Impacts of Humans on Ecosystems

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Impacts of Humans on Ecosystems

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Objectives

• G.3.11 State that ozone in the stratosphere
  absorbs ultraviolet (UV) radiation.
• G.3.9 - Outline the effects of UV radiation on
  living tissues and biological productivity.
• G.3.10 Outline the effects of
  chlorofluorocarbons (CFCs) on the ozone layer.
• G.3.7 - Define biomagnification.
• G.3.8 - Explain the cause and consequences of
  biomagnification, using a named example.

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Impacts of Humans on Ecosystems

The Ozone Hole
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Stratospheric ozone

• Review earth science
• Stratosphere
• 7 30 miles above sea level.
• Ozone layer.

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Stratospheric ozone

• Ozone in the stratosphere absorbs ultraviolet
  (UV) radiation.
• UV radiation is energy that can break chemical
  bonds in molecules such as DNA causing
  mutations, which lead to cancer.
• Three types of UV radiation UVA, UVB, UVC.
• UVA has the longest wavelength is least
  energetic.

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Stratospheric ozone

• Ozone in the stratosphere absorbs UV radiation.
• Ozone forms when radiation or electrical
  discharge separates the two atoms in an oxygen
  molecule (O2), which can then individually
  recombine with other oxygen molecules to form
  ozone (O3).

Some UVA is absorbed in the formation of
ozone. Some UVB is absorbed in the destruction
of ozone.
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Stratospheric ozone

• Ozone in the stratosphere absorbs UV radiation.
• Some UVA is absorbed in the formation of ozone.
• Some UVB is absorbed in the destruction of ozone.

Most of the UV that reaches the ground is
the less dangerous UVA.
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Effects of UV radiation

• Life on Earth remained microscopic until
  development of free oxygen in the atmosphere 3.4
  billion yrs ago
• Thereafter, life remained in the ocean until the
  ozone layer formed. Life washed out was fried by
  UV light.
• Only after the ozone layer formed 600 million
  yrs ago could life move onto the land.

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Effects of UV radiation

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Effects of UV radiation

• Direct human health effects
• Suppression of immunity leads to more disease.
• Eye damage cataracts blindness.

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Effects of UV radiation

• Direct human health effects
• Both UVA UVB rays damage skin.
• Sunburn is a sign of short-term
  overexposure.
• Premature aging skin cancer
  are side
  effects of prolonged
  exposure.

UVA penetrates deeper
Collagen fibers are weakened.
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Effects of UV radiation

• Direct human health effects
• Skin cancer
• UVB does more damage
  to skin, but
  most blocked
  by clouds, clothing, glass.
• UVA is greatest threat
  
  penetrates to living skin
  cells and damages DNA.

The ABCDs of skin cancer.
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Effects of UV radiation

• Direct human health effects
• Skin cancer
• Sunscreens SPF
• Sun Protection Factor
• Time needed to produce a
  sunburn on protected
  skin relative
  to time need-
  ed to produce a sunburn
  on unprotected skin. If it
  normally takes 20 minutes
  
  
  to burn, SPF 2 doubles
  time to 40 minutes. SPF
  15 or above is consid-
  ered best.

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Effects of UV radiation

• Damage to biological links in the food chain
• UV kills ocean plankton, leads to reduced fish
  harvests.
• Stunted plant growth reduces crop yields.

Sunburned leaves
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Effects of CFCs on the ozone layer

• Human activities are depleting atmospheric ozone.

Chlorofluorocarbons (CFCs) destroy ozone,
creating an ozone hole over parts of the earth.
Areas beneath the hole are more prone to UV
radiation.
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Effects of CFCs on the ozone layer

• Human activities are depleting atmospheric ozone.
• One chlorine or bromine molecule can destroy
  100,000 ozone molecules, causing ozone to
  disappear much faster than nature can replace
  it.

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Biomagnification

• Biomagnification is the increase in concentration
  of a chem-ical as it passes from one level in a
  food chain to the next
• This occurs because the chemical is fat soluble
  and not excreted in the urine, or it is not
  degraded.
• Since creatures at high trophic levels must
  eat a lot of lower- level creatures, chemicals
  build up in them.

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Biomagnification

• DDT in the food chain
• DDT a pesticide to kill mosquitoes and other
  insects.
• Used to reduce insect-borne disease like
  malaria.
• Poisons accumulate in creatures at the
  top of the food chain.

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Biomagnification

• DDT in the food chain
• The chemical builds up in predatory birds and
  affects their ability to form a shell around
  their eggs. The eggs are crushed
  during incubation, and the bird population drops
  (ex the California condor).

By 1987 there were fewer than 30 condors.
Today there are gt100.
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Biomagnification

• Mercury in the food chain
• Source industry and agricultural pesticide.
• Bacteria convert inorganic Hg to methylmercury.

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Biomagnification

• Mercury in the food chain
• Methylmercury builds up in fatty tissues.
• Accumulates from lt1 ppb to over 5000 ppb in large
  fish.

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Biomagnification

• Mercury in the food chain
• Impacts

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Biomagnification

• Beware of what you eat.

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Impacts of Humans on Ecosystems

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Objectives

• Fl.17.16 Discuss the environmental impacts
  resulting from human activity.
• Fl.17.11 Compare costs and benefits of
  renewable and nonrenewable resources.
• Fl.17.12 Discuss consequences of sustainable
  land use.
• Fl.17.8 Discuss reasons for conservation of
  biodiversity
• Fl.17.13 Discuss the need for environmental
  monitoring
• Fl.17.14 Assess the need for adequate waste
  disposal.
• Fl.17.15 Discuss effects of technology on
  environmental quality.
• Fl.HE.13 Evaluate how environmental and
  personal health are interrelated.

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Earth is an island

• We have limited resources on the planet.

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Earth is an island

• Humans have changed the planet through
• Agriculture, industry, technology, overpopulation

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Earth is an island

• Sustainable land use
• Over-grazing of live- stock, excessive
  ag- riculture, overpopu- lation strip land
  of its regenerative ca- pacity, and it
  can no longer sustain life.

Desertification
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Earth is an island

• As non-renewable resources
  (coal, oil) become scarcer,
  renewable resources be-
  come less costly, non-pollut-
  ing alternatives.

Hydro, solar, wind, geothermal energy
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Earth is an island

We dont recycle enough!
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The biodiversity crisis

• Extinctions have occurred since life began on
  Earth, but the current high rate, accelerated
  by humans, creates a crisis.

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The biodiversity crisis

• Ecological threats to biodiversity.
• Habitat destruction (and fragmentation)
• Responsible for 73 of endangered species.
• Rainforest cut for logging, then used for
  agriculture
• Introduced species
• Those that humans moved from native locations to
  new geographic regions.
• Australian melaluca trees in Florida out- compete
  native plants.
• Pythons in the Everglades eat natives food.
• Dogs cats also compete for food of natives.
• Snakes on Guam eat eggs of native birds.
• Goats, sheep, cattle change the ecosystem.

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The biodiversity crisis

• Habitat destruction Life that is considered to
  be less important is often pushed aside in the
  name of Development.

Haiti Dominican Republic
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The biodiversity crisis

• Introduced species are those that humans have
  moved from native locations to new geographic
  regions.
• They generally upset food webs by adding new
  predators (includes pathogens) or competitors.

The cat disturbs the food web.
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The biodiversity crisis

• Accidental introduction into Florida
• Burmese python into the Everglades
• Escaped pets (or abandonment)
• Eat rodents larger animals (young gators) -
  prey of Florida panthers (could eat them, too.)

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The biodiversity crisis

• Intentional introduction into Florida
• The Australian melaluca tree
• Originally (1875 1900) planted as a windbreak
  and to control erosion around levees, then by
  developers to dry up the Everglades for housing.
• Out-competes other plants for light less
  diversity.

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The biodiversity crisis

• Species extinction
• Humans (aliens to most of the planet) are causing
  major extinctions planet-wide.
• Over-hunting of passenger pigeons and dodo birds.
• Wild, formerly-domesticated goats pigs are
  killing native Hawaiian plants birds.

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The biodiversity crisis

• The U.S. Endangered Species Act defines
• Endangered species as one in danger of extinction
  throughout its range
• 993 species in the US
• 71 species listed in Florida
• Florida panther
• West Indian manatee
• Threatened species as one likely to become
  endangered in the foreseeable future.

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The biodiversity crisis

• Ecological consequences
• 1) Loss of genetic diversity
• If a local population dies out, genes
  could disap- pear that might help the
  species adapt to new en- vironmental
  conditions, such as global warming.
• 2) Loss of species diversity
• A species may be critical to another
• 3) Loss of ecosystem diversity
• Loss of a pattern of energy flow -
• a food chain or food web disrupted

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The biodiversity crisis

• Loss of ecosystem
  diversity Pine rock- lands
  of S. Florida
• Loss of 98 due to development
• Fragmentation of habitats

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The biodiversity crisis

• Economic threats to biodiversity
• Overexploitation
• Harvesting of wild plants animals at rates that
  exceed the ability of those populations to
  rebound.
• Tropical woods for furniture (generations to
  repopulate)
• Tropical birds, reptiles, orchids are taken for
  sale.
• Hunting as a sport or for food

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The biodiversity crisis

• Economic consequences
• Some lost species may have provided new food
  sources or medicines.
• Many cancer drugs are botanicals.
• Plants can be sources of synthetic fuels and
  foods.

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Conservation of Biodiversity

• Reasons for the conservation of biodiversity
• Ecological
• Economic
• Aesthetic
• Ethical

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Conservation of biodiversity

• Ecological advantages of conservation
• Preserving genetic, species, ecosystem
  diversity.
• All help to maintain stable ecosystems (food,
  water).

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Conservation of Biodiversity

• Economic advantages of conservation
• Maintaining US parklands can provide jobs for
  rangers, vendors, amusement operators (guides,
  ski lifts, boat docks, etc.). Forests provide
  income from sustainable logging.

Old Faithful, Yellowstone National Park
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Conservation of Biodiversity

• Economic advantages of conservation
• Eco-tourism brings tourists and money both within
  and outside the US.
• Ex Costa Rican rainforest

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Conservation of Biodiversity

• Aesthetic reasons for conservation
• Nature can be beautiful and peaceful - a respite
  from the daily grind and modern technology -
  and
• Inspirational

Yosemite National Forest
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Conservation of Biodiversity

• Ethical reasons for conservation
• What right do humans have to disturb life for the
  other inhabitants of earth and to presume our
  needs are most important?

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Conservation of Biodiversity

• Ethical reasons for conservation
• It is wrong to take and take and take until there
  is little more than people on the face of the
  planet.

Coruscant
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Conservation
US stamps specific taxes that support
conservation