D4.2 Stability and change (year 6) Flashcards
State the requirements for a sustainable ecosystem
- sufficient supply of energy
- nutrient recycling
- genetic diversity
- climate variable remaining within tolerance levels
Example of a possible tipping point in ecosystem sustainability
Amazon rainforest:
- 17% has already been cleared for logging, ranching etc
- The large ecosystem influences its own climate, where the rainforest vegetation produces huge amounts of water vapour by transpiration
- the evaporation of water produces a cooling effect, influencing airflow and rainfall in the region.
- it is not known how much more of the rainforest needs to be cleared before a tipping point is reached, and the ecosystem is unable to sustain itself
What are mesocosms?
A self-contained system that provides a living environment for organisms.
- A sealed glass vessel is prefered over open vessels to prevent the entry/exit of matter while still allowing for the transfer of energy.
What are keystone species?
Organisms of any type that play an important role in the biodiversity of an ecosystem.
- their impact is not based on numbers but by their impact on the prevalance and population levels of other organisms within the ecosystem
- there is a disproportionate effect on the ecosystem if keystone species are removed, risking ecosystem collapse
Describe sustainable harvesting of natural resources with 1 example of plants and animals each
Sustainability depends on the rate of harvesting being lower than the rate of replacement
Chilean sea bass:
- in the 1990s the Chilean sea bass was in danger as fishing was not regulated, and due to long lining, where hundreds of bait were set on a long line.
- Since 2000, the fishing industry agreed to practice sustainable fishing practices that have minimal effects on other species of fish
- the fish population is monitored to make sure repopulation is taking place, and the no. of illegal uncertified fishing vehicles are now 0
Black cherry trees:
- Large areas were once clear-cut to make farming fields, completely removing all trees.
- Now, current logging practices do not remove the surround trees. Instead, an Aborist selects the trees that can be removed sustainably.
- removing a single tree leaves light gaps in the forest, allowing black cherry and other specimens to grow and establish
- the selective logging does not occur at a pace faster than the growth of remaining trees.
Factors affecting the sustainability of agriculture
sustainable agriculture meets the food and textile needs without endagering the ability of future generations to do the same
- Soil erosion (erosion of topsoil by excess rain, wind strips the soil of its organic nutrients)
- leaching of nutrients (rain/irrigation carries away nutrients from the plant roots)
- Supply of fertilizers (Expensive, demand often exceeds supply)
- pollution due to agrochemicals (pollution of watersupply by fertilizer and chemical pesticides)
- carbon footprint (agriculture contribute 12% of total amount of greenhouse gases)
How does eutrophication take place
- Fertilizers containing nitrogen and phosphate are leached into water sources, where the influx of minerals causes algae to grow excessively
- the greatest growth grows at the top of water, preventing light from penetrating into the water below
- This causes a need for extra decomposition by aerobic bacteria, depleting the dissolved oxygen conc. in water = other aerboic organisms die
Describe biomagnification + 2 examples
Harmful substances build up in organisms at the top of the food chain
Mercury:
- Mecury levels increasing in organisms at the top of aquatic food chains
- This mercury is released from the burning of coal and production of cement, and converted into methyl mercury by microorganisms at the bottom of the food chain
- accumulates in fatty tissues of consumers at higher levels
- Humans are exposed to high levels of mercury by eating long-lived fish near the top of the food chain, causing severe health effects like neurological damage
Dichloro-Diphenyl-Trichloroethane (DDT):
- effective, inexpensive insecticide that was mass-sprayed from aircraft
- entered bodies of water, absorbed by phytoplankton in aquatic bodies.
- accumulated in fatty tissues of consumers at higher levels
- DDT altered the metabolism of calcium for birds with fish as their primary food source = thin-shelled eggs produced which could not withstand the mass of a parent bird during incubation
- DDT is now banned worldwide except for some areas with malaria
Describe effects of macro/microplastics on the ocean
Macro/microplastics are nonbiodegradable, and will remain in the environment virtually forever.
- Plastic in the oceans tend to get caught up in ocean vortexs called GYRES, a swirling mass of debris
- plastic pollution in the ocean causes sea turtles to eat plastic bags thinking they are jellyfish, plastic rings from canned drinks to trap wildlife, microplastics filling the stomachs of wildlife after accidental ingestion
Describe the process of rewilding + 1 example
- introduction of apex predators
- introduction of keystone species
- stopping agricultue and resource harvesting
Hinewai Reserve in NZ:
- fosters regeneration of native vegetation and wildlife
- open to public via walking paths
What is ecological succession
The change over time in species over an area. Triggered by abiotic and biotic factors in an ecosystem
Succession events can be classified as:
- Primary succession: When new land is created and a series of communities emerge. Begins with no life
- Secondary succession: Follows the disturbance of a primary succession, when the ecosystem is drastically altered by an event, and the remains are used as a starting point for further changes
Describe the changes occuring during primary succession
- increased species diversity, size of plants, primary production
- more complex food webs, increased nutrient cycling
- The PIONEER species appear (first living organisms)
- After many years, a climax community may have developed as there is a mature ecosystem
Describe cyclical succession + 1 example
Although succession in most ecosystems leads to a uniqe set of organisms at each stage, sometimes a cyclical pattern emerges rather than a single unchanging climax community.
WOOD PASTURE:
horned, unpalatable bushes grow in open pasture > trees grow using bushes as protection against herbivores > shade of trees restrict growth of bushes > tree dies of natural causes and bushes can grow again > cycle continues
- dependent on the action of large herbivores (wildebeasts, elephants etc.) maintaining most of the area as grassland pasture
Describe climax communities + examples of human interference
Climax communities are the result of ecological succession until a particular stable community is formed, where it is ecologically stable and will not usually change unless environemtnal conditions change/there is human interference:
- e.g. removing forests for lifestock grazing
- drainage of wetlands for development
