D4.2 Flashcards
Stability and Change
Sustainability of Ecosystems
What does Sustainability mean?
- A sustainable ecosystem is not necessarily unchanging –> just that the changes have been slow enough so that organisms have adpated with the changes to still thrive.
- What makes an ecosystem sustainable by definition is that it can fully support itself without any outside influence.
- Human influences are much more likely to disrupt than help the ecosystem.
Sustainability of Ecosystems
What is an Ecological ‘Tipping Point’?
- A healthy ecosystem may be able to endure some degree of disruption and remain sustainable and self-sufficient.
- The point where after that much damage, –> ecosystem can no longer sustain itself and starts to collapse –> is the tipping point.
- Importmant concept to consider when humans utilise ecosytems for resources –> and the resilience of the ecosystem is usually used as a justification.
Sustainability of Ecosystems
Examples of Naturally Sustainable Ecosystems
Long-standing sustainable ecosystems
- The Amazon rainforest in South America is the largest rainforest in the world.
- One way it is sustainable –> own water cycle (the transpiration from all the plant life creates the water vapor that causes cooling, air flow and rainfall.)
- Currently 17% of the rainforest has been depleted, maing around the edge.
- There have already been temperature and rainfall shifts, suggesting a tipping point could be close.
Sustainability of Ecosystems
Examples of Naturally Sustainable Ecosystems
- The Daintree Rainforest in Northern Australia is estimated to be 180 million years ago.
- The Borneo Lowland Rainforest has existed for 140 million years.
- The Namib desert in South Africa is largely intact and stable. The thick fog has created a unique environmental factor for some well adapted species to thrive.
Sustainability of Ecosystems
Requirements for Sustainability
A sufficient supply of energy.
- A sustainable ecosytem needs sufficient energy to meet the needs of all the organisms.
- All energy originates as sunlight which is unlimited so the key here is that there has to be sufficient plant life to photosynthesis enough –> to create enough glucose/ carbon compounds –> meet the needs of every trophic level in the ecosystem.
Sustainability of Ecosystems
Requirements for Sustainability
Nutrient Recyling
- Ecosystems contain finite nutrients and temporary organisms.
- Thus a sustainable ecosystem has to have processes that cycle nutrients from dead organisms back into the ecosystem.
- Decomposers play the crucial role in this –> they help with the cycling of carbon, nitrogen and phosphurous (and other trace elements)
- Relates to the issue of deforestation –> as removed of trees removes the potential to recycle their nutrients.
Sustainability of Ecosystems
Requirement for Sustainability
Genetic Diversity
- In reference to species biodiversity, genetic diversity is vital for ensuring a species can adapt to changes in their environment.
- If an ecosystem contains many organisms with plenty of genetically diverse alleles –> likely to withstand smaller changes and not face extinctions that disrupt the food webs and stability of the ecosystem.
Sustainability of Ecosystems
Requirement for Sustainability
Response to Climate Change
- A healthy sustainable ecosystem –> has enough genetic diversity for its species to maintain a wide range of tolerance –> ensure they can withstand some climate changes.
- But, human activities are causing rapid and severe changes that are challenging even resilient ecosystems.
Sustainability of Ecosystems
Environmental Disruptions to Sustainability
The most prevalent disruptions to an ecosystem’s sustainability include:
- Overharvesting and removal of crops or trees that disrupt nutrient recycling.
- Erosion casuing the loss of nutrients.
- Eutrophication which is too many nutrients in water leading to plant overgrowth.
- Selective removal of important species by poaching (some species called keystone species are especially important so the impact would be more significant)
Mesocosms
What is a Mesocosm?
- A small experimental area that is set up as an ecological experiment.
- A working model of an ecosystem - either in nature as field work or created in a lab.
- Most commonly they are sealed containers with the necessities to function as a SELF-CONTAINED-SUSTAINABLE mini ecosystem.
- Used to manipulate variables to understand ecosystem impacts.
Mesocosms
Sealed Glass vs Open Tank Mesocosms
- Open tank terrariums are not true models of sustainable ecosystems –> given matter can either enter or exit (water vapour exiting - oxeygn entering)
- A properly modelled sustainable ecosystem should be sealed so matter must be recycled for it to be sustained.
- Transpiration provides the water needed, and carbon dioxide and oxegyn are cycled by plant and animal life.
- The reason for their transparency, is so that that sunlight (the energy source) can enter the system.
Mesocosms
Aquatic vs Terrestrial Mesocosms
- A mesocosm can be made to mimic a terrestrial or aquatic ecosystem.
- Terrestrial mesocosms are often called terrariums and then tend to require more components to build an effective soil and are harder to sustain in a classroom –> as recycling matter is harder to sustain and requires adequete decomposers.
Mesocosms
Winogradsky Columns
- A winogradsky column is a microbial mesocosm.
- Creates layers that differ in their abiotic environments that allow different bacteria to thrive.
- Eg., there is more sulphur at the bottom and more oxegyn at the top –> which impacts which bacteria can survive in that environment.
- It is a way to see the different between faculative vs obligate anaerobes (which are dependent on oxegyn for celluar respiration –> ATP)
Keystone Species and Resource Sustainability
What are Keystone Species?
- A keystone species is ANY TYPE OF ORGANISM THAT PLAYS AN IMPORTANT ROLE IN THE BIODIVERSITY OF THEIR ECOSYSTEM.
- Specifically, they play a disproportionate impact for their size, and ecosystem collapse is likely if they are removed.
- (Note: Many keystone species are apex predators, there are examples from every trophic level)
Keystone Species and Resource Sustainability
What is meant by ‘trophic cascade?’
- When a keystone species is removed, it has an impact on the other trophic levels.
- In particular, when the removal of a top predator destabilises the trohpic levels below it –> disrupts the balance of the ecosystem, (called a trophic cascade)
- Also referred to as a ‘top down’ control over population sizes.
- Trophic cascade is a more general term –> impacts on the whole ecosytem.
