© Cengage Learning 2015

Biology Concepts and Applications | 9e

Starr | Evers | Starr

© Cengage Learning 2015

Chapter 44

Human Effects on the Biosphere

© Cengage Learning 2015

44.1 Why Are So Many Species

Threatened of Endangered?

• All over the world, humans are replacing

wildlife habitat with our dwellings,

factories, and farms

• We also put species at risk

– Competing with them for resources

– Overharvesting them

– Introducing non-native competitors

• The rate of species extinctions is rising;

many types of biomes are threatened

© Cengage Learning 2015

Why Are So Many Species Threatened of

Endangered? (cont’d.)

• A species is considered endangered when

one or more of its populations have

declined or are declining

– Endangered species

• A species that faces extinction in all or a part of its

range

– Threatened species

• Species likely to become endangered in the near

future

© Cengage Learning 2015

Why Are So Many Species Threatened of

Endangered? (cont’d.)

A White abalone.

B Pyne’s ground plum.

C Texas blind salamander.

D Florida perforate reindeer lichen.

© Cengage Learning 2015

Why Are So Many Species Threatened of

Endangered? (cont’d.)

• Human activities threaten other species by

destroying or degrading habitat

• Around the globe, alteration of habitats by

farming, grazing, and logging are major

contributors to species loss

© Cengage Learning 2015

44.2 What Are the Effects of Desertification

and Deforestation?

• Desertification occurs when plowing or

grazing removes plants and exposes

topsoil to wind erosion

• Fewer plants means less transpiration;

rainfall decreases

• In a positive feedback cycle, drought

encourages desertification, which worsens

drought

© Cengage Learning 2015

What Are the Effects of Desertification and

Deforestation? (cont’d.)

A Dust cloud in the Great Plains during the 1930s. B Dust blows across the Atlantic from North Africa.

© Cengage Learning 2015

What Are the Effects of Desertification and

Deforestation? (cont’d.)

• Tropical forests continue to disappear at

an alarming rate

• In addition to immediate destruction of

forest organisms, deforestation

encourages flooding, and raises risk of

landslides in hilly areas

• Deforestation also affects local weather –

temperatures rise, and reduced

transpiration results in less rainfall

© Cengage Learning 2015

What Are the Effects of Desertification and

Deforestation? (cont’d.)

• Forests take up and store huge amounts

of carbon, so deforestation also

contributes to global climate change

– Deforested areas also become nutrient-poor

• Experimental deforestation increased

runoff of essential soil nutrients such as

calcium (compared with undisturbed

forest)

© Cengage Learning 2015

What Are the Effects of Desertification and

Deforestation? (cont’d.)

© Cengage Learning 2015

ANIMATION: Hubbard Brook Experiment

To play movie you must be in Slide Show Mode

PC Users: Please wait for content to load, then click to play

Mac Users: CLICK HERE

© Cengage Learning 2015

44.3 How Does Trash Degrade Habitats?

• Trash:

– Buried in the ground (such as lead from

batteries) can contaminate groundwater

– Dumped at sea (such as plastics) harms

marine life

• Plastic and other garbage that enters our

coastal waters persists for many years

– Avoid buying plastics, or be sure to recycle or

dispose of them properly

© Cengage Learning 2015

How Does Trash Degrade Habitats?

(cont’d.)

A B

© Cengage Learning 2015

44.4 What Are the Effects of Acid Rain?

• Pollutants disrupt physiological processes

of organisms

– Sulfur dioxides from coal-burning power

plants, and nitrogen oxides from burning gas

and oil, are common air pollutants

– Pollutant

• Substance that is released into the environment by

human activities and interferes with the function of

organisms that evolved in the absence of the

substance or with lower levels

© Cengage Learning 2015

What Are the Effects of Acid Rain?

(cont’d.)

• Dry acid deposition: dry dust particles

coated with airborne sulfur and nitrogen

• Wet acid deposition (acid rain): pollutants

combine with water and fall as acidic

precipitation

• Acid rain

– Low pH rain that forms when sulfur dioxide

and nitrogen oxides mix with water vapor in

the atmosphere

© Cengage Learning 2015

What Are the Effects of Acid Rain?

(cont’d.)

• Acid rain in aquatic habitats

– Prevents fish eggs from developing

– Kills adult fish

• Acid rain in forests

– Burns tree leaves

– Makes trees more susceptible to insects and

pathogens

© Cengage Learning 2015

What Are the Effects of Acid Rain?

(cont’d.)

• Acid rain alters composition of soils

– Positive hydrogen ions displace positive

nutrient ions such as calcium, causing nutrient

loss

– Acidity causes soil particles to release metals,

such as aluminum that harm plants

© Cengage Learning 2015

ANIMATION: Effect of air pollution in

forests

To play movie you must be in Slide Show Mode

PC Users: Please wait for content to load, then click to play

Mac Users: CLICK HERE

© Cengage Learning 2015

44.5 What Are the Effects of Ozone

Depletion and Pollution?

• Ozone is said to be “good up high, but bad

nearby”

– In the upper atmosphere, the ozone (O3) layer

absorbs most incoming ultraviolet (UV)

radiation that damages DNA and causes

mutations

– Near the ground, it is a harmful pollutant

© Cengage Learning 2015

What Are the Effects of Ozone Depletion

and Pollution? (cont’d.)

• In the mid-1970s, scientists noticed that

Earth’s ozone layer (10.5 to 17 miles

above sea level) was thinning, particularly

over Antarctica (the “ozone hole”)

• In 1987, countries worldwide agreed to

phase out production of

chlorofluorocarbons (CFCs) and other

ozone-destroying chemicals – but existing

CFCs break down very slowly

© Cengage Learning 2015

What Are the Effects of Ozone Depletion

and Pollution? (cont’d.)

Antarctica

© Cengage Learning 2015

What Are the Effects of Ozone Depletion

and Pollution? (cont’d.)

• Near the ground, ozone irritates eyes and

respiratory tracts of humans and wildlife,

and interferes with plant growth

• Ground-level ozone forms when nitrogen

oxides and volatile organic compounds

released by burning or evaporating fossil

fuels are exposed to sunlight

– Warm temperatures speed the reaction

© Cengage Learning 2015

44.6 What Are the Effects of Global

Climate Change?

• Climate change is the most widespread

threat to habitats worldwide

– Thermal expansion/meltwater from glaciers

flood coastal wetlands

– Temperature changes disrupt life-cycle events

(e.g., tree flowering, animal migration, and

breeding seasons)

– Some species are moving to higher latitudes

or elevations; those that cannot move are

stressed or dying

© Cengage Learning 2015

What Are the Effects of Global Climate

Change? (cont’d.)

• Many weather patterns are expected to

change as rising land and sea

temperatures affect evaporation, winds,

and currents

• Examples

– Extremes in rainfall patterns: periods of

drought interrupted by unusually heavy rains

– Increase in hurricane intensity

© Cengage Learning 2015

What Are the Effects of Global Climate

Change? (cont’d.)

© Cengage Learning 2015

What Are the Effects of Global Climate

Change? (cont’d.)

Muir Glacier in Alaska (1940)

Muir Glacier in Alaska (2004)

© Cengage Learning 2015

44.7 What Is Conservation Biology?

• Conservation biologists survey and seek

ways to protect the world’s existing

biodiversity

– Conservation biology

• Field of applied biology that surveys biodiversity

and seeks ways to maintain and use it

– Biodiversity

• Of a region, the genetic variation within its species,

variety of species, and variety of ecosystems

© Cengage Learning 2015

What Is Conservation Biology? (cont’d.)

• Biological wealth (biodiversity) is

measured at three levels:

– Genetic diversity within species

– Species diversity

– Ecosystem diversity

• Biodiversity is declining at all three levels,

in all regions

© Cengage Learning 2015

What Is Conservation Biology? (cont’d.)

• Healthy ecosystems are essential to

human survival:

– Produce our oxygen and food

– Remove, decompose, and detoxify wastes

– Prevent erosion and reduce risk of flooding

– Allow for new medicines to be derived from

compounds in wild species

– Encourage plant breeders to use genes in

wild species to protect and improve crops

© Cengage Learning 2015

What Is Conservation Biology? (cont’d.)

• People often oppose environmental

protections because they fear adverse

economic consequences

• Conservation biologists help determine

which regions should be targeted for

protection first by identifying hot spots

– Threatened region with great biodiversity that

is considered a high priority for conservation

efforts

© Cengage Learning 2015

What Is Conservation Biology? (cont’d.)

© Cengage Learning 2015

What Is Conservation Biology? (cont’d.)

© Cengage Learning 2015

What Is Conservation Biology? (cont’d.)

• Ecological restoration

– Actively altering an area in an effort to restore

or create a functional ecosystem

– Required when a natural ecosystem has been

degraded or destroyed

– Example: Louisiana’s coastal wetlands

© Cengage Learning 2015

What Is Conservation Biology? (cont’d.)

© Cengage Learning 2015

44.8 How Can We Reduce Our Impact?

• Ultimately, the health of our planet

depends on our ability to recognize the

principles of energy flow and resource

limitation

• The goal is living sustainably

– Meeting the needs of the present generation

without reducing the ability of future

generations to meet their own needs

© Cengage Learning 2015

How Can We Reduce Our Impact?

(cont’d.)

• People in industrial nations use enormous

quantities of resources, and the extraction,

delivery, and use of these resources has

negative effects on biodiversity

– Example: In the U.S., an average new home

contains about 500 pounds of copper wiring

and plumbing

• Strips vegetation and soil; produces waste; causes

air and water pollution

© Cengage Learning 2015

How Can We Reduce Our Impact? (cont’d.)

A B

© Cengage Learning 2015

How Can We Reduce Our Impact?

(cont’d.)

© Cengage Learning 2015

44.9 A Long Reach

• In the Arctic, unusually warm temperatures

are affecting the seasonal cycle of sea ice

melting and formation

– Polar bears can only reach their main prey by

traveling across ice

• Other threats – high amounts of mercury

and organic pesticides are carried to polar

regions by winds and ocean currents

– Have been found in tissues of polar bears

© Cengage Learning 2015

A Long Reach (cont’d.)

• Eight countries, including the U.S., control

parts of the Arctic and have rights to

extensive oil, gas, and mineral deposits

– Melting ice sheets make it easier to remove

minerals and fossil fuels from the Arctic

– Extracting these resources will further harm

Arctic species that are already threatened by

global climate change

© Cengage Learning 2015

A Long Reach (cont’d.)