Unit 4 - APES

Module 3 - Aquatic Biomes

• A biome and species in the biome are determined by a few factors such as temperature, salinity, nutrient availability or turbidity.

• 70% of Earths surface - body of water.

• Water is found in 5 main areas, not including water vapor and precipitation. 

  • 97% oceans - salt water

  • 3% fresh water - ice / glaciers, groundwater / aquifers, lakes / rivers, atmosphere / such as water vapor.

What are the major freshwater biomes? - low salinity

• Streams and rivers

  • Freshwater - underground springs, runoff (rain , melting snow), streams (narrow, small amounts of water), rivers (wider, more water)

  • Streams combine with rivers at one point allowing a river formation 

  • Streams, rapid flowing rivers - low algae / plants - instead have OG from terrestrial biomes and leaves providing energy for organisms

  • Fast moving streams have turbulent water (rapids), water & air mix, causes atmospheric oxygen to get dissolved. 

  • High O supports salmon and trout, low O supports catfish

  • Threats to streams and rivers - excess nutrients / pollutants 

• Lakes and ponds

  • Standing water - too deep to support emergent vegetation

  • Lakes larger than pools

  • Fish in ponds - sunfish, bass, pike

Littoral zone - The shallow zone of soil and water in lakes and pounds near the shore here most algae and emergent plants such as cattails grow. - highest photosynthesis

Limnetic zone - A zone of open water in lakes and ponds as deep as the sunlight can penetrate. - Phytoplankton - only photosynthesis organisms in this zone. 

Profoundal zone - A region of water where sunlight does not reach, below the limnetic zone in very deep lakes.  - Nutrients not taken up. Bacteria decomposes detritus and consumes oxygen. DO low, cant support large organisms. 

Benthic zone - The muddy bottom of a lake, pond, or ocean beneath the limnetic and profundal zones.

• Lakes can also be classified through fertility levels. 

  • Oligotrophic - Describes a lake with low level of phytoplankton due to low level oh phytoplankton due to low amounts of nutrients in the water. 

    • Negative impacts to oligotrophic lakes is that they are getting polluted due to human activities cause high nutrient levels, causing less clear, more algae. 

  • Mesotrophic - Describes a lake with a moderate level of fertility.

  • Eutrophic - Describes a lake with high fertility. - high algae, high water turbidity,

• Freshwater Wetlands

  • Def : An aquatic biome that is submerged or saturated by water for at least part of each year, but shallow enough to support emergent vegetation.

  • types - swamps, marshes, and bogs

  • Contain trees, non woody vegetation such as cattails and sedges

  • Bogs - acidic wetlands - include moss and spruce trees

  • Most productive biome - absorb large amounts of rainwater, reduces floods, filter pollutants, provide for drinking water

What are major marine biomes?

• Estuaries and Salt Marshes 

  • Estuaries - Areas along the coast where the freshwater of rivers mixes with salt water from the ocean. 

    • Productive areas for plants and algae, filters pollutants

  • Salt marsh - Found along the coast in temperate climates, a marsh containing nonwoody emergent vegetation. 

    • Habitat for fish and shellfish, recently pollution here is an issue

• Mangrove Swamps 

  • Occur along tropical and subtropical coasts and like freshwater swamps, contains trees whose roots are submerged in water.

  • Salt tolerant

  • Often grown in estuaries, can be found along shallow coastlines which lack freshwater. 

  • Protect coast from erosion and storm damage

  • Shelter habitat

  • ⅓ of mangroves have been destroyed by humans for habitat or agriculture

• Intertidal Zone

  • A narrow band of coastline that exists between the levels of high tide and low tide.

  • Steep, rocky - broad, mudflats

  • Stable environment during high tide

  • Harsh conditions such as organisms exposed to high levels of direct sunlight, high temp. , dry outs during low tide

  • Home to algae, mussels, crab, sea stars, etc..

  • Threats : oil spills, pollution, chemicals

• Coral Reefs

  • Most diverse marine biome, found in warm, shallow waters beyond the shoreline in tropical regions. 

  • Shallow waters where sunlight can reach

  • Coral live in low nutrient and food areas

  • When digesting food releases CO2 and nutrients, algae uses that to produce sugars, which coral uses to gain energy

  • Coral live is vast colonies

  • Even after decomposition their limestone skeleton remains

  • Coral bleaching is also a growing problem, where algae inside corals die causing the coral to turn white. 

    • This algae death is known to occur because of lower pH, high water temps. Or a disease. 

• The Open Ocean

  • Contains deep ocean water that is located away from the shoreline where sunlight can no longer reach the ocean bottom. 

  • Like pond or lake, ocean also divided into zones.

    • Photic Zone - Upper layer of ocean water where the ocean receives enough sunlight for photosynthesis.

      • Major photosynthesis organisms. 

      • Forms the base of the food web including fish, wales, phytoplankton.

    • Aphotic Zone - The deeper layer of ocean water that lacks sufficient sunlight for photosynthesis. 

      • No sunlight - no plants - no photosynthesis 

      • Some bacteria can be found, they use chemosynthesis, which is a process to generate energy using methane and hydrogen sulfide. 

        • This bacteria forms deep-ocean food web including tube worms, etc.. 

      • Includes organisms which can generate their own light - jellyfish, squid, etc..

Module 34 - Aquaculture and Sustainable Forestry

Environmental benefits and consequences of Aquaculture : 

• Benefits : 

  • Increased global fish production

  • Boost economies of developing countries

• Negative Effects : 

  • Global demand is increasing

  • Many different factors to consider, when keeping the fish secure, netted and protected

  • Waste water is pumped out on the other side including many pollutants

  • Fish that escapes can harm wild fish populations 

Some inventions were made to dispose fish waste, filtration, repumping water, etc… this can help to reduce environmental impacts. 

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.

Module 19 - Plate Tectonics

• 4.6 billion years ago, Earth formed from cosmic dust.

Layers of the Earth…  

Core - The innermost zone of the Earths interior, composed mostly of iron and nickel. It includes a liquid outer layer and a soldi inner layer.

Mantle - The layer of Earth above the core, containing magma, the asthenosphere, and the solid upper mantle. 

• Has three layers             

  • Inner layer contains magma and molten rock

  • Asthenosphere - The layer of Earth located in the outer part of the mantle, composed of semi-molten rock. 

  • Crust - distinct layer 

Lithosphere - The outermost layer of Earth, including the solid upper mantle and crust.

Made up of numerous plates

Before the 1900s people believed that continents and oceans were in a fixed spot, however they soon find out that continents and ocean floors are slowly moving… 

The Theory of Tectonic Plates

German meteorologist - Alfred Wegner proposed a theory where all the continents were joined and called Pangaea. 

• Evidence for different fossils were found in South America and Africa, but are separated by an ocean. 

This is possible as the theory that ocean floors were flat was proven wrong, instead there are many mountains and canyons underwater, leading to the idea of plate tectonics. They believed the lithosphere consists of number of tectonic plates.

Plate Tectonics - The theory that the lithosphere of Earth is divided into plates, most of which are in constant movement. 

Earthquakes and Volcanoes 

Earthquakes : 

• Sometimes plates movements are not slow. The rocks could collide or slide too quick causing a Earthquake - student movement of Earths crust caused by a release in potential energy from the movement of tectonic plates.

• Magnitude measured with the Richter scale.

• For each unit increase the value increases by 10. 

  • Ex. 7.0 magnitude is 10 times larger than 6.0 magnitude.

Volcanoes : 

• Heat causes plums of hot magma to well upwards, producing hot spots, places where molten material from the mantle reaches the lithosphere. 

• When a plate moves over the hot spot, it creates a volcano due the plate melting.

If earthquakes or volcanoes occur underwater it causes a Tsunami, a series of waves un the ocean caused by seismic (vibrations) activity or undersea volcano that causes massive displacement of water.

Divergents, Convergent, and Transform Boundaries

Oceanic plates are more dense that tectonic plates, they both “float” above denser material. The movements of both occur in response to the circulation of magma in the mantle. 

• Tectonic plates move away from each other, divergent boundary occurs, an area below the ocean where tectonic plates move away from each other. 

  • Divergent boundaries in the ocean floor cause seafloor spreading, where rising magma forms new oceanic crust on the seafloor at the boundaries between those plates.

    • Locations of divergent boundaries can produce volcanoes, earthquake and rift valleys.

• Convergent boundaries, which occur as one plate moves towards another plate and collides. 

  • There are two outcomes : 

    • Subduction - The process in which the edge of an oceanic plate moves downward beneath the continental plate and is pushed towards the center of Earth. 

      • In areas where subduction occurs we can see island arcs, which are chains of islands formed by volcanoes as a result of two tectonic plates coming together. 

    • Collision zone - An area where two continental plates are pished together and the colliding forces push up the crust to form a mountain range. 

• Transform fault boundary - An area where the tectonics plates move sideways past each other. 

  • In these areas a fault is common, a fracture in rock caused by the movement of the Earths crust. 

Consequences of Plate Movement on Biodiversity

Since continents are moving, the weather and geographic barrier / location has changed, causing certain species to adapt, or go extinct. 

Due to this sometimes the continent which has two plates break apart, creating two separate continents with different climates, and environmental factors. 

Environmental and Human Impacts of Earthquakes and Volcanoes

Earthquakes : 

• Moderate earthquakes could cause fires, contamination in water and even building destruction. Quality of the building is important as the magnitude could easily break it down. Epicenter also affects the intensity of the earthquake and damage. 

• Safety precautions must be taken when dangerous materials are used in eqarth quake active areas such as nuclear powers. 

Volcanoes : 

• The eruptions can result in habitat destruction, air quality reduction, etc…

• An example volcano erupted ash which contain silicon dioxide which is destructing to aircrafts such as airplanes, so air travel was banned until that was cleared.

These two disasters have impacts on biodiversity and humans which are in close proximity. 

Module 28 - Impacts of Overfishing

Causes and Consequences of Overfishing : 

• Leads to fishery decline, reducing fish populations.

• Global fish production has doubled in the last 40 years due to aquaculture, but wild-caught fish have declined. 

• Coastal populations such as Africa and Asia, rely on fish for protein.

• No single country has an incentive to protect fish stocks in international waters.

Fishery Collapse : 

• Defined as a 90% or more decline in the fish population.

  • Example : A 2006 study found 30% of global fisheries had collapsed. 

• Overfishing has led to a decline in large predatory fish like cod, tuna and sharks.

Major Commercial Fishing Methods : 

• Purse Seine Nets - Surrounds entire schools of fish.

• Bottom Trawl Nets - Drag along the ocean floor, damaging habitats.

• Midwater Trawl Nets - Used in the middle of the water column.

• Gill Nets - Fish get caught in holes too small for them to escape.

• Longlines - Baited hooks that can be miles long, often leading to bycatch.

Bycatch (Unintentional Catch of Non-target Species)

• Affects sharks, sea turtles, and other marine species.

• Some countries enforce regulations to reduce bycatch.

Fishery Collapses and Recovery Efforts

Northwestern Atlantic Fisheries (Cod Collapse) : 

• Overfishing led to a major decline in cod populations by the 1990s. 

• Even after strict regulations, recovery has been slow. 

Alaska Salmon Fishery (Successful Recovery Example) : 

• Overfishing in the early 1900s led to a decline in salmon populations.

• In 1973, a quota system was introduced, stabilizing and eventually increasing salmon populations.

Sustainable Fishing Practices : 

• International cooperation is necessary as fish stocks cross national borders.

• Governments regulate fishing through quotas, gear restrictions, and habitat protection.

• Consumer awareness : Organizations such as Environmental Defense Fund,  rank seafood choices as “Best”, “Good”, or “Avoid” to promote sustainable fishing.

  • Example : The Maine lobster fishery is considered sustainable due to strict regulations.

Key elements : 

• Overfishing threatens marine biodiversity and food security.

• Some fisheries have collapsed, while others (like Alaska salmon) have recovered due to management efforts. 

• Sustainable fishing relies on regulations, quotas, and consumer awareness.

Module 10 - Island Biogeography

1. Introduction to Island Biogeography

    •    Definition: The study of how species are distributed and interact on islands.

    •    Larger islands tend to support more species than smaller islands.

2. Species-Area Relationship

    •    Species-Area Curve: Shows the relationship between island size and species richness.

    •    Larger islands contain more species due to greater habitat diversity and resources.

    •    Equation:  (straight-line relationship on a log scale).

    •    Logarithmic Form:

Log S = zlogA + log c

    •  S   = species richness

    •  A   = island area

    •  z   = slope of the line

    •  c  = intercept

This formula shows that as island area increases, species richness increases in a predictable way.

3. Factors Affecting Species Richness on Islands

•     1.    Island Size: Larger islands support more species.

•     2.    Isolation (Distance from Mainland):

    •    Closer islands receive more migrating species.

    •    Farther islands have lower immigration rates.

4. Observations from Studies

    •    Studies in the West Indies, Malaysia, Philippines, and New Guinea confirm a linear species-area relationship.

    •    Wetlands in Ontario show similar patterns (species-area curves hold true for non-oceanic isolated habitats).

5. Ecological Effects of Island Size

    •    Small islands:

    •    Lack large predators.

    •    Overpopulation of primary consumers leads to overgrazing.

    •    Example: Lago Guri (Venezuela) – Small islands lost predators, leading to excessive herbivory and lower plant survival.

    •    Large islands:

    •    Support a stable food chain with predators and diverse species.

6. Combined Effects of Island Area and Distance

    •    Larger islands near the mainland have the highest species richness.

    •    Far islands have fewer species even if they are large (fewer immigrations).

    •    Example: Bird species in the South Pacific – Larger islands closer to New Guinea had more species.

7. Observing Island-Like Effects on Mountains

    •    Mountain “islands”: Higher mountains in the U.S. Southwest had more mammal species.

    •    More isolated mountain ranges had fewer species, mimicking true islands.

8. Experimental Demonstration of Distance Effect

    •    Researchers tested colonization by studying small islands in Florida with mangrove trees.

    •    Islands closer to the mainland had faster recolonization rates after disturbances.

Key Takeaways

•  Larger islands = More species

•  Closer islands = Higher immigration, more species

•  Island-like habitats (wetlands, mountains) follow similar species-area patterns

•  Predator presence on large islands maintains ecological balance

Experiment on Island Distance and Colonization

    •    Researchers studied small islands off Florida, measuring invertebrate species before and after fumigation.

    •    Islands closer to the mainland had faster recolonization and more species.

    •    Islands farther away had slower recolonization and fewer species.

Model of Island Biogeography

    •    Scientists developed a model predicting species numbers based on island size and distance from the mainland.

    •    Key curves:

    •    Colonization rate (orange curve): Higher when species are low, declines as the island fills.

    •    Extinction rate (blue curve): Increases as more species compete for resources.

    •    Equilibrium point (Ŝ): The number of species stabilizes where colonization = extinction.

Effects of Island Size and Distance

    •    Larger islands: Lower extinction rates, can support more species.

    •    Smaller islands: Higher extinction rates, fewer species.

    •    Near islands: Higher colonization rates, more species.

    •    Far islands: Lower colonization rates, fewer species.

    •    Prediction: Large near islands have the most species, small far islands the least.

Implications for Species Conservation

    •    Larger protected land areas support more biodiversity.

    •    Islands near the mainland are easier to repopulate after species loss.

    •    Knowledge of island biogeography helps guide conservation efforts.

Island Species Vulnerability to Invasive Species

    •    Many island species are specialists, highly adapted to specific conditions.

    •    Lack of predators and exposure to few diseases makes them vulnerable.

    •    Example: The brown tree snake introduced to Guam led to massive declines in birds, bats, and lizards.

    •    Generalist invasive species (rats, snakes, mosquitoes) often outcompete native specialists.

Extinction Risk of Island Species

    •    Almost half of recorded extinctions in the past 400 years were island species.

    •    90% of extinct bird species were from islands.

    •    Conservation efforts must prioritize protecting island habitats and preventing invasive species.

Module 48 - Human Impacts on Wetlands and Mangroves

Human Impacts on Water Availability 

• Humans after water availability by controlling its movement.

• Water is moved through channels, dams and diversions. 

• Only 3% of Earth's water is freshwater, and even less is accessible for human use. 

Levees and Dikes 

• Levees : Built along rivers to prevent flooding. 

  • Problems : Prevent nutrient-rich flooding, increase sediment transport downstream, and can fail. (ex. Hurricane Katrina)

• Dikes : Built to prevent ocean waters from flooding land (common in the Netherlands). 

Dams 

• Purpose : Generate electricity, control floods, store water and recreation. 

• Impacts : 

  • Flooding large areas, displacing people (ex. Three Gorges Dam in China displaced 1.3 million people). 

  • Interrupts fish migration (fish ladders help). 

  • Reduces seasonal flooding, harming ecosystems. 

• Dam Removal : Some dams are being removed to restore ecosystems (Ex. Klamath River for salmon migration). 

  • Three Gorges Dam in China us the largest, with major environmental and social effects. 

  • Fish ladders help fish migrate past dams. 

Aqueducts

• Transport water from one place to another.
  Examples : Catskill Aqueduct (NYC) and Colorado River Aqueduct (Los Angeles). 

• Can fragment ecosystems and reduce water flow in source regions. 

River Diversion Consequences

• Can reduce water flow downstream, affecting ecosystems. 

• Example : Aral Sea, shrank due to river diversion for irrigation. 

Desalination (Saltwater - Freshwater)

Distillation : Boils water leaving salt behind (high energy use).

Reverse Osmosis : Forces water through a membrane, leaving brine behind. 

Used mainly in Middle Eastern and North African countries. 

Water Availability 

• Freshwater distribution is uneven worldwide. 

• Middle East and North Africa have the lowest water availability.    

Human Impacts on Wetland and Water Bodies 

• Causes : Development, pollution, overfishing, dams. 

• Effects : 

  • Loss of biodiversity and fish habitats.

  • Increased flooding and shoreline erosion.
    Decline in wetlands due to agriculture and urbanization. 

  • Example : The US has lost over 50% of its wetlands since the 1600s. 

Eutrophication and its Consequences

• Cause : Excess nutrients (fertilizers, sewage, farm runoff) lead to over growth of algae production. 

• Effects : 

  • Algal blooms block sunlight and produce toxins.

  • Oxygen depletion (hypoxia) leads to dead zones in water bodies. 

  • Example : Over 500 dead zones, worldwide, including the Golf of Mexico. 

Oxygen Sag Curve

• What it is : The relationship of oxygen concentrations to the distance from a point source of decomposing sewage or other pollutants. 

• Effects : 

  • Clogs waterways, affecting fish and plant life. 

  • Alters the ecosystem as a whole, and can affect food chains. 

Sediments - inputs of nutrients to aquatic ecosystems are often associated with inputs of sediments that erode from terrestrial landscapes which get carried long distances with flowing streams and rivers.

Thermal Pollution 

• Causes : Industries and Power Plants release heated water into natural bodies of water. 

• Effects : 

  • Warmer water holds less oxygen - harming aquatic life. 

  • Sudden temperature changes (thermal shock) can kill many species. 

• Example : Nuclear power plants use cooling towers to reduce thermal pollution 

• Solutions : 

  • Using cooling ponds before releasing water. 

  • Recycling water un closed cooling systems. 

Noise Pollution 

• Cause : Human activities like ships, submarines, sonar, and underwater drilling, 

• Effects : 

  • Disturbances in marine animal communication / navigation. 

  • Can harm species like whales and dolphins. 

• Examples :

  • US Navy sonar training impacts marine mammals. 

Module 58 - Ocean Acidification

Ocean Warming occurs due to an increase in CO2 levels. 

Impacts on Marine Species 

Due to the changes in water, many marines species who live there try to move to another area. Shifts in distributions of fish could alter the fishing and economic impacts in the area.

Ocean Warming:

* Oceans have absorbed about 90% of excess heat from global warming, resulting in a 1.5-2°C increase.

* This warming alters the distribution of marine species as they adapt.

Ocean Acidification:

* Increased atmospheric CO2 causes more CO2 to dissolve into the ocean.

* This forms carbonic acid, lowering ocean pH.

* Lower pH makes it harder for shell-building organisms (snails, clams, mussels, corals, crustaceans) to build shells, potentially causing population declines and harming coral reefs.

International Agreements on Climate Change:

* The Kyoto Protocol (1997) aimed to reduce greenhouse gas emissions from industrialized countries by 5.2% below 1990 levels by 2012.  Some countries exceeded this goal, others did not.

* The Paris Agreement (2015) is a pledge by 196 countries to keep global warming below 2°C above preindustrial levels.

Module 24 - Clear Cutting

1. Increased soil erosion: Removing trees exposes soil to wind and water, leading to nutrient loss and sediment runoff into streams, harming aquatic life.  Steeper slopes are particularly vulnerable to landslides.

2. Altered water temperature and oxygen levels: Increased sunlight reaching streams after clear-cutting raises water temperature, reducing dissolved oxygen and harming aquatic organisms.

3. Reduced biodiversity:  The removal of trees reduces habitat diversity, impacting various species. While clear-cutting can sometimes increase diversity in already heavily forested areas, it generally leads to a decrease.

4. Increased atmospheric carbon dioxide:  Clear-cutting increases soil decomposition, releasing more carbon dioxide into the atmosphere and contributing to climate change.

5. Soil compaction: Heavy machinery used in clear-cutting can compact soil, reducing water infiltration and increasing runoff.

While clear-cutting can be economically efficient and sometimes beneficial in specific situations (e.g., creating habitat for certain species), its negative environmental impacts often outweigh the advantages.  Sustainable forestry practices should be prioritized to minimize these negative effects.

Clear-Cutting:

1. Definition:

  Clear-cutting is a forestry practice where most or all trees in an area are uniformly cut down.

2. Advantages:

   - Economically efficient and cost-effective.

   - Simplifies replanting efforts since the entire area can be replanted at once.

   - Can create open spaces that some species may prefer.

3. Disadvantages:

   - Leads to habitat destruction and loss of biodiversity.

   - Increases soil erosion and runoff, which can degrade water quality.

   - Alters local microclimates and can increase temperatures.

   - Reduces carbon sequestration, contributing to climate change.

   - Can lead to the invasion of non-native species.

4. Environmental Impacts:

   - Soil Erosion: Without tree roots to stabilize the soil, erosion rates can significantly increase.

   - Water Quality: Increased runoff can carry sediments and pollutants into nearby water bodies, affecting aquatic ecosystems.

   - Biodiversity: Clear-cutting can lead to the loss of species that depend on forest habitats.

   - Climate Change: Trees absorb carbon dioxide; removing them releases stored carbon back into the atmosphere.

5. Alternatives to Clear-Cutting:

   - Selective Cutting: Only some trees are cut down, preserving the overall structure and biodiversity of the forest.

   - Shelterwood Cutting: Trees are removed in phases over several years, allowing new growth to establish under the protection of older trees.

   - Agroforestry: Integrating trees and shrubs into agricultural landscapes to maintain forest cover while allowing for crop production.

6. Regulations and Management:

   - Sustainable forestry practices aim to balance economic needs with environmental protection.

   - Certification programs like the Forest Stewardship Council (FSC) promote responsible forest management.

Vocab : 

Rangelands - Dry, open grasslands primarily used for grazing cattle. 

Forest - Land dominated by trees and the other woody vegetation and sometimes used for commercial logging.

Tree Plantation - A large area typically planted with a single fast-growing tree species. 

Endangered Species Act - A 1973 US law designed to protect plant and animal species that are threatened with extinction, and the habitats that support those species.

Module 53 - Lethal Dose 50% (LD50) and Dose-Response Curves

53-1 : How are dose response curves are used to estimate lethal doses of chemicals?

Dose-response study - A study that exposes animals or plants to different amounts of a chemical and then looks for a variety of possible responses, including mortality or changes in behaviour or reproduction.

Dose-response curves illustrate the relationship between chemical dose and effect (e.g., mortality).  Scientists use these curves to determine the LD50, the lethal dose causing 50% mortality in a population.  The LD50 is determined graphically by finding the dose corresponding to 50% mortality on the y-axis of the dose-response curve.  Dose-response studies are crucial for assessing the risk of pollutants and establishing safety guidelines.  Acute studies expose organisms for short durations, while chronic studies involve longer exposures.  Different philosophies exist for regulating chemicals based on risk assessment.

Acute studies - An experiment that exposes organisms to an environmental hazard for a short duration of time. 

Chronic studies - An experiment that exposes organisms to an environmental hazard for a long duration. 

LD50 - The lethal dose  of a chemical that kills 50 percent of the indiv iduals in a dose response study.

Methods for assessing the risk of environmental hazards using dose-response curves.  A key concept is the LD50 (lethal dose 50%), which represents the concentration of a substance causing 50% mortality in a population.  Scientists also use ED50 (effective dose 50%), representing the concentration causing a non-lethal harmful effect in 50% of a population, and NOEL (no-observed-effect level), the highest concentration with no harmful effects.

Risk assessment involves identifying potential hazards and determining their magnitude.  Regulatory agencies often use data from animal studies (rats and mice) to estimate safe exposure levels for humans, typically by dividing the LD50 or ED50 values obtained from animals by 1000 to account for species differences and safety margins.  The process also considers sublethal effects (harmful but non-lethal effects) and chronic studies (long-term effects).

Small summary - The text describes the process of determining safe exposure levels for chemicals using LD50, ED50, and NOEL values, along with risk assessment, acceptance, and management strategies.  The key is to extrapolate from animal studies to human populations, using conservative safety factors.

Sublethal effect - The effect of an environment hazard that does not kill an organism but which may impair an organisms behaviour, physiology, or reproduction. 

ED50 - The effective dose of a chemical that causes 50 percent of the individuals dose-response study to display a harmful, but nonlethal, effect.

No-observed-effect level (NOEL) - The highest concentration of a chemical that causes no lethal or sublethal effects. 

Risk Assessment Process:

1.  Risk assessment involves determining the probability and severity of harm from hazards.  Qualitative assessments categorize risks as low, medium, or high. Quantitative assessments use data to calculate probabilities.

2.  Risk perception often differs from actual risk.  For example, people may overestimate the risk of plane crashes while underestimating the risk of heart disease.

3.  Quantitative risk assessment uses the formula: Risk = Probability of exposure * Probability of harm given exposure.

4.  A case study on PCBs illustrates the risk assessment process.  The EPA determined that consuming contaminated fish posed a significant risk, leading to recommendations for river dredging.

Risk Acceptance:

1.  Risk acceptance is the level of risk considered tolerable.  This is often the most challenging step in risk analysis.

2.  Information alone may not be sufficient to overcome risk aversion.

Key Concepts:

*   Qualitative vs. Quantitative Risk Assessment

*   Risk Perception vs. Actual Risk

*   Dose-Response Relationships (implied in the PCB case study)

*   Risk Management (briefly mentioned)

Two approaches exist for managing chemical risks:

1.  Innocent-until-proven-guilty:  A chemical is considered safe until proven harmful. This approach prioritizes allowing beneficial chemicals to market quickly but may lead to delayed responses to harmful substances.

2.  Precautionary principle:  If a substance poses a plausible risk, action is taken to reduce or eliminate the hazard, even without definitive proof of harm. This prioritizes safety but might slow the introduction of beneficial chemicals.

The text uses arsenic and asbestos as examples.  Arsenic regulation demonstrates the conflict between scientific data and economic interests. Asbestos illustrates the delayed response under the innocent-until-proven-guilty approach, resulting in significant health consequences and economic costs.  The Stockholm Convention (2001) represents a global effort to regulate hazardous chemicals, reflecting a shift towards the precautionary principle.

Innocent-until-proven-guilty principle - A principle based on the belief that a potential hazard should not be considered an actual hazard until scientific data definitively demonstrate that it actually causes harm. 

Precautionary principle - A principle based based on the belief that when a hazard is plausible but not yet certain, we should take actions to reduce or remove the hazard.

Stockholm Convention - A 2001 agreement among 127 nations concerning 12 chemicals to be banned, phased out, or reduced.

Module 34-2 : Sustainable Forestry

Reforestry - The natural or intentional restocking of trees after clear-cutting to repopulate the forest, reduce erosion, and begin the process o 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. 

Occupational and Safety Administrations states that logging is the most dangerous occupation in the Unites States. 

Pros : 

• Encourages natural growth

• Creates jobs to promote these methods

Other Sustainable Logging Techniques 

• Forest certification organizations : Designate wood for purchase which have been sustainably harvested. 

  • Prices usually higher

  • “Chain of custody” - Proof that the sustainable methods are being used. 

• IPM starts can be used for forest management.

  • Biocontrol

  • Attempts to exclude insect pests 

  • Fires 

Fire Management

Important for nutrient cycling and regeneration. 

Vegetation killed by fire allow early successional species to grow. 

Suppressing fires was done by many, leading to dead biomass accumulation. 

In order to prevent this, Prescribed burn - When a fire is deliberately set under controlled conditions, thereby decreasing the accumulation of dead biomass on the forest floor, is used.

Reduces risk of uncontrolled natural fires 

Poor management 

Due to humans mismanagement large fires on public or private land can occur. 

California's forest are a great example - it seems to be almost half of these fires were caused by a utilities electrical network. (poor equipment)

Yellowstone National Parks fire, another great big one. Very dry day. 25,000 fought the fires. 

However it did provide benefits  for the ecosystems as the soil is rich and grew many successional species. 

Module 59 : Invasive Species, Endangered Species, and Human Impacts on Biodiversity

• Most invasive species are R-selected species, generalist species 

• Usually rapid spread of invasive species because they often have no natural enemies

59-1 : What are the threats posed by invasive species?

- Invasive Species:

  - Kudzu introduced to the US for erosion control, now invasive.

  - Silver carp outcompetes native fish and poses safety hazards by jumping.

  - Controlling invasive species is challenging; prevention is essential.

  - Measures include inspection of goods and restrictions on untreated wood.

- Endangered Species:

Species that are likely to go extinct in the near future. 

  - Categories:

    - Extinct: No longer exists.

    - Endangered: High risk of extinction.

    - Threatened: Likely to become endangered.

    - Near-threatened: At lower risk.

    - Least-concern: Not currently at risk.

  - Endangered species percentages vary across groups (e.g., amphibians highly affected).

  - Current extinction rate suggests a possible sixth mass extinction.

  - Amphibians experiencing the greatest global declines.

  - Amphibians have the highest percentage of threatened or endangered species.

HIPPCO! - Acronym for factors that led to decreasing biodiversity

Habitat destruction

Invasive species

Population growth (human)

Pollution

Climate Change

Over exploitation

Habitat Fragmentation

Large habitats are broken up into smaller, isolated areas. 

Causes : 

• Construction of roads and pipelines

• Clearing of land for agriculture

• Logging

Some species may benefit from this, but usually has a negative impact. 

These species could be generalists who can thrive in edge habitats or any abiotic conditions.

Global climate change can cause habitat loss via changes in temperature, precipitation, and sea level rising. 

Some organisms have been somewhat or completely domesticated are now managed for economic returns, such as honeybee colonies and domestic livestock. This domestication can have a negative impact on the biodiversity of that organism. 

Average global temperatures rise, habitats may be lost due to : 

• Rising sea levels

• Coastal inundation

• Changes in precipitation patterns 

Domestication involves artificial selection, provide humans with food, medicine, labor and pollination services. 

Artificial selection reduces genetic diversity , and the genetic pool.

Mitigate Biodiversity Loss

• Protected areas

• Habitat corridors 

• Restoration

• Sustainable land use

Invasive Species

They can live and sometime thrive, outside of their normal habitat. Sometimes be beneficial but usually considered invasive as they threaten native species.

Often generalists, r-selected species which may outcompete native species for resources.

Controlled through human intervention.

Ways to control: 

• Cleaning, drying boat

• Prevent dumping

• Clean boots, shoes, socks, when going into new areas

• Firewood where it was cut to prevent spread of wood-borne pathogens

• Introduce competitor species / predator / species - specific pathogen

• Physical removal

• Pesticides

Endangered Species

A variety of factors can lead to a species becoming threatened with extinction, such as being extensively hunt, having limited diet, selective pressures, being outcompeted by invasive species or having specific and limited habitat requirements.

Not all species will be in danger on extinction when exposed to the same changes in their ecosystem. Species that are able to adapt to changes in their environment or that are able to move to a new environment are less likely to face extinction.

Lacey Act - A U.S. act that prohibits interstate shipping of all illegally harvested plants and animals.

Marine Mammal Protection Act - A 1972 US law that prohibits the killing of all marine mammals in the United States and prohibits the import or export of any marine mammal body parts.

Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) - A 1973 treaty formed to control the international trade of threatened plants and animals. 

Module 46-2 : Noise Pollution

Noise pollution is sound at levels high enough to cause physiological stress and hearing loss. 

Sources of noise pollution in urban areas include transportation, construction, and domestic and industrial activity. 

Using the decibel scale (dBA) on the logarithmic scale can cause hearing damage, to any hearing above 85dBAs.

Hearing loss can be permanent. 

Other health risks are high blood pressure. Heart disease, stress, depression and anxiety. 

Some effects of noise pollution on animals in ecological systems include stress, the masking of sounds used to communicate or hunt, danging hearing and causing changes to migratory routes.