Transcript Chapter_6_honors_notes_kane2

Humans in the Biosphere
Honors Biology Chapter 6
The Tragedy of the Commons
• Areas used by everyone are no one’s
responsibility
• Leads to misuse; loss of resources
Renewable Resources
• Resources can
regenerate (living) or
• Resources that can be
recycled through
biogeochemical cycles
• Examples
– Trees
– Water
Renewable resources are NOT
necessarily UNLIMITED.
• Freshwater is a
renewable resource,
BUT there are events
that CAN make it very
limited. For example:
– Drought
– Pollution
Nonrenewable Resources
• Cannot be replenished
by natural processes.
• Examples:
– Fossil fuels
Is a tree population renewable
or nonrenewable?
• Individual trees are
renewable
• A population of trees
may not be, because
the ecosystem they
were in may change
forever once the trees
are gone.
Sustainable Development
• Using resources without depleting them
• Providing for human needs without causing
long-term damage to the environment
• Must take into account
– Functioning of ecosystems
– Human economic systems
Sustainable Development
Strategy - Example
• Using insects instead
pesticides to control
pests
Land Resources - Soil
• Renewable or not?
– Renewable if managed properly
Mismanagement of Soil
Resources
• Soil Erosion
– Wearing away of surface soil by water and
wind
– Results when land is plowed, and roots that
hold soil in place are removed
Mismanagement of Soil
Resources
• Desertification
– Misuse of soil causes
once productive areas
to become deserts
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Dry climate
Farming
Overgrazing
Drought
Forest Resources
• Ways in which forest
resources are used by
people
– Building
– Burning
Forest Resources
• Ways in which forests provide ecological
services
– Forests as “lungs of the Earth”
• Absorb CO2 and release O2
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Store nutrients
Provide habitat and food for organisms
Moderate climate
Limit soil erosion
Protect freshwater supplies
Are Forests Renewable
Resources?
• Maybe – it depends on the forest
– Our temperate deciduous forests seem to
come back pretty well after cutting, though not
always exactly as they were
– Old Growth Forests are NOT renewable
• Ancient trees and ecosystems
• Will not be replaced by a similar ecosystem if cut
– The plants and animals dependent on the anceint trees in
the system would die
– Even if allowed to come back, the ecosystem would never
return to its present state.
Old Growth Forest
Deforestation
• Definition: The loss of forests
• Deforestation can lead to
– Severe soil erosion
– Erosion can wash nutrients out of the soil
– Grazing or plowing after deforestation can
cause permanent changes in the soils that
prevent regrowth of trees.
Fishery Resources
• Overfishing
– Harvesting fish at a rate
greater than they can replace
themselves by reproduction
– 1950 – 1990
• Fish harvest dramatically
increased
• Fish populations
dramatically declined
• “Tragedy of the Commons”
– Fishing of certain species
banned
• Some populations have
seen recovery
Aquaculture
• Raising aquatic
animals for human
consumptions
– Good: provides food
for people without
drawing from natural
populations
– Disposal of wastes
from the aquatic
animals can be a
source of pollution
Pollutant
• A harmful material that
can enter the biosphere
through the land, air or
water.
• Pollutants released from
burning fossil fuels
include:
– Carbon dioxide
– Nitrates and Sulfates
– Particulates
Air Resources
• Smog
– Mixture of chemicals
that results in a
brown/gray haze in the
atmosphere.
• Mostly due to
– Automobile exhaust
– Industrial emissions
What are particulates
• Microscopic particles
of ash and dust that
can enter the nose
mouth and lungs
causing health
problems
Nitrates and Sulfates
• Combine with water vapor
in the air
• Create Acid Rain
– Kills plants by damaging
leaves
– Change soil chemistry
– Change chemistry of
standing water ecosystems
– Dissolves and releases
toxic elements that may be
bound up in soil
• mercury
Freshwater Resources
• People use freshwater for
– Drinking
– Washing
– Watering crops
– Industry
– Recreation
Pollution Threatens Freshwater
Supplies
• Improperly discarded chemicals can enter
streams and rivers
• Wastes discarded on land can seep through soil
into groundwater supplies
• Sewage containing phosphorus and nitrogen
encourages algae growth
• Sewage can also spread disease
– Though most cities due try to treat sewage before it
enters water ways…
– Still, animal waste runs off cow pastures, etc.
Protection of Wetlands and the
sustainable use of water
• Wetlands act to purify
water that passes
through them
• Saving wetlands
means cleaner water
Primary use of water in the U.S.
• Agriculture
– Uses ¾ of freshwater
The Value of Biodiversity Terms
• Biodiversity
– 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
– number of different species in the biosphere
• Genetic diversity
– sum total of all the different forms of genetic information carried
by organisms living on Earth
Why is biodiversity of practical
value to humans?
• Species of many kinds have provided us
with foods, industrial products and
medicines
• Inherent value just of its own merit
Threats to Biodiversity – Human
Impacts
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Altering habitats
Hunting species to extinction
Introducing toxins into the environment
Introducing foreign species into a new
environment
Habitat Alteration
• Natural habitats may be destroyed when land is
developed
• As habitats disappear, the species that live in
them vanish
• Habitat fragmentation
– The splitting up of ecosystems as developments take
up land area
• Habitats become biological islands – isolated
• The smaller the island, the smaller the number of species and
population sizes – the more vulnerable they are.
Habitat fragmentation
Demand for Wildlife Products
• Demand for animal
species products has
caused extinction by
hunting
– Carolina parakeet
– Passenger pigeon
Pollution – Biological
Magnification
• Certain pollutants are NON-biodegradable
• When producers take chemicals these into their bodies,
they are stored in tissues rather than altered and
excreted.
• When consumers eat the producers, they consume more
concentrated amounts of the chemical
• This pattern repeats itself as you move up the food chain
and the toxin gets more an more concentrated.
Biological Magnification
• Definition: phenomenon in which the
concentration of certain compounds in each
organism in a food chain increases
DDT and Biological
Magnification
• Decade After WWII
• Pesticide industry prompted the benefits of DDT
before the consequences of its use were
understood.
• By the 1950s scientists learned that:
– DDT persists in the environment
– DDT is transported by water to areas far from where it
is applied
– By this time, DDT was already a global problem
DDT and Biological
Magnification
• Who was affected
– Pelicans, ospreys, eagles
– Top of the food chain
– Affected calcium deposition in eggs – made
them weak and easy to crush
• Weight of parent while incubating eggs crushed
eggs
Other pollutants and biological
magnification
• PCBs
– Great Lakes
– Endocrine system problems in lots of animals
including humans
– Concentration in Herring Gull eggs is 5,000
times greater than in phytoplankton at base of
food web
Other Pollutants and Biological
Magnification
• Mercury
– By-product of plastic production
– Plastic production and coal power plants
– Expelled into rivers/oceans
– Bacteria at the bottom mud convert to a more
harmful substance
• Methyl mercury
• Accumulates in tissues of organisms including
humans
Introduced / Invasive Species
• Species that are introduced into a new
environment
• May be no natural predators
• Reproduce rapidly
• Take over habitat
• Crowd out native species
• Reduce biodiversity in native ecosystems
Zebra mussels
• Native to freshwater lakes
of southeast Russia
• Spread began in 1700s
• First discovered in this
country in Great Lakes in
1988
• Ballast water from ships
probably responsible for
introduction
Kudzu
• Introduced intentionally in
1876 as a forage crop and
ornamental plant
• From 1935 to 1950
farmers were encouraged
to plant it to prevent
erosion
• The southern U.S. has
near perfect conditions for
this plant to grow out of
control, which it has done.
Northern Snakehead
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Native to China, Russia, Korea
Top level predator
First reported in U.S. in 2000 in pond in Maryland
Found in pond in Chesapeake Bay watershed –
pond was drained and the fish were destroyed
• A man admitted releasing two snakeheads into
the pond after purchasing them in NY
• 19 found in Potomac River in 2004
• Found in other states now
Conserving Biodiversity
• Conservation
– Wise management of natural resources,
including the preservation of habitats and
wildlife
– Conservation seeks to protect biodiversity
Conservation Strategies
• Preventing single
species extinction
• Example – Zoos
– Establish captive
breeding programs
– Raise and protect
animals until
population is stable –
then return to wild.
Conservation Strategies
• Now more focused on protecting entire
ecosystems
– Ensures that natural habitats and interactions of many
different species are preserved at the same time
– Much bigger challenge
• Governments and conservation groups must work together to
set aside land, etc.
• Even though the U.S. has lots of national parks, etc., this is not
nearly enough to protect biodiversity
Hot Spots
• Places where large numbers of habitats
and species are in immediate danger of
extinction as a result of human activity
• Hot spot strategy MAY help to focus efforts
Effects of Ecosystem Protection
on People
• Regulations to reduce
hunting/fishing may
place financial
hardships on people
for several years
• But what will
consequences be if
nothing is done?
Ozone depletion
• Ozone layer
– 20 – 50 km above Earth’s surface
– Made of O3
– A pollutant at Earth’s surface
– Protects people from UV radiation
Ozone depletion
• Hole in ozone was
discovered in 1970s
– Image is from 2006
• Over Antarctica
• Continued to grow larger
and last longer
• 1974 – Cause of ozone
hole determined
– Chlorofluorocarbons (CFCs)
• Propellants in aerosol cans
• Coolant in refrigerators, air
conditioners, etc.
Ozone depletion
• 1987, US and many other nations began
reducing use of CFCs
• Today they are mostly banned
• Effects of ban will not be seen right away
– CFCs linger for years in the atmosphere
– Ozone hole should shrink and disappear in 50
years
Global Climate Change
• Greenhouse Effect
– CO2 in atmosphere allows
high energy UV radiation
– Warms Earth
– Earth radiates heat back
towards space as low
energy infrared radiation
• Not strong enough to
penetrate CO2
• Heat remains to keep
climate on Earth moderate
– Greenhouse Effect is
GOOD and NEEDED
• Without it Earth would be
MUCH colder
Problem
• Too much CO2 traps
too much heat
• Result is global
warming
• Too much CO2 in
atmosphere due to
– Burning of fossil fuels
– Reduction in forests,
etc.
Global Warming
• Definition – increase of average
temperature of the biosphere
• Records show:
– Since 1900 temp has risen .6 C
– Since 1980 temp has risen .2 to .3 C
– 1990s were warmest decade on record
– 1998 was warmest year on record
Is global warming due to human
activity?
• Earth’s climate does fluctuate naturally
– Remember, there was once an ice age
– Glaciers have advanced and retreated over
geologic history
• Couldn’t the rise in temperatures we’re
observing be part of this natural
fluctuation?
Evidence for global warming
being caused by human activity
• The current temperature increases are unlike
anything ever observed in history
• They directly coincide with humans increased
burning of fossil fuels
• The vast majority of scientists agree that the
evidence shows humans are impacting global
warming
• Still there is controversy among some…
– Careful to consider the sources…
Possible Effects of Global
Warming
• Average global
temperatures will increase
by 1-2 degrees C by 2050
• Sea level rise due to
melting ice caps
– Coastal ecosystems
– Coastal human
communities
• N. America – more
droughts?
• Entire ecosystems change
as climates change