Community ecology - The study of interactions among species
Symbiosis - Two species living in a close and long-term association with one another in an ecosystem
Competition - The struggle of individuals, either within or between species, to obtain a shared limiting resource
Competitive exclusion principle - The principle stating that two species competing for the same limiting resource cannot coexist
Resource partitioning - When two species evolve to divide a resource based on differences in their behavior or morphology
Predation - An interaction in which one animal typically kills and consumes another animal
Parasitoids - A specialized type of predator that lays eggs inside other organisms (the host)
Herbivory - An interaction in which an animal consumes plants or algae
Mutualism - An interaction between two species that increases the chances of survival or reproduction for both species
Photosynthesis - The process by which plants and algae use solar energy to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂)
Commensalism - An interaction between two species in which one species benefits and the other species is neither harmed nor helped
Native species - A species that lives in its historical range, typically where it has lived for thousands or millions of years
Exotic species - A species living outside its historical range
Alien species - Alternative term for exotic species
Why it occurs: Resource partitioning occurs because of the competitive exclusion principle. When two species compete for the same limiting resource, natural selection favors individuals that overlap less with the other species in resource use. This reduces competition between the species.
What happens to species: Over many generations, competing species evolve to reduce their overlap in resource use through three main methods:
Temporal partitioning - Using the same resource at different times (e.g., wolves and coyotes hunting at different times of day)
Spatial partitioning - Using different habitats (e.g., desert plants with different root depths)
Morphological partitioning - Evolving different body sizes or shapes (e.g., Galápagos finches with different beak shapes for different foods)
| Type of Interaction | Species 1 | Species 2 |
|---|---|---|
| Competition | - | - |
| Predation | + | - |
| Parasitism | + | - |
| Herbivory | + | - |
| Mutualism | + | + |
| Commensalism | + | 0 |
Biome - Plants and animals found in a particular region of the world
Terrestrial biome - Geographic region categorized by average annual temperature, precipitation, and distinctive plant growth forms
Aquatic biome - Aquatic region characterized by salinity, depth, and water flow
Habitat - Specific area where a particular species lives; subset of a biome
Temperature Categories:
Cold (<5°C): Tundra, Taiga
Temperate (5-20°C): Rainforest, seasonal forest, shrubland, grassland
Tropical (>20°C): Rainforest, savanna, hot desert
1. Tundra - Cold, treeless, 4-month growing season - Permafrost prevents deep roots - Low shrubs, mosses, lichens - Slow decomposition → organic soil accumulation
2. Taiga (Boreal Forest)
- Coniferous evergreens, cold winters - 50-60°N latitude - Poor soils,
short growing season - Major lumber source
3. Temperate Rainforest - Coastal, moderate temps, high precipitation - Giant trees (redwoods 90m tall) - 12-month growing season - Heavily logged
4. Temperate Seasonal Forest - Warm summers, cold winters, >1m precipitation - Deciduous trees (oak, maple, beech) - Fertile soils, high productivity - First converted to agriculture
5. Shrubland (Chaparral) - Hot dry summers, mild wet winters - Fire-adapted drought-resistant shrubs - Mediterranean climates - Ideal for grape cultivation
6. Temperate Grassland - Cold winters, hot dry summers - Rainfall determines grass height - Most fertile soils (98% converted to farms) - Frequent wildfires
7. Tropical Rainforest - Warm, wet, 20°N-20°S of equator - Highest biodiversity, multiple vegetation layers - Rapid decomposition = poor soils despite high productivity - 24,000 ha cleared annually
8. Savanna - Warm temps, distinct wet/dry seasons - Grasslands with scattered deciduous trees - Trees drop leaves in dry season - 99% converted in some regions
9. Hot Desert - ~30°N/S, extremely dry, hot - Water-storing plants with spines - Annual vs perennial plant strategies - Threatened by climate change
Soil Fertility: Grassland > Seasonal forest > Rainforest > Shrubland > Taiga > Tundra > Desert
Growing Season: Tropical (12 months) > Temperate (6-10 months) > Cold (4-6 months)
Decomposition Rate: Tropical > Temperate > Cold
| Biome | Location | General Climate | Soil | Dominant Plants | Animals found in biome |
|---|---|---|---|---|---|
| Tropical rainforest | Near the equator | Hot, wet all year | Poor, thin | Tall trees, vines, epiphytes | Jaguars, monkeys, frogs |
| Desert | Around 30° N & S | Very hot, very dry | Sandy, poor | Cacti, succulents | Camels, lizards, roadrunners |
| Tropical seasonal forest - Savanna | Africa, S. America, Australia | Warm, wet summers, dry winters | Fairly good | Grasses, a few trees | Zebras, lions, cheetahs |
| Woodland-Shrubland | Mediterranean, S. California | Hot dry summers, mild wet winters | Low nutrients | Shrubs, small trees | Quail, coyotes, rabbits |
| Temperate Grassland | Central NA, S. America, Asia | Cold winters, hot summers | Rich, deep | Grasses, wildflowers | Bison, prairie dogs, snakes |
| Northern coniferous forest | Canada, Russia, N. Europe | Cold, some rain | Poor, acidic | Pine, spruce, fir | Bears, moose, wolves |
| Temperate Seasonal Forest | Eastern US, Europe, China | Warm summers, cold winters | Rich | Oak, maple, hickory | Deer, foxes, squirrels |
| Tundra | Arctic, high mountains | Very cold, little rain | Frozen, poor | Moss, lichen, small shrubs | Polar bears, foxes, caribou |
| Temperate Rainforest | Pacific NW, Chile, NZ | Mild, rainy | Low nutrients | Fir, spruce, redwoods | Deer, salamanders, frogs |
Temperature, Rainfall
Tropical Rainforest
Tundra
Because Bananas are a tropical plant and none of the biomes within the US would be very good for growing them. Also importing them from countries with a lower median income can lead to a lower price.
Littoral Zone: Shallow water near shore where plants and algae grow. Most photosynthesis happens here.
Limnetic Zone: Open water where sunlight reaches but rooted plants can’t survive. Only floating algae live here.
Profundal Zone: Deep water with no sunlight. No plants can live here, and oxygen is very low.
Benthic Zone: Muddy bottom of water bodies made of sediments and organic matter.
Oligotrophic Lake: Low-nutrient lake with clear water and few algae.
Mesotrophic Lake: Medium-nutrient lake.
Eutrophic Lake: High-nutrient lake with lots of algae. Water looks green like pea soup.
Coral Bleaching: When stressed corals lose their algae, turn white, and die.
Photic Zone: Upper ocean where sunlight allows photosynthesis.
Aphotic Zone: Deep ocean with no sunlight or photosynthesis.
Chemosynthesis: How bacteria make energy using chemicals instead of sunlight.
Land Biomes:
Water Biomes:
Land Biomes:
Water Biomes:
Main Limiting Factors:
Structure:
Human Threats:
Both land and water biomes:
| Biome | Water Depth (Shallow/Deep) | Salinity (Salty or Not) | Flow/Still | Plants Found | Animals Found | Zones (if any) |
|---|---|---|---|---|---|---|
| Streams/Rivers | Shallow to Deep (varies) | Not salty (freshwater) | Flowing | Algae, mosses, riparian plants | Fish (trout, salmon), insects, amphibians | Headwaters, floodplain, riparian zone |
| Ponds/Lakes | Shallow and Deep zones | Not salty (freshwater) | Still | Algae, cattails, water lilies | Fish, amphibians, zooplankton, insects | Littoral, limnetic, profundal, benthic |
| Freshwater Wetlands | Shallow | Not salty (freshwater) | Still/slow | Grasses, reeds, cattails | Amphibians, insects, birds, fish, mammals | No formal zones |
| Salt Marshes/Estuaries | Shallow | Salty & fresh mix (brackish) | Flowing/tidal | Salt-tolerant grasses, algae | Fish, shellfish, birds, crabs, mammals | Intertidal |
| Mangrove Swamps | Shallow | Salty (coastal) | Tidal flow | Mangrove trees, algae | Fish nurseries, crabs, birds, reptiles | Intertidal |
| Intertidal Zones (coasts) | Shallow (exposed at times) | Salty (marine) | Tidal | Seaweeds, algae | Crabs, mollusks, starfish, shorebirds | High, middle, low tide zones |
| Coral Reefs | Shallow | Salty (marine) | Still/tidal | Coral, algae (zooxanthellae), seagrasses | Fish, mollusks, crustaceans, sea turtles | Photic |
| Open Ocean | Deep | Salty (marine) | Currents | Phytoplankton, kelp (near surface) | Whales, sharks, jellyfish, fish, zooplankton | Photic, aphotic, benthic |
Reservoir - Components of biogeochemical cycles that contain matter (air, water, organisms)
Sink - A reservoir that stores atoms and molecules
Aerobic respiration - Cells convert glucose + oxygen → energy + CO₂ + water
Greenhouse gases - Atmospheric gases that trap heat near Earth’s surface
Global warming - Increased global temperatures due to human greenhouse gas production
Nitrogen fixation - Converts N₂ gas into forms plants can use (NH₃/NO₃⁻)
Nitrification - NH₄⁺ → NO₂⁻ → NO₃⁻ conversion by bacteria
Assimilation - Plants/algae incorporate nitrogen into tissues
Mineralization/Ammonification - Decomposers break down organic matter → NH₄⁺
Denitrification - NO₃⁻ → N₂O → N₂ conversion in oxygen-poor environments
Anaerobic - Lacks oxygen | Aerobic - Has abundant oxygen
Leaching - Dissolved molecules transported through soil via groundwater
Major impacts: - Fossil fuel combustion - Rapidly moves carbon to atmosphere - Deforestation - Releases stored carbon, reduces CO₂ absorption
Result: CO₂ increased from 280 ppm (1800) to 420 ppm today
Largest carbon sink: Sedimentary rocks (limestone/dolomite)
Major impacts: - Synthetic fertilizers - Humans now fix more N than nature - Agricultural runoff - Excess nitrogen leaches into ecosystems - Fossil fuel burning - Creates nitrate deposition
Consequences: Reduced species diversity, altered plant communities, acid precipitation
Largest nitrogen sink: Earth’s atmosphere (78% N₂ gas)
Carbon Cycle: 7 processes - Fast: photosynthesis, respiration, exchange, combustion - Slow: sedimentation, burial, extraction
Nitrogen Cycle: 5 transformations 1. Fixation (N₂ → NH₃/NO₃⁻) 2. Nitrification (NH₄⁺ → NO₃⁻) 3. Assimilation (plant uptake) 4. Mineralization (organic N → NH₄⁺) 5. Denitrification (NO₃⁻ → N₂)
Algal bloom: A rapid increase in algal population in waterways caused by excess nutrients (especially phosphorus) that increases algae biomass.
Hypoxic: Low oxygen conditions in water, often resulting from algae decomposition consuming dissolved oxygen.
Dead zone: Water areas where oxygen levels become so low that fish and aquatic animals die, typically caused by algal blooms and decomposition.
Transpiration: Water release from plant leaves into the atmosphere during photosynthesis.
Evapotranspiration: Combined water loss through evaporation and transpiration from ecosystems.
Runoff: Water flowing across land surfaces into streams and rivers toward the ocean.
Autotrophs (Producers): Plants, algae, and bacteria that use solar energy to produce sugars through photosynthesis.
Cellular Respiration: Process by which cells convert glucose and oxygen into energy, CO₂, and water.
Anaerobic Respiration: Converting glucose into energy without oxygen (less efficient than aerobic respiration).
Primary Productivity: Rate of converting solar energy into organic compounds over time.
Gross Primary Productivity (GPP): Total solar energy captured by producers via photosynthesis.
Net Primary Productivity (NPP): Energy captured by producers minus energy used for respiration.
Biomass: Total mass of all living matter in a specific area.
Standing Crop: Amount of biomass present at a particular time.
NPP = GPP - R - NPP = Net Primary Productivity - GPP
= Gross Primary Productivity
- R = Respiration by producers
Math Problem: Tropical rainforest has NPP = 8,500 kcal/m²/year and GPP = 21,000 kcal/m²/year. Find R.
NPP = GPP - R 8,500 = 21,000 - R R = 12,500 kcal/m²/year
Terrestrial Plants (Green): Use chlorophyll which absorbs red and blue light but reflects green light. All wavelengths available on land.
Deeper Water Plants (Red Algae): Water absorbs red light in upper 1m but blue light penetrates to 100m. Red algae evolved additional pigments to capture available blue light at depth.
Heterotroph (Consumer): Organism that must obtain energy by consuming other organisms.
Primary Consumer (Herbivore): Consumer that eats producers. Examples: zebras, grasshoppers.
Carnivore: Consumer that eats other consumers.
Secondary Consumer: Carnivore that eats primary consumers. Examples: lions, hawks.
Tertiary Consumer: Carnivore that eats secondary consumers. Examples: bald eagles.
Trophic Levels: Successive levels of organisms consuming one another.
Food Chain: Linear sequence of consumption from producers through consumers.
Scavengers: Organisms that consume dead animals (vultures).
Detritivores: Organisms that break down dead tissues into smaller particles (dung beetles).
Decomposers: Fungi and bacteria that convert organic matter into recyclable elements.
The 10% Rule: Only about 10% of energy transfers from one trophic level to the next.
Trophic Pyramid: Representation of energy/biomass distribution among trophic levels.
Food Web: Model showing energy flow through interconnected food chains.
Given: Primary producers have 8,700 J
Answer: Secondary consumers would have 87 Joules.
• Biodiversity: Variety of life at multiple scales; indicator of environmental health
• Genetic Diversity: Genetic variation among individuals in a population; helps species adapt to changes
• Species Diversity: Number of species in a region or ecosystem
• Habitat Diversity: Variety of habitats in an ecosystem; supports different species types
• Specialists: Species with narrow habitat requirements (koalas only eat eucalyptus)
• Generalists: Species that survive in wide range of conditions (white-tailed deer)
• Ecosystem Diversity: Variety of ecosystems in a region
• Species Richness: Number of different species in an area
• Species Evenness: Whether species have similar population sizes or one dominates
• Enhanced stability during environmental changes • Faster recovery from disturbances • Higher primary productivity • Multiple species can fill similar roles if one is lost
• More vulnerable to disruptions • Slower recovery from disturbances • Higher risk of collapse when key species are lost
• Provides long-term population survival through adaptation • Enables disease resistance • Critical for agriculture - genetic variety helps combat new diseases • Loss affects species for thousands of years (cheetah example)
• Creates stable ecological networks • Provides species redundancy for ecosystem functions • Increases productivity through species interactions • Example: diverse soil fungi improve plant growth
• Supports both specialist and generalist species • Allows many species to coexist in different niches • Provides refugia during environmental changes • Loss affects specialists more than generalists initially
Ecosystem services: The processes by which life-supporting resources such as clean water, timber, fisheries, and agricultural crops are produced.
Provisions: Goods produced by ecosystems that humans can use directly (examples: lumber, food crops, medicinal plants, natural rubber).
Provisioning Services - Timber for construction and paper - Maple syrup from sugar maples - Wild berries, nuts, and mushrooms - Medicinal plants like ginseng
Regulating Services - Carbon storage to mitigate climate change - Water cycle regulation through transpiration - Air purification by filtering pollutants - Soil erosion prevention
Supporting Services - Nutrient cycling through leaf decomposition - Wildlife habitat provision - Soil formation from organic matter - Pollination by forest insects
Cultural Services - Recreational hiking and camping - Aesthetic beauty for photography - Educational value for ecology studies - Spiritual benefits from nature connection
Provisioning Services - Commercial fishing (salmon, crabs, oysters) - Salt production through evaporation - Seaweed harvesting - Shellfish aquaculture
Regulating Services - Storm surge protection for coasts - Water filtration before reaching ocean - Carbon sequestration in salt marshes - Flood control during high tides
Supporting Services - Nursery habitat for juvenile marine species - Nutrient cycling between fresh and saltwater - Primary productivity from marsh grasses - Migration sites for waterfowl
Cultural Services - Birdwatching and wildlife observation - Recreational boating and fishing - Marine biology research sites - Cultural significance for indigenous communities
Island biogeography: The study of how species are distributed and interacting on islands.
Species-area curve: How the number of species on an island increases with island area.
Two main factors determine species number:
Flightless ground-nesting birds are most vulnerable because they: - Cannot escape predators - Build accessible nests - Lack predator defenses - Have specialized diets
Small, far islands because they: - Support small populations (extinction-prone) - Receive few replacement colonists - Have limited habitat diversity - Cannot support complex food webs
Ecological Tolerance (Fundamental Niche): The range of abiotic conditions where a species can survive, grow, and reproduce.
Realized Niche: The actual conditions where a species lives after biotic interactions (competition, predation, disease) further limit its distribution.
Geographic Range: Areas of the world where a species actually lives.
Mass Extinction: Large numbers of species going extinct over short time periods due to major environmental changes.
Five historical mass extinctions occurred when environmental changes exceeded species’ tolerance limits: - 251 million years ago: 90% marine species extinct from unknown environmental changes - 65 million years ago: Meteorite impact blocked sunlight, halting photosynthesis
Human activities push species beyond tolerance through: - Rapid climate change: Faster than species can adapt or migrate - Habitat destruction: Eliminates suitable environments - New stressors: Invasive species, pollution, disease
Species go extinct when: 1. No suitable habitat remains within tolerance range 2. Physical barriers prevent migration 3. Better competitors occupy new habitats 4. Changes occur too rapidly for adaptation
Periodic disruptions - Regular, predictable disruptions like day/night cycles or tidal cycles.
Episodic disruptions - Somewhat regular disruptions like rain/drought cycles every 5-10 years.
Random disruptions - Unpredictable disruptions like volcanic eruptions or hurricanes.
Resistance - How much a disruption can affect ecosystem energy and matter flows. High resistance means the ecosystem maintains function despite disturbance.
Resilience - The rate an ecosystem returns to its original state after disruption. High resilience means quick recovery.
Intermediate disturbance hypothesis - Ecosystems with intermediate disturbance levels have higher species diversity than those with very high or low disturbance.
The hypothesis works because: - Low disturbance: Competitive species dominate and outcompete others - High disturbance: Only fast-reproducing, hardy species survive - Intermediate disturbance: Balance allows both competitive and resilient species to coexist
Example: New England marine algae with periwinkle snails. Few snails = competitive algae dominate. Many snails = only unpalatable algae survive. Intermediate snail density = 12 algae species coexist.
Causes: Ice ages trap water in ice sheets (lowering levels), warming periods melt ice (raising levels). Driven by Earth’s orbital changes.
Impacts: During last Ice Age, levels dropped 120+ meters. After warming, rose 85+ meters. Coastal areas repeatedly switched between land and marine ecosystems.
Why: Animals follow seasonal food availability and suitable habitats.
Example: Serengeti migration - millions of wildebeest, zebras, and gazelles migrate in circular patterns following seasonal rains. They move to areas where rains create fresh vegetation, returning when original areas recover.
Evolution - A change in the genetic composition of a population over time.
Microevolution - Evolution at the population level (e.g., different varieties of apples).
Macroevolution - Evolution that gives rise to new species, genera, families, classes, or phyla.
Artificial selection - Humans determine which individuals breed based on desired traits.
Natural selection - The environment determines which individuals survive and reproduce.
Fitness - An individual’s ability to survive and reproduce.
Adaptation - A trait that improves an individual’s fitness.
Allopatric speciation - Speciation that occurs with geographic isolation.
Sympatric speciation - Evolution of one species into two without geographic isolation.
Natural Selection Requirements: - Individuals produce excess offspring - Not all offspring survive - Individuals differ in traits - Traits can be passed to offspring - Trait differences affect survival/reproduction
Random Processes: - Gene flow - Individuals move between populations, altering genetic composition - Genetic drift - Random mating changes genetic composition (more likely in small populations) - Bottleneck effect - Population reduction decreases genetic variation - Founder effect - Small colonizing group creates genetically distinct population
Slow evolution: Cichlid fish evolved ~200 species over millions of years in Lake Tanganyika
Rapid evolution: Atlantic cod evolved smaller size and earlier maturity after decades of fishing pressure targeting large individuals
Very rapid evolution: Genetically modified organisms (GMOs) can gain new traits instantly through gene insertion
Ecological succession - Predictable species replacement over time.
Primary succession - Begins with bare rock, no soil. Secondary succession - Begins with soil intact.
Pioneer species - Survive with little/no soil. Keystone species - Low abundance, large community effects.
Indicator species - Demonstrate ecosystem characteristics.
Primary: Pioneer species (lichens, mosses) → soil formation → grasses → trees
Secondary: Disturbance leaves soil → rapid recolonization → early trees → shade-tolerant trees
Species richness: Increases then plateaus
Biomass: Increases and plateaus
Productivity: Increases then declines (mature forests =
low productivity, high standing crop)
Keystone: Beavers (create ponds), sea stars (control mussels), flying foxes (pollinate plants)
Indicator: Mayflies (clean water), E. coli (sewage contamination), lichens (air quality)
Population growth rate (intrinsic growth rate): Number of offspring produced minus deaths in a given time period.
Biotic potential: Maximum population growth under ideal conditions with unlimited resources.
K-selected species: Species with low growth rates that increase slowly to carrying capacity.
Carrying capacity: Maximum number of individuals an environment can support (denoted as K).
Overshoot: Population exceeding carrying capacity.
Dieback: Rapid population decline due to death.
Generalists: Live under wide range of conditions, broad diets, adaptable to change (gray kangaroos)
Specialists: Narrow conditions/diets, vulnerable to environmental change (koalas eating only eucalyptus)
r-selected species because they reproduce rapidly, produce many offspring, and can quickly exploit new environments.
Type I: High survival until old age (K-selected: elephants, humans)
Type II: Constant death rate throughout life (chipmunks, squirrels)
Type III: High early death, survivors live long (r-selected: fish, frogs)
Trapping data show cyclical oscillations: hare populations peak first, followed by lynx 1–2 years later. As hares overconsume vegetation, their numbers crash, causing lynx to decline from lack of prey. Reduced predation then allows hares to rebound—repeating the cycle.
When resources like food or nesting sites decline:
Example: Logging reduces nesting cavities for goldeneye ducks, lowering their population even if food is plentiful.
Population size = (Immigrations + births) - (emigrations + deaths)
%Change = New - Original / Original x 100%
Immigration: The movement of people into a country or region from another country or region.
Emigration: The movement of people out of a country or region.
Crude Birth Rate (CBR): The number of births per 1,000 individuals per year.
Crude Death Rate (CDR): The number of deaths per 1,000 individuals per year.
Age Structure Diagram: A visual representation of the number of individuals within specific age groups for a country, typically expressed separately for males and females, with each horizontal bar representing a 5-year age group.
Total Fertility Rate (TFR): An estimate of the average number of children that each woman in a population will bear throughout her childbearing years (typically ages 15-49).
Replacement-Level Fertility: The total fertility rate required to offset the average number of deaths in a population in order to maintain the current population size, assuming there is no net migration.
Global Population Growth Rate:
Global population growth rate (%) = [CBR - CDR] / 10
Where: - CBR = Crude birth rate (births per 1,000 people per year) - CDR = Crude death rate (deaths per 1,000 people per year) - Divided by 10 to convert from per 1,000 to percentage
National Population Percent Growth Rate:
National population % growth rate = [(CBR + immigration) - (CDR + emigration)] / 10
Where: - CBR = Crude birth rate (births per 1,000 people per year) - Immigration = number of people moving into the country (per 1,000 people per year) - CDR = Crude death rate (deaths per 1,000 people per year) - Emigration = number of people moving out of the country (per 1,000 people per year) - Divided by 10 to convert from per 1,000 to percentage
TFR is typically lower in developed countries for several reasons. Women tend to delay having their first child due to pursuing education and employment opportunities, which reduces their childbearing years. Higher income levels correlate inversely with TFR. Additionally, developed countries provide better access to family planning services and birth control information, allowing women greater control over reproduction.
Declining population: TFR below replacement level
No growth (stable) population: TFR at replacement level
Growing population: TFR above replacement level
Calculation of replacement-level fertility for a no-growth country:
In developed countries, replacement-level fertility is typically about two children per woman plus a small amount extra. This calculation is based on:
In developing countries, replacement-level fertility is higher because infant and child mortality rates are higher, meaning more births are needed to ensure enough individuals survive to reproductive age to maintain the population.
The key assumption is that there is no net migration (immigration equals emigration). If net migration is positive, a country can maintain or grow its population even with a TFR below replacement level.
Doubling time: The number of years it takes a population to double in size.
Rule of 70: A method to determine doubling time by dividing 70 by the percentage population growth rate. - Formula: Doubling time (years) = 70 / growth rate (%)
Theory of demographic transition: A theory stating that countries move from high to lower birth and death rates as they transition from preindustrial to industrialized economic systems.
Characteristics: - Preindustrial period with high infant mortality - Large families provide economic benefits (labor) - Poor sanitation and lack of healthcare
CBR and CDR: Both HIGH and EQUAL (no growth)
Characteristics: - Modernization begins with better sanitation and healthcare - Death rates drop but families still have many children - Population momentum occurs
CBR and CDR: CBR HIGH, CDR DROPS (rapid growth)
Characteristics: - Improved economy and education - Increased affluence and birth control access - Smaller families become preferred
CBR and CDR: Both DECREASE toward equality (slowing growth)
Characteristics: - High affluence and development - Aging population with fewer workers - Increased elderly care costs
CBR and CDR: CBR BELOW CDR (both LOW, population declines)
Plate tectonics: The theory that the lithosphere of Earth is divided into plates, most of which are in constant motion.
Earthquake: A sudden movement of Earth’s crust caused by a release of potential energy from the movement of tectonic plates.
Hot spots: Places where molten material from Earth’s mantle reaches the lithosphere.
Volcano: A vent in the surface of Earth that emits ash, gases, or molten lava.
Tsunami: A series of waves in the ocean caused by seismic activity or an undersea volcano that causes a massive displacement of water.
Divergent boundary: An area below the ocean where tectonic plates move away from each other.
Seafloor spreading: Rising magma forms new oceanic crust on the seafloor at divergent boundaries.
Convergent boundary: An area where one plate moves toward another plate and collides.
Subduction: The process in which the edge of an oceanic plate moves downward beneath the continental plate.
Island arcs: A chain of islands formed by volcanoes as a result of two tectonic plates coming together and experiencing subduction.
Transform boundary: An area where tectonic plates move sideways past each other.
Fault: A fracture in rock caused by a movement of Earth’s crust.
Plate tectonics impacts biodiversity through continental movement, which changes climates and creates or removes geographic barriers.
Example: Australia and Antarctica split apart and moved to different climatic regions. This separation led to allopatric speciation, where isolated species evolved along different paths. Species had to adapt to new climates or face extinction, with some evolving into entirely new species due to geographic isolation.
Physical weathering: The mechanical breakdown of rocks and minerals.
Chemical weathering: The breakdown of rocks and minerals by chemical reactions or dissolving of chemical elements from rocks.
Acid rain (acid precipitation): Precipitation high in sulfuric acid and nitric acid.
Erosion: The physical removal of rock fragments from a landscape or ecosystem.
Porosity: The size of the air spaces between particles.
Water holding capacity: The amount of water a soil can hold against the draining force of gravity.
Permeability: The ability of water to move through the soil.
┌─────────────────────────────────────────────────────────┐
│ O HORIZON (Organic Layer) │
│ Organic detritus in various stages of decomposition. │
│ Humus (fully decomposed matter) in lowest section. │
├─────────────────────────────────────────────────────────┤
│ A HORIZON (Topsoil) │
│ Organic material (including humus) mixed with minerals. │
├─────────────────────────────────────────────────────────┤
│ E HORIZON (Zone of Leaching) │
│ Iron, aluminum, and dissolved acids removed. Found in │
│ some acidic soils. Not present in all soils. │
├─────────────────────────────────────────────────────────┤
│ B HORIZON (Subsoil) │
│ Primarily mineral material with very little organic │
│ matter. Nutrients accumulate here. │
├─────────────────────────────────────────────────────────┤
│ C HORIZON (Parent Material Layer) │
│ Least-weathered horizon, similar to parent material. │
└─────────────────────────────────────────────────────────┘Note: Most soils have either an O or A horizon, usually not both.
Sandy Loam ranges: - Sand: approximately 50-70% - Silt: approximately 15-30% - Clay: approximately 0-20%
Sandy loam is dominated by sand with moderate silt and low clay content, creating well-draining soil that retains some moisture and nutrients.
Albedo: Percentage of incoming sunlight reflected from a surface. Snow/ice (80-95%) vs. forests (10-20%).
Saturation Point: Maximum water vapor air can hold at a given temperature. When temperature drops, water condenses → precipitation.
Hadley Cells: Convection currents between equator and 30°N/30°S. Warm air rises at equator → precipitation. Cool, dry air sinks at 30° → deserts.
Intertropical Convergence Zone (ITCZ): Latitude with most intense sunlight where Hadley cells converge. Shifts 23.5°N to 23.5°S yearly, creating tropical wet/dry seasons.
Polar Cells: Air rises at 60°N/60°S (precipitation), sinks at poles (90°N/90°S), returns to 60°.
Ferrell Cells: Convection currents between 30° and 60° latitudes. Driven by Hadley and polar cells. Creates variable mid-latitude winds.
Coriolis Effect: Deflection of moving objects due to Earth’s rotation. Creates prevailing wind patterns by deflecting air currents east or west.
EXOSPHERE (600-10,000 km) | 0-1,700°C | Satellites orbit here
THERMOSPHERE (85-600 km) | up to 2,000°C | Blocks X-rays/UV | Auroras
MESOSPHERE (50-85 km) | 0 to -90°C | Meteors burn up here
STRATOSPHERE (16-50 km) | -60 to 0°C | OZONE LAYER (O₃)
| Absorbs UV-B and UV-C
TROPOSPHERE (0-16 km) | -52°C to warmest | DENSEST layer
| Weather occurs here
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EARTH'S SURFACE2A[AGas Composition: Nitrogen (78%) + Oxygen (21%) + Other gases (1%) - Greenhouse gases (CO₂, CH₄, N₂O) = small amount but warm Earth by 33°C - Density and pressure decrease with altitude
NORTH POLE (90°N)
↓ sinking
POLAR CELL → Polar Easterlies
↓
60°N ← rising
↓
FERRELL CELL → Westerlies
↓
30°N ← sinking
↓
HADLEY CELL → NE Trade Winds
↓
EQUATOR ← rising (ITCZ)
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EQUATOR ← rising (ITCZ)
↑
HADLEY CELL → SE Trade Winds
↑
30°S ← sinking
↑
FERRELL CELL → Westerlies
↑
60°S ← rising
↑
POLAR CELL → Polar Easterlies
↑ sinking
SOUTH POLE (90°S)Earth rotates once every 24 hours → day/night cycle
Cause: Earth’s axis tilted 23.5° + orbit around Sun - Hemisphere tilted toward Sun = summer (direct rays, long days) - Hemisphere tilted away = winter (oblique rays, short days)
June Solstice (Jun 20-21)
N. Hemisphere Summer
☀️
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Sept Equinox ------🌍------ March Equinox
(Sep 22-23) (orbit) (Mar 20-21)
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December Solstice (Dec 21-22)
S. Hemisphere SummerSolar radiation → convection currents → Coriolis effect → prevailing winds → climate patterns → biome locations
Earth’s tilt creates seasons and shifts the ITCZ, determining where and when precipitation falls globally.
Watershed: All the land in an area that drains into a particular stream, river, lake, or wetland.
Description: The total land surface that drains water into the watershed’s outlet (can range from a few hectares to thousands).
Effect on Water Amount: 1. Larger areas collect more total precipitation 2. More water is channeled to the outlet 3. Example: Mississippi River drains nearly one-third of the U.S.
Description: Distance along the main water flow from beginning to outlet.
Effect on Water Amount: 1. Greater length increases travel time to outlet 2. Affects timing and concentration of water flow 3. Works with area to determine total water volume
Description: The steepness of land within the watershed.
Effect on Water Amount: 1. Gentle slopes: water moves slowly, more infiltration, less runoff, minimal erosion 2. Steep slopes: water moves fast, less infiltration, more runoff, substantial erosion and sediment
Description: Composition of soil particles (sand, silt, clay).
Effect on Water Amount: 1. Sandy soils: highly permeable, water infiltrates rapidly, less surface runoff 2. Clay soils: less permeable, more surface runoff, carries sediment easily
Description: Plants and root systems present in the watershed.
Effect on Water Amount: 1. With vegetation: roots hold soil, increase infiltration, reduce runoff, absorb nutrients 2. Without vegetation: increased erosion, more runoff, more sediment loss
Gyre: A large-scale pattern of water circulation that moves clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
Upwelling: The upward movement of ocean water toward the surface as a result of diverging currents.
Thermohaline circulation: An oceanic circulation pattern that drives the mixing of surface water and deep water.
Rain shadow: A region with dry conditions found on the leeward side of a mountain range as a result of humid winds from the ocean causing precipitation on the windward side.
El Niño–Southern Oscillation (ENSO): A reversal of wind and water currents in the South Pacific.
La Niña: Following an El Niño event, trade winds in the South Pacific reverse strongly, causing regions that were hot and dry to become cooler and wetter.
Direction: - Northern Hemisphere: Clockwise rotation - Southern Hemisphere: Counterclockwise rotation
Climate Effects: - Cold currents along west coasts → cooler temperatures (California Current) - Warm currents along east coasts → warmer temperatures (Gulf Stream)
Where: Along west coasts of continents
Process: Surface currents diverge → deeper water rises to replace it
Importance: - Brings nutrients from ocean bottom - Supports large phytoplankton populations → large fish populations - Critical for commercial fisheries
Process: 1. Gulf Stream carries warm water to cold North Atlantic 2. Evaporation and freezing leave salt behind → cold, salty water 3. Dense water sinks to ocean bottom 4. Deep current moves past Antarctica → northern Pacific 5. Water rises and returns to Gulf of Mexico (takes hundreds of years)
Climate Impact: England is 20°C (36°F) warmer in winter than Newfoundland (similar latitude) due to Gulf Stream
Climate Change Concern: Glacier melting → less salty North Atlantic → water won’t sink → could shut down circulation → much colder western Europe
Windward side (facing wind): - Humid ocean air rises up mountain - Adiabatic cooling → condensation - Heavy precipitation falls - Lush vegetation
Leeward side (away from wind): - Dry air descends mountain - Adiabatic heating - Warm, dry conditions → desert
Frequency: Every 3 to 7 years
What Happens: 1. Trade winds weaken or reverse 2. Warm water moves eastward toward South America 3. Suppresses upwelling off Peru coast 4. Lasts weeks to years
Global Impacts: - Reduced upwelling → fish populations crash - Southeastern U.S.: Cooler and wetter - Northern U.S., Canada, southern Africa, Southeast Asia: Unusually dry - Crop failures and food shortages - 2015-2016 ENSO: ~100 million people faced food shortages
Timing: Follows El Niño event
What Happens: Trade winds reverse back stronger than normal
Effects: Opposite of El Niño - hot/dry regions become cool/wet
Cycle: After La Niña, climate returns to normal for several years
Effect of soil compactness on the total gross growth of Brassica rapaTragedy of the commons: The tendency of a shared, limited resource to become depleted if it is not regulated in some way.
Externality: The cost or benefit of a good or service that is not included in the purchase price of that good or service, or otherwise accounted for.
Clear-cutting: A method of harvesting trees that involves removing all or almost all of the trees within an area.
Selective cutting: The method of harvesting trees that involves the removal of single trees or a relatively small number of trees from the larger forest.
Ecologically sustainable forestry: An approach to removing trees from forests in ways that do not unduly affect the viability of other noncommercial tree species.
Tree plantations: A large area typically planted with a single fast-growing tree species.
Endangered Species Act: A 1973 U.S. law designed to protect plant and animal species that are threatened with extinction, and the habitats that support those species.
Imagine a communal pasture where many farmers graze their sheep. Each individual farmer benefits from raising as many sheep as possible, so they are tempted to add more sheep to the pasture. However, when the total number of sheep exceeds the carrying capacity of the land, the sheep overgraze the pasture so plants cannot recover. The common land becomes degraded through loss of vegetation and soil erosion, and the sheep no longer have adequate nourishment. Eventually, the entire community suffers because farmers made decisions based only on short-term gain without considering the common good.
Why it happens: People act from self-interest for short-term gain without agreement or regulation on resource use.
Outcome: The shared resource becomes depleted and degraded, harming everyone in the long run.
Global fisheries are treated as commons, with fish being harvested from international waters without proper regulation. This has led to overexploitation and rapid decline of many commercially harvested fish species and has upset the balance of entire marine ecosystems.
Why it happens: No single entity owns or regulates these waters, so individual fishing operations maximize their catch without considering the sustainability of the fish populations.
Outcome: Fish populations decline dramatically, ecosystems are disrupted, and future fishing becomes less viable for everyone.
Clear-cutting has multiple negative environmental impacts:
Erosion: Especially on slopes, clear-cutting increases wind and water erosion, causing loss of soil and nutrients. This adds silt and sediment to nearby streams, harming aquatic populations by clogging fish gills.
Mudslides: Denuded slopes become prone to dangerous mudslides.
Soil compaction: Heavy machinery leads to soil compaction, reducing water infiltration during rain events, causing more erosion and increased flooding.
Carbon dioxide release: Increased sunlight and heat reaching the soil leads to increased microbial decomposition, releasing more CO₂ from the soil and contributing to climate change.
Water temperature increase: More sunlight reaches rivers and streams, raising water temperatures. Since colder water holds more dissolved oxygen, this results in lower oxygen concentrations that can harm aquatic species.
Biodiversity loss: Clear-cutting causes habitat alteration and destruction, breaking up large forests into smaller fragments, which decreases biodiversity.
Soil degradation: Fire or herbicides used to remove vegetation before replanting reduce soil organic matter and may contaminate water runoff.
Note: In heavily forested regions (like northern New England), clear-cutting can actually increase habitat diversity because it creates open areas in otherwise densely forested landscapes.
Environmental Positives: - Can increase habitat diversity in heavily forested regions - Can create suitable habitat for certain desired bird and mammal species - Ideal for fast-growing tree species with high sunlight requirements
Environmental Negatives: - Facilitates erosion - Reduces biodiversity - Increased sunlight raises temperature of soils and nearby rivers/streams - Releases carbon dioxide and contributes to climate change
Economic Positives: - Less expensive - Easiest method
Economic Negatives: - May reduce long-term timber value if soil becomes depleted
Environmental Positives: - Ideal for shade-tolerant tree species - Less extensive environmental impacts - Maintains forest structure with trees of varying ages
Environmental Negatives: - Still requires logging roads that fragment habitat and compact soil - May select against desirable individuals or species (removing the best trees) - Repeated selective cutting over generations may leave less desirable trees
Economic Positives: - Maintains forest productivity over time
Economic Negatives: - More expensive - More difficult to implement
Environmental Positives: - Maintains forest in as natural a state as possible - Often done without using fossil fuels - Protects both plants and animals
Environmental Negatives: - Still involves some habitat disruption
Economic Positives: - Provides long-term forest health
Economic Negatives: - Costly - More difficult - Yields less timber - Hard to compete economically with mechanized logging
Question 1: Convert to hectares and express in scientific notation for each.
Total forest in tropics of Central and South America: - 8,750,000 km² × (100 ha/1 km²) = 875,000,000 ha - Scientific notation: 8.75 × 10⁸ ha
Protected areas: - 3,500,000 km² × (100 ha/1 km²) = 350,000,000 ha - Scientific notation: 3.50 × 10⁸ ha
Question 2: Identify the percent of forest in protected areas.
Percent protected = (3.50 × 10⁸ ha) ÷ (8.75 × 10⁸ ha) = 0.40 × 100% = 40%
Answer: Approximately 40% of the forest in the tropics of Central and South America is in protected areas.
Agribusiness (Industrial Agriculture): Agriculture that applies mechanization and standardization to food production. Large-scale operations with extensive machinery and fossil fuel use.
Green Revolution (Third Agricultural Revolution): A shift in twentieth-century agricultural practices including mechanization, fertilization, irrigation, and improved crop varieties that dramatically increased food output.
Organic Fertilizer: Fertilizer composed of organic matter from plants and animals, typically animal manure and decomposed crop residues.
Synthetic Fertilizer (Inorganic Fertilizer): Commercially produced fertilizer using fossil fuels. Highly concentrated and produced by combusting natural gas to fix atmospheric nitrogen.
Waterlogging: Soil degradation from prolonged water saturation that impairs root growth by preventing oxygen access.
Salinization: Soil degradation when salts in irrigation water concentrate on soil surface through evaporation, reaching toxic levels that impede plant growth.
Pesticides: Natural or synthetic substances that kill or control pest organisms. The U.S. applies ~454 million kg annually, 90% for agriculture.
Insecticide: A pesticide targeting insects and other invertebrates that consume crops.
Herbicide: A pesticide targeting plant species (weeds) that compete with crops.
Monocropping: Large plantings of a single crop species or variety, often 405+ hectares in the U.S.
Energy Subsidy: The fossil fuel and human energy input per calorie of food produced beyond solar energy. Example: 5 calories input for 1 calorie of food = energy subsidy of 5.
Economic Pros: Reduces labor costs; economies of scale benefit large farms; faster planting and harvesting.
Economic Cons: High costs ($150,000+) make machinery unaffordable for small farms, creating competitive disadvantages and farm consolidation.
Environmental Pros: Increases production efficiency.
Environmental Cons: Heavy fossil fuel reliance (17% of U.S. commercial energy goes to food system); encourages monocropping, causing soil erosion and biodiversity loss.
Economic Pros: Reduces pesticide costs; increases yields and revenues; creates drought/salt-tolerant varieties. By 2020: 94% of U.S. corn, 96% of soybeans were GMO.
Economic Cons: Higher seed costs; creates dependency on seed companies; may limit market access.
Environmental Pros: Can reduce pesticide use; allows farming in harsh conditions; nutrient-enhanced crops (golden rice).
Environmental Cons: Risk of genes spreading to wild relatives; reduces genetic diversity; may eliminate beneficial traits; encourages monocropping.
Economic Pros: Maintains soil productivity; dramatically increases yields; synthetic fertilizers are concentrated and efficient.
Economic Cons: Significant investment required; vulnerable to fossil fuel price fluctuations.
Environmental Pros: Organic fertilizers improve soil structure and release nutrients slowly, reducing runoff.
Environmental Cons: Synthetic fertilizers require fossil fuels; causes nutrient runoff into waterways (Central Valley, Mississippi watershed); contributes to water pollution and eutrophication.
Economic Pros: Enables crop growth in arid regions (California’s Imperial Valley); 16% of irrigated land produces 40% of world’s food; increases yield reliability.
Economic Cons: Requires infrastructure and pumping costs; soil degradation reduces land value.
Environmental Pros: More efficient water use; targeted water delivery.
Environmental Cons: Depletes groundwater and aquifers; causes saltwater intrusion; leads to waterlogging and salinization; diverts water from natural ecosystems.
Economic Pros: Protects crops and maintains yields; reduces losses; enables consistent harvests.
Economic Cons: Ongoing expense; repeated applications needed; pest resistance requires more expensive chemicals.
Environmental Pros: Selective pesticides can target specific pests with minimal harm to others.
Environmental Cons: Harms beneficial organisms (pollinators, predators); contaminates waterways; health risks for farm workers; broad-spectrum types kill indiscriminately; reduces biodiversity.
Definition: The mechanical process of turning over and breaking up soil using tools or machinery to prepare land for planting crops.
Why It’s Done: - Prepares soil for planting by creating a suitable seedbed - Helps incorporate crop residues and organic matter into the soil - Controls weeds by burying them - Aerates compacted soil - Facilitates water infiltration
Environmental Effects:
Negative: - Soil Erosion: Exposes bare soil to wind and water erosion, leading to loss of topsoil (as noted in the text, certain U.S. farmland loses an average of 1 metric ton of topsoil per hectare per year to wind erosion) - Loss of Soil Structure: Breaks down soil aggregates and disrupts soil biology - Carbon Release: Releases stored carbon from soil into the atmosphere as CO₂, contributing to climate change - Habitat Destruction: Disrupts soil ecosystems and organisms
Positive: - Can improve short-term soil aeration and drainage - Helps mix nutrients throughout the soil profile
Economic Effects:
Positive: - Increases short-term crop yields by creating optimal planting conditions - Reduces initial weed competition
Negative: - Requires expensive equipment and fuel (tractors, plows) - Long-term soil degradation can reduce productivity and require more inputs - Increased erosion leads to loss of valuable topsoil
Definition: A traditional farming method where vegetation is cut down and burned to clear land for cultivation. After a few years of farming, the land is abandoned and allowed to regenerate while farmers move to a new plot.
Why It’s Done: - Clears land quickly for planting in forested areas - Burning releases nutrients from vegetation into the soil as ash - Provides temporary fertilization for crops - Traditional method used by subsistence farmers, especially in tropical regions - Works well when population density is low and fallow periods are long enough
Environmental Effects:
Negative: - Deforestation: Permanently removes forest when fallow periods are too short or populations grow - Biodiversity Loss: Destroys habitat for native species - Air Pollution: Burning releases smoke, particulate matter, and greenhouse gases - Soil Degradation: Without adequate fallow periods, soil nutrients become depleted - Climate Impact: Contributes to atmospheric CO₂ and reduces carbon sequestration - Erosion: Exposed soil is vulnerable to erosion, especially in tropical areas with heavy rainfall
Positive: - Can be sustainable with long fallow periods (10-20+ years) and low population density - Allows forest regeneration when practiced traditionally - Maintains some biodiversity when rotation periods are adequate
Economic Effects:
Positive: - Low initial cost (minimal equipment needed) - Provides food for subsistence farmers - Ash provides free fertilization initially
Negative: - Yields decline rapidly after initial planting - Requires large land areas for rotation - Not economically viable for commercial agriculture - Long-term soil degradation reduces future productivity - Clearing new land becomes increasingly difficult as available forest diminishes
Definition: Substances added to soil to provide essential nutrients (primarily nitrogen, phosphorus, and potassium) that foster plant growth where one or more nutrients are lacking.
Types: - Organic Fertilizers: Composed of organic matter from plants and animals (manure, compost, crop residues) - Synthetic/Inorganic Fertilizers: Produced commercially, normally with the use of fossil fuels (concentrated chemical nutrients)
Why They’re Done: - Replenish nutrients removed from soil when crops are harvested - Increase crop yields and productivity - Allow continuous production on the same land - Compensate for nutrient depletion in intensive agriculture - Enable crops to grow in nutrient-poor soils
Environmental Effects:
Negative: - Nutrient Runoff: Excess nitrogen and phosphorus wash into waterways, causing eutrophication and dead zones - Water Pollution: Contaminates drinking water sources - Fossil Fuel Dependence: Synthetic fertilizer production (especially nitrogen) requires large amounts of fossil fuel energy - Greenhouse Gas Emissions: Production and application release CO₂ and N₂O (a potent greenhouse gas) - Soil Acidification: Some synthetic fertilizers can lower soil pH over time - Groundwater Contamination: Leaching of nitrates into aquifers
Positive: - Dramatically increases crop yields (essential to the Green Revolution) - Allows sustained food production on the same land - Organic fertilizers improve soil structure and biology - Can restore degraded soils when used properly
Economic Effects:
Positive: - Significantly increases crop yields and farm revenues - Higher productivity per acre of land - Enables commercial-scale agriculture - Lower food prices for consumers due to increased production - Essential for feeding growing global population
Negative: - Synthetic fertilizers represent a major expense for farmers - Heavy reliance on fossil fuels makes costs vulnerable to energy price fluctuations - Environmental cleanup costs from nutrient pollution - Organic fertilizers may provide lower short-term yields compared to synthetic options - Over-application wastes money without additional benefit
Aquifer: Pore spaces within permeable rock and sediment that store groundwater.
Unconfined Aquifer: Porous rock covered by soil where water easily flows in and out. Rapidly recharged.
Confined Aquifer: Aquifer surrounded by impermeable rock or clay. Recharges very slowly (10,000-20,000 years); water is under pressure.
Groundwater Recharge: Process by which precipitation percolates through soil into groundwater.
Spring: Water that naturally percolates up to the surface from an aquifer opening.
Artesian Well: Well drilled into confined aquifer where pressure causes water to rise, sometimes requiring no pump.
Water Footprint: Total daily per capita freshwater use for a country (agriculture, industry, residences divided by population).
Cone of Depression: Area around a well lacking groundwater, created when withdrawal exceeds recharge rate.
Definition: Pesticides that remain in the environment for years to decades
Example: DDT (dichlorodiphenyltrichloroethane)
Adverse Effects: - Accumulate in fatty tissues of animals through bioaccumulation - Can biomagnify up the food chain - DDT caused eagles and pelicans to lay eggs with thin shells that cracked during incubation - Long-term environmental contamination - Banned in the U.S. in 1972 due to environmental damage
Definition: Pesticides that break down relatively rapidly, usually in weeks to months
Example: Glyphosate (trade name: Roundup)
Adverse Effects: - Must be applied more often due to rapid breakdown - Overall environmental impact may not always be lower than persistent pesticides despite breaking down faster - Repeated applications increase exposure and costs - Can still cause runoff into surface waters and groundwater pollution
Pesticide resistance develops through artificial selection, a process similar to natural selection:
Genetic Variation: Large pest populations contain significant genetic diversity; a few individuals naturally have genes that make them less susceptible to pesticides
Selection Pressure: When pesticide is applied, it kills most susceptible individuals but some resistant individuals survive
Differential Survival: Resistant individuals survive and reproduce while susceptible individuals die
Increased Frequency: The next generation contains a larger fraction of resistant individuals because they inherited resistance genes from survivors
Evolution Over Time: With repeated pesticide applications, resistant individuals make up larger portions of the population, and resistance becomes more effective
Pesticide Failure: Eventually the pesticide becomes significantly less useful, requiring farmers to use higher doses or develop new pesticides
This cycle of pesticide development → pest resistance → new pesticide development is called the pesticide treadmill. It’s an example of a positive feedback system where the solution (pesticide) creates the problem (resistance) that requires more of the solution.
Genetic engineering aims to reduce pesticide use and increase crop resistance to pests and herbicides.
Bt Crops (Bacillus thuringiensis): - Gene from soil bacterium Bacillus thuringiensis inserted into crop plants (especially corn) - Produces natural toxin that kills lepidopteran larvae (butterfly and moth pests like bollworm and European corn borer) - Plants produce their own insecticide in their leaves - Reduces need for external pesticide applications
Herbicide-Tolerant (HT) Crops: - “Roundup Ready” gene allows crops to resist herbicide Roundup (glyphosate) - Farmers can spray herbicide on fields to control weeds without harming crop plants - Widely used in corn, soybean, and cotton - Enables no-till agriculture practices
An alternative approach using multiple techniques: - Crop rotation and intercropping - Pest-resistant crop varieties - Creating habitats for natural predators of pests - Limited, strategic pesticide use
CAFO (Concentrated Animal Feeding Operation): Large indoor or outdoor structure designed for maximum animal occupancy and meat output, with animals confined in small spaces (e.g., 2,500 hogs or 50,000 turkeys per building).
Manure Lagoon: Large, rubber-lined pond that holds livestock manure. Bacteria break down the waste before it’s spread on fields as fertilizer.
Free Range Grazing: Allowing animals to graze outdoors on grass for most or all of their lifecycle.
Nomadic Grazing: Moving herds to seasonally productive feeding grounds over long distances, mimicking natural migration patterns and allowing vegetation regeneration.
Overgrazing: Excessive grazing that reduces/removes vegetation and erodes soil, occurring when animals graze too long in one location.
Desertification: Transformation of arable land to desert or unproductive land due to climate change or destructive land use like overgrazing.
Fishery: A commercially harvestable fish population within a particular ecological region.
Fishery Collapse: Decline of a fish population by 90% or more, harming both aquatic biodiversity and fishing livelihoods.
Bycatch: Unintentional catch of nontarget species while fishing, reducing populations of sharks, sea turtles, and other organisms.
Meat requires significantly more land than crops for the same caloric output:
Water & Waste: - Contamination of waterways from manure runoff (56,000 km of polluted rivers in 22 states) - Risk of manure lagoon leaks contaminating groundwater - CAFOs produce over 2,000 tons of manure annually per facility
Air Quality: - Manure lagoons release CO₂, methane, and nitrous oxide (greenhouse gases) - Anaerobic decomposition in waste storage
Land Degradation: - Nutrient runoff from over-applied manure - Overgrazing erodes soil and removes vegetation - Can lead to desertification in semiarid regions
Other Issues: - Antibiotic use creates resistant microorganisms - High fossil fuel energy use - Stream bank damage from improperly managed livestock
For CAFOs: - Properly lined manure lagoons to prevent leaks - Careful manure application to fields (avoid over-application) - Monitor for overflows and contamination
Alternative Methods: - Free-range: Natural waste dispersal, reduced antibiotics, soil processing by decomposers - Nomadic grazing: Rotation allows vegetation regeneration, mimics natural systems - Short-duration, high-density grazing followed by rotation - Overall: Reduce meat consumption to decrease demand
| Aspect | CAFOs | Free-Range | Nomadic Grazing |
|---|---|---|---|
| Economic Viability | High profits, low costs, lower consumer prices | Higher costs and prices, uses more land | Viable for low-productivity soils |
| Environmental Impact | High: massive waste, water contamination, greenhouse gases, high energy use | Lower: natural waste processing, less fossil fuel, more sustainable | Lowest: mimics nature, allows regeneration, prevents degradation |
| Land Use | Minimal direct space but large feed production footprint | More land needed | Large areas required for rotation |
| Sustainability | Low sustainability | Moderate-high if properly managed | Highest sustainability |
| Key Issues | Antibiotic resistance, ethical concerns, pollution | Can damage streams if mismanaged, higher prices | Requires large areas and mobility |
| Benefits | Fast growth, maximum output, feeds many people cheaply | Reduced disease/antibiotics, maintains grasslands | Soil carbon increase, mimics natural systems |
Trade-off Summary: CAFOs maximize efficiency and profit but minimize sustainability; free-range offers moderate efficiency with improved sustainability at higher costs; nomadic grazing provides maximum sustainability under specialized conditions.
Economic & Food Security: - Large immediate catches provide income for fishing industry - Over 3 billion people get 20% of animal protein from fish - Modern technology (sonar, spotter planes) enables efficient fishing - Factory ships can process catches for months at sea - Single nets can capture 3,000 tuna (450,000 kg) at once
Population & Ecosystem Collapse: - 30% of fisheries experienced 90% population decline - By 2017, 34% of fisheries were overfished - Loss of keystone species causes cascading ecosystem effects - Bycatch reduces nontarget species (sharks, sea turtles) - Dragnets damage ocean floor habitats (coral, sponges, plants) - Loss of juvenile fish and biodiversity
Industry Decline: - Fishers work harder but catch fewer fish - Fishery collapses force closures (e.g., Northwestern Atlantic cod) - Loss of livelihoods for fishing, processing, and selling - Tragedy of the commons: no individual country incentive to protect stocks
Management Solutions: - Quota systems (e.g., Alaska salmon recovery after 1973) - Government moratoriums on depleted fisheries - International cooperation required (fish cross borders) - Community-based regulation (e.g., Maine lobster) - Consumer choices for sustainable fish - Protection of critical marine habitats
Key Lesson: Short-term economic gains from overfishing lead to long-term environmental collapse and economic devastation, requiring sustainable management and reduced consumption.
Ores: Concentrated accumulations of minerals from which economically valuable materials can be extracted, typically characterized by the presence of valuable metals but can also include salt or sand.
Metals: Elements that conduct electricity and heat energy and perform other important functions. Examples include copper, nickel, aluminum, and gold.
Reserve: The known quantity of a resource that can be economically recovered. A resource is economically recoverable if its concentration in host rock is high enough to be profitably mined.
Strip mining: The removal of overlying vegetation and “strips” of soil and rock (overburden) to expose underlying ore when it’s relatively close to Earth’s surface.
Open-pit mining: A technique that creates a large visible pit or hole in the ground, used when resources are close to the surface but extend both horizontally and vertically beneath it.
Mountaintop removal: A technique where the entire top of a mountain is removed with explosives, with tailings deposited in lower-elevation regions.
Placer mining: The process of looking for minerals, metals, and precious stones in river sediments using water to separate heavier items from lighter materials.
Subsurface mining: Mining techniques used when desired resources are more than 100 meters (328 feet) below Earth’s surface, involving horizontal tunnels and vertical shafts.
Open-pit mining accesses resources close to the surface that extend both horizontally and vertically. These more accessible, high-concentration ores are generally mined first.
Subsurface mining targets resources more than 100 meters deep. As accessible ores are depleted, operations must pursue lower-concentration, less accessible ores at greater depths, requiring more energy and creating more disturbance, pollution, and waste.
Open-pit mining: - Creates large visible pits - Produces significant dust and particulate matter - Contaminates water percolating through tailings - Completely removes soil (may be replaced with reclamation) - Destroys habitat over large surface areas
Subsurface mining: - Less visually apparent impacts - Creates acid mine drainage from water passing through tailings - Requires continuous pumping that lowers pH of nearby soils and streams - Road construction fragments habitat - Emissions from fossil fuel-powered equipment
Open-pit mining is generally less expensive with lower labor costs, fewer safety requirements, and more efficient large-scale extraction.
Subsurface mining is almost always more expensive, requiring extensive infrastructure (tunnels, shafts, elevators), continuous pumping, and higher insurance and safety costs.
Habitat destruction: Mining roads and railroad beds fragment habitat. Surface mining causes complete habitat destruction over mined areas.
Soil impacts: Strip mining removes vegetation and soil, increasing erosion. Soil removal may not be effectively replaced even with reclamation.
Water contamination: Mine tailings contaminate water through percolation. Acid mine drainage occurs when water becomes acidic and leaches metals from tailings, damaging ecosystems.
Air pollution: Surface mining produces dust and particulates. All mining creates emissions from equipment. Coal mining releases methane, a potent greenhouse gas.
Mine tailings: Waste materials containing chemicals, rock residues, and trace metals contaminate land and water. In mountaintop removal, tailings obstruct rivers and contaminate groundwater.
Stream and river damage: Mountaintop removal deposits tailings in valleys, permanently altering waterways. Placer mining contaminates rivers with sediment and sometimes toxic mercury.
Mercury contamination: Used in some placer mining operations, mercury is highly volatile and harmful to plants, animals, and humans, particularly damaging children’s central nervous systems.
Long-term degradation: As easily mined resources deplete, extraction becomes more expensive and environmentally destructive, generating greater amounts of tailings.
Ecological Footprint: A measure of the area of land and water an individual, population, or activity requires to produce all the resources it consumes and to process the waste it generates. Expressed in hectares (ha).
Fair Earthshare: The area of biologically productive land on Earth divided by the number of people on Earth (currently 1.6 ha per person).
Carbon Footprint: A measure of the total carbon dioxide and other greenhouse gas emissions from the activities, both direct and indirect, of a person, country, or other entity.
Embodied Energy: The energy required to manufacture a product.
Land needed for: food production, water/energy use, clothing, structures, transportation, waste processing, and product manufacturing
| Country | Hectares per person | Times over Fair Earthshare |
|---|---|---|
| United States | 8.0 ha | 5× |
| Germany | 4.7 ha | 3× |
| China | 3.7 ha | 2.3× |
| World Average | 2.8 ha | 1.75× |
| India | 1.2 ha | Below fair share |
Developed Countries (Larger): - More automobiles and appliances - Higher resource consumption - Larger meat consumption - More manufacturing waste
Developing Countries (Smaller): - Fewer consumer goods - Less energy consumption - Less resource-intensive lifestyles
Transportation (30% of U.S. total): - Cars/SUVs/light trucks: 57% - Heavy-duty trucks: 24%
Food (15-30% of household): - Meat: 57% - Dairy: 18%
Ways to Reduce: Reduce meat consumption, substitute chicken for beef, use public transit
| Aspect | Ecological Footprint | Carbon Footprint |
|---|---|---|
| Scope | Comprehensive | Greenhouse gases only |
| Measurement | Hectares of land | Tons of CO₂e |
| Includes | All environmental impacts | Climate-related emissions |
Sustainability: Being able to use a resource or engage in an activity now without jeopardizing the ability of future generations to engage in similar activities later.
Sustainable Development: Development that balances current human well-being and economic advancement with resource management for the benefit of future generations.
Maximum Sustainable Yield (MSY): The largest quantity of a renewable resource that can be harvested indefinitely, typically when the population is maintained at about one-half the carrying capacity.
Environmental Indicators: Measurements that describe the current state of an environmental system or the Earth.
Developed nations (17% of global population) use disproportionate resources: - Own 62% of world’s automobiles - Consume 36% of all meat and fish - Release 35% of carbon dioxide
Crop rotation: Planting different crop species from season to season or year to year on the same plot of land.
Intercropping: Physical spacing of different crops growing simultaneously in close proximity to promote biological interaction.
Biocontrol: Using biological organisms to control agricultural pests.
Sustainable agriculture: Fulfills food and fiber needs while enhancing soil quality, minimizing nonrenewable resource use, and maintaining economic viability.
Soil conservation: Preventing erosion while increasing soil depth, nutrient content, and organic matter.
Windbreaks: Tall objects planted to break wind and prevent soil erosion.
Strip cropping: Planting crops with different spacing and rooting characteristics in alternating rows to prevent erosion.
Contour plowing: Plowing and harvesting parallel to topographic contours.
Cover crop: Crop planted when soil would otherwise be bare to reduce erosion.
Terracing: Shaping sloping land into flat, step-like terraces.
Perennial plants: Plants living multiple years without needing replanting each season.
No-till agriculture: Not tilling or plowing soil between seasons in annual crop fields.
Green manure: Plant material grown to be plowed under at season’s end.
Limestone: Ground calcium carbonate rock used as fertilizer.
Rotational grazing: Rotating farm animals to different pastures to prevent overgrazing.
Delaney Clause: Clause designed to prevent cancer-causing food ingredients (1958).
IPM uses varied techniques to control pests while minimizing pesticide inputs and increasing output. Techniques include crop rotation, intercropping, biocontrol, and limited pesticide use.
Crop Rotation: Planting different crops each season reduces crop-specific pests and diseases. When pests emerge and find a different crop, they lack a suitable host and die. Example: Colorado potato beetles overwinter in soil, so rotating away from potatoes eliminates their food source.
Biocontrol/Natural Predators: Providing habitats for natural predators of crop pests. Example: Wasps lay eggs in caterpillars (crop pests), so providing wasp habitats encourages them to control caterpillar populations naturally.
Method 1 - Contour Plowing Plowing parallel to topographic contours prevents water erosion while maintaining plowing advantages.
Method 2 - No-Till Agriculture Leaving crop residues and not plowing between seasons keeps intact roots holding soil in place, reducing wind and water erosion. Undisturbed soil regenerates natural horizons and reduces CO₂ emissions through less oxidation. Retains 83% of native grassland carbon versus only 71% for tilled farmland.
Reforestation: The natural or intentional restocking of trees after clear-cutting to repopulate the forest, reduce erosion, and begin the process of removing carbon dioxide from the atmosphere.
Sustainable Forestry: A methodology for managing forests so they provide wood while also providing clean water, maximum biodiversity, and maximum carbon sequestration in both trees and soil.
Prescribed Burn: When a fire is deliberately set under controlled conditions, thereby decreasing the accumulation of dead biomass on the forest floor.
Environmental: - Reduces pressure on overfished wild populations - More energy efficient than wild-caught fishing (less travel distance) - Above-ground tanks reduce disease transmission and prevent fish escape to wild populations
Economic: - Helps meet growing global demand for fish - Provides protein for over 1 billion undernourished people - Boosts economies of developing countries - Expected to be responsible for all increases in global fish production through 2050
Environmental: - Wastewater contains feces, uneaten food, and antibiotics that pollute water - Can spread bacteria, viruses, and pests (like sea lice) to wild populations - Escaped fish may compete with, interbreed with, or spread diseases to wild fish - High-density habitats promote disease and require antibiotic use - Requires water and energy for filtration, heating/cooling
Economic: - Could negatively impact ocean fishing operations - Higher costs for sustainable operations
Positive Effects: - Liberates nutrients tied up in dead biomass for new growth - Creates openings for early successional species - Provides nutrient-rich habitat that attracts herbivores - Supports natural nutrient cycling and regeneration - Reduces risk of uncontrolled, catastrophic fires
Example: The 1988 Yellowstone fires burned over one-third of the park but created new habitats for early successional plants that attracted wildlife. Today, over 30 years later, the forest has fully recovered.
Biofuels - Liquid fuels such as ethanol or biodiesel created from processed or refined biomass.
Carbon Neutral - An activity that does not change atmospheric CO₂ concentrations.
Coal - A solid fuel formed primarily from the remains of trees, ferns, and other plant materials that were preserved 280 million to 360 million years ago.
Peat - A precursor to coal, made up of partly decomposed organic material, including mosses.
Lignite - A brown coal that is a soft sedimentary rock that sometimes shows traces of plant structure; it typically contains 60 to 70 percent carbon.
Bituminous Coal - A black or dark brown coal that contains bitumen (asphalt). It typically contains up to 80 percent carbon.
Asphalt - Also known as bitumen; a thick, oily substance found in bituminous coal and tar sands.
Anthracite (Hard Coal) - Contains greater than 90 percent carbon. It has the highest quantity of energy per volume of coal and the fewest impurities.
Crude Oil - A mixture of hydrocarbons such as oil, gasoline, kerosene as well as water and sulfur that exists in a liquid state underground and when brought to the surface.
Tar Sands (Oil Sands) - Slow-flowing, viscous deposits of bitumen or asphalt, mixed with sand, water, and clay.
Capacity - The maximum electrical output of something such as a power plant.
Cogeneration - The use of a fuel to both generate electricity and deliver heat to a building or industrial process. Also known as combined heat and power.
Wood: - Heating and cooking (2-3 billion people worldwide) - Primary heating fuel for ~3 million U.S. homes - Made into charcoal (twice the energy content per unit mass)
Coal Types: - Lignite - Lower energy content; electricity generation - Bituminous Coal - Electricity generation and industrial processes - Anthracite - Highest energy content; maximum energy applications
Natural Gas: - Electricity generation and industrial processes - Home use: cooking, heating, water heaters - Vehicle fuel (CNG) and portable uses (LPG)
Crude Oil: - Refined into gasoline, diesel, kerosene, tar, asphalt - Best for mobile combustion (vehicles)
Tar Sands: - Surface mining extraction; produces crude oil - More energy-intensive than conventional drilling
Natural gas is considered the cleanest fossil fuel.
Composition: 80-95% methane (CH₄), 5-20% ethane, propane, and butane
Why it’s cleanest: - Very few impurities - Produces less particulates, sulfur dioxide, and carbon dioxide than oil or coal - Burns cleanly (though still produces CO₂, a major greenhouse gas)
COGENERATION POWER PLANT
Fuel (Coal/Natural Gas)
↓
[Boiler/Combustion]
↓
STEAM
/ \
/ \
↓ ↓
[Turbine] [Heat for Buildings/
↓ Industrial Process]
[Generator]
↓
ELECTRICITYEfficiency: Cogeneration achieves up to 90% efficiency vs. ~35% for electricity generation alone and ~75% for steam heating alone.