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Ecosystem vulnerability and resilience


Ecosystem vulnerability and resilience Syllabus: Vulnerability and resilience of ecosystems-impacts due to natural stress-impacts due to human modifications to energy ... – PowerPoint PPT presentation

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Title: Ecosystem vulnerability and resilience

Ecosystem vulnerability and resilience
  • Syllabus
  • Vulnerability and resilience of ecosystems
  • -impacts due to natural stress
  • -impacts due to human modifications to energy
    flows, nutrient cycling and relationships
    between biophysical components

Definition of vulnerability
  • Vulnerability is the ecosystems sensitivity to
    stresses that ca upset the ecological dynamic
  • These may be natural or human induced stresses.
  • All ecosystems are vulnerable but they do vary in
    their sensitivity to change.

  • What types of natural stress could be in an
    intertidal wetland?

Natural stress
  • In intertidal wetlands the majority of natural
    stress comes from salinity and tidal movements.
  • The intertidal wetlands must be able to survive
    extreme conditions of mainly salt water at high
    tide, fresh water at low tide and times of flood
    and brackish water at other times.
  • The saline water is a very difficult condition
    for plants to survive in.

Natural stress
  • Changes to tidal movements through increased
    run-off or altered drainage can cause the roots
    of mangroves to be inundated for longer than
    normal periods affecting their pneumatophones.
  • It can also be pushed past its threshold level if
    water quality is changed. Thus even healthy
    ecosystems are vulnerable to change.

Natural stress
  • Some species such as oysters and molluscs have
    been used as indicator species, with any decline
    in their numbers indicating the ecosystem is
    under stress.
  • A decline in nutrient levels will also affect
    primary productivity and thus bring about change.

Natural stress
  • The grey mangrove accomplishes this by excluding
    salt in the root system, salt glands in the leaf,
    and waxy leaves to minimize water loss.
  • However it is vulnerable to changes in salinity

Natural stress
  • Today's cheetahs are almost carbon copies of each
  • Low genetic variability is a factor that
    increases the vulnerability of the world's
    cheetah populations to a wide variety of diseases
    and physiological defects.
  • A population genetic survey of over 200
    structural loci previously revealed that the
    South African cheetah (Acinonyx jubatus jubatus)
    has very little crossing over of chromosomes when
    fertilisation takes place.

Natural stress
  • The apparent consequences of such genetic
    uniformity to the species include
  • (i) great difficulty in captive breeding,
  • (ii) a high degree of juvenile mortality in
    captivity and in the wild, and
  • (iii) a high frequency of spermatozoal

Natural stress
  • Cheetahs are often persecuted by other predators,
    who steal their food, eat their cubs, and even
    attack the adults.  For these reasons, cheetahs
    life span in the wild is about 4 to 5 years, but
    they have been to known to live up to 15 years in
  • The cheetah is considered the most endangered big
    cat today. 
  • Human excess is probably the major factor pushing
    the cheetah toward extinction - robbing them of
    living space, limiting their food supply, 
    illegal hunting.

Natural stress
  • Some scientists believe that the cheetah
    population was nearly destroyed 10,000 years ago
    by a catastrophic event such as a disease or
    natural disaster that left only 1,000 or so
    surviving . 
  • In 1900 - approx 100,000 cheetah worldwide. 
  • Present estimates place their number at 10-15
    thousand with about 1/10 of those living in

Natural stress
  • Volcanoes can exert enormous natural stress on
    ecosystems in the short to medium term.
  • The ecosystem can eventually begin to recover as
    the volcanic material can provide nutrients for

Natural stress
  • As of February 1996, the current eruption has
    destroyed 181 homes.
  • Buildings, structures, roads, trails, and
    facilities have been destroyed in Hawaii
    Volcanoes National Park and in Harry K. Brown
    county park. Numerous archaeological sites have
    been buried.
  • Total losses exceed 61 million, making this
    eruption the most costly ever in Hawaii.
  • More than 500 acres (200 hectometers) of new land
    has been added to the island.
  • 1.7 billion cubic yards (1.3 billion cubic m) of
    lava has been erupted.

  • How would cane toads modify energy flows in an

Human modifications to energy flows
  • Cane toads were deliberately introduced from
    Hawaii to Australia in 1935, to control scarab
    beetles that were pests of sugar cane.
  • In 2002, Cane Toads occur throughout the eastern
    and northern half of Queensland and have extended
    their range to the river catchments surrounding
    Kakadu National Park in the Northern Territory.

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Human modifications to nutrient cycling
  • Nutrient cycling would be altered by climate
    change in ways that could exacerbate existing
    water quality problems such as eutrophication.
  • Eutrophication of lakes results when nutrient
    inputs from catchments and recycling from bottom
    sediments are large.
  • The result is excessive production of blue-green
    algae which reduces water quality.

Human modifications to nutrient cycling
  • In a warmer climate, the longer period of summer
    conditions would increase the solubility of
    phosphates in sediment and increase nutrient

Relationships between biophysical components
  • Lebanon's tourist and fishing industries remain
    battered by what has been described as the
    country's worst environmental catastrophe, which
    erupted when Israeli warplanes struck the Jiyeh
    power plant in mid-July, spilling up to 110,000
    barrels of fuel oil into the clear Mediterranean
  • Fewer than 3,500 barrels have been cleaned up.
    Lebanon couldn't start any offshore operation for
    weeks, waiting for Israel to lift its naval and
    air blockade on Sept. 8.

Relationships between biophysical components
  • The timing is quite essential with an oil spill.
    The more you wait, the more it spreads.
  • It is marine life that could suffer the worst
    consequences, because in the Mediterranean,
    currents don't come in often enough to sweep away
  • Lebanese waters are known as a passage for
    migrating fish, particularly tuna. The oil, which
    sank to the bottom of the sea, where it threatens
    plants and fish that live on the sea floor, could
    resurface unless treated and contaminate the
    coast for years to come.

Relationships between biophysical components
  • It could take up to 10 years for the ecosystem
    of the eastern Mediterranean to recover fully.
  • Several countries including France, Spain and
    Italy have sent teams to help the Lebanese navy
    with the cleanup, which could cost 100 million.
  • Lebanon, meanwhile, plans to sue Israel for
    damages, though it has not said how much it will

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Definition of Resilience
  • Resilience relates to the continuity of
    ecosystems and their ability to endure changes
    and disturbances while maintaining the same level
    of productivity and the same relations among
  • Resilience means that when a population is
    drastically reduced, it still has capacity to
    recover thanks to its regenerating potential and
    the balanced distribution of forest types and age

Examples of resilience?
  • Biological diversity appears to enhance the
    resilience of desirable ecosystem states, which
    is required to secure the production of essential
    ecosystem services.
  • The diversity of responses to environmental
    change among species contributing to the same
    ecosystem function, which we call response
    diversity, is critical to resilience.
  • Response diversity is particularly important for
    ecosystem renewal and reorganisation following

  • Why might the Antarctic food web lack resilience?

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