Transcript I. Introduced species II. Human impacts III. The

CHAPTER 20
Human Impacts on the
Environment
Outline:
I. Introduced species
II. Human impacts
III. The biodiversity crisis
IV. Conservation biology
V. The goal of sustainable development
About 12% of all
known bird species
are endangered
One-third of all
vertebrate species
live on just 15% of
Earth’s land
Purposefully
introduced
invasive species
have cost the US
economy $130
billion
Human impact
I. Introduced Species
• Are species that humans intentionally or
accidentally move from the species’ native
(home) locations to new geographic
regions.
• Examples:
– The European starling
– Argentine ants
– The zebra mussel
What is the number of introduced species in the US?
Can you name some species native to the US?
European starlings
Argentine ants ganging up on a
NATIVE red ant
Zebra mussels
II. Human Impact on
Ecosystems
– Human population has markedly changed
natural habitat systems.
• A. Impacts on Chemical cycles
– Carbon- increased burning of fossil fuels
– Nitrogen & Phosphorus - fertilizers & sewage
treatment facilities 
– Water – irrigating crops & deforestation
Carbon dioxide producers
Eutrophication causing algal bloom
Deforestation
Human impacts of
releasing toxins
– The release of new toxic materials cannot
be degraded by microorganisms
– Toxins can accumulate in tissues of
animals
– Biological magnification
• A process in which toxins become more
concentrated in successive trophic levels of a
food web
Human Impact on the
Atmosphere and Climate
– Carbon Dioxide Emissions
• Since industrial revolution CO2 has increased in
atmosphere
– The Greenhouse Effect
• Retains solar heat in the atmosphere
– Increased global temperatures have
potentially disastrous consequences
Remember the film?
Increase atmospheric CO2, temp variation
Factors influencing greenhouse effect
How do changes in number of
producers and consumers influence
production and uptake of global CO2?
How do different types of industry influence global CO2?
– Depletion of Atmospheric Ozone
• The ozone layer absorbs UV radiation
• Thinning since 1975 due to CFC’s
• Consequences– Increased skin cancer, cataracts
– Amphibian population declines
Thickness of ozone layer decreasing
1979
2000
III. The Biodiversity Crisis
– Human activity is causing a decline in the
Earth’s great variety of life
– A. Biodiversity has three main components
1. the diversity of ecosystems
2. the variety of species that makeup communities
3. the genetic variation within each species
Tropical rain forest
– B. The Loss of Species
– The current mass extinction - worldwide
•
•
•
•
Caused by human activity
Broader & faster than past extinctions
12% of known bird species
24% of known mammal species are threatened
with extinction
• Biologist Edward O. Wilson has compiled the
Hundred Heartbeat Club
– Species with fewer than 100 individuals
Philippine eagle
Chinese river dolphin
Javan rhinoceros
C. Three Main Causes of
the Biodiversity Crisis
–1. Habitat Destruction
•
Is the single greatest threat to biodiversity
–2. Introduced Species
•
Ranks second behind habitat loss. Can cause
rapid extinctions
– 3. Overexploitation of wildlife
Habitat destruction
Introduced species
Lake Victoria, East Africa
Overexploitation
Do you like bluefin tuna?
Do you eat sushi?
D. Why Biodiversity Matters
– Humans rely on biodiversity for
• Food, clothing, shelter, oxygen, soil fertility,
medicinal substances
– Endemic species
• Are those found nowhere else
– The loss of diversity
• Limits the potential for new discoveries of food
and medicine
IV. Conservation Biology
A science that seeks to counter
the loss of biodiversity
– Biodiversity hot spots
• Small areas with an exceptional concentration
of species, including endemics
Terrestrial biodiversity hot spots
Notice California
Do you understand why its important to preserve biodiversity in CA?
Conservation at the
Population & Species
Levels
– The U.S. Endangered Species Act (ESA)
• Definition: endangered species
– “…a species in danger of extinction throughout all or a
significant portion of its range”
• Definition: threatened species
– “…a species likely to become endangered in the
foreseeable future”
Habitat & Population
Fragmentation
– Fragmentation can results in
• A decrease in the overall size of populations
• A reduction in gene flow among subpopulations
• Harmful side effect of human habitation
Mt. Hood National Forest
?
Northern spotted owl
What Makes a Good
Habitat?
– Identifying the specific combination of
habitat factors that is critical for a species
is fundamental to conservation biology
• Example: Polar Bears
Conserving Species amid
Conflicting Demands
– Competing demands for habitat
• The owl
• Wolf
• Grizzly bear
• Bull trout
VS
• Jobs in
• Timber
• Mining
• Loss of livestock
• Camping safety
– Edges and corridors between ecosystems
• Promote dispersal & help sustain populations
Especially important to species that migrate
between different habitats seasonally
Natural edges between ecosystems
Edges created by human activities
Heavily logged rain forest in Malaysia
An artificial corridor
V. The Goal of
Sustainable
Development
– Sustainable development
• Balances human needs with the health of the
biosphere
– The goal of sustainable development
• Is the long-term prosperity of human societies
and the ecosystems that support them
Some Ways You Can
Promote Sustainability
Reduce consumption
• Buy less
• Avoid excess packaging
• Avoid products make from non-renewable resources
• Fix things rather than discarding them
Be more energy efficient
• Bike, walk, take public transportation, drive less
• Share rides
• Purchase efficient appliances and vehicles
Promote recycling
• Recycle at home and at work
• Purchase products made from recycled materials
Promote research and education
• Talk about environmental issues with friends, family
• Sponsor environmental initiatives on your campus
• Serve as a role model through your actions
…more on Table 20.1
Biophilia and an
Environmental Ethic
– Edward O. Wilson
• Biophilia
 the human desire to affiliate with other life
in its many forms, is innate
…Respect Earth’s biodiversity
Near Walden pond
…the look of ‘biophilia’ on his face
1. Severe population _________ is one of the most severe
consequences of habitat degradation.
2. Carbon dioxide traps heat and warms the atmosphere, a process
called the _________ effect.
3. It is hard to protect species such as the monarch butterfly, sea
turtles, and many songbirds, because they _________.
5. Fertilizer runoff can result in the _________ of lakes.
6. The goal of _________ development is to ensure that each
generation inherits adequate resources and a stable environment.
7. Most biodiversity hot spots are in the _________.
8. Biological _________ of pesticides harms animals at the top of
the food chain.
10. Human alteration of _________ is the greatest threat to biodiversity.
14. The Earth is facing a serious _________ crisis.
18. The _________ is a law that protects endangered and threatened
species.
20. In the US, 25% of prescriptions contain substances derived
from _________.
22. Burning of _________ fuels produces carbon dioxide that may
contribute to global warming.
Reading Assignment for:
Next week, 12/4/07 & 12/6/07
Chapter 17
The Evolution of Animals