rate of population increase– Many small offspring– Little to no parental care or protection– Reproductive opportunists

• K-selected species, competitors – reproduce later in life and have a small number of offspring with fairly long life spans– Few large offspring– High parental care

Positions of r- and K-Selected Species on the S-Shaped Population Growth Curve

Top-down Regulation

Chapter 10

Forestry

Forests Vary in Their Make-Up, Age, and Origins

• Old-growth or primary forest – uncut or regenerated primary forest that has been undisturbed for 200 years or more– 36% of world’s

forests– ¾ found in Russia,

Canada, Brazil, Indonesia and Papua New Guinea

Forests Vary in Their Make-Up, Age, and Origins

• Second-growth forest – result from secondary ecological succession; develop after forest destruction– 60% of world’s

forests

Rotation Cycle of Cutting and Regrowth of a Monoculture Tree Plantation

Fire, Insects, and Climate Change Can Threaten Forest Ecosystems

• Surface fires– Usually burn leaf litter

and undergrowth• Kill seedlings and small

trees• Spare most mature

trees; allow wildlife to escape

– Stimulate seed germination• Sequoia and jack pine

– Burn away flammable ground material• Prevents more

destructive fires

Fire, Insects, and Climate Change Can Threaten Forest Ecosystems

• Crown fires – Extremely hot:

burns whole trees– Kill wildlife– Increase soil

erosion– Occur in forests

that have not experienced surface fires for several decades

Unsustainable Logging is a Major Threat to Forest Ecosystems

• Increased erosion– Sediment runoff into

waterways

• Habitat fragmentation– Loss of biodiversity

• Invasion by– Nonnative pests– Disease– Wildlife species

Natural Capital Degradation: Building Roads into Previously Inaccessible Forests

Unsustainable Logging is a Major Threat to Forest Ecosystems

• Major tree harvesting methods:– Selective cutting– Clear-cutting– Strip cutting

We Can Improve the Management of Forest Fires

• The Smokey Bear educational campaign– Forest Service and

National Advertising Council

– Convinced public that ALL forest fires are bad• Increases the likelihood

of crown fires• Threaten 40% of federal

forest lands from fuel buildup and slash (logging debris)

We Can Improve the Management of Forest Fires

• Prescribed fires – careful planning

• Herds of goats to eat underbrush (CA)

• Allow fires on public lands to burn

Degradation of Tropical Forest: Positive Feedback Loop

• Step 1: Roads– Cut deep into a forest for logging and settlement– Selective cutting; large trees fall but bring small

trees with them because of vines and canopy

• Step 2: Ranchers buy land– Cattle ranchers use land for grazing– After overgrazing herds move

• Step 3: Settlers buy land for harvesting– Grow food to survive– Soil nutrients depleted after a few years and land is barren

Grasslands

• Rangelands – unfenced grasslands in temperate and tropical climates that supply forage (vegetation) for grazing (grass-eating) and browsing (shrub-eating) animals

Grasslands

• Pastures – managed grasslands or enclosed meadows usually planted with domesticated grasses or other forage

Important ecological services of grasslands

• Soil formation• Erosion control• Nutrient cycling• Storage of

atmospheric carbon dioxide in biomass

• Maintenance of diversity

Riparian Zones

• Thin strips of lush vegetation along streams or rivers– Livestock tend to

aggregate around natural water sources

Natural Capital Degradation: Overgrazed and Lightly Grazed Rangeland

Restoration of Grazing Lands

Case Study: Stresses on U.S. Public Parks

• 58 Major national parks in the U.S.

• Biggest problem may be popularity– Noise – Congestion– Pollution– Damage or destruction to vegetation and

wildlife

• Repairs needed to trails and buildings

Natural Capital Degradation: Damage From Off-Road Vehicles

Endangered Natural Capital: Biodiversity Hotspots in the U.S.