Download Chapter 6 Humans in the Biosphere

Chapter 6
Humans in the Biosphere
6-1 Changing Landscape
Earth as an Island
All Organisms that live on Earth:
Share Limited resources
Depend on these for long term survival
Rely on natural ecological processes to keep
these resources
Human participate in food webs &
chemical cycles
Ecosystems provide:
1. Breathable air
2. Drinkable water
3. Fertile soil
4. Storage & recycling of nutrients
Human activities are the most important source
of environmental change on the planet
These include:
1. Hunting & Gathering – led to mass extinction of
animals
2.
Agriculture – practice of farming
Benefits of the Green Revolution
a. Greatly increased the world’s food supply
b. Plant breeders developed new varieties of crops
c. Use of chemical fertilizers
Challenges for the Future
a. Large scale monoculture – can lead to insect pests &
disease
b. Chemical pesticides can harm beneficial insects & can
contaminate water supplies
c. Need to find enough water for irrigation
3. Industrial Growth & Urban Development
Industrial revolution :
–
–
–
–
added machines & factories
Led to industrial productivity & scientific knowledge
Gave us mobility
Provides modern convenience
Adverse effects:
–
–
–
–
–
Need for energy
Waste
Pollution
Suburban growth consumes farmland & natural
habitats
Stresses plant & animal populations
6-2 Renewable and Nonrenewable
Resources
Environmental goods may be classified
as renewable or nonrenewable
Renewable:
1. Can be regenerated if they are alive
2. If not alive, can be replenished by
chemical cycles
3. Not necessarily unlimited
4. Examples: fresh water, trees
Nonrenewable:
1. A resource that can not be
replenished by natural processes
2. Once (depleted) used up→ gone
forever
3. Examples: fossil fuels
Sustainable development
→ is a way of using natural resources w/out
depleting them
→ of providing for human needs w/out causing
long-term environmental harm
To work well, sustainable development must:
1. Take into account both:
Functions of ecosystems
&
Ways that human economic systems operate
2. Must enable people to live comfortably &
improve their situation
Land Resources
Land – resources that provides space
(humans) & raw materials for industry
If managed properly it is a renewable
resource
Fertile soil = a mixture of sand, clay, rock
particles & humus
Topsoil- uppermost layer of the soil
Good topsoil absorbs & retains moisture
–Allows excess water to drain
–Is rich in nutrients
–Low in salts
–Produced by long-term interactions
between soil & its plants
Problems:
– Soil erosion – wearing away of surface soil
by wind & water
– Desertification – one productive area
turned into deserts by farming,
overgrazing & drought
Sustainable development practices
include:
– Contour plowing – fields plowed across
slope
– Leaving stems & roots to help hold the soil
in place
Forest Resources
Important resource because:
– They provide products
Examples:
– Wood
– Paper
– Fuel
– They perform services
Examples:
– Lungs- remove CO2 & Produces O2
– Store nutrients
– Provide habitats
– Moderate climate
– Limit soil erosion
– Protect freshwater supplies
Temperate forest are considered renewable
resources
Old-growth forests are forests never cut
before
– A nonrenewable resource
– When logged, they may lose the rich variety
of species
Problem = Deforestation – loss of forests
– Leads to severe erosion
– Grazing or plowing causes permanent
changes to local soils & microclimates
Sustainable development practices include:
1.Harvest selectively
2.Replant tree farms
3.Breeding new varieties that grow faster
Fishery Resources
Fish are a valuable source of food
Problem – Over-fishing – catching fish faster
then they can reproduce
They were providing food, but the population of
fish species were shrinking
No one took responsibility for maintaining this
resource
It is a renewable resource
Sustainable development practices include:
US Fisheries Service developed guidelines for
commercial fishing:
Specifies how many fish & of what size
Aquaculture – raising aquatic animals for food
Problems: can pollute water & damage
aquatic ecosystems
Air Resources
Common resource that we use to breathe
Problem: Smog – mixture of chemicals that occurs as a
gray – brown haze
Mostly due to automobile exhaust & industrial
emissions
Is considered a pollutant – harmful material that
enters the biosphere
Comes from burning fossil fuels
Contains toxic chemicals ex: nitrates & sulfates
Also have particles – microscopic particles of ash
& dust
Putting the nitrates & sulfates into air → changes to
acid
Acid rain – kills plants & changes chemistry of soil &
standing water
Sustainable development practices include:
Industry uses smokestack technology
Autos have strict emission standards
Clean air regulations
Freshwater Resources
Uses:
1. Drinking
2. Washing
3. Watering crops
4. Making Steel
Is a renewable resource, but the supply is limited
Problems:
Pollution is caused by
–
–
Improperly discarded chemicals
Domestic sewage – wastewater from sinks & toilets
Contain microorganisms that can cause disease
N & P can cause growth of algae & bacteria
Sustainable development practices Include
–
–
–
Cities & towns treat wastewater
Water passing wetland → purify water
Reduce demand → conservation
6-3 Biodiversity
Diversity = variety
Biodiversity – sum total of the genetically
based variety of all organisms
Ecosystem diversity – variety of habitats,
communities & ecological processes
Species diversity – # of different species in
the biosphere
Genetic diversity – sum total of all the
different forms of genetic information
carried by all organisms on Earth today
One of earth’s greatest natural resources is
biodiversity
Provide us with food , industrial products &
medicines
Threats to Biodiversity
Extinction - when a species disappears
from all of its range
Endangered species – population of
species is low enough, it is in danger
of extinction
As population numbers decline, species diversity
is lost
Caused by human activities
1.
Habitat alteration – when land is developed
a. Provides organisms’ needs which are then a more
limited resource.
b. Developments can cause habitat fragmentation – a
process that splits ecosystems into pieces (islands)
c. The habitat islands formed have fewer species, smaller
populations which make the species more vulnerable
to any disturbance
2.
Demand for wildlife products
a. Hunting for food or other products
b. Some body parts (horns) have “medicinal” properties
c. CITES bans international trade in products from
endangered species
3. Pollution
a. Occurs when toxic compounds accumulate in
tissues of organisms
b. Example = pesticide DDT
c. Biological magnification – harmful substances
concentrate in organisms at higher trophic levels
in a food chain or web
d. Those at highest risk are found top – level
carnivores
4. Introduced Species – apparently harmless
plants & animals that humans transport to
new areas
a.
b.
c.
d.
In new habitats these become invasive species
They reproduce rapidly
New habitat lacks parasites & predators
Zebra mussels – ( Missouri)-are driving native
species away
Conserving Biodiversity
Conservation – wise management of natural
resources
Strategies include:
– Breeding programs at zoos which manage
individual species
– Protecting entire ecosystems protects habitats,
species & species interactions by setting aside
land for park & reserves
– Marine sanctuaries protect coral reefs & marine
mammals
Conservation challenges: try to maximize
benefits while minimizing economic costs
6-4 Charting a Course for the Future
Ozone Depletion
Ozone layer – the part of the atmosphere that
contain relatively high concentration of
ozone gas O3
A naturally occurring layer that is necessary to
absorb UV radiation
Overexposure to UV rays causes
1. Sunburn
2. Cancer
3. Damage eyes
4. Disease Resistance
5. Damage Plant Tissue
Problem = holes in the natural layer over
Antarctica & Arctic
Holes caused by CFC’s
CFC’s were widely used as coolant, aerosol
propellant & production of plastic foam
1987 use was banned; but there are still
effects because CFC molecules linger
Current data shows that the holes should
shrink & disappear in ~ 50years
Global Climate Change
All life depends on temperature & rainfall
Global warming – increase in the average
temperature of the biosphere
Evidence: Two hypotheses
1. This is part of a larger natural cycle of
climate change
2. Humans are causing the warming trend
Data shows that CO2 concentrations have been
rising for 200 years
Human activities that add more CO2 by:
1. Burning fossil fuels
2. Cutting & burning forests
Possible effects of Global Warming
– Effects are based on computer models
– Sea levels may rise and flood coastal areas
– North America may experience more
drought
– Long term climate change will affect
ecosystems
Value of a Healthy Biosphere
Ecosystems provide goods & services
To maintain healthy systems, every
individual must make wise choices in
the use & conservation of resources
Examples:
1. Use less water
2. Plant Trees
3. Dispose of waste properly
4. Recycle