Transcript Document

Anthropogenic Effects (Terrestrial)
Human Population Growth
• Probably the largest ecological problem
the Earth is facing today
• Each individual requires a minimum
amount of resource
– Food, water, shelter, fuel
• If the human population exceeds the
carrying capacity, the population will be
forced to decline
• Carrying Capacity – the maximum population size
that a particular environment is able to maintain
for a given period.
– At population sizes greater than the carrying capacity,
the population decreases
– At population sizes less than the carrying capacity, the
population increases
– At population sizes = the carrying capacity, the
population is stable
• Equilibrium Point – the population density that =
the carrying capacity.
Cultural Carrying Capacity
• ‘There should be no more people in a country
than could enjoy daily a glass of wine and piece
of beef for dinner.’
– Robert Malthus (~1805)
• We could live at the maximum carrying capacity
and devote all of our farmland to growing food for
direct human consumption (all bread and water,
no wine and steak)
– But is this what we want?
Human Population
Growth
• Estimated at 6.1 billion
in 2000
• Growing approximately
1.33% per year (214,000
per day)
• Population will double
in about 52 years
• Growth is actually
greater than
exponential growth
• No population can
continue to grow
without limit
Earth’s Carrying Capacity
• Difficult to estimate (what will be the limiting factor?)
• Most estimates predict about 10 – 12 billion people
(2000)
Ecological Footprint
•
•
Ecological footprint – amount of land needed to produce the
resources needed by the average person in a country
Methods:
1.
Correct consumption data for trade imports and exports
Consumptionwheat= production + imports – exports
2.
Convert to land area needed to produce the item
Awheat = Cwheat / ywheat
A=total area needed, C=consumed, Y=yield
3.
Obtain per capita ecological footprint by dividing by population
size
fwheat = awheat/population size
Ecological footprint in relation to
available ecological capacity.
It would take about 3 times the current land area of
Earth if all 6.1 billion people consumed the same as
the 276 million people in the US
Per Captia Ecological Footprint
(Hectares of land per person)
Country
10.9
United States
5.9
The Netherlands
India
Country
1.0
Total Ecological Footprint
(Hectares)
3 billion
hectares
United States
The Netherlands
India
94 million hectares
1 billion
hectares
Resources
• Ecological Resource – anything an organism
needs for normal maintenance, growth, and
reproduction
• Economic Resource – anything obtained from the
environment to meet human needs and wants
– Food, water, shelter, manufactured goods,
transportation, communication, and recreation
Resource Classification
• Perpetual resource – continually renewed
on a human time scale
– Solar energy, wind
• Renewable resource – can be replenished
as long as harvest is sustainable
– Timber, fisheries, fresh water
• Non-renewable resource – exist in a fixed
stock
– Fossil fuels, metals
Resources
Perpetual
Direct
solar
energy
Nonrenewable
Winds,
tides,
flowing
water
Fossil
fuels
Metallic
minerals
Nonmetallic
minerals
(iron,
copper,
aluminum)
(clay, sand,
Phosphates)
Renewable
Fresh
air
Fresh
water
Fertile
soil
Plants and
animals
(biodiversity)
Ecosystem Degradation
• When environmental conditions become
altered in such a way that they exceed the
range of tolerances for one or more
organisms in the biotic community, the
ecosystem becomes degraded.
• Loses some capacity to support the
diversity of life forms that are best suited
to its particular physical environment.
Anthropogenic
• Ecosystems can be degraded by natural
catastrophes
– Volcanoes, earthquakes, hurricanes
• When ecosystem degradation is humaninduced, we call that anthropogenic
effects.
– Waste disposal, dam construction, wetland
drainage
• Cannot control natural degradation, but
we can control our activities.
Ecosystem Damage
• Adverse alteration of a natural system’s
integrity, diversity, or productivity.
– Pollution is the major cause of environmental
damage
• Pollutant – a substance or form of energy,
such as heat, that adversely alters the
physical, chemical, or biological quality of
natural systems or that accumulates in the
cells or tissues of living organisms in
amounts that threaten their health or
survival
Acute Pollution Effects
• Occur immediately upon or shortly after
the introduction of the pollutant.
– Death is usually the effect
• Nitrite 96 hour LC50  acute toxicity.
• Twenty five million gallons of North
Carolina hog sewage.
Chronic Pollution Effects
• Act in the long term; they are not noticed
until several months, years or decades
after the introduction of the pollutant.
• Nitrite slows fish growth  chronic
toxicity
• Synergistic Effect – combined effect of
two chemicals is greater or more harmful
than the sum of their individual effects.
Bioaccumulation
• The storage of chemicals in an organism in
higher concentrations than are normally found in
the environment.
• N and P is found in higher concentrations of
phytoplankton than in the environment
– Actively concentrate (transport) N and P across their
cell membranes
• Fat soluble compounds also move across cell
membranes and dissolve in fats (lipids).
– Tend to stay in the organism and thus accumulate
– If they were soluble in water, then they would flush out
• DDT and PCB’s bioaccumulate.
Bioaccumulation of Tributylin (TBT)
• TBT is a chemical found in nautical paint
that was found in oysters along the coast
of California in the late 1980s’.
– Probably caused shell thickening and chamber
malformations
• Some oysters had TBT concentrations
30,000 times higher than in the water.
Bioaccumulation of Nitrite
• Nitrite is taken up by chloride cells
– Actively transported
• Acutely toxic to shortnose sturgeon
fingerlings
– 96 hour LC50 = 11.3 ± 8.17 mg/L
• When exposed to 2.17 mg/L for 5 days,
nitrite levels in the blood plasma were 63
times the concentration in the water.
Biomagnification
• Defined as the accumulation of chemicals in
organisms in increasingly higher concentrations
at successive trophic levels.
• Consumers at higher trophic levels ingest a
significant number of individuals, along with the
fat-soluble pollutants stored in their tissue.
• Top carnivores may accumulate poisons in
concentrations high enough to prevent their eggs
from hatching, cause deformities, or even death.
– Concentrations in predators can be a million times
higher in predators than the concentration in the soil or
the water
Terrestrial Biomagnification
• DDT used to control elm bark beetle
(Dutch elm disease).
Aquatic Biomagnification
• PCB’s dumped into the Great Lakes and
move through the food chain
One of the reasons the
Brown Pelican became
endangered.
Brown Pelican Recovery
• The Brown pelican was abundant in LA in 1950.
• Texas populations significantly declined between
1957 and 1961. LA’s population was eliminated.
– Listed as endangered in the US on October 13,
1970
• Primary cause of decline was pesticides: DDT
compounds (DDE and DDD), and PCB’s (dieldrin
and endrin).
– These chemicals were moved through the food chain
– Impaired reproductive success (egg shells became very
thin and would often collapse)
• Populations have since recovered
– DDT banned in 1972
– Egg shells have shown increasing thickness
Environmental Mercury
• Usually implicated in fish consumption
advisories: 1.0 ppm methyl mercury
warrants fish consumption advisories in
the US.
• Natural Sources:
– Volcanoes, soil, under sea vents, mercury-rich
geologic zones, freshwater, oceans, plants,
forest fires etc.
• Anthropogenic Sources
– Mining and industrial applications, waste
incineration, coal-fired plants, paint,
thermometers, etc.
Mercury Chemistry
• Elememental mercury (Hg0)
– Most common form of environmental mercury
– High vapor pressure, low solubility, does not
combine with inorganic or organic ligands, not
available for methylation
• Mercurous Ion (Hg+)
– Combines with inorganic compounds only
– Can not be methylated
• Mercuric Ion (Hg++)
– Combines with inorganic and organic
compounds
– Can be methylated
Methylation
• Basically a biological process by microorganisms
in both sediment and water
• Influenced by environmental variables that affect
both the availability of mercuric ions for
methylation and the growth of the methylating
microbial populations.
– Rates are higher in anoxic environments,
freshwater, and low pH
– Presence of organic matter can stimulate growth of
microbial populations, thus enhancing the
formation of methylmercury (sounds like a swamp
to me!)
Methylation
• Biological methylmercury production can vary
due to seasonal changes in:
– Nutrients, oxygen, temperature, and
hydrodynamics
• Measurements of total mercury concentrations in
the sediment do not provide information on the
form of mercury present, methylation potential, or
availability to organisms locally and downstream.
– If environmental conditions are conducive for
methylation, methylmercury concentrations may be high
in proportion to the supply and distribution of total
mercury
Methylmercury Bioaccumulation
• Mercury is accumulated by fish, invertebrates,
mammals, and aquatic plants.
• Inorganic mercury is the dominate environmental
form of mercury, it is depurated about as fast as it
is taken up so it does not accumulate.
• Methylmercury can accumulate quickly but
depurates slowly, so it accumulates
– Also biomagnifies
• Percentage of methylmercury increases with
organism’s age.
Methylmercury Bioaccumulation
• Uptake and depuration rates vary between tissues within an
organism.
• Partitioning of mercury between tissues within aquatic
organisms is influenced by the chemical form of mercury
and route of exposure (diet or gills).
– About 99% of mercury found in fish muscle tissue is
methylmercury (due to its preferential uptake, ability to be
transferred among tissues, and slow depuration).
• Marine mammals have among the highest concentrations of
mercury found in all marine organisms (liver highest
concentration)
• Invertebrates usually have a lower percentage (of total
mercury) of methylmercury in their tissues than do fish and
marine mammals.
– This percentage can greatly vary from 1% in deposit feeding
polychaetes to close to 100% in crabs.
Methylmercury Bioaccumulation
• Sediment is main source of mercury, but the
foodweb is the main pathway for aquatic
systems.
• High trophic level species tend to accumulate the
highest concentrations of mercury.
– Fish-eating predators have the highest
• Mercury concentrations in higher trophic species
often do not correlate with concentrations in
environmental media.
– However, correlations have been made between
sediment and lower trophic species that typically have a
high percentage of inorganic mercury, and between
mercury concentrations in higher trophic species and
their prey items.
Environmental
mercury has
increased due to
anthropogenic causes
http://water.usgs.gov/wid/FS_216-95/FS_216-95.html
Percent of sites in Louisiana that have mercury
advisories that include each group of fish. Total
sites listed = 16.
Species
% Sites
Largemouth Bass
75
Bowfin
69
Crappie
56
FW Drum
50
Catfish
25
Buffalo
19
Sunfish
19
Top predators tend to be listed more often.
Mercury Toxicity
• Influenced by the form of mercury, environmental
media, environmental conditions, the sensitivity
or tolerance of the organism, and the life history
stage.
• Toxic effects occur because mercury binds to
proteins and alters protein production or
synthesis.
– Effects include reproductive impairment, growth
inhibition, developmental abnormalities, and altered
behavioral responses
– Can affect the nervous system (coordination, sense of
touch, taste, and sight
– Particularly damaging to developing embryos
Environmental PCB’s
• Polychlorinated biphenyl’s – a group of highly
toxic chlorinated industrial chemicals used as
dielectrics, coolants and lubricants in
transformers and other electrical equipment,
weatherproofers, and to prolong residual activity
of pesticides.
– Usually released to the environment as a mixture
with other chemicals
– Fire resistant, low volatility, relatively stable and
persistent = good for industry, bad for
environment.
Environmental PCB’s
• Had been used for about 25 years until PCB
poisoning of birds and people were noticed in
1966.
• By the late 1970’s, evidence of extreme
persistence and adverse health effects had
resulted in a ban on their manufacture in some
industrialized countries.
• PCB’s are carcinogenic, can cause an increase in
bacterial infections, liver lesions, and genetic
defects.
Bioaccumulation
• PCB’s are not soluble in water, but are
soluble in fat.
• Therefore, they tend to bioaccumulate and
biomagnify.
– Can increase as much as a 1,000-fold as they
move up the food chain/
Environmental Effects
• Seals and porpoises
– Induced reproductive impairment
• Minks
– Embryo toxicity
• Birds
– Eggshell thinning
• Turtles (red-eared slider)
– Hormone disrupting effects with sex
determination
Hudson River and PCB’s
• Between 1947 and 1977, General Electric dumped
an estimated 1.3 million pounds of PCB’s into the
Hudson River.
– Source’s were two capacitor manufacturing plants
• PCB’s are now found in the Hudson Rivers
sediments and wildlife.
• One study showed that breast milk taken from
women around the Hudson River was seven
times the amount permitted in cow’s milk.
• Commercial fishing was shut down because of
PCB concentration found in the fish.
Hudson River Clean-up
• We can do nothing, and new sediment will
eventually bury the PCB’s.
– Overtime, PCB levels in the wildlife will decline
– This is the approach being taken on Lake Hartwell, SC
• We can dredge out the contaminated soil.
– Physically remove the contaminated sediment and haul
somewhere else
– Who wants that shipment?
• Two opposing sides for dredging the Hudson
River.
Those That Say No to Dredging
• Mostly it’s the officials for G.E. saying
dredging would not be good.
– The five year project would devastate this
ecosystem
– “It’s almost like clear-cutting a forest.” Adam
Ayers, GE Biologist
– PCB’s would be ‘resuspended’
– Could take 20 years for the fishery to recover
– Many people do not want the waste to be put
near their home
Those That Say Yes To Dredging
• EPA and private citizen groups
– Permanent removal of PCB’s is good
– Acknowledge that citizens along the river will
be disturbed while the dredging occurs
– Will lessen the spread of PCB’s throughout the
Hudson
– Environmental dredging techniques work like a
vacuum, and minimize the amount of
resuspension
Love Canal
• William T. Love decided he wanted to build a 7
mile canal approximately 4 miles upstream of
Niagara Falls to generate electricity and allow
ships to bypass the falls.
• However, only a mile of the canal was dug when
he had to abandon this project.
Overview of the
Canal area. The
canal is marked by
the arrow.
The northern
branch of the
Niagara River and
Grand Island, New
York, are visible at
the bottom of the
photo. North is at
top.
Love Canal
• By 1920, Love’s land was sold at public auction
and became a municipal and chemical disposal
site.
• From 1942 – 1953 the Love Canal Landfill was
used principally by Hooker Chemical, one of the
many chemical plants located along the Niagara
River.
– Nearly 21,000 tons of ‘toxic chemicals’ were
dumped at the site
• In 1953, the landfill was filled to capacity and
Hooker covered it with layers of dirt.
• The Niagara Board of Education then purchased
the land for one dollar.
Love Canal
• When Hooker sold the land, it gave a warning as
to what chemicals were buried on site.
• The area then became a housing development.
– Homeowners were not told of the potential hazards
– An elementary school was actually built directly on the
former landfill
• From the late 1950’s to the early 1970’s residents
submitted repeated complaints of odors and
‘substances’ surfacing in their yards.
• City officials assisted by covering the
‘substances’ with dirt or clay
– Including those found on the playground at the 99th
Street School
Love Canal
• By 1978, the Love Canal neighborhood included
800 private, single-family homes, 240 low-income
apartments, and the 99th Street Elementary
School.
• April 1978, a reporter wrote a series of articles on
hazardous waste problems in the Niagara Falls
area, including the Love Canal area
• Residents were beginning to question health
risks and noting already existing inexplicable
health problems.
– Children and animals were experiencing chemical burns
from playing with dirt.
– Birth defects, miscarriages, low birth-weight, cancers
and respiratory disorders were found here
Love Canal
• An official report came out showing the level of
contamination
– April 25, 1978 the New York State Commissioner of
Health issued a determination of public health hazard
existing in the Love Canal Community
– He ordered the Niagara County Health Department to
remove exposed chemicals from the site and install a
protective fence around the area
• August 1978, then president Jimmy Carter
declared the Love Canal area a federal
emergency.
– 239 families living in the first two rows of homes
encircling the landfill were relocated
– May 21, 1980 another 710 families were relocated
1980: Southern portion of the Canal, facing East.
The LaSalle Expressway is visible at bottom.
Love Canal Today
• Original landfill area (the canal) is buried under a
plastic liner, clay and topsoil in a fenced area
declared permanently off-limits.
– Many homes were also buried
• Rest of the Love Canal area is said to be safe and
the Love Canal Revitalization Agency has sold
232 of 239 renovated homes.
– Now known as Black Creek Village
• People feel safe because of the level of testing
done
What Is The Endocrine System
• Complex network of chemical signals and
messages that control many immediate and lifelong bodily responses and function
– Growing taller, developing male or female
characteristics, and reacting to fear are all partially
directed by endocrine hormones
• All vertebrates have an endocrine system that
works with the nervous system to:
– Maintain the body’s internal state (nutrition metabolism,
excretion, water and salt balance)
– React to stimuli from outside the body
– Regulate growth, development and reproduction
– Produce, use and store energy
Endocrine System
• Three parts:
– Glands respond to stimuli and release
chemical signals for specific target cells
– Hormones are the chemical signals
– Target cells have receptor proteins, which bind
to the specific hormones and set off a chain of
events
• Turn on genes to make new proteins (for growth or
sexual and reproductive maturity).
• Or, alter the activity of existing cellular proteins
(faster heart beat, regulate blood sugar levels)
How Hormones Work
Endocrine Disrupting Chemicals
• Endocrine disrupters can either be synthetic
chemicals or natural plant compounds
(phytoestrogens) that may affect the endocrine
system.
• Endocrine disrupters alter hormonal functions by
several means.
– Mimic or partly mimic the sex steroid hormones
estrogens and androgens
– Block, prevent or alter hormonal binding to hormone
receptors or influencing cell signaling pathways
– Alter production and breakdown of natural hormones
– Modify the making and function of hormone receptors
Modes of Action
• Receptor Binding - Mimic can bind to protein
receptors and produce
– Normal response, abnormal response, no response
(blocked receptor)
Exposure To Endocrine Disrupting
Chemicals
• Food, air, water, soil, household products
and probably through breast milk and
during development in our mother’s
womb.
• Human health risks with these low-level
yet constant exposures are still largely
unknown and highly controversial
Endocrine Disrupters
• Synthetic chemicals found in pesticides and
industrial products, Dioxins, PCB’s, DDT
• Usually have little effect on organism exposed
– Effect is on the offspring
PBDE’s: A Growing Concern
• Polybrominated diphenyl ethers (PBDEs) – a
class of flame retardants that reduces fire
potential and intensity of foam and plastic
products.
– Added during or after manufacturing to lower the risk of
fire and reduce flammability of fabric, polyurethane
foam, and plastics
– When heated, they release Bromide atoms that choke
fires
• Increasing amounts are being detected all over
the world in plants, animals, and people.
• Some are estrogenic while others interfere with
thyroid function that may alter brain development
affecting:
– Memory, learning, and behavior
Polybrominated diphenyl ethers
About 135 million pounds are produced annually
Used in auto seat headrests, furniture,
electronics
Why a Concern
• Not much is known about this chemical, but
rapidly rising environmental levels, increased
exposure, likely permanent brain effects, and
similarity to PCBs spark concern.
• Can concentrate in fat, thus they are able to
bioaccumulate and biomagnify.
• Are also believed to be endocrine disrupters.
– Some resemble thyroid hormone thyroxin and others
are estrogenic
– Fetal and infant exposure through mother’s blood and
breast milk permanently altered behavior, learning, and
memory in rodent experiments.
PBDEs in the Environment
• Found worldwide – including the Arctic
– Concentrations are said to double every three to five
years
– US has the highest exposure (probably due to the strict
fire codes)
• Recent studies found:
– 80 ppb in Great Lake salmon
– Almost 90% of FW fish tested in Virginia were
contaminated with a PBDE
– Sewage sludge contained a mix of PBDEs similar to
polyurethane
– Increasing amounts are found in Arctic wildlife (grey
seals, sperm whales, polar bears)
• However, environmental levels are still lower than
PCB levels.
Regulation
• US has no plans to bar or restrict PBDE
production or use
• But, the US EPA is reviewing health and
safety information on PBDEs and will
report conclusions next spring.
Stop here
Global Effects – CO2 Emissions
• Combustion of fossil fuels and vegetation
releases carbon dioxide to the atmosphere
Important Greenhouse Gases
Global Warming
(a) Rays of sunlight
(b) The earth's surface absorbs much of (c)
penetrate the lower
the incoming solar radiation and
atmosphere and warm the
degrades it to longer-wavelength
earth's surface.
infrared radiation (heat), which rises
into the lower atmosphere. Some of
this heat escapes into space and
some is absorbed by molecules of
greenhouse gases and emitted as
infrared radiation, which warms the
lower atmosphere.
As concentrations of
greenhouse
gases rise, their molecules
absorb and emit more infrared
radiation, which adds more
heat to the
lower atmosphere.
1.2
Average temperature over past 900,000 years
1.0
0.8
0.6
0.4
Model of greenhouse
gases + aerosols +
solar output
17
16
15
14
Average surface tem
perature (°C)
Observed
0.2
13
12
11
10
9
900
800 700 600 500 400 300 200 100Present
Thousands of years ago
0.0
-0.2
Average surface temperature (°C)
Temperature change (°C) from 1860–99 mean
Temperature Increase
Average temperature over past 130 years
15.0
1860 1880 1900 1920 1940 1960 1980 2000 2010
Year
14.8
14.6
14.4
14.2
14.0
13.8
13.6
1860 1880 1900 1920 1940 1960 1980 2000 2020
Year