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Human Impact on Ecosystems

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Title: Human Impact on Ecosystems


1
Human Impact on Ecosystems
  • Unit II

2
Humans in the Biosphere
  • The human population is still growing, but the
    earth is not, and this places increasing demands
    on Earths air, water, land, and living things
  • Understanding how humans interact with the
    biosphere is crucial to protecting these
    resources
  • Industry technology give humans a strong
    advantage in competing w/ other species for
    limited resources
  • Human activity uses as much energy as all of
    Earths other multicellular species combined
  • Hunting and gathering, agriculture, industry and
    urban development have significantly transformed
    the biosphere
  • Human activities can change the flow of energy in
    an ecosystem and reduce the ability of ecosystems
    to recycle nutrients.

3
The Green Revolution
  • The green revolution was introduced in the 1950s
    by the government as an effort to greatly
    increase the yields of rice, wheat, and other
    crops
  • Using highly productive varieties of certain
    crops
  • Using monoculture large fields cleared, plowed,
    and planted with the same crops year after year
  • Relied on pesticides, fertilizers, and large
    equipment to support large growing areas
  • Benefits increased food production
  • Problems depletion of energy and water
    supplies, pest species enabled to reproduce on a
    vast scale, pesticides can be potentially
    harmful, fertilizers can interfere with food webs
    and biogeochemical cycles

4
The Industrial Revolution
  • The era known as the Industrial Revolution was a
    period in which fundamental changes occurred in
    agriculture, textile and metal manufacture,
    transportation, economic policies and social
    structure (1760-1850).
  • Dense human communities
  • Human waste products
  • Reduction in habitats
  • Pollution
  • Overuse of wildlife products

5
Environmental Resources
  • Environmental resources can be classified into 2
    types renewable and nonrenewable
  • Renewable Resources can regenerate and are
    therefore replaceable (trees)
  • Nonrenewable resources one that cannot be
    replenished by natural processes (coal, oil, and
    natural gas)
  • Renewable resources are NOT NECESSARILY
    unlimited! Fresh water is renewable but can
    become limited by drought or overuse.
  • Fossil fuels form over hundreds of millions of
    years from deeply buried organic materialswhen
    they are depleted, they are gone forever!!!!

6
Sustainable Use
  • Sustainable use is a way of using natural
    resources at a rate that does not deplete them
  • Land resources
  • Forest resources
  • Ocean resources
  • Air resources
  • Water resources
  • A sustainable system operates without causing
    long-term harm to the ecological resources on
    which it depends
  • Example alternative methods of pest control
    that do not involve harmful chemicals

7
Land Resources - Renewable
  • Provides space for cities, etc. Important for
    the soils where crops are grown. If managed
    properly, soil is renewable.
  • Plowing removes the roots that hold soil in
    placewhich increases the rate of soil erosion
    (wearing away of surface soil by water wind).
  • In dry climate parts of the world, a combination
    of farming, overgrazing, and drought has turned
    once productive areas into deserts (a process
    called desertification).
  • Prevention contour plowing (plowing across
    slopes of land to reduce erosion, leaving stems
    roots of previous crops to help hold soil)

8
Forest Resources
  • Forests are dubbed the lungs of the earth b/c
    they remove CO2 and produce O2. They also store
    nutrients, provide habitats and food for
    organisms, limit soil erosion, and protect
    freshwater supplies.
  • Forests can be renewable or non-renewable
    depending on the type. For example, an old
    growth forest is considered non-renewable because
    of the amount of time it would take to replace
    the forest.
  • Deforestation can lead to severe erosion and loss
    of nutrients and habitats
  • Prevention harvest mature trees to promote the
    growth of saplings, utilize tree farms

9
Ocean Resources
  • The ocean is a vast source of species and food
    supply! In addition, some 75 of the earths
    available oxygen is produced by ocean species.
  • The increased rate of commercial fishing has had
    a severe impact on the worlds ocean species!
    Pollution of water systems is also an increasing
    concern!
  • Prevention limit catching of certain types of
    fish prevent pollution dumping from industry

10
Air Resources
  • Air is used every time we breathe!
  • Smog (mixture of chemicals appearing as a
    gray-brown haze) in cities results from
    automobile exhaust.
  • A pollutant is a harmful material that can enter
    the biosphere through the land, air, or water!
  • The burning of fossil fuels is a major
    contributor to the earths pollution problem and
    can lead to acid rain (gases combined with water
    vapor in the air and form drops of nitric and
    sulfuric acid)can drift for miles before falling
    as acid rain.

11
Water Resources
  • Although fresh water is a renewable resource, the
    total supply of fresh water is limited!
  • Pollution threatens water in several ways
  • Protections of the natural systems involved in
    the water cycle are essential for maintaining
    safe, fresh water sources.

12
Biodiversity
  • Biodiversity is the sum total of the genetically
    based variety of all organisms in the biosphere
  • Biodiversity is one of the Earths greatest
    natural resources food, industrial products,
    medicines
  • Ecosystem diversity includes the variety of
    habitats, communities, and ecological processes
    in the living world
  • Species diversity is the number of different
    species in the biosphere
  • Genetic diversity is the sum total of all the
    different forms of genetic information carried by
    all organisms living on Earth today

13
Human Threats to Biodiversity
  • Habitat Alteration Fragmentation
  • Development often splits ecosystems into pieces
    (habitat fragmentation).
  • Creates habitat islands.
  • Fewer species can survive here and they are more
    vulnerable to further disturbances or climate
    changes.

14
Human Threats to Biodiversity
  • Demand for Wildlife Products
  • Endangered species are now protected from being
    hunted in the US. This is still a problem in
    other parts of the world, such as Africa, South
    America, and Southeast Asia.

15
Human Threats to Biodiversity
  • Introduced Species
  • the accidental or intentional introduction of new
    plants animals into an area.
  • invasive species -a new species able to reproduce
    rapidly because their new habitat lacks the
    natural population controls they face in their
    old habitat.
  • Cane Toads in Austraila
  • Kudzu in America
  • African Bees in South America

16
Kudzu
17
Conserving Biodiversity
  • Today, conservation efforts focus on protecting
    entire ecosystems as well as single species
  • Most often, the need to protect biodiversity is
    greatest in countries that are least able to do
    so. These are known as hot spots immediate
    danger of extinction of species as a result of
    human activity
  • Example rainforests are found in developing
    countries

18
Biological Hot Spots
  • In an effort to locate problem areas and set up a
    list of conservation priorities, conservation
    biologists identify hot spotsplaces where
    significant numbers of habitats and species are
    in immediate danger of extinction as a result of
    human activity.

19
Changing the Future
  • Many biologists are now concerned about the
    biological effects of 4 types of global change
  • The thinning, or depletion of the ozone
  • Global warming
  • Acid Precipitation
  • Biological Magnification

20
A Thinning Ozone
  • Our atmosphere contains a concentration of ozone
    gases called the ozone layer. Ozone molecules
    consist of 3 oxygen atoms.
  • Function absorbs harmful UV radiation before it
    reaches Earths surface (global sunscreen).
  • Studies suggest that the ozone has been gradually
    thinning since 1975.
  • The problem of thinning ozone is caused by CFCs
    (chlorofluorcarbons) used as propellants in
    aerosol cans, to produce plastic foam, and as
    coolants in a/c systems. In cold atmospheres
    such as in space, CFCs allow UV to break apart
    ozone molecules.
  • The US has joined other countries in phasing out
    the use of CFCs.

21
Ultraviolet Radiation
A threat to the continuation of life
Visible
Infrared (IR)
UV
Humans DNA damage Cancer Crops Productivity
decrease Ocean plants Death?
22
Ultraviolet Radiation
stratospheric ozone layer
UV
destroy
CFCs refrigeration electronics foam
packaging spray propellants
1996 CFC decrease noticed 2006 stabilization?
23
Size of the Antarctic Ozone Hole
North America
30
20
Antarctica
Average Area millions sq km
10
0
1979
2001
Prediction 50 years to return to 1980 size
24
Global Warming
  • Earths temperatures remain within a range
    suitable for life because of the biospheres
    natural insulating blanket the atmosphere
  • Carbon dioxide, methane, water vapor, and other
    gases trap heat energy and maintain Earths
    temperature range
  • The function of these gases is similar to glass
    in a greenhouse they trap the heat energy of
    sunlight inside Earths atmosphere.
  • The natural situation in which heat is retained
    by this layer of greenhouse gases is called the
    greenhouse effect.
  • These greenhouse gases allow solar energy to
    penetrate the earths atmosphere, where much of
    the sunlight that hits the Earths surface is
    converted to heat energy and reflected back into
    the atmosphere.
  • The same greenhouse gases do not allow the heat
    to readily escape the atmosphere, but instead,
    trap it inside. The Earth is heating up!

25
Global Warming
  • Human activities may be causing climate change by
    increasing carbon dioxide concentration in the
    atmosphere!
  • Rising atmospheric CO2 - since the Industrial
    Revolution, the concentration of CO2 in the
    atmosphere has increased greatly as a result of
    burning fossil fuels.
  • Human-produced greenhouse gases include carbon
    dioxide CO2 , methane CH4, nitrous oxide N2O
  • The predicted consequences of global warming
    include
  • sea level rise
  • increased plant primary productivity
  • increased storm severity
  • changes to patterns of rainfall
  • changes to ocean circulation patterns

26
Acid Rain
  • The burning of wood and of fossil fuels,
    including coal and oil, releases oxides of sulfur
    and nitrogen that react with water in the
    atmosphere, forming sulfuric and nitric acid,
    respectively.
  • The acids eventually fall to Earths surface as
    acid precipitation rain, snow, sleet, or fog
    that has a pH of less than 5.2.
  • This acid precipitation lowers the pH of streams
    and lakes and affects soil chemistry and nutrient
    availability.
  • The main causes of acid rain are emissions from
    ore smelters and electrical generating plants.

27
Ecological Effects from Acid Rain in Lake System
  • Changes begin to occur as soon as a lake starts
    to lose it natural bases or alkalinity.
  • A large reduction in the number of plankton
    invertebrates.
  • The rate of decomposition of organic matter
    decreases
  • Direct effects on fishes reproductive cycles.
  • A calcium deficiency in fish leads to bone
    malformation.
  • Fish can suffocate as their gills become clogged
    with aluminum hydroxide.
  • Songbirds are effected by eating insects
    contaminated with toxic metals.

28
Biomagnification
In biomagnification, there is a tendency for
pollutants to concentrate as they move from one
link in a food chain to anothertop level
carnivores suffer the most harmful effects of
biomagnification.
29
Biomagnification DDT
  • Dichlorodiphenyltrichloroethane (DDT)
  • Used as a pesticide from 1939-late 1960s fat
    soluble compound - it is not broken down by
    metabolic processes in bacteria, plants, or
    animals
  • When DDT is picked up by organisms, they do not
    eliminate it from their bodies. As a result,
    something unexpected happens. DDT is picked up,
    concentrated, and stored by aquatic plants and
    algae.
  • When herbivores eat those plants, they
    concentrate DDT to levels ten times higher than
    levels found in plants! When carnivores eat
    herbivores, the toxic substance is concentrated
    further in a process called biological
    magnification.
  • The worlds production has substantially
    decreased since it was banned in the West
  • Detected in mud of deep sea and snow ice of
    Antarctica
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