The health and maintenance of biodiversity and ecosystem function is highly dependant on the presence of large areas of natural vegetation that contain a variety of vegetation types and habitats. These habitats are present throughout the entire ecosystem. The combination of factors related to features such as geology, soil, vegetation, water, fire, aspect, exposure, etc contribute to providing a complex array of ecosystem attributes which influence the biodiversity of the area.

Changes to the vegetation structure and plant species composition through vegetation clearing has the potential to result in significant short term and long term ecological consequences. Simplification of vegetation structure can also have similar effects to broad scale vegetation clearing, particularly in relation to loss of fauna habitats.

Key Threatening Processes

Key threatening processes are the things that threaten - or could threaten - the survival or evolutionary development of species, populations or ecological communities. There are a number of Key Threatening Processes relating to vegetation clearing and fragmentation that are listed in the NSW Threatened Species Conservation Act, 1995:

• 'Clearing of Native Vegetation’.
• 'Removal of Dead Wood and Dead Trees’. 
• 'Loss of Hollow-bearing Trees' (to find out more about the importance of tree hollows go to Tree Hollows and Nest Boxes).

The NSW Native Vegetation Act (2003) and supporting Regulations also address matters relating to cleaing of native vegetation.

Causes of the Clearing and Fragmentation of Native Vegetation

The main types of clearing and fragmentation of native vegetation include:

• Conversion of areas of native vegetation to crops, improved pasture or plantations.
• Urban development and associated development for industry and/or infrastructure (for example quarries, mines, factory sites, dams, roads, railways, power lines).
• Removal of understorey e.g. bushfire asset protection zones, along roadsides or at picnic areas and "cleaning up" of native vegetation. Removal of one stratum (layer) may result in the loss or long term modification of the structure of the native vegetation and also plants species composition.

Impacts of Threats

• Loss of species diversity and abundance, including soil organisms, fungi, invertebrates, bacteria etc
• Loss of food sources, fauna habitat, breeding grounds and nesting sites (including a variety of age classes of trees for hollows)
• Imbalance to the hydrological cycles, which fundamentally change local soil and climate conditions, and levels and chemical composition of the local water table.
• Ecosystem fragmentation and creating 'edge' effects. This increases exposure to the sun and wind, changes in water cycles, local air temperatures and invasion by opportunistic pests (plant and animal).
• Fragmentation reduces ecosystem function and decreases habitat connectivity and patch size which adversely affects species movement and viability.
• Expansion of dryland salinity.
• Degradation of the riparian zone.
• Increased greenhouse gas emissions.
• Reduced leaf litter layer and changes to soil biota thereby reducing a key foraging substrate for birds, mammals and reptiles.
• Altered recycling rates of nutrients which affects the viability of habitats.²
• Altered soil characteristics and composition.
• Increased habitats for invasive species.
• Loss of understorey vegetation and a negative impact on natural regeneration of the vegetation community

The Local Problem

• Increased levels of urbanization in the last 60 years has resulted in extensive vegetation clearing and fragmentation in the Central Coast region.
• Areas predominantly affected by vegetation clearing have been located along the coastal areas. More pressure is now being placed on areas west of the F3 Freeway for residential and industrial development.
• Many of the vegetation communities affected by vegetation clearing are not represented in conservation reserves.
• Clearing for urban and industrial development is resulting in either total vegetation removal or isolation of small areas of habitat in reserves or riparian corridors.
• Ongoing vegetation removal is required to maintain undeveloped areas as bushfire asset protection zones. This results in ongoing loss of vegetative cover and protective habitat.

Community Actions

Local residents, landholders and community groups can become involved in activities that can assist with local biodiversity management and address issues relating to vegetation clearing and fragmentation through a range of actions and activities including:

• Controlling weeds on your land.
• Reducing grazing pressure using stock controls such as fencing.
• Planting seeds and tubestock using local native species and seed sources.
• Developing landscape or property plans that consider the ecology of local areas by planning for corridors, reducing edge effects and limiting future clearing.³
• Becoming a member of your local environmental volunteer group and get involved in local activities.
• Participating in rehabilitation programs with your local Landcare, Bushcare or Dunecare group.
• Seeking input from local indigenous groups.
• Improving your skills, knowledge and understanding of native vegetation protection and rehabilitation techniques.

Useful Web Links

• Natural Resources Management – www.nrm.gov.au
• Department of the Environment and Water Resources - www.environment.gov.au
• Department of Environment and Climate Change - www.environment.nsw.gov.au
• Integrated Catchment Management Plan for the Central Coast 2002 - www.hcr.cma.nsw.gov.au

Further Reading

• Lindenmayer, D.B. and Burgman (2005) Practical Conservation Biology, CSIRO Publishing Australia.
• Lindenmayer, D.B. and Fisher, J (2006) Habitat Fragmentation and Landscape Change, CSIRO Publishing Australia.

• Department of Environment and Conservation (updated 16 December 2004), ‘Clearing of native vegetation—key threatening process declaration’, NSW Scientific Committee Final determination, Retrieved 8 September 2006 from http://www.nationalparks.nsw.gov.au/.

• Department of Environment and Conservation (gazetted 17 Nov 2006) ‘Loss of hollow-bearing Trees- Key Threatening Process’ NSW Scientific Committee Final determination. http://www.nationalparks.nsw.gov.au/.

Bibliography

1. Department of Environment and Heritage, 2001(updated 20 June 2004) ‘Biodiversity issues and challenges: clearing,       fragmentation degradation of native vegetation of marine habitat’, Australia State of The Environment Report: Biodiversity Theme Report. Retrieved 8 September 2006 from http://www.deh.gov.au/soe/2001/biodiversity/biodiversity04-1b1.html.
2. Department of Environment and Conservation (updated 16 December 2004), ‘Removal of Dead Wood, dead trees and     logs—key threatening process declaration’, NSW Scientific Committee Final determination, Retrieved 8 September 2006 from http://www.nationalparks.nsw.gov.au/.
3. Greening Australia 2001, ‘Native Vegetation’, Greening Australia Queensland Training Development Division.