Impacts of Humans on Ecosystems

Impacts of Humans on Ecosystems

ObjectivesObjectivesG.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.

Impacts of Humans on EcosystemsImpacts of Humans on Ecosystems

TheTheOzoneOzoneHoleHole

Stratospheric ozoneStratospheric ozoneReview Review

earth science: earth science:

Stratosphere 7 – 30 miles

above sea level.Ozone layer.

Stratospheric ozoneStratospheric ozoneOzone 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.

Stratospheric ozoneStratospheric ozoneOzone 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.

Stratospheric ozoneStratospheric ozoneOzone 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.

Effects of UV radiationEffects of UV radiationLife 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.

Effects of UV radiationEffects of UV radiation

Effects of UV radiationEffects of UV radiationDirect human health effects:

Suppression of immunity leads to more disease.Eye damage – cataracts & blindness.

Effects of UV radiationEffects of UV radiationDirect 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.

Effects of UV radiationEffects of UV radiationDirect 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 ABCD’s of skin cancer.

Effects of UV radiationEffects of UV radiationDirect human health effects:

Skin cancer Sunscreens – SPF – SPF –

Sun Protection Factor 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.

Effects of UV radiationEffects of UV radiationDamage to biological links in the food

chain:UV kills ocean plankton, leads to reduced fish harvests.Stunted plant growth reduces crop yields.

Sunburned leaves

Effects of CFCs on the ozone layerEffects of CFCs on the ozone layerHuman 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.

Effects of CFCs on the ozone layerEffects of CFCs on the ozone layerHuman 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.

BiomagnificationBiomagnificationBiomagnification 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.

BiomagnificationBiomagnificationDDT in the food chain

DDT – a pesticide to kill mosquitoes and other insects.

Used to reduce insect-borne disease like malaria.

Poisons accumulate Poisons accumulate in creatures at the in creatures at the

top of the food top of the food chain.chain.

BiomagnificationBiomagnificationDDT 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 >100.

BiomagnificationBiomagnificationMercury in the food chain

Source: industry and agricultural pesticide.Bacteria convert inorganic Hg to methylmercury.

BiomagnificationBiomagnificationMercury in the food chain

Methylmercury builds up in fatty tissues.Accumulates from <1 ppb to over 5000 ppb in large fish.

BiomagnificationBiomagnificationMercury in the food chain

Impacts:

BiomagnificationBiomagnification Beware of what you eat.

Impacts of Humans on Ecosystems

Impacts of Humans on Ecosystems

ObjectivesObjectives

Earth is an islandEarth is an islandWe have limited resources on the planet.

Earth is an islandEarth is an islandHumans have changed the planet

through…Agriculture, industry, technology, overpopulation

Earth is an islandEarth is an islandSustainable 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.

DesertificationDesertification

Earth is an islandEarth is an islandAs non-renewable resources

(coal, oil) become scarcer, renewable resources*

be- come less costly, non-pollut- ing alternatives.

*Hydro, solar, wind, geothermal energy

Earth is an islandEarth is an island

We don’t recycle enough!

The biodiversity crisisThe biodiversity crisisExtinctions have occurred since life began

on Earth, but the current high rate, accelerated by humans, creates a crisis.

The biodiversity crisisThe biodiversity crisis

The biodiversity crisisThe biodiversity crisisHabitat destruction: Life that is

considered to be “less important” is often pushed aside in the name of Development. Haiti Dominican RepublicHaiti Dominican Republic

The biodiversity crisisThe biodiversity crisisIntroduced 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.

The biodiversity crisisThe biodiversity crisisAccidental introduction into Florida

Burmese python into the EvergladesEscaped pets (or abandonment)

Eat rodents & larger animals (young gators) - prey of Florida panthers (could eat them, too.)

The biodiversity crisisThe biodiversity crisisIntentional introduction into Florida

The Australian melaluca treeOriginally (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.

The biodiversity crisisThe biodiversity crisis

The biodiversity crisisThe biodiversity crisis

The biodiversity crisisThe biodiversity crisisEcological 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

The biodiversity crisisThe biodiversity crisisLoss of ecosystem

diversity: Pine rock- lands of S. Florida:

Loss of 98% due todevelopment

Fragmentation of habitats

The biodiversity crisisThe biodiversity crisis

The biodiversity crisisThe biodiversity crisisEconomic 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.

Conservation of BiodiversityConservation of BiodiversityReasons for the conservation of

biodiversity:EcologicalEconomicAestheticEthical

Conservation of biodiversityConservation of biodiversityEcological advantages of conservation

Preserving genetic, species, & ecosystem diversity.

All help to maintain stable ecosystems (food, water).

Conservation of BiodiversityConservation of BiodiversityEconomic 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

Conservation of BiodiversityConservation of BiodiversityEconomic advantages of conservation

Eco-tourism brings tourists and money both within and outside the US.

Ex: Costa Rican rainforest

Conservation of BiodiversityConservation of Biodiversity Aesthetic reasons for conservation

Nature can be beautiful and peaceful - a respite from the daily grind and modern technology - and…InspirationalYosemite National Forest

Conservation of BiodiversityConservation 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?

Conservation of BiodiversityConservation 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

ConservationConservation

US stamps – specific taxes that support conservation