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Ecosystem vulnerability and resilience Syllabus: Vulnerability and resilience of ecosystems -impacts due to natural stress -impacts due to human modifications.

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Presentation on theme: "Ecosystem vulnerability and resilience Syllabus: Vulnerability and resilience of ecosystems -impacts due to natural stress -impacts due to human modifications."— Presentation transcript:

1 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

2 Definition of vulnerability  Vulnerability is the ecosystem’s 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.

3 Question  What types of natural stress could be in an intertidal wetland?

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.

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.

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.

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.

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.

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.

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.

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 approx 100,000 cheetah worldwide.  In approx 100,000 cheetah worldwide.  Present estimates place their number at thousand with about 1/10 of those living in captivity.  Present estimates place their number at thousand with about 1/10 of those living in captivity.

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.

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.

14 Question  How would cane toads modify energy flows in an ecosystem?

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.

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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.

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.

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.

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.

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.

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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.

26 Examples of resilience?

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.

28 Question  Why might the Antarctic food web lack resilience?

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