Vulnerability and resilience
The following locational factors can affect the functioning of ecosystems:
- distance from the sea
- microclimatic features
Ecosystems that are restricted to relatively small areas or have already been subject to
extensive disturbance are especially vulnerable.
Ecosystems that have low levels of interdependence are much more vulnerable to change. For example if an organism can rely on only one form of producer for its survival, and the producer population is wiped out then the consumer is it great risk of also being wiped out in the area.
- genetic: Genetic diversity favours the survival of a species as it increases the chance that some members of the population will have the characteristics to be able to withstand changes in environmental conditions
- species: The greater the species diversity within an ecosystem the more able the ecosystem will be to
- ecosystem: The greater the number of habitats, biotic communities and ecological processes occurring, the easier it will be for the
ecosystem to recover from threats or changes in environmental conditions.
Example: Rhino - genetic diversity
“Two species of rhino in Asia—Javan and Sumatran—are Critically Endangered. A subspecies of the Javan rhino was declared extinct in Vietnam in 2011. A small population of the Javan rhino still clings for survival on the Indonesian island of Java. The small size of the Javan rhino population is in itself a cause for concern. Low genetic diversity could make it hard for the species to remain viable.”
Example: Coral Reefs - species diversity
Coral reefs are widely known for their stunning array of color, shape and forms of life, making them a model for extreme biodiversity. Hidden within the multitude of reef inhabitants, but no less important, is their genetic diversity— variability inDNA that gives species the capacity for adaptation, speciation and resilience in the face of stress.
Example: Borneo - ecosystem diversity
“Although Borneo conjures images of dense tropical rainforests, the landscape offers a mosaic of varied habitats: mangroves, peat swamp and swamp forests, ironwoods, heath and montane forests. These areas form part of a complex ecosystem that has evolved over thousands of years.”
Natural changes to Ecosystems:
- Immediate – e.g. drought, flood, fire, volcanic eruptions, storm surge,
cyclone. Immediate natural changes can have a dramatic effect on ecosystems, and
in severe cases can wipe out the ecosystem in it’s entirety.
- Gradual – e.g. natural fluctuations in climate, movement of species, adaptation to changes – natural selection. Gradual changes are likely to cause long-term changes to an ecosystem, such as changes to species found and numbers of species, functioning of the ecosystem.
Examine links about Charles Darwin and the theory of evolution.
- Immediate – deforestation, overgrazing, ploughing, erosion, pesticides, toxic substances, urbanisation, mining and war
- Gradual – salinisation and soil waterlogging, compaction and erosion, pollution, habitat loss, species loss, loss of biodiversity, introduction of exotics, climate change
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a landscape converted to alternative uses (Brinson, 1988, 1993b). Because many wetlands are adjacent to surface waters, they often represent the best opportunity for natural improvement of water quality because of their filtering and transformation capacity. Uplands also can provide retention and transformation, but they are often preferentially allocated to other land uses—such as agriculture and urban development—that generate nutrients and sediments, and are more remote from surface waters.
When wetlands are seasonally dry, they can be temporarily cease some functions, such as support of aquatic habitat, but retain others, such as the capacity to store surface water. Because the return of functions associated with saturation can be contingent on maintenance of the physical and hydrologic conditions under which the wetland developed, alteration of wetlands during dry phases is likely to be detrimental to their functional integrity.
Individual wetlands function in part through interaction with the adjacent portions of the landscape and with other wetlands. For example, flyway support for waterfowl is a collective function of many wetlands. Likewise, no single wetland or aquatic site could support anadromous fish. The connections between individual wetlands, aquatic systems, and terrestrial systems are critical to the support of many organisms. Furthermore, flood control and pollution control are determined by the number, position, and extent of wetlands within watersheds. Thus, the landscape gives proper context for the evaluation of some wetland functions.
Maintenance of biodiversity, water quality, and natural hydrologic flow regimes in part depends on the total wetland area and on the types of wetlands within regions (Preston and Bedford, 1988). As wetland acreage declines within a watershed, some functional capacities, such as maintenance of water quality or waterfowl populations, also decline. In this way, cumulative loss of wetland gradually impairs some landscape-level functions (Gosselink and Lee, 1989; Gosselink et al., 1990; Preston and Bedford, 1988). This occurs not only through loss of surface area, but also through reduction in average size, total number, linkage, and density of wetlands (Johnston, 1994b). Many wetland functions and their associated value to society depend on the connections among wetlands and between wetlands and adjacent aquatic and terrestrial systems. For example, river floodplain wetlands form natural corridors for the migration of fish, birds, mammals, and reptiles (Brinson et al., 1981). Uses of uplands can affect the physical, chemical, and biotic characteristics of wetlands. Paving or agricultural uses, for example, affect the amount and quality of water that reaches adjacent wetlands. Where the use of uplands is intensive, as in urban areas, wetlands often show signs of stress (Ehrenfeld and Schneider, 1993).
Scarcity may magnify the value of wetlands. For example, in an urban