© Cengage Learning 2015 p783

Chapter 30

Human Effects on the Biosphere

© Cengage Learning 2015

Why Are So Many Species Threatened or

Endangered?

• Endangered species: Faces extinction in

all or part of its range

• Threatened species: Likely to become

endangered in the near future

www.fws.gov/endangered/

© Cengage Learning 2015

Why Are So Many Species Threatened or

Endangered?

A White abalone.

C Texas blind salamander.

• Habitat destruction

• Competing with them for resources

• Overharvesting them

• Introducing non-native competitors

© Cengage Learning 2015

Desertification • Plowing/grazing removes plants, topsoil exposed

to wind erosion

• Fewer plants means less transpiration; rainfall

decreases

• In a positive feedback cycle, drought encourages

desertification, which worsens drought

© Cengage Learning 2015 Figure 44-4 p787

Deforestation • immediate destruction of forest organisms

• encourages flooding, raising risk of landslides in hilly areas

• temperatures rise, and reduced transpiration results in less

rainfall

• contributes to global climate change with loss of CO2

uptake

• increased runoff of essential soil nutrients such as calcium

© Cengage Learning 2015

How Does Trash Degrade Habitats?

Plastic and other garbage that

enters our coastal waters

persists for many years

• Disposable diapers 100 yrs

• Fishing line 100 yrs

• Plastic bag 50 yrs

• Cigarette filter 10 yrs

The Greenhouse Effect

• Certain gases in the atmosphere act like a

greenhouse by preventing heat from leaving,

keeping the planet warm

The Greenhouse Gases

• Naturally occurring

– Carbon dioxide (CO2)

– Methane (CH4)

– Water vapor

• Synthetic

– Chlorofluorocarbons (CFC)

• Aerosol sprays

• Refrigerants

• Styrofoam production

Photosynthesis Atmosphere Respiration

Combustion of

fossil fuels

Ocean

The CO2 Cycle

CO2 uptake by photosynthesis roughly equals CO2

release by cellular respiration. However,

deforestation and burning of fossil fuels flood CO2

into atmosphere.

CO2 levels have rapidly increased since the

Industrial Revolution

Measuring CO2 levels in ancient air

• http://earththeoperatorsmanual.com/seg

ment/5

© Cengage Learning 2015

What are hot spots?

Threatened regions with great biodiversity

that are considered a high priority for

conservation efforts

© Cengage Learning 2015

What is ecological restoration?

• Restoring or creating a functional ecosystem

• Required when a natural ecosystem has

been degraded or destroyed

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Environmental impacts of resource extraction

Average new home in U.S. contains about 500

pounds of copper wiring and plumbing. Open pit

mining strips vegetation and soil; produces waste;

causes air and water pollution

© Cengage Learning 2015

How Can We Reduce Our Impact?

• Learn about threats to ecosystems in your

area. Support efforts to preserve and restore

local biodiversity.

© Cengage Learning 2015

How Can We Reduce Our Impact?

• Carbon footprint: Amount of

greenhouse gas emitted as the result of the

actions of a single individual

• We can reduce our carbon footprints by

reducing our use of electricity,

driving less, and

recycling.

© Cengage Learning 2015

How Can We Reduce Our Impact?

• Eating locally grown fresh foods may

lower the greenhouse gas emissions that

result from food processing and

transportation.

How many Earths does it take for everyone to live

the same lifestyle as you?

• Take the Ecofootprint quiz at http://www.footprintnetwork.org/en/index.php/GFN/page/calculators/