(Unit 5) AP Environmental Science

Tragedy of the Commons

individuals will use shared/public resources in their own self interest, degrading them. must be a public resource

Examples of Tragedy of the Commons

overgrazing, overfishing, water and air pollution, and overuse of groundwater

Why does TOC occur?

no one owns the resource, no one directly suffers the consequences of depleting, degrading, or overusing it

people assume others will overuse the resource if they do not

there is no penalty for overuse

Overfishing can lead to _________

fishery collapse (population crash) loss of income and starvation

Air pollution from coal power plants could lead to ______

bronchitis, asthma, increased healthcare costs

Pesticide runoff from farms ___

contaminates drinking water

How to solve TOC

private land ownership(individual or government), fees or taxes for use, fines, criminal charge for pollution

Examples of how to solve the TOC

clean air act, clean water act, safe drinking water act, bureau of land management

Soil Erosion

caused by loss of stabilizing root structure, removes soil organic matter and nutrients from the forest, deposits sediments in local streams

Direct effects of clearcutting

soil erosion, increased soil and stream temperature, flooding and landslides

Increased soil and stream temperature

loss of tree shade increases soil temperature, soil has lower albedo than leaves of trees, loss of tree shade along rivers and streams warms them, erosion of sediments into rovers also warms them

Flooding and landslides

logging machinery compacts soil, increased sunlight dries out soil, loss of root structure = erosion of topsoil and O horizon, all of these factors decrease H2O holding capacity of soil causing flooding and landslides

Tree plantations

areas where the same tree species are repeatedly planted, grown, and harvested

Tree plantations lower biodiversity because ____

biodiversity, mature forests are replaced with single species forests, less species diversity = lower resilience, less habitat diversity for other organisms

Tree plantations are all the same age which ______

lowers biodiversity further, no dead trees for woodpeckers, insects, decomposers

Forest benefits:

filtering of air pollutants, removal and storage of CO2 from atmosphere, habitat for organisms

Filtering of air pollutants:

stomata (leaf pores) remove VOCS, NO2, PM from air and stored in trees

Removal and storage of CO2 from atmosphere:

trees take in CO2, store carbon as sugar, wood, other tissue and releases O2

Smog

volatile organiz compounds combine with nitrogen oxide and sunlight to form ozone, commonly known as smog

Deforestation consequences:

reduces air filtering and carbon storing services, cutting trees down releases CO2 from decomposition of leftover organic material, the slash and burn method releases CO2, N2O and water vapor into the atmosphere

Ecologically sustainable forestry

forestry that minimizes damage to ecosystem, selective cutting or strip cutting, using human and pack animal labor to minimize soil compaction from machinery, replanting same species being logged, maximizes long term productivity of land and preserves forest for future generations

Sustainable forestry practices

using recycled wood, or simply reusing without recycling, wood can be chipped and used as mulch for gardens or agricultural fields, replanting of trees in areas that have been deforested, selectively removing diseased trees to prevent spread of infection through entire forest

Fire supression steps

stopping natural fires is the practice of putting out all natural forest fires as soon as they start, leads to more biomass buildup as putting out fires immediately leads to more dry biomass buildup, makes future fires worse, close monitoring can prevent fire damage and worse fires in the future

Prescribed burns

dead biomass builds up which is fuel for large forest fires that stored nutrients trapped in dead biomass, dead trees = susceptible to disease and pest spread, small, controlled fires burn lots of dead biomass which uses up dead biomass (fuel) preventing larger forest fires later, this then promotes nutrient recycling, nutrients in dead biomass are recycled → new growth

The green revolution

shift in agriculture away from small, family operated farms to large, industrial-scale agribusiness, increased use of mechanization, GMOs, irrigation, fertilizers, and pesticides

Pros of the green revolution

greatly increases efficiency of lands, short-term profitability, and food supply, decreased world hunger and increased earth’s carrying capacity for humans

Cons of the green revolution

soil erosion, biodiversity loss, ground & surface water contamination

Mechanization

increased use of tractors for plowing and tilling fields, and combines for harvesting = increased yield + profits, increases reliance on fossil fuels (gasoline/diesel fuel), emits GHGs to atmosphere → climate change, heavy machinery also compacts soil, decreasing H₂O holding capacity which makes topsoil more prone to erosion

High-yield variety (HYV) crops

hybrid, or genetically modified crops that produce a higher yield, hybrid = cross-pollinating different species, or parent plants with ideal traits, increased yield and food stability in regions previously prone to famine (India, Pakistan, Mexico)

GMOs

crops with new genes “spliced” into their genome, have genes for drought tolerance, pest resistance, faster growth, and larger fruit/grain, increases profitability with fewer plants lost to drought, disease, or pests + larger plant size + yield/acre

Cons of GMOs

all genetically identical so gen. diversity is decreased and susceptibility to diseases or pest is increased

Synthetic fertilizer

man made ammonium, nitrate, phosphate

Organic fertilizer examples

manure and compost

Pros of synthetic fertilizer

increases yield and profits with more key nutrients needed for plant growth (N, P, K) added to the soil

Cons of synthetic fertilizer

excess nitrate, phosphate are washed off fields and into nearby waters where they cause eutrophication (algae blooms), require FFs for production, releasing CO2 (climate change), contaminates groundwater for drinking, don’t return organic matter to soil, water carries excess nutrients into groundwater or into surface waters

Irrigation

drawing water from the ground or nearby surface waters and distributing it on fields to increase plant growth, make agriculture possible in many parts of the world that are naturally too dry

Cons of irrigation

can deplete groundwater sources, especially aquifers, over watering can drown roots (waterlogging; no O2 access) and cause soil salinization (increase salt level in soil)

Pesticides

increase in use of synthetic pesticides - chemicals sprayed on crops that kill weeds, insects, rodents and other pests that eat or damage crops, increases yield and profits with fewer plants lost to pests, can wash off crops in runoff and kill or harm non-target species in local soil or waters

Monocropping

growing one single species (corn, wheat, soy) of crop, h ighly efficient for harvest, pesticide and fertilizer application

Cons of monocropping

greatly decreases biodiversity (more prone to pests, fewer natural predators), increases soil erosion (crops harvested all at once and soil left bare), decreases habitat diversity for species living in the area

Tilling

mixing and breaking up soil to make planting easier, also loosens soil for roots

Cons of tilling

increases erosion by loosening topsoil, breaking up leftover root structure from harvest, loss of organic matter & topsoil nutrients over time, increased PM in air (rerp. irr) and sediments in nearby water (turbidity)

What is turbidity?

the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air

Slash and burn

cutting down vegetation and burning it to clear land for ag. & return nutrients in plants to soil, increases PM in air (asthma), lowers albedo, making area warmer

What is albedo?

the fraction of light that is reflected by a body or surface

Furrow irrigation

trench dug along crops and filled with water, easy and inexpensive; water seeps into soil slowly, ~66% efficient, 33% lost to runoff and evaporation

Drip irrigation

most efficient, but also most costly, over 95% efficient, holes in hose allow water to slowly drip out, avoids waterlogging and conserves waters

Flood irrigation

flood entire field; easier but more disruptive to plants, can waterlog the soil and drown plants, 80% efficient - 20% runoff/evaporation

Spray irrigation

ground or surface water pumped into spray nozzles, more efficient (less water loss) than flood or furrow, more expensive (requires energy for pumps and movement of sprinklers

Waterlogging

overwatering can saturate the soil, filling all soil pore space with water, doesn’t allow air into pores, so roots can’t take in O2 they need, can stunt growth or kill crops

Solution to waterlogging

drip irrigation, or soil aeration - poking holes or cores in soil to allow air in & water to drain through soil

Soil salinization

the process of salt building up in a soil over time, groundwater used for irrigation naturally has small amounts of salt, water evaporates, and salt is left behind in soil, over time, it can reach toxic levels, dehydrating plant roots and preventing growth,

Solution to soil salinization

drip irrigation, soil aeration, flushing with fresh water, switch to freshwater source

Global human water use - industrial

power plants, metal/plastic manufacturing

Global human water use - municipal

households (toilet, shower, drinking water)

Global human water use - agriculture

water for livestock, irrigation water for crops

Groundwater

H2O stored in pore space of permeable rock & sediment layers

Aquifers are ____

useable groundwater deposits for humans and are replenished by groundwater recharge (rain water percolating down through soil inside)

Unconfined aquifers _____

recharge quickly and are longer-term water deposits that recharge more slowly

Saltwater intrusion:

excessive pumping near coast lowers water table pressure, allowing saltwater to seep into groundwater

Cone of depression:

forms when water table is lowered by excessive pumping, depleting water and drying nearby wells

Pesticides

chemicals that are toxic to pests

Rodenticides kill _____

rodents

Fungicides kill ____

fungi

Insecticides kill _____

insects

Herbicides kill _____

plants

Pesticides can cause ____

pests to become resistant to pesticide with overuse, genetic biodiversity gives some pests resistant traits to pesticide, pesticide artificially selects for pests with resistance by killing all the non-resistant individuals, leaving only resistant ones

Gene for pest resistant trait is added to the plant _____

through genetic modification

Roundup ready crops:

genetically modified to be resistant to broad herbicide meaning roundup will kill weeds, but not crops

GM crops are all genetically _____

identical so there is no genetic diversity in the population

If there is disease or pest that does affect the GM crops, they’re all _____

vulnerable and there’s no chance of a genetic mutation providing an adaptive trait

IPM basics

using a variety of pest control methods that minimize environmental disruption and pesticide use, researching and monitoring pests and targeting methods to specific pest life cycles, biocontrol, crop rotation, and intercropping

Biocontrol

introducing a natural predator, parasite, or competitor to control the pest population, can include actually purchasing and spreading the control organisms in fields, or building homes for them/planting habitat they need to attract them naturally

Crop rotation

planting a different crop each season. many pests prefer one specific crop or crop family, they lay eggs in the soil so when larvae hatch they have preferred food source, can prevent pests from becoming established since it disrupts their preferred food choice, also disrupts weed growth since different crops can be planted at different times, preventing bare soil from being taken over by weeds

Intercropping

“push-pull” system can be used, “push” plants emit volatile chemicals that naturally repel pests away from crop, “pull” plants emit chemicals that attract moths to lay eggs in them, instead of crop, can provide habitat, or “pull” plants that emit chemicals that attract natural pest predators

Pros of IPM

reduces death and mutation of non-target species from, reduces effects on human consumers of produce, reduces contamination of surface & ground water by agricultural runoff with pesticides

Cons of IPM

can be more time consuming and costly than just crop dusting pesticides

CAFOs

also called feedlots - densely crowded method where animals are fed grain (corn) to raise them to as quickly as possible,

Pros of CAFOs

maximizes land use and profit (most meat production per/unit of area), minimizes cost of meat for consumers

Cons of CAFOs

given antibiotics and growth hormones to prevent disease outbreak and speed meat production, animals produce large volume of waste which can contaminate nearby surface or groundwater, produces large amounts of CO2, CH4 (methane), and N2O (greenhouse gasses → climate change)

Manure Lagoons

large, open storage pits for animal waste, waste contains: ammonia (N), hormones, antibiotics, fecal coliform bacteria (e. coli), heavy rain can flood lagoons and contaminate nearby surface and ground water with runoff, denitrification of ammonia in manure produces N2O (extremely powerful GHG), can be emptied and buried in landfills, or turned into fertilizer pellets

GHG are ______

greenhouse gases in the atmosphere that contribute to the greenhouse effect and warm the planet

Free range grazing

animals (usually cows) graze on grass and grow at a natural rate without growth hormones,

Pros of free range grazing

no need for antibiotics with dispersed population, doesn’t require production of corn to feed animals, waste is dispersed over land naturally, acting as fertilizer instead of building up in lagoons, animals can graze on land too dry for most crop growth

Cons of free range grazing

requires more total land use/pound of meat produced, more expensive to consumer

Overgrazing

too many animals grazing an area of land can remove all the vegetation (grass) which leads to topsoil erosion, animals also compact soil, decreasing H2O holding capacity → more erosion, desertification can occurr

Desertification:

can occur if plants are killed by overgrazing and soil is compacted so much that it can’t hold enough water anymore

Overgrazing solution:

rotational grazing (moving animals periodically) can prevent overgrazing, can even increase growth of grass by distributing manure (natural fertilizer) and clipping grass back to size where growth is most rapid

Inefficiency of meat

producing meat for humans to eat is far less efficient than producing plants in terms of energy, land and water use, energy needed to plant, grow, harvest plants to feed to animals plus energy to bring water to animals, needed to house animals, to slaughter and package, land and water

Soil conservation

agricultural techniques that minimize erosion, (US is losing topsoil to erosion 10x faster than it forms)

Soil conservation prevents loss of _______

nutrients in topsoil, soil moisture, decomposers in topsoil, organic matter that traps soil moisture

Contour plowing

plowing parallel to natural slopes of the land instead of down slopes prevents water runoff and soil erosion, forms mini terraces that catch water running off, conserving soil and water

Terracing

cutting flat “platforms” of soil into a steep slope, flatness of terraces catches water and prevents it from becoming runoff and eroding soil

Perennial crops

crops that live year round and are harvested numerous times, longer, more established roots and prevention of bare soil between harvest

Windbreaks

using trees or other plants to block the force of the wind from eroding topsoil, can be used as a source of firewood, fruit (income), can provide habitat for pollinators and other species

No till

leaving leftover crop remains in soil instead of tilling under, adds organic matter to soil (nutrients, soil cover, moisture), prevents erosion from loosened soil

Strip cropping

another name for intercropping, alternating rows of dense crops (hay, wheat) with rows of less dense crops (corn, soy, cotton) to prevent runoff from eroding soil from less dense rows of crops

Improving soil fertility

methods of restoring nutrient levels in the soil (N, P, Ca, Mg)

Green manure

leftover plant matter from a cover crop - a crop planted in the offseason, between harvest and replanting of main crop, cover crop roots stabilize soil limiting topsoil erosion, remains of cover crops (green manure) left on field breakdown to release nutrients into the soil

Limestone ____

releases calcium carbonate (base) which neutralizes acidic soil