Session 3: Ecological Disturbance Flashcards
What is ecological disturbance and what are some examples?
Ecosystems sometimes change due to ecological disturbance such as fire, floods, and storms (natural), and land clearing for urban development/agriculture/industry/etc., dam creation for water catchment or electricity generation, and the introduction of invasive species (human caused disturbance), and more.
What are the ways of measuring ecological disturbance?
Population density (using sampling techniques), Species diversity and richness (using the Simpson’s reciprocal index), The presence and distribution of indicator species (to measure levels of pollution), Direct measure of pollutants, Canopy coverage and relative light intensity (could measure with a lux meter), Biomass (via the average width of tree stems at a specified height), and Edaphic/soil factors such as erosion (via depth), water retention (via drainage), pH and nutrient content,
What is HIPPO?
An acronym to summarise the decline of Earth’s biodiversity: Habitat loss, Invasive species, Pollution, Population, Overuse. It is ranking the devastation each factor causes (habitat loss causes the most damage to biodiversity)
What is habitat loss (in terms of HIPPO)?
Habitat destruction where natural habitat is rendered functionally unable to support the species present. The organisms that previously used the site are then displaced or destroyed, reducing biodiversity. Habitat loss can be caused by conversion of natural areas to farms, houses, etc, the fragmentation of ecosystems by human activities (housing, transportation, agriculture, etc.), and the simplification of genetic diversity and complex ecosystems by planting/selecting monocultures (monoculture is when there is only one species/organism in an area, e.g. crop growth).
What are the consequences of deforestation?
loss of species, more carbon emissions (forests absorb CO2), the water cycle (ground water and transpiration), soil erosion, and the disruption of normal nutrient cycling.
What are the causes of marine habitat loss?
Waste, pollution, and chemical effluent, Dams decrease natural nutrient-rich runoff, cut off fish migration routes, and curb freshwater flow, increasing the salinity of coastal waters, Destructive fishing techniques like bottom trawling, Tourism (boats, snorkelers, and scuba divers) - direct contact with fragile wetland and reef ecosystems., Spills of crude oil and other substances kill thousands of birds and fish and leave a toxic environment that can persist for
years
Describe introduced invasive species.
An endemic species naturally occurs in a particular habitat or ecosystem, an alien species or invasive species is a species that is introduced either intentionally or accidentally by humans to an area it does not usually occur. A species becomes invasive when it competes and with endemic species for resources and competitive exclusion occurs (the endemic species struggles to survive).
What are the characteristics of invasive species?
rapid reproduction, fast growth, high dispersal, tolerant to different conditions, and able to live off a variety of foods.
How do invasive species impact ecosystems and economies?
Ecological: they reduce native biodiversity, they prey on local species, they can spread disease, and they can upset the balance of the local ecosystem.
Economic: expensive to eradicate and can cause damage to industries (e.g. agriculture).
What are methods of controlling invasive species?
physical control (removal/weeding, culling, trapping, barriers, fences, etc), chemical control (poisons and herbicides), prevention (legislation, quarantine), and biological control (use of other organisms).
What is island biogeography and how has it helped conservation?
Island biogeography is the idea that an equilibrium between organisms is established over time on an isolated place like an island. It is used to understand how human development affects an ecosystem and hence how we can fix the consequences of human development, etc. and make the ecosystem how it is meant to be.
What qualities are best for conservation and nature reserves?
large habitats (more resources, migration can occur, greater biodiversity), corridor effect (joining regions with a protected bridge area, etc. to allow for migration, foraging, movement, etc.), and the edge effect (less edge to a reserve in order to protect organisms.)
What is in situ conservation?
When the species remains in their natural habitat but some management is still necessary, such as control of alien/invasive species, reintroduction of native species, limiting predators, feeding programs, and limiting access to humans, certain animals, etc.
What is ex situ conservation?
What a species is removed from its natural habitat, e.g. botanic gardens, zoos, and captive breeding programs. It is intended to remove a species from threat, especially when it is endangered.
Describe the invasive species: Sweet Vernal Grass
Native to Eurasia and Northern Africa, it has been introduced all over the world but in Australia it is mainly eastern NSW, the ACT, Victoria, Tasmania, south-eastern SA, and south-western WA. Believed to be introduced through hay transport and the sale of commercial seed mixtures, as a pasture grass/food for horses, etc. in the 1800s. Sweet vernal grass can prevent native plant regeneration, spread contaminated agricultural produce, contaminate conservation areas, and it grows in areas that have been eroded or destroyed by human activity. It is considered a weed because it has competitively dominant features, and can grow in a range of conditions (is very tolerant). Herbicides, hand removal/weeding, and burning are often used to control/manage sweet vernal grass.
