APES Review Lesson #3

Keepin’ it classy!

Plate Tectonics: the Earth’s lithosphere is

divided into plates, most of which are in

constant motion

The movement of the plates is driven by

convection in the mantle

Seafloor spreading creates new crust at ridges

at the bottom of the ocean (mid-Atlantic ridge)

Plate contact includes

Divergent

Convergent

Transform fault

Divergent boundaries create rift valleys (ex:

the Rift Valley in Africa)

Convergent boundaries create

Oceanic to continental creates subduction zones

which push up long, narrow coastal mountain

ranges such as the Andes (Nazca plate into South

American plate)

Continental to continental creates uplift, creating

tall mountain ranges such as the Himalayas (Indian

plate into the Eurasian plate)

Transform boundaries create faults, the

slippage of which produces earthquakes

Rocks come in three “flavors”

Igneous—formed directly from magma

Sedimentary—formed when mud, sand or gravel is

compressed

Metamorphic—formed when igneous or

sedimentary rocks are subjected to high

temperature and pressure

Exposed rock is subjected to weathering and

erosion

Weathering can be

Physical

Chemical

Soil links the abiotic lithosphere to the

biosphere!

Soil has geologic (rock/mineral) components

and organic components

Ecosystem services provided by soil include

Breaking down organic materials and recycling

nutrients

Providing habitat

Filtering water

Plant growth medium

Soil characteristics depend on

Parent material

Age

Plant community

Climate

Topography

Soil Horizons

O horizon

Organic detritus like, leaves, pine needles, twigs

and animal bodies in various stages of

decomposition

A horizon

Topsoil

Zone where organic and mineral materials are

mixed together

Plant roots are found here

E horizon

Zone of leaching

Occurs mostly in acidic soils

Fe, Al and organic acids from O and A are leach

through E to the B where they accumulate

B horizon

Subsoil

Mostly minerals with very little organic matter

C horizon

Least weathered zone

Similar in composition to the parent material

Soil Properties

Texture

Relative percentages of sand, silt and clay

Permeability

How quickly soil drains

Sand is most permeable, clay is least permeable

Best agricultural soil is loam (40/40/20)

Soil texture is important to how an ecosystem

responds to pollution

If the soil is sandy, groundwater can be

contaminated by pollution infiltration

Soil degradation can be caused by

Erosion due to topsoil disturbance

Compaction (humans, machines, livestock)

Intensive agriculture (herbicides, pesticides,

fungicides, fertilizers)

Irrigation (salinization)

Mining is the extraction of mineral resources

from the Earth’s crust

Ores are concentrated accumulations of

minerals from which economically valuable

minerals can be extracted

Overburden is the economically undesirable

rock covering ore

Two types of mining

Surface

Subsurface

Surface mining includes

Strip mining—the removal of strips of overburden to expose ore

Once the resource is extracted from the ore, the waste material is called spoils or tailings

Spoils/tailings are returned to the fill in the strips

Open pit mining—a large hole is dug to access the ore

Copper mining is open pit

Mountaintop removal

Miners blowup an entire mountaintop with explosives to expose the ore

ALL forms of surface mining are HIGHLY environmentally destructive!!

Subsurface mining is used to reach ores that are

significantly below the Earth’s surface

Coal, diamonds and gold are mined subsurface

(although coal is also dug in strip mines)

Subsurface mining is genrally less environmentally

destructive than surface mining

General Mining Act of 1872, Surface Mining and

Reclamation Act of 1977, Clean Air Act, Clean Water

Act, the Safe Drinking Water Act and CERCLA

(Superfund) regulate the environmental effects of

mining

STUDY TABLE 8.2 ON PAGE 228 IN FRIEDMAN

AND RELYEA FOR ENVIRONMENTAL EFFECTS

OF MINING

LAND USE

Case Study: Julia Butterfly Hill and Luna

Northern California

Privately held stand of old growth redwood trees

scheduled to be clear-cut

Julia organized a “tree sit”—activists climb trees

scheduled to be cut and stay there as long as

possible to save them from logging and gain time

for legal proceedings

Julia occupied Luna, a 180 ft. redwood for TWO

YEARS without coming down!

Why do we care? Her actions brought worldwide attention to the

destructive practice of clear cutting

The logging company agreed to protect Luna and sell the U.S. government 7,500 acres of old growth forest in the area

The logging company eventually had to file for bankruptcy due to their legal debt from fighting the environmentalists

Some people called Julia a criminal because she did her “tree sit” on private land and blocked a legal activity (just because its legal doesn’t mean its right!)

LAND USE

Humans use land in a variety of ways

Agriculture

Housing

Recreation

Industry

Mining

Waste disposal

All land use has environmental consequences

Tragedy of the Commons

The tendency of a shared, limited resource to become depleted because people act from self-interest for short-term gain

Overfishing and overgrazing are good examples

Can be avoided by practicing maximum sustainable yield (MSY)—the maximum amount that can be harvested without compromising the future availability of a resource

In actuality, MSY is very hard to calculate because of the difficulty in obtaining birth rates, death rates and estimating the carrying capacity of the ecosystem

Rangelands

Dry, open grasslands

Most common land type in the U.S.

Often overgrazed, causing environmental problems

such as

Loss of vegetation

Land erosion and subsidence

Forests

Used for logging

Timber is culled from both private (73%) and U.S.

National Forests (27%)

Timber harvesting includes clear-cutting and

selctive cutting

Clear-cutting: removes all trees in an area

PROS

Easiest, cheapest harvesting method

Land often seeded with comercially valuable seedlings shortly after harvest so all trees are the same age

CONS

Increases wind and water erosion

Causes soil loss and sedimentation of nearby waterways

Denuded soil prone to landslides

Increases direct sunlight to streams, raising water temperatures, which harms aquatic species

Herbicides often used on the land prior to seedling replanting

Same-age/type trees reduces biodiversity

Selective cutting: removes single trees or

relatively small numbers of trees from many in

a forest

PROS

Creates gaps in which seedlings can be planted,

resulting in different age trees

Less loss of biodiversity because trees of different

species/ages remain

CONS

Costs more to plan and implement

Still must build logging roads to haul out cut trees

Heavy logging often replaces forests with tree

plantations—large areas planted with fast-

growing, commercially valuable species

Tree plantations are easily clear-cut and

replanted

Because of the managed cycle of clear-cutting

and replanting, tree plantations never develop

into mature forests

These managed cycles often deplete the land

of nutrients

Using fire to manage forests

Fires free up nutrients tied up in dead biomass

Cleared areas provide space for early successional

species

Suppressing fire is dangerous and leads to an

excess of dead biomass, which can fuel an out-of-

control fire and which can also harbor pests

Prescribed burns reduce the risk of uncontrolled

natural fire and assist with nutrient cycling

National Park System

Based on the “multi-use” principle (just like

rangelands and forests)

First park was Yellowstone in 1872

Began with the “preservation” mindset and has

progressed to the “conservation” mindset

Are often “victims of their own success”…too

many human visitors which reduces biodiversity

and creates waste and pollution

National Wildlife Refuges

The only federal public lands managed for the

primary purpose of protecting wildlife

National Wilderness Areas

Set aside with the intent of preserving large areas

of intact ecosystems

Allow only limited human use

NO logging, road building or mining allowed

Land use for residential areas is increasing rapidly

Urban sprawl is the creation of urbanized areas that spread into rural areas and is characterized by clusters of housing, retail, office building, “big box” stores and miles of large roads (“suburbia”)

People in suburban areas drive TWICE as much as those in urban areas

Suburban homes are larger than urban homes, and take up more land area

Sprawl displaces agricultural land, increasing the distance from farmers to consumers

Feeding the World

Humans were gatherers/hunters until about

10,000 years ago

Agriculture began around 10,000 years ago

and the human population became more

sedentary (agricultural revolution)

Undernutrition

Not consuming enough calories to be healthy

Has increased globally since 1996

Malnutrition

A diet lacking in the proper balance of protein,

carbohydrates, vitamins and minerals

A person can be overweight and malnourished!

Famine

A condition where food insecurity is widespread

and extreme, and many people die in a short period

of time

Anemia

Iron deficiency

Most common nutritional deficiency worldwide

Overnutrition

Eating too many calories and improper foods

Causes people to be overweight

Becoming very common in developed countries—WHO estimates there are over 1 billion overweight people worldwide

Consumption of meat increases with income and consumption has been increasing globally and in the U.S.

The primary reason for undernutrition and malnutrition is POVERTY; poverty and the “wealth gap” between rich and poor is increasing worldwide

Starvation is usually the result of unequal food

distribution, rather than actual food scarcity

With the world population expected to be 9 to

11 billion by 2050, in order to feed everyone,

we’ll need to…

Put more land into agricultural production

Improve crop yields

Reduce meat consumption (sorry, folks!)

Harvest more ocean resources

The Green Revolution began in the 1940’s in

the U.S.

Goal was to increase crop yields through selective

breeding of high-yield seed varieties

Also used wide-scale mechanization, irrigation,

fertilization and chemical pest control

The Green Revolution has allowed us to feed

more people, but has had serious negative

environmental consequences

Mechanization involves economies of scale,

which means that the cost of production falls

as output increases

Profits increase with size, so larger farms

outcompete smaller ones

Also leads to monocropping, because specialized

equipment is needed to plant and harvest each type

of crop

Irrigation allows crops to be grown in dry

areas where they wouldn’t normally be able to

grow and make already productive land VERY

productive. But…

It depletes groundwater and aquifers (Ogallala)

In coastal areas, in can cause saltwater intrusion

into freshwater wells

It can cause soil degradation through

Waterlogging—when soil remains submerged for

extended periods of time, which impairs root growth

Salinization—when small amounts of salts naturally

present in groundwater become concentrated on the soil

surface and impedes plant growth

Agriculture removes nutrients from the soil

which must somehow be replaced

Nutrients can be replaced with fertilizers,

which contain primarily nitrogen and

phosphorus (limiting factors for plant growth)

Two types of fertilizers

Organic: composed of composted plant and animal

waste

Synthetic: produced from combusting natural gas

(fossil fuel based)

Synthetic fertilizer advantages

Easy to apply

Can be customized for the crop

Concentrated, so a little goes a long way

Designed to be applied once per growing season

Disadvantages

Manufacturing uses fossil fuels in an energy-intensive process

Concentration leads to runoff, leading to eutrophication

Do not add organic matter to the soil, so does not feed the microorganisms or increase soil quality

Monocropping: growing large amounts of a

single crop variety, usually genetic clones

Most common agricultural practice in the U.S.

Efficient, if used with mechanization, irrigation

and fertilizer

Can lead to soil erosion from wind

Also prone to pests because the plants are

genetically similar (so pesticides must be used

continuously)

Pesticides are natural or synthetic chemicals

designed to kill or control organisms people

consider pests

Insecticides target insects

Herbicides target “weed” species

Rodenticides target rodents

Can be broad-spectrum (kill many different

types of pests) or selective (focus on a narrow

range of organisms)

Selective pesticides are usually a better choice

environmentally (biodiversity)

Some pesticides (DDT) are persistent—they

remain in the environment for a long time

Persistent pesticides tend to bioaccumulate.

They build up in the fatty tissues of organisms,

so the top-level consumers in an ecosystem

have the highest concentration in their bodies

Non-persistent pesticides are thought to be

safer, but must be repeatedly applied, so their

overall environmental impact may not actually

be lower

Pesticide treadmill (positive feedback loop)

Genetically Modified Organisms (GMOs)

offer possibilities

increasing yields for crops and livestock, which

may reduce global hunger

May be bred to be resistant to pests, leading to less

fertilizer costs (and more profit) for the farmer

May be bred to tolerate drought and poor soil

Genes may be added to make the crop more

nutritious (like adding a sweet potato gene to rice

plant to produce vitamin A-enriched rice; vitamin

A deficiency is the #1 cause of childhood

blindness)

…and drawbacks

Are they safe from human consumption? We don’t

know!

GMOs reduce biodiversity (they’re all clones)

when they cross pollinate with native species

GMOs are patented, which means agribusiness

companies, like Monsanto, own the rights to the

seed

Regulation/labeling of GMOs in the U.S. is

currently non-existent, so we don’t know where

they are (probably everywhere!)

Alternatives to conventional agriculture

Shifting agriculture (slash and burn)/subsistence

farming—often leads to desertification (expansion

of desert into already dry areas)

Nomadic grazing

Sustainable agriculture

Intercropping—two or more species of crop are planted

in the same field at the same time

Crop rotation—rotation of crops in the same field

during different seasons (usually with nitrogen heavy

and nitrogen fixing crops)

Agroforestry—intercropping food crops with trees

Contour plowing—plowing parallel to the topography

of the land to reduce erosion and retain moisture

No till or low till agriculture—reduced tillage reduces wind erosion and oxidation of topsoil

Integrated Pest Management (IPM)

The goal is not to eliminates pests completely, but to reduce the economic impact of pests to a reasonable level

Techniques include

Crop rotation

Intercropping

Using pest-resistant crop varieties

Creating habitats for pest predators

Biological pest control (predator introduction or pheromone lures)

Limited use of specific (not broad-spectrum) pesticides

Organic farming: the production of crops without the use of synthetic fertilizers or pesticides

CAFOs: concentrated animal feeding operations

High density confined animals

Animals given antibiotics and nutrient supplements to reduce density-dependent diseases

Routine use of antibiotics is leading to resistant “superbugs” in animals and people

Waste runs off into waterways and causes eutrophication and disease (hog farming and pfiesteria??)

Fish and shellfish can be farmed on CAFOs,

too…Aquaculture

Animals must be provided with food and

antibiotics

Clean water is pumped into one end of the

enclosure and water contaminated with uneaten

food, antibiotic residue, bacteria, viruses and feces

flows out the other end (yummy!)

Diseases from farms can infect non-farmed species

Almost 100% of catfish and trout and over 50% of

shrimp and salmon eaten in the U.S. are farmed