Transcript Ch. 27 – Human Impact on Earth Resources

Ch. 27 – Human Impact on Earth Resources
•As any population increases, its demand for natural
resources increases as well.
•Any type of organism can have an impact on its
environment if its population becomes large enough.
•A population growth is the increase in the size of a
population over time.
•An initial population is small until the number of
reproductive adults increases. This will cause the
population of that organism to increase rapidly if there
are enough resources to continue the growth.
•Exponential Growth – a pattern of growth in which a
population grows faster as it increases in size. This
causes a population explosion.
•Fig. 27-3 (pg. 713)
• Most populations wouldn’t be able to continue
in an exponential growth pattern because of the
lack of resources.
• What organisms may have a higher success
rate? How about lower?
• Carrying capacity – the number of organisms
that any given environment can support.
• If a population hasn’t reached its carrying
capacity there will continue to be more births
than deaths.
• Once the carrying capacity is reached then the
population is at equilibrium an the number of
births and deaths equal out.
• Density-independent factors – are environmental
factors that affect population growth.
– Ex. Droughts, floods, storms, pollution
– These factors affect any population regardless of size.
• Density-dependent factors – increasingly affect a
population as the population’s size increases.
– Ex. Disease, parasites, and lack of food.
• Human Population Growth is still in the exponential
growth stage and may continue to grow for at least
another 50 years.
– It hasn’t reached its carrying capacity.
• The current rate of growth clearly cannot continue
forever. A demand for resources will continue to
increase steadily.
Human Impact on Land Resources
• An average person in North America consumes a
renewable yield of approximately 12 acres of forest
and farmland.
• Mining by surface and subsurface has big affects on
the environment. The government requires mining
companies to restore the ground to its original
contours and replant vegetation in the process of
reclamation.
• Biodiversity (wide variety of species) is important in
maintaining a stable ecosystem for organisms to live
in.
• Monocultures of one specific crop makes it easy for
farmers but provides risks in the form of plant specific
diseases, pests, and fungi.
• Pesticides are helpful to farmers by eliminating
insects, but there are drawbacks.
• A lot of pesticides kill pollinating and decomposers
(beneficial) insects.
• Insects reproduce quickly which cause them to build
resistance to pesticides.
• The runoff and wind may carry pesticides to rivers,
lakes, streams which causes harm to other organisms.
• Crop rotation is an excellent way for farmers to keep
topsoil fertile. Instead of adding artificial fertilizers
– Farmers rotate their crops with clover, alfalfa, or other crops
that are great nitrogen fixers and put nutrients back into the
ground.
• A big reason topsoil is lost is due to deforestation –
the clearing of forested land.
• 70% of North American’s live in a urban or suburban
area.
• The expansion of urban areas has a huge effect on
the environment. The effect is a loss of natural
habitats for a balanced environment.
• A lot of the global warming increase may be due to
expansions of urban areas.
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This wipes out plants for release of oxygen.
Pavement reflects more light & less rainfall is absorbed.
More greenhouse gases are released.
More solid wastes produced.
• These wastes are leaking from landfill as toxins.
• Lots of techniques have been implemented to
decrease the hazards caused from urban
expansion.
– Barriers for landfills.
– Wetlands are recognized and protected.
– Contaminated soils are removed and toxic
chemicals are destroyed from the soils with heat.
– Bioremediation is a technique to treat contaminated
soils with bacteria that eat toxic materials and
convert them to less-harmful substances.
• Video - Environment
Human Impact on Air Resources
• Smog – photochemical haze triggered by solar
radiation reacting with hydrocarbons and
nitrogen oxides (car exhausts).
• Ozone is the major chemical (3 oxygen atoms)
in smog.
– Ozone is helpful in the upper atmosphere for
filtering out harmful U.V. light.
– When ozone combines with air pollutants it harmful
to eyes, noses, throats, lungs, and plants.
• Pollution can be in the form of particulate
matter. Dust, pollen, ash, and asbestos fibers.
– They cause breathing difficulties and lung diseases.
• Humans have a major effect on air pollution with
global warming, ozone depletion, and acid
precipitation.
• Video – Global Warming
• Global Warming occurs from greenhouse effect, in
which the average surface temperature increases.
– This is largely due to the burning of fossil fuels, which
produce carbon dioxide as a bi-product.
– Since the Industrial Revolution (1850s) humans have been
burning fossil fuels consistently.
– Fig. 27-18 (pg.725)
• This could cause major effects on climate patterns.
– Glaciers melting and flooding shore lines, plant and animal
species may not adapt well.
• Could this be a trend or are humans causing drastic
climatic changes.
• Video – slowing global warming
• CFCs from human uses was the cause of ozone
depletion since the 1980s.
• Acid precipitation – precipitation with a pH less than 5.
• Forms when sulfur dioxide and nitrogen oxides
combine with atmospheric moisture.
• Coal generated by power plants produce acid forming
gases. Scrubbers are added to the power plants to
reduce the pollutants.
• The acid rain affects surface waters of aquatic
ecosystems and plants and animals. The acid rain
also damages stone buildings, statues, metal
structures, and especial limestone structures.
• Video – air pollution
Human Impact on Water Resources
• Freshwater is used by humans in several ways
– bathing, drinking, cooking, and washing.
– 378 billion liters of water was used per day in 1995.
– The greatest demand on water comes from
industry, including power plants that use water for
cooling purposes.
• Water Pollution
– Point Sources – generated pollution from a single
point of origin, such as a sewage-treatment plant or
an industrial site
– Nonpoint Sources – generated from widely spread
areas, such as runoff from pesticides, fertilizers,
roads, parking lots, etc.
• The Safe Drinking Water Act (1974) and the
Clean Water Act (1972). These laws made
water safer and cleaner for the ecosystem and
human consumption. They helped reduce
water pollution.
• Water Conservation
– Efficient irrigation practices, landscaping plants,
improving delivery systems, raise water rates,
recycle cooling water & waste water for industries.
– Fix leaky pipes, toilets, faucets, etc.
– Efficient showerheads, toilets, outdoor watering,
etc.