Ecosystems at risk

Ecosystems at risk

Rainforests have disappeared from the Australian continent over millions of years. The changes in climate over this time, pushed rainforests into smaller and smaller areas where the conditions for their development and functioning were met. During European settlement rainforest areas were extensively cleared for timber and converted to agricultural lands. 

Fragmented, altered and diminished, the rainforests of NSW are ecosystems at risk, vulnerable to natural stress and human induced modifications, such as:

• Clearing and development

• Weeds and feral animals

• Human visitation

• Severe weather events

• Climate change

• Fire

Ecological sustainability

The conservation of rainforest ecosystems to achieve ecological sustainability is a priority for community and government agencies. However, as pressures from an increasing population and our climate continues to change, future management decisions within rainforest areas become more complex and uncertain. 

Activities

1. Access the NSW Department of Planning, Industry and Environment Key threatening processes to describe the meaning of key threatening process.

2. Access the list of key threatening processes and identify those that impact rainforest ecosystems. 

3. Evaluate:

• the nature of the threat; natural stress or human induced modification 

• the speed to which the threatening process operates.

4. Determine the most significant threats facing rainforest ecosystems.

5. Explain the meaning of sustainability, ecological sustainability, carrying capacity and sustainable development. 

Ecological vulnerability and resilience 

Ecosystems are dynamic places with continual changes occurring within the atmosphere, hydrosphere, lithosphere and the biosphere over time. These changes are the result of natural and human induced disturbances that place stress on the system's ability to function normally. The changes that take place are the biogeographical processes of invasion, modification and succession. An ecosystem is considered resilient if it is able to adapt and return to normal functioning after stress. Vulnerability refers to how susceptible the ecosystem is to stress leaving it susceptible to invasion that may ultimately lead to succession. 

Factors that lead to resilience in rainforest ecosystems include:

• genetic and species diversity

• diversity of ecological processes such as different pathways for nutrient and energy cycling, pollination and seed dispersal

• ecosystem overlaps leading to additional ecological processes and species evolution

• ecosystem separations and extent that leads to genetic divergence and the evolution of new species.

Natural regeneration, resilience and adjustments in response to natural stress

Disturbances within a rainforest ecosystem stimulates the regeneration of new plants and species. The disturbances can be large scale such as destruction from a landslide, land clearing or grazing, or small in scale such as walking track constructions and the natural death of a single tree.

When a gap in the canopy is created, light is able to reach the otherwise shaded forest floor. This disturbance triggers ecological succession that in resilient rainforests leads to regeneration and a restoration of the rainforest. 

In areas where there has been large scale change the rainforest may be unable to regenerate naturally. Human intervention through bush rehabilitation and regeneration may need to occur to bring the rainforest back. 

Biogeographical processes of invasion, modification and succession 

Vulnerable rainforest ecosystems may experience species invasions that lead to modifications within the ecosystem. As new species colonise, rainforest species decline and the number of introduced species increase, which may result in a change in forest structure and composition. 

Succession will result from changes in the biophysical environment:

• A change in the understory microclimate caused by unsustainable logging practices or fire. As large gaps in the canopy open, light intensity increases, leading to a decrease in humidity and moisture and an increase in temperature and wind.

• A warmer and drier microclimate from gaps in the canopy or from a warming and drier climate. 

• Decomposition slows as leaf litter dries reducing the amount of nutrients in the system. 

• Changed conditions affect populations within the ecosystem, leading to further flow on effects in nutrient and energy recycling. 

Warmer, drier conditions are favourable to eucalypt species and other dry sclerophyll vegetation such as wattles, tea trees and banksias. As sclerophyll species invade succession to sclerophyll forest will occur.  

At times rainforests are able to invade and modify surrounding wet sclerophyll forests. The factors that lead to rainforest expansion include:

• a change in stream course. Earth moving and a change of land use can alter and redirect natural drainage lines leading to an increase in water availability.

• an increase in water nutrients from runoff through agricultural and urban environments providing additional nutrients for rainforest species. 

• a change in fire regimes. Areas may experience a decrease in fire frequency. 

Activities

1. Access the NSW National Parks and Wildlife Service Under the Canopy PDF to describe natural regeneration that occurs in rainforest ecosystems. 

2. Explain how rainforests demonstrate resilience. In your answer describe species adaptations.

3. Define invasion, modification and succession in ecosystems.

4. Explain the processes of invasion, modification and succession that may occur in rainforests ecosystems. 

Ecosystem change and a changing climate 

Rainforests, due to their diversity have evolved to be resilient to many of the human induced stresses they encounter. However, the rate of human induced change is intensifying and rainforest ecosystems are now experiencing increased pressures from the effects of anthropogenic climate change and more frequent and intense bushfires. 

Climate projections for rainforest areas include:

• an increase in average temperatures, a decrease in relative humidity, reduced moisture and higher evapotranspiration

• an increase in frequency and severity of extreme weather events heatwaves, floods, fires and storms

• an increase in pest species and pathogens as climate conditions shift

• sea-level rise and coastal erosion.

Climate change and fire

The 2019-2020 Black Summer Fires brought to attention the impact of climate change on our natural environments. 

Scientists now recognise the link between our changing climate and an increase in forest fires. 

• Read about bushfires as an impact of climate change at Adapt NSW. 

• View the YouTube video (01.55min): How does climate change affect bushfires? By the Climate Council. 

• Read the Climate Council report by Professor Lesley Hughes Be Prepared: Climate change and the NSW bushfire threat

Activities

1. Explain how current climate projections will lead to impacts in rainforest ecosystems.

2. Explain the link between climate change and increased bushfire risk. 

3. Investigate the Climate Council. Analyse the videos and reports for accuracy and bias. 

4. Discuss the nature of change and the rate of change in NSW rainforests.

Conducting fieldwork

Complete the following activities to guide fieldwork in the investigation of rainforest vulnerability and resilience.  

Key fieldwork inquiry questions:

• What evidence of natural stress and human induced modifications can be identified in the rainforest ecosystem?

• What evidence is there of rainforest vulnerability and resilience? 

• What fieldwork methodologies and equipment can be used to observe and measure stress and vulnerability and resilience in rainforest ecosystems?

• How will our results be recorded?

• How do we draw conclusions?

For further assistance in conducting fieldwork contact:

• NSW Department of Education Environmental and Zoo Education Centres

• NSW National Parks and Wildlife Service.

Pre-work

Prior to fieldwork conduct research into traditional and contemporary land use in your rainforest ecosystem.

• Identify the traditional Aboriginal Peoples of the area and describe the ways they connected with Country.

• Identify European utilitarian uses of the land from logging and grazing to more contemporary uses for conservation and tourism.  

• Create a timeline of land use and analyse the stresses the ecosystems has encountered overtime. 

• Identify features that will allow for an assessment of vulnerability and resilience in rainforest ecosystem.

Observations

Fieldwork includes making and recording observations that provide evidence for rainforest vulnerability and resilience. Observations focus on past and contemporary land use, changes in abiotic and biotic factors and current management practices. 

1. View the  gallery of images to identify threatening processes in the rainforest. 

2. Explain how data collected in the field helps land managers analyse the impacts of human induced modifications.

3. Explain how this can help to inform management.