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 of Earth’s biodiversity; cane toads

Kudzu, a Japanese plantKudzu

HUMAN IMPACT ON ECOSYSTEMS Burning of fossil fuels is the most likely cause of global warming

The increased use of fossil fuels Impact on the Carbon Cycle –raises the level of CO 2 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 of tropical 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 birds 25 ppm DDT in large fish 2 ppm DDT in small fish 0.5 ppm DDT in zooplankton 0.04 ppm DDT in water ppm

It was once thought that the atmosphere could 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 protective ozone 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 depletionozone 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 species will 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 seeks to counter the loss of biodiversity

A biodiversity hot spot Biodiversity “Hot Spots” –a relatively small area with an exceptional 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 the biodiversity 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 with the health of the biosphere The goal of sustainable development –the long-term prosperity of human societies and 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

–promote dispersal and help sustain populations –especially important to species that migrate between different habitats

A zoned reserve Zoned Reserves –an extensive region of land that includes one or more areas undisturbed by humans

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