Transcript Chapter 6 Bio Rochex

Chapter 6 - Humans in the Biosphere
6-1 Human Activities that affect the
biosphere
1.
2.
3.
4.
Hunting and gathering
Agriculture
Industry
Urban development
Our resources are:
air, water, land and living things
Our resources provide:
raw materials for goods we need
services like temperature control, water
purification and good soil
Issues in the news
• Cod fishing banned off New England Coast
• The pipeline
• Fracking
How have human activities affected the earth?
1. Hunting and Gathering to obtain food
2. Agriculture – farming crops & raising livestock provide
a large, dependable food supply that is able to be stored
 Large scale irrigation (requires water to be diverted or
removed from underground aquifers)
 Machinery
 High-tech, monoculture crops (leads to problems with
pests and plant diseases)
 Fertilizers
 Pesticides
 The Green Revolution (has helped double world food
production over the last 50 years)
How have human activities affected the earth?
3. Industry
 Human society and its impact on the biosphere
were transformed by the Industrial Revolution,
which added machines and factories to civilization
 Powered mostly by fossil fuels: coal, oil & natural
gas
4. Urban Development
 Discarded industrial waste pollutes air, water, soil.
 Dense human communities also produce waste.
 Suburban growth consumes farmland and stresses
native plants and animals.
6-2
Renewable and Nonrenewable Resources
• Renewable resources like trees can regenerate if
they are alive, or can be replenished by
biochemical cycles if they are nonliving.
– Human activities affect the quality & supply of
renewable resources such as land, forests, fisheries,
air, and fresh water.
• Nonrenewable resources like coal, oil and natural
gas cannot be replenished by natural processes
because they took millions of years to form.
Sustainable Development
• A way of using natural resources without
depleting them, and of providing for human
needs without causing long-term
environmental harm.
• Five characteristics of sustainable use are:
1.
2.
3.
4.
5.
Stability
Flexibility
Appropriate technology
Efficiency
Productivity
SOIL
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•
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A renewable resource that must be protected
Food crops grow best in fertile soil—a mixture of
sand, clay, rock particles, and humus (material
from decayed organisms).
Soil erosion: the wearing away of surface soil by
water and wind.
Plowing the land removes the roots that hold the
soil in place, and increases the rate of soil erosion.
Desertification: process by which productive
areas are turned into deserts.
– Caused by farming, overgrazing and drought.
Sustainable-Development Practices
that protect the soil
• contour plowing—fields are plowed across the
slope of the land to reduce erosion
• leaving stems and roots of the previous year's
crop in place to help hold the soil
• planting a field with rye rather than leaving it
unprotected from erosion
Forest Resources
• Earth’s forests are an important resource for the products
they provide and for the ecological functions they perform.
• Forests
• provide wood for products and fuel.
• remove carbon dioxide and produce oxygen; the
“lungs of the earth”!
• store nutrients.
• provide habitats and food for organisms.
• moderate climate.
• limit soil erosion.
• protect freshwater supplies.
Forest Resources
• Temperate forests are renewable; trees grow back.
• Old-growth forests in Alaska & Pacific Northwest are
nonrenewable because they take centuries to grow.
• Deforestation effects:
• Erosion washes away nutrients in the topsoil
• Growing or plowing can permanently change local soils
preventing regrowth
• Forest Management includes
• Tree geneticists are breeding new, faster-growing trees that
produce high-quality wood.
• Selective harvesting protects the young trees
Fishery Resources
• Overfishing has greatly reduced the amount of fish in
parts of the world’s oceans; in this case fisheries are not
renewable.
• Sustainable Development:
• The U.S. National Marine Fisheries Service has issued
guidelines that specify how many fish, and of what size, can
be caught in various parts of the oceans.
• The regulations have helped fish populations recover.
• Aquaculture:
• The raising of aquatic animals for human consumption, which
is called aquaculture, is also helping to sustain fish resources.
Air Resources
• Smog is a mixture of chemicals that appears as a
haze in the atmosphere
– Due to car and industrial emissions
– Affects people’s health
• Strict automobile emissions standards and cleanair regulations have improved air quality in many
cities, but air pollution is still a problem
• Combustion processes release gases into the
atmosphere that react with water to form acid
rain.
Freshwater Resources
• Water is a renewable resource but the supply of
fresh water is limited and threatened by pollution.
• Sources of pollution include:
– Runoff of discarded chemicals
– Seepage of pollutants enter underground water supplies
– Domestic sewage containing compounds that encourage
growth of algae and bacteria in fresh water
– Domestic sewage containing microorganisms that
spread disease
Sustainable Use of Water
• Protect natural purification systems in the water
cycle – wetlands, forests and other vegetation
• Conserve water in homes, industry and
agriculture
6-3 Biodiversity
• Biodiversity: the sum total of the genetically
based variety of all organisms in the biosphere
• Ecosystem Diversity: the variety of habitats,
communities and ecological processes in the
living world
• Species Diversity: the number of different
species in the biosphere
• Genetic Diversity: the sum total of all the genetic
information carried by all organisms
Why Biodiversity is Important
– Biodiversity is one of Earth's greatest natural
resources.
– Species of many kinds have provided us with
foods, industrial products, and medicines—
including painkillers, antibiotics, heart drugs,
antidepressants, and anticancer drugs.
– If we protect the ecosystem, we preserve the
habitat and the species at the same time.
Threats to Biodiversity
Human activity can reduce biodiversity by:
1. Altering habitats through global warming, land
development and habit fragmentation
• Small, biological “islands” form where fewer species can live.
• These small populations are more vulnerable to further human
impacts and climate change
2. Hunting species to extinction
• As the population of an endangered species declines, the
species loses genetic diversity
3. Commercial demand for wildlife products
4. Pollution can introduce toxic compounds into food webs
• Biological magnification can occur
5. Introducing foreign species to new environments
• Invasive species have no natural predators
• EX: kudzu, spurge and zebra mussels
Invasive Species
Kudzu Vine
Biological Magnification
• Concentrations of a harmful substance increase in
organisms at higher trophic levels in a food chain
or food web.
• Toxic compounds accumulate in their tissues and
become magnified at each step in the food chain!
– EXAMPLE: the pesticide DDT
• It is nonbiodegradable – means it cannot be broken down
and organisms cannot eliminate it from their bodies
• DDT was banned in the 1970s and affected populations
have recovered
Biological Magnification
Conserving Biodiversity
• Conservation is the wise management of natural
resources, including preservation of habitats and
wildlife.
• Many efforts are aimed at managing endangered
species.
• Conservation efforts focus on both protecting the
ecosystems (natural habitats) as well as the species
that interact there.
• Challenges:
– People may have to change how they earn a living
– New regulations have to be based on solid research,
maximize benefits, and minimize cost
6-4 Charting a Course for the Future
Researchers are gathering data to monitor
and evaluate the effects of human
activities on two important systems in the
biosphere:
• the ozone layer high in the atmosphere
• the global climate system
Ozone Depletion
• Between 20 and 50 kilometers above Earth's
surface, the atmosphere contains a relatively
high concentration of ozone gas, O3.
• This layer of the atmosphere is called the ozone
layer.
• The ozone layer absorbs a good deal of harmful
ultraviolet, or UV, radiation from sunlight before
it reaches Earth's surface.
• UV exposure can cause cancer, damage eyes,
decrease resistance to disease and damage
plants and phytoplankton
Ozone Depletion
– In the 1970s, scientists discovered a hole in
the ozone layer over Antarctica and a similar
ozone hole appeared over the Arctic
– Gases called chlorofluorocarbons, CFCs, were
found to be the cause
– CFCs are now banned but were once widely
used in aerosol cans, as coolants for air
conditioners, and in the production of plastic
foams
– Current data predict that the ozone holes
should shrink and disappear within 50 years.
Global Climate Change
• Many scientists are concerned about strong
evidence that climate is changing.
• The increase in the average temperature of the
biosphere is called global warming.
• The most widely accepted hypothesis is that burning
fossil fuels and cutting & burning forests adds CO2 to
the atmosphere faster than the carbon cycle can
remove it.
• As a result the atmosphere’s natural greenhouse
effect is intensified and it retains more heat
• Methane gas, CH4, is also a GHG. 25% of manmade
global warming is due to CH4 & comes from leaks
Global Climate Change
• One sign of global warming is melting polar ice.
• Computer models suggest average global surface temps
will increase by 1 to 2 degrees by 2050
• Each degree of increase in global temperature will
cause sea level to rise 1 meter.
• Methane has a large effect for a brief period (a net
lifetime of 8.4 years in the atmosphere), whereas
carbon dioxide has a small effect for a long period (over
100 years). (Wikipedia)
We can make a difference
• Research and concern have led to actions that
have slowed ozone depletion, replenished
fisheries, restored major rivers, reduced urban
runoff and banned dangerous substances to
name only a few.
The Green Revolution: in the 50’s, government effort to dramatically increase
food production; monoculture crops calls for large land areas to be cleared
and planted with a single crop each year
Renewable vs non-renewable resources
Global Warming/greenhouse gases/
Ozone Depletion/CFCs
Acid Rain
The tragedy of the commons: Refers to the idea that any resource that is
open to everyone will eventually be destroyed because everyone can use the
resource but no one is responsible for preserving it.
Sustainable practices: Methods of using natural resources without depleting
them.
Biological Hot Spot
Biological Magnification
Invasive Species
Benefits and Costs to the four ways human activities have
changed the biosphere
Benefits
1. HUNTING & GATHERING
• Figured out how to hunt
successfully
2. AGRICULTURE
• Produced more food reliably
(the Green Revolution)
3. INDUSTRIAL REVOLUTION
• Machines and factories
4. URBAN DEVELOPMENT
• Better standard of living,
technology, conveniences
• Humans gathered in larger
settlements, cities, enabling the
development of culture and
civilization & exchange of ideas
& knowledge
Costs
•
Hunted some animals to extinction
•
Use of chemicals produced pollution
•
Based on rapid use of nonrenewable
fossil fuels & produced more
pollution
•
Increased dense populations in cities
= concentrated wastes & rapid use of
resources
loss of land and natural habitats for
plants & animals
•