• One-third of all plant and vertebrate species live on just 1.5% of Earth’s land

• Every year, humans destroy an area of tropical rain forest equal to the size of West Virginia

HUMAN IMPACT

• Introduced species

Introduced Species

– #2 cause of extinction and loss ofEarth’s biodiversity; cane toads

• Kudzu, a Japanese plant

HUMAN IMPACT ON ECOSYSTEMS

• Burning of fossil fuels is the mostlikely cause of global warming

• The increased use of fossil fuels

Impact on the Carbon Cycle

– raises the level of CO2 in the atmosphere

• Sewage treatment facilities and fertilizers

Impact on the Nitrogen Cycle

– add large amounts of nitrogen and phosphates to aquatic systems, causing heavy growth of algae

• Destruction oftropical rain forest

Impact on the Water Cycle

– alters local and global weather patterns

• The Hubbard Brook Experimental Forest is a study site for nutrient cycling in a forest ecosystem

Deforestation and Chemical Cycles: A Case Study

Completion of tree cutting

Altered

Control

• Humans are adding new toxics to ecosystems and they often cannot be degraded by microorganisms

The Release of Toxic Chemicals to Ecosystems

• Biological magnification

DDT concentration increase of 10 million times

DDT in fish-eating birds25 ppm

DDT in large fish2 ppm

DDT in small fish0.5 ppm

DDT in zooplankton0.04 ppm

DDT in water0.000003 ppm

• It was once thought that the atmospherecould absorb our gaseous waste products; smog

• The ozone layer

Depletion of Atmospheric Ozone

– absorbs UV radiation, preventing most of it from striking organisms in the biosphere

• Our protectiveozone layer

– started thinning due to the build up of CFCs (chlorofluorocarbons)

(a) Ozone hole

(b) Thickness of ozone layer

Monthly averages for October

• The consequences of ozone depletion

– are quite severe for all life on Earth

• The current mass extinction

The Loss of Species

– caused by human activity

– broader and faster than other past extinctions

• At the current rate of destruction over one half of all plant and animal specieswill be gone by the end of this century

• 1. Human destruction of habitat

The Three Main Causes of the Biodiversity Crisis

• 2. Introduced species

Introduced Species

• 3. Overexploitation of wildlife

Overexploitation

• Humans rely on biodiversity for

Why Biodiversity Matters

– food, clothing, shelter

– oxygen, soil fertility, medicinal substances

• Conservation biology

CONSERVATION BIOLOGY

– a goal-oriented science that seeksto counter the loss of biodiversity

• A biodiversity hot spot

Biodiversity “Hot Spots”

– a relatively small area with anexceptional concentration of species

Tropical forest hot spots

Chaparral hot spots

Equator

• Endemic species

– found nowhere else; common in hot spots

– highly sensitive to habitat degradation

• Much of the discussion of thebiodiversity crisis centers on species

Conservation at the Species Level

• The U.S. Endangered Species Act

– an endangered species is “in danger of extinction throughout all or a significant portion of its range”

• Conservation biology

Conserving Species amid Conflicting Demands

– deals with relationships between biology and society

• Competing demands for habitat are always an issue

• Sustainable development

Sustainable Development

– balances human needs withthe health of the biosphere

• The goal of sustainable development

– the long-term prosperity of human societiesand the ecosystems that support them

Habitat Fragmentation

• Population fragmentation

– the splitting and consequent isolation of portions of populations by habitat destruction

• A movement corridor

– a narrow strip or series of small clumps of quality habitat connecting otherwise isolated populations

An artificial corridor

Corridors

• Corridors

– promote dispersal and help sustain populations

– especially important to species thatmigrate between different habitats

• A zoned reserve

Zoned Reserves

– an extensive region of land that includesone or more areas undisturbed by humans

• The areas surrounding zoned reserves are buffer zones that support both agriculture and tourism