Just like each and every one of you reading this, ecosystems are diverse, complicated and depend upon various natural processes for their continued existence. Some are resilient and some are vulnerable when faced with particular stressors, just as a group of people will have varied levels of vulnerability and resilience. It is the collection of coping mechanisms that enable some people to deal with the same stress that may see some people unable to function.
Ecosystems encounter various stressors, both natural and human. All too often it is easy to think of and consider the various human threats to ecosystems, but it is important that there are significant threats to ecosystems not initiated by humans. Threats can include both natural and human changes at varied rates including gradual and immediate.
Natural Changes
Immediate: drought, flood, volcanic eruption, landslip, cyclone, storm surge, disease and tsunami. These cause rapid, and often irreversible change.
Gradual: Changes in climate, movement of species, adaptation to change, ecological succession. These are slow, often unobservable changes that occur all the time.
Human Induced Changes
Immediate: Deforestation, overgrazing, ploughing, soil erosion, pesticides, toxic substances, urbanisation, mining war etc.
Gradual: Salinisation, soil waterlogging, soil compaction, pollution, habitat loss, species loss, introduction of species, toxic substances and so on.
Causes of ecosystem vulnerability
Location: The location of an ecosystem affects its functioning. At a global scale, latitude, distance from the sea and altitude play decisive roles in determining climate and ultimately the particular nature of ecosystems.
Some ecosystems are located in environments considered extreme: deserts, polar regions and high mountain peaks, hypersaline lagoons and areas of nutrient deficiencies. Organisms capable of living in such conditions are, by necessity, highly specialised.
Proximity to large concentrations of people is another important contributing factor to ecosystem vulnerability. As populations grow so does the demand for land. Urban, industrial and agricultural landuses destroy natural ecosystems, while the oceans, rivers and the atmosphere become dumping grounds for pollutants.
Extent: The extent (size) of any particular ecosystem is the product of a variety of factors. Recent research has shown that the boundaries of ecosystems tend to overlap each other.
Ecosystems that are restricted to relatively small areas or have already been disturbed extensively are especially vulnerability.
Biodiversity: Biodiversity is usually considered at three levels: genetic diversity, species diversity and ecosystem diversity.
Genetic diversity: is the variety of genetic information contained in all the individual plants, animals and micro-organisms. Genetic diversity occurs within and between populations of species as well as between species.
Species diversity: is a measure of the number of species at each trophic level of an ecosystem. In simple terms, the greater the species diversity the more robust the ecosystem: if the population of one producer or consumer organism crashes there are other producers or consumers available that can fulfil a similar function in the ecosystem.
Ecosystem diversity: refers to the diversity present within ecosystems in terms of habitat differences, biotic communities and the variety of ecological processes.
Linkages: Interdependence, or linkages, is related to species diversity. The greater the level of interdependence within an ecosystem the greater its ability to absorb change. The loss of a primary consumer from a food web, for example, is unlikely to have a major impact on secondary consumers if there is a range of alternative primary consumers on which to feed.
(Global Interactions 2, Kleeman, Hamper, Rhodes & Forest, p. 24-26)
Ecosystem Resilience
“Ecosystem resilience refers to the capacity of an ecosystem to recover from disturbance or withstand ongoing pressures.1 2 It is a measure of how well an ecosystem can tolerate disturbance without collapsing into a different state that is controlled by a different set of processes. Resilience is not about a single ideal ecological state, but an everchanging system of disturbance and recoveryEcosystem resilience refers to the capacity of an ecosystem to recover from disturbance or withstand ongoing pressures.1 2 It is a measure of how well an ecosystem can tolerate disturbance without collapsing into a different state that is controlled by a different set of processes. Resilience is not about a single ideal ecological state, but an everchanging system of disturbance and recovery.”
(Ecosystem Resilience, GBRMPA, 2017)
Elasticity: is the rate of recovery of an ecosystem properly following disturbance
Amplitude: refers to the threshold level of strain beyond which return to the original state no longer occurs
Malleability: of the ecosystem is the difference between the ecosystem’s final recovery level and the pre-stress level; the greater the difference, the less resilient is the ecosystem.
(Global Interactions 2, Kleeman, Hamper, Rhodes & Forest, p. 27)
Case Study: Impacts due to natural stress
Using spatial technology to map ecological succession
The following trio of images are sourced from NASA’s Earth Observatory and detail the initial devastation and subsequent ecological succession within the ecosystem surrounding Mt St Helens, Washington, USA. This trio of ‘false-colour’ satellite images highlight areas of vegetation (red), bare rock and volcanic debris (grey) and clear water (blue).
August 29, 1979
September 24, 1980
September 10, 2009.
Introduced species
After watching the video, undertake some research to identify one faunal and floral introduced species that is negatively affecting the alpine ecosystem of the Kosciuszko region of the Snowy Mountains. Identify the characteristics of this species and its various impacts.
Ecological succession
- Define the following terms; ecological succession, primary ecological succession and secondary ecological succession.
- What is a pioneer species? Give one example.
- What is a climax community and what it is it largely determined by?
- What type of succession is being studied by ecologists at Mt St Helens?
Ecosystem Impacts due to human-induced modifications
The impacts of human induced modifications to ecosystems in modern times have been increased in the following ways:
- The speed at which humans can change ecosystems have never been greater
- The scale of ecosystem change humans are capable of has never been larger, extending to the global level.
- The earth’s human population is growing at an alarming rate and is considered a key driver of biodiversity loss
Click on this ESRI map to investigate trends in biodiversity and biodiversity loss at a national, regional and international level.
- Describe the spatial distribution of areas that have now have ‘low levels of original species abundance’.
- Is there a relationship between areas of high levels of population density on a global scale and locations of low ‘level of original species abundance’?
- Describe the spatial trends in biodiversity levels of vascular plants.
- Describe the spatial trends in biodiversity levels of mammals.
(WWF Living Planet Report, 2016)
Select one of the following threats, undertake research and create an informative 3 minute documentary to share with others.
The World Wildlife Fund’s Living Planet Report 2016 provides a wealth of information and case studies for you to utilise.
(WWF Living Planet Report, 2016)
(WWF Living Planet Report, 2016)
The flow of consumption
Connectography 