Sydney Turpentine – Ironbark Forest faces daily threats
The small amount of Sydney Turpentine-Ironbark Forest remaining is subject to pressures that threaten its health and survival. Sustainably looked after for tens of thousands of years by traditional custodians, everything changed for Sydney Turpentine-Ironbark Forest when Europeans arrived in Hornsby Shire. Beginning in the late 1700s, trees were felled for timber followed by wide-spread clearing of the forest for farming. With the construction of railway lines and road expansion, suburbs replaced the once-rural areas. As Sydney's population grew, land-use development continued a-pace and the forest was almost squeezed out of existence. You can find out more by reading Hornsby Thematic History.
In 2022, Sydney Turpentine-Ironbark Forest is still under threat from many factors. Left alone and without help, these negative impacts would accumulate, and Sydney Turpentine-Ironbark Forest could quickly decline and become extinct.
Weeds
Exotic plants, including weeds and garden escapees, constantly enter bushland and can take over all layers of a forest. This is especially the case along bushland edges and waterways, and in small or narrow patches of bushland that are surrounded by development. Think again if you don’t believe there are plants that can overpower the robust Turpentine and other canopy trees. Groundcover weeds such as Wandering Trad (Tradescantia fluminensis) can completely block the light reaching the forest floor. No matter how robust the tree, their seeds and seedlings need space and light to germinate and grow. This can’t happen with a thick blanket of weeds covering the ground.
Stormwater
As deep soils are replaced by concrete and bitumen for roads and footpaths, and buildings and facilities for the Shire’s growing population, there is increasingly less space for rain to be slowly absorbed into the ground where it falls. Now when it rains, urban creeks become raging torrents fed by pipes and gutters channelling water that has fallen on these hard surfaces quickly into our natural waterways and bushland. Along the way, this stormwater will carry with it any seeds or plant parts swept up in its path, loose soils, and nutrients such as fertilisers. With creeks flowing higher and faster than is natural, stormwater can reach far into bushland, laying down nutrient-rich sediments. Many bushland weeds thrive in these conditions and their growth can out-compete the native bushland plants. With much bushland located downslope of developed areas, water shedding directly from neighbouring properties can also give weeds the upper hand on the edges of bushland. Council’s Catchment Remediation Program of the last few decades continues to reduce the magnitude of these impacts. Council’s Water Sensitive Hornsby Strategy assesses the Shire’s water sensitive performance and identifies actions to mitigate the impacts of urban stormwater on bushland.
Dumping
Dumping is where natural or manufactured materials are taken into the forest, or moved within the forest, and left there. Natural materials include soil, rock and garden or tree prunings. Manufactured materials found in bushland include concrete and other building materials, discarded items such as furniture, and waste. Building up land or dumping material on top of the forest’s natural ground surface can starve the soil of oxygen and light. Seeds can’t germinate beyond a certain depth, and roots and other living things below the ground need oxygen to survive. The patch of forest affected cannot regenerate and its health declines.
Clearing
Clearing of Sydney Turpentine-Ironbark Forest is not just limited to the cutting down of trees but involves the removal or killing of any of the plants (including shrubs, grasses and groundcovers) which make up this unique ecological community. Unauthorised clearing is a threat to the survival of Sydney Turpentine-Ironbark Forest. It includes private properties encroaching onto public land to create extra space, cutting or poisoning of trees and plants to improve views or access to sunlight or to prevent leaves and branches dropping into properties, track building to access natural areas, and concerns about bush fire. Depending on the extent, some of these activities can be authorised by governments, including local Councils and state and national governments. If not authorised, and because of the critically endangered status of Sydney Turpentine-Ironbark Forest, these clearing activities can be considered illegal.
Clearing of Sydney Turpentine-Ironbark Forest is exacerbated by the digging up of soil by hand tools or machines. Sydney Turpentine-Ironbark Forest contains many living things below the ground surface. Digging up soil damages the future of the forest (in the location it occurs) by removing roots and vital stores of seed and the underground stems, bulbs and tubers of various plants. Digging also damages the roots of trees and other plants that grow alongside the cleared area.
Depending on the extent, some clearing activities can be authorised by governments, including local Councils. The reason why approvals may be granted is to provide places for people to live, work and recreate, or to manage risks to life and property. Any approval process requires rigorous environmental assessments, and options must be considered that reduce or eliminate any impacts on the forest.
Disease
Phytophthora and Myrtle Rust are exotic pathogens that damage bushland ecology and cause the death of plants in certain susceptible areas. These diseases can be spread by people or vehicles moving through bushland and unknowingly picking up pathogens on their shoes, clothes and tyres.