ECOSYSTEMS AT RISK
- Define the term Ecosystem
Ecosystem: A functioning entity made up of the interactions between living organisms and their nonliving environment. The amount and types of air, energy, water and nutrients determine the numbers and types of organisms that an ecosystem contains.
- Why are there diverse ecosystems?
As the quantity and type of air, energy, water and nutrients varies around the world, there are a wide variety of different ecosystems such as arid, coral reefs, coniferous forests, alpine etc.
In addition, biophysical interactions, the building blocks of ecosystems occur in varying amounts and interact differently across the globe, leading to diverse ecosystems.
Ecosystems are often classified according to aspects of the physical environment and are usually defined by the boundaries between habitat types.
- Ecosystems defined by climate: desert, alpine, polar and mediterranean
- Ecosystems defined by vegetation: tropical rainforest, savannah
- Ecosystems defined by physical features: coral reefs, intertidal reefs.
Ecosystems are either terrestrial (land based) or aquatic (water based).
Diversity in terrestrial ecosystems can occur from:
- Variations in temperature
- Variations in precipitation
- Humidity, sunlight exposure
- Physical terrain
Diversity in aquatic ecosystems (e.g. ponds, rivers, coral reefs etc.) can occur from:
- Variations in salinity
- Variations in sunlight penetration
- Variations in dissolved nutrients
- How do ecosystems function?
Ecosystem Functions: Processes that organisms and ecosystems perform or participate in that provide products and/or consequences for themselves, for other species and ecosystems in the community or region.
- Sun is the source of all energy on earth (it provides heat and light energy). Autotrophs convert the sunlight into chemical energy via photosynthesis). These producers are located at the first trophic level. At each trophic level energy is lost in the form of heat.
- Detritivores (decomposers) allow energy to be ‘recycled’. They return nutrients.
- Energy flows show how energy is transferred between organisms within an ecosystem. All organisms require energy for growth, maintenance, reproduction.
- Heterotrophs cannot produce their own energy and as a result rely on consuming other organism to obtain their essential energy. Primary consumers eat plants.
- Involves the movement and exchange of matter back into the production of living matter
- Primary producers obtain dissolved nutrients from water which they absorb and which they use in the process of photosynthesis
- When herbivores consume the producers, nutrients are passed up through the food web.
- This enables nutrients from the nonliving environment (in the form of water found in the biophysical environment) to be cycled to the living environment and eventually back to the non living environment with the aid of detritivores.
- Like energy, at each level of the food chain, like energy, nutrients are lost and as a result a larger bulk bust be consumed to achieve desired nutrient levels.
- Types of nutrient cycles include
- Carbon cycle (Cellular level. Used for structure and growth)
- Oxygen cycle (Used for respiration)
- Nitrogen cycle (Used for respiration and to make amino acids)
- Phosphorus cycle (Regulates protein synthesis and is used in cell division)
- Sulfur cycle (Forms amino acids, proteins and enzymes)
- Water cycle (Used in photosynthesis)
- There are three areas where nutrients are held
- Litter (Surface layer of vegetation (dead material))
- Biomass (Living organisms)
- Plants can’t absorb atmospheric nitrogen, however there are bacteria which can. The bacteria convert N2 (Nitrogen Gas) to NH3 (Ammonia) (Nitrogen fixation) with the aid of enzymes. Other bacteria can then convert the ammonia to nitrates (Nitrification) which the plants can absorb.
- Lightning can also slit the nitrogen in the air as can humans (this process is used to create synthetic fertilisers)
- Denitrifying bacteria can break the cycle. These take the oxides from the cycle and turn it back into gaseous N2, which they release into the atmosphere.
- The plants which consume the nitrogen that has been assimilated (transferred) are consumed by animals and eventually are consumed by detritivores who return the nitrogen to the soil.
- Carbon allows organisms to have structure and fuel their bodies.
- Plants absorb CO2 (carbon dioxide), which they use in photosynthesis. Photosynthesis produces glucose which in the process of respiration they convert into energy.
- A byproduct of respiration is CO2, which plants use in photosynthesis thus completing the cycle.
- Carbon can also be obtained by animals consuming plants. Excess carbon held in plants is used for growth.
- When animals and plants die the carbon remains and this can be compacted into fossil fuels which give off carbon dioxide when combusted.
- Light requirement and photosynthesis
- Optimum temperature range
- Temperature and rate of growth of plants
- Plant intolerance below freezing
- Temperature and cellular reactions
- 10o minimum for effective photosynthesis
- 35o wilting point for many plants
- Precipitation is the most important single factor influencing distribution of biomes and ecosystems as water is needed for photosynthesis, transportation of nutrients, growth and germination.
- Low rainfall results in a desert biome
- Some precipitation, however, is more effective than others
- Sudden downpours are unable to be absorbed by the soil.
- Steeper slopes have better drainage, thinner soils and less acidic soil.
- Steeper slopes are more prone to erosion
- Quality of soil affects vegetation growth and vice versa
- Vegetation helps to form the soils
- Vegetation helps break underlying rock
- Vegetation adds humus from dead leaves
- Large forest trees require thick soils that are secure
- There are pockets of gases in the soil - well aerated soil allows plant growth
- Plants use oxygen for respiration
- Oxygen must be replenished in the soil via rainfall
- Rainfall leaches CO2 down below the root zone
- Capacity for soil to retain water can affect plant
- With an increase in altitude
- Why are ecosystems at risk and what does at risk mean
- Describe impacts on ecosystems due to natural stress
Examples of natural stress:
- Pyroclastic Flows
- If habitat destruction is severe then species may become extinct. If fauna have no places to live they may migrate. Flora cannot move as easily so they may perish - leading to a breakdown in energy flows.
- Describe impacts on ecosystems due to human induced modifications
Examples of human induced modifications:
- Pesticide and toxin release by humans into aquatic systems leads to a buildup of green algae, starving the water of oxygen. This leads to the death of fish and disruptions to energy flows.
- Introduction of foreign species (especially consumers) can have devastating effects. Typically this will lead to a readjustment of the equilibrium but in worst case scenarios it can lead to extinction of species. Major disruptions to energy flows can arise.
- How vulnerable and resilient are ecosystems to stress?
All ecosystems operate in a state of dynamic equilibrium as change happens all the time. Level of vulnerability depends on how small a change will upset the equilibrium. Some ecosystems are therefore more resilient than others.
Resilience: The ability to withstand shock and return to normal functioning after a period of disturbance.
Major factors influencing vulnerability of an ecosystem (BELL):
- Three levels of biodiversity need to be considered:
- Genetic Diversity
- Reduces inbreeding and helps the population with stress through evolution over time.
- Refers to the number of species at each trophic level. Greater the species diversity, the more able the ecosystem is to cope with change.
- Refers to having a variety of ecosystems in one place. If there are many, they will have linkages and be more resilient.
- The bigger the ecosystem, the more resilient it likely is. Small ecosystems are especially vulnerable.
- E.G. Pockets of rainforest which have small populations of large number of species.
- Kenilworth Racecourse has a small population of Micro Frog inside it. Large development has stunted the extent of sandveld. As a result ecologists have vegetated freeways and encourage homeowners to vegetate their gardens with native plants to connect the fragments, increasing resilience.
- Microclimates can make specialised ecosystems in small areas, many of these extreme
- If things change, species become vulnerable as plants can’t move quickly.
- E.G. on top of Mt Kilimanjaro there is snow which has lead to a small ecosystem. Should the snow melt, the plants would not be able to move and will become very vulnerable.
- If ecosystems are near concentrations of people, degradation happens more rapidly.
- Greater the level of interdependence, the better they can absorb change.
- Antarctic food chains have poor linkages. As a result reductions in krill populations have had severe impacts on whales.
- Outline the importance of ecosystem management and protection
There are various ways ecosystems are managed and/or protected but typically it involves humans setting aside a designated area of land that is regulated and overlooked. If we were to lose some of our ecosystems, various planetary processes would be disrupted potentially causing major disruption. We protect ecosystems for reasons including:
Management: A process that aims to conserve ecosystems and restore natural resources while meeting the needs to current and future generations.
Protection: Typically involves limiting the human interactions in the area which management allows.
- Ecosystems that are placed on the World Heritage Conservation Council’s World Heritage Lists are done due to
- “Outstanding universal value from aesthetic or scientific points of view”
- Preserving these areas allows us to share them with future generations as well and have them for national record
- In Australia many national parks such as Kakadu are World Heritage sites which ensures that the ecosystems are protected and are less subject to human impact.
- Many plants and animals are useful for humans in ways that we perhaps haven’t even discovered yet.
- Over 25% of Western pharmaceuticals are derived from rainforests - an ecosystem where humans have not discovered every specie.
- In addition as food sources become scarcer, keeping as many species alive could improve humanity’s chances of survival in the long run. Almost all food crops are located in developing countries, areas where large development and environmental damage is occurring. Thus it is important to manage ecosystems.
- Source of all primary industries
- Environmental degradation reduces the utility value of an ecosystem.
- Clearing the mangroves in Homebush Bay may lead to a depletion of fish meaning less utility value from fishing.
Maintenance of Genetic Diversity:
- Ecosystems that are richer in diversity tend to have greater resilience as there is more chance of a species or individual which has a resistance to a particular stress.
- The greater gene pool means that the ecosystem is less vulnerable to collapse
- The earth’s diversity has come as a result of millions of years of genetic variations being bred and species as a result evolving.
- Diversity is important to keep as if an ecosystem collapses it can affect food and medical sources.
- Ecosystems should be preserve for future generations. Ecosystems can provide people with their
- Spiritual needs
- Religious needs
- Inspirational needs
- Aesthetic needs
- Recreational needs
- Uluru is an example of all of these
Need to allow natural change to proceed
- Natural change leads to diversity within our ecosystems via evolution. In order to ensure the continuation of evolution, large areas of representative ecosystems are preserved. Criteria of representative ecosystems include:
- Being large enough to protect
- Having boundaries that reflect environmental as opposed to political needs
- Taking into account the needs of locals
- Be well managed
- Have a buffer zone around them where human activity can be managed.