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 Slide 2
Definition of vulnerability Vulnerability is the ecosystems
sensitivity to stresses that ca upset the ecological dynamic
equilibrium. These may be natural or human induced stresses. All
ecosystems are vulnerable but they do vary in their sensitivity to
change. Slide 3 Question What types of natural stress could be in
an intertidal wetland? Slide 4 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. Slide 5 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. Slide 6 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. Slide 7 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 levels.
Slide 8 Natural stress Today's cheetahs are almost carbon copies of
each other. 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. Slide 9 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 abnormalities. Slide 10
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 zoos.
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 zoos. The cheetah
is considered the most endangered big cat today. 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. Slide 11 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. 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. In 1900 - approx 100,000 cheetah worldwide. Present
estimates place their number at 10-15 thousand with about 1/10 of
those living in captivity. Present estimates place their number at
10-15 thousand with about 1/10 of those living in captivity. Slide
12 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 regrowth. Slide 13 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. Slide 14 Question How would cane toads modify
energy flows in an ecosystem? Slide 15 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. Slide 16 Slide 17 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. Slide 18 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 recycling. Slide 19 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 waters. 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. Slide 20 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
pollutants. 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. Slide 21 Relationships between biophysical components It
could take up to 10 years for the ecosystem of the eastern
Mediterranean to recover fully. 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. 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 claim. Lebanon,
meanwhile, plans to sue Israel for damages, though it has not said
how much it will claim. Slide 22 Slide 23 Slide 24 Slide 25
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 populations. 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 classes. Slide 26 Examples of resilience?
Slide 27 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 change. Slide 28 Question Why might the Antarctic food
web lack resilience? Slide 29 Slide 30 Slide 31
