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Key threatening processes
Biodiversity threats
Key threatening processes
A key threatening process is defined as a process that threatens or may threaten the survival, abundance or evolutionary development of a native species or ecological community. The Environment Protection Biodiversity Conservation Act 1999 lists 21 key threatening processes and the Biodiversity Conservation Act 2016 identifies 39 (Department of Agriculture, Water and the Environment, 2020).
Once a process has been nominated, the Threatened Species Scientific Committee considers the process for inclusion in a proposed priority assessment list. Once the list is finalised it becomes available for the public and experts to comment. After the assessment the relevant Minister decides whether a threatening process is eligible for listing under the EPBC Act or BC Act (Department of Agriculture, Water and the Environment, 2020).
The following is a narrative summarising and grouping the main key threatening processes that occur within the Wagga Wagga LGA.
Clearing of native vegetation
Clearing of native vegetation refers to the removal of endemic species of trees, shrubs, herbs, forbs, groundcovers and native grasses. These vegetation communities provide habitat for native fauna. Other activities that impact habitat include removal of timber for firewood and collection of rocks for use in urban backyards. The removal of these naturally occurring objects have degraded many native environments that provide habitat, foraging areas and protection against predation and the elements. Clearing of native vegetation often results in flow-on effects including dryland salinity, soil and bank erosion, increased greenhouse gas emissions, increased habitat for weed and pest species, loss of leaf litter, and changes to soil biota. These flow-on effects are also considered key threatening processes and are detailed below.
Another major flow-on effect is fragmentation, the process by which initially contiguous areas of habitat are separated into a number of smaller areas. This creates small isolated populations with limited gene flow between populations, leading to inbreeding issues, reduced potential to adapt to environmental change and reduced resilience to disease. The hostility of the surrounding (cleared) environment is a major factor in limiting movement of species between patches.
Weed and pest species
The main pest species in the Wagga Wagga LGA include Red Deer, Fallow Deer, Pigs, Goats, Rabbits, Foxes, Feral Dogs and Cats. Foxes are a major predator of native animals and ground nesting birds. The other noted pest mammal species are destructive to the environment, causing detrimental impacts on the habitat of native species. Introduced herbivorous animal species, including deer, goats and rabbits compete for food and habitat, and carnivorous animal species prey upon native animals. These and other introduced animals can also damage native plants and degrade natural habitats. Carp are a major pest species founded in the Murrumbidgee River and tributary creeks. Carp are a vigorous species that out compete our native fish for food, habitat and breeding sites. Weeds within Wagga Wagga LGA have potential to pose a serious threat to our natural environment, agricultural productivity and the health of the community. Weeds are those plant species that can potentially bring harm to individuals and the broader community. They are difficult to control and have potential to spread quickly within and outside the Wagga Wagga
LGA.
The invasion of escapee garden plants, including aquatic plants, can compete with native plants for resources such as light and nutrients. They can aggressively invade areas, displacing native plants and animals. There are also a number of invasive native species that have a similar impact.
Plant and animal disease
A variety of plant and animal diseases are listed as key threatening processes, and while not necessarily prevalent in the Wagga Wagga LGA some can spread easily and do pose a risk. This includes infection of amphibians with Chytrid fungus, Psittacine beak and feather disease affecting endangered parrot species, and infection of native plants by Phytophthora, Myrtaceae rust and Psyllid associated die-back.
Altered fire regimes
Periodic burning plays an important role in the development and maintenance of grassy ecosystems. However, frequent burning can limit recruitment of flora species, cause local extinctions of fire sensitive species, facilitate the spread of some exotics (e.g. Coolatai Grass), reduce habitat (fallen logs, hollow trees, leaf litter) and threaten fauna populations. Where fires occur very close together in time, key features can be disrupted. If high frequency fire is sustained it will consequently lead to a loss of plant species, a reduction in vegetation structure and a corresponding loss of animal species.
Alteration of the natural flow regimes
Three processes that have predominantly altered flows in rivers and streams and their floodplains and wetlands in NSW are the construction of dams, including weirs and off-river storages, diversion of flows, extraction for irrigation and the construction of levees, bridges and other structures. A high proportion of these alterations have major effects on the area of floodplains inundated by natural flood flows. This reduces the area available for nutrient cycling and affects many ecological processes. As a result, floodplain productivity, fish productivity and flood dependent populations are reduced. (NSW Department of Planning, Industry and Environment, 2019)
Loss of hollow bearing trees
Hollows are developed by decaying fungi within the trunks and branches of trees. Once the decayed material collapses, an internal cavity is developed, and access is provided by branches breaking. The creation of a hollow can take up to 150 years to develop. There are a number of species including threatened species that are reliant on hollows for shelter and nesting. With limited hollows available, the survival of already threatened species is at risk. (NSW Department of Planning, Industry and Environment, 2019)
Removal of dead wood and trees
Dead trees and branches often contain hollows used by many native species for habitat. A reduction in hollows limit the ability of many native species to breed or avoid predators. Fallen
timber also provides camouflage, and protection for some ground dwelling native species. Removal of dead wood may also result in the removal of plants, altering the habitat and may introduce weeds and disease.
Climate change
Climate change is predicted to be the greatest long-term threat to biodiversity in many regions and is listed as a key threatening process in State and Commonwealth legislation. Projections of future changes in climate NSW include increasing temperatures and temperature extremes, increasingly severe droughts, rising sea levels, possible decreasing rainfall, regional flooding and reduced water availability in the Murray Darling Basin (NSW Department of Planning, Industry and Environment, 2020).
Temperature and rainfall fluctuate greatly, with large variability in seasonal and regional climatic conditions bringing heatwaves, storms, droughts, floods and bushfires, which can have devastating effects on the environment, human life and property. This process exacerbates natural variability, making it more difficult to manage our landscapes and ecosystems and the human activities that depend on them. Communities already affected by climate variability will be challenged by a climate shift, and there will be additional demands on things like our emergency services and health system. Scientists agree that the earth’s rising temperatures are causing a shift in our long-term weather patterns (longer and hotter heat waves, more frequent droughts, heavier rainfall, and more powerful storms) which is known as ‘climate change’. While climate change is a key threatening process in itself, it also exacerbates all of the key threatening processes listed above.
Image: Chloe Smith
