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.
Keystone Species and Resource Sustainability
What is soil erosion?
- Soil erosion is the loss of the upper soil layer.
- This upper layer called topsoil is the most nutrient rich so its loss has follow on impacts on the ecosystem.
- Can be the results of excess rain + wind
- Farmers can plant simple crops (clover/rye) to just cover the soil and hold it in place –> limit erosion.
Keystone Species and Resource Sustainability
What is leaching?
- Leaching occurs when rain/ irrigation water dissolves nutrients such as nitrogen and phosphorus in the soil and then carries them away from the roots of the plants.
- The run-off chemicals often end up in water –> more problems.
- Excess ferilisers can make leaching more pronounced.
Keystone Species and Resource Sustainability
What are agrochemicals?
- A chemical that is used in agriculture.
- Most notably fertilisers + chemical pesticides.
- They lead to multiple problems, including eutrophication and pollution of aquatic environments.
Keystone Species and Resource Sustainability
What is meant by a ‘carbon footprint?’
- The total amount of greenhouse gases (including carbon dioxide and methane)
- Eg., agriculture is estimated to contribute around 9/12% of the greenhouse gases, due to the combustion for machinery, fertilisers, clearing forests to create farmland and transportation of crops.
Keystone Species and Resource Sustainability
What is tillage?
- One of the ways that agriculture has a higher carbon footprint, is because of tillage.
- Tillage is the preparing of soil for a crop and involves loosening by plowing, harrowing and cultivations, usually by mechanical means, which require fossil fuel combustion to run.
Keystone Species and Resource Sustainability
The Removal Method for studying Keystone Species
- To determine whether a speices is in fact a keystone species, the best experimental method is to remove that species from a secion of the exosystem, then record the changes in the biodiversity of the exosystem as a result.
- Can be done in reverse, by observing the impact of returning a species to an ecosystem and seeing how it benefits it (like wolves being retunred to Yellowstone)
Keystone Species and Resource Sustainability
The work of Robert Paine and Sea Stars
- The removal method and its important discovery regarding keystone species was done by Robert Pain
- He manuakky removed a sea star from an interdidal zone
- This the star’s prey, the mussel, to take over, and reduce the space for algae and other invertabrates.
- There was 15-10 of these species with the sea stars present, and less than 5 without, signalling the sea stars as a keystone species.
Keystone Species and Resource Sustainability
The three requirements for resource sustainability
- The requirements for the options for more sustainable resource use:
- 1) Nutrient availability - presence of saprotrophs to recycle nutrients.
- 2) Detoxification of wastes - turning resources into usable or at least non-harmful elements.
- 3) Energy availability - access to sunlight (and producers to produce the food needed.)
Keystone Species and Resource Sustainability
The factors needed for agriculture Sustainability
- To ensure agriculture becomes sustainabile, it involves addressing the factors limiting it.
- 1) Erosion: planting cover crops to protect topsoil.
- 2) Leaching: minimise fertiliser use and manage irrigation water carefully.
- 3) Agrochemical use: look for biological alternatives
- 4) Tillage: reduce or look for less mechanical alternatives.
- 5) Monocultures: look for alternative plantation concepts with multiple species.
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