Resource extraction and impacts on Earth systems: WACE Year 12 Earth and Environmental Science
“Analyse the effects of resource extraction on Earth systems and evaluate rehabilitation”
Extracting resources disturbs all four Earth spheres: mining removes and reshapes the geosphere, alters drainage and can pollute the hydrosphere, releases dust and gases to the atmosphere, and clears habitat from the biosphere. Rehabilitation aims to restore landform stability, soil and vegetation, but full recovery of complex ecosystems is difficult.
What this dot point is asking
SCSA wants you to analyse impacts across the spheres and evaluate how well rehabilitation works. A strong answer connects a specific extraction method to a specific impact and a management response, rather than listing harms in isolation.
Extraction methods
The method depends on the resource and how deep it lies.
- Open-cut (open-pit) mining removes overburden to reach near-surface ore. Most Pilbara iron ore and Darling Range bauxite are mined this way.
- Underground mining follows deeper ore bodies through shafts and tunnels.
- In-situ and solution methods extract some resources by pumping fluids underground.
- Extraction of groundwater and fossil fuels uses wells and bores.
Impacts on the geosphere
Mining physically removes rock and reshapes the land. Open-cut pits, waste rock dumps and tailings storage change landforms permanently. Removing vegetation and topsoil exposes the ground to erosion, and subsidence can occur over underground workings. Tailings, the fine waste left after the valuable mineral is removed, must be stored to prevent collapse and leakage.
Overburden: rock and soil removed to reach ore. Tailings: fine waste left after processing ore. Acid mine drainage: acidic, metal-rich water produced when sulfide minerals oxidise. Rehabilitation: returning a disturbed site to a stable, productive or natural state.
Impacts on the hydrosphere
Mining can lower water tables when pits are dewatered, drawing down aquifers that ecosystems and towns rely on. A major hydrosphere risk is acid mine drainage: when sulfide minerals such as pyrite are exposed to air and water, they oxidise to produce sulfuric acid that dissolves heavy metals. The resulting acidic, metal-laden water can contaminate rivers and groundwater for decades.
Acid mine drainage forms when pyrite reacts with oxygen and water to generate sulfuric acid. The low pH then mobilises toxic metals, so a single chemical reaction can degrade water quality long after a mine closes, making prevention far cheaper than remediation.
Impacts on the atmosphere
Extraction releases dust from blasting, hauling and crushing, which reduces air quality and can settle on vegetation. Diesel machinery and processing release carbon dioxide and other gases. Processing some ores, and burning fossil fuels, adds greenhouse gases that connect to the climate content of Unit 4.
Impacts on the biosphere
Clearing land for mines removes habitat and fragments ecosystems, reducing biodiversity. Noise, light and altered water flows disturb wildlife. In biodiverse areas such as the jarrah forest of the Darling Range, bauxite mining clears forest that supports many endemic species, so the biosphere impact is significant even where the area mined at any one time is limited.
Rehabilitation and its limits
Rehabilitation tries to reverse damage and is usually a legal condition of mining.
- Reshaping pits and dumps to stable, free-draining landforms.
- Replacing stockpiled topsoil, which holds seeds and soil organisms.
- Revegetating with local native species and controlling weeds and erosion.
- Treating or capping acid-generating waste and monitoring water quality.
Rehabilitation can restore stable landforms and vegetation cover, but rebuilding the full structure and species diversity of an original ecosystem can take many decades and may never fully succeed. This is why minimising disturbance and progressive rehabilitation during operations are emphasised.
To judge rehabilitation, compare the restored site against a reference (undisturbed) site using measurable indicators: native species richness, vegetation cover, soil stability and water quality. If the restored site approaches the reference values over time, rehabilitation is succeeding; persistent gaps in biodiversity show recovery is incomplete.
- Listing impacts without naming the sphere
- SCSA analysis questions reward linking each impact to the geosphere, hydrosphere, atmosphere or biosphere.
- Assuming rehabilitation fully restores ecosystems
- Landform and cover can be restored faster than complex biodiversity.
- Ignoring acid mine drainage
- It is a classic long-term hydrosphere impact examiners expect you to explain.
- Forgetting monitoring
- Evaluation needs measured indicators compared with a reference site, not assertions.
Exam-style questions
Questions in the style of SCSA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
WACE 2021-style8 marksAnalyse the effects of open-cut iron ore mining on each of the four Earth spheres, using a named region such as the Pilbara.Show worked answer →
An 8 mark analysis question rewards a distinct, linked impact for each sphere.
- Geosphere
- Open-cut mining strips overburden and removes vast volumes of rock, creating pits, waste dumps and tailings storage that permanently reshape Pilbara landforms; topsoil loss exposes ground to erosion.
- Hydrosphere
- Dewatering pits below the water table draws down aquifers important in an arid region; sediment and any process water can degrade surface and ground water, and exposed waste can affect water chemistry.
- Atmosphere
- Blasting, hauling and crushing generate dust that lowers air quality and settles on vegetation; diesel machinery emits carbon dioxide and other gases.
- Biosphere
- Clearing removes and fragments habitat, reducing biodiversity; noise, light and altered water flows disturb wildlife, and dust affects plants.
A strong answer links each impact to the specific sphere and to the mining activity causing it, rather than listing harms generally.
Markers reward one clear, correctly attributed impact per sphere, ideally with the Pilbara context.
WACE 2023-style7 marksEvaluate the effectiveness of rehabilitation in reversing the Earth-system impacts of resource extraction.Show worked answer →
A 7 mark evaluation must weigh what rehabilitation can and cannot reverse.
- What it can reverse
- Reshaping pits and dumps into stable, free-draining landforms restores landform stability (geosphere). Returning stored topsoil and revegetating with native species re-establishes vegetation cover and begins biosphere recovery. Capping acid-generating waste and monitoring water quality addresses the hydrosphere risk.
- What it cannot fully reverse
- Full ecosystem structure, species diversity and ecological function recover slowly and may never reach the original state, especially in biodiverse areas like jarrah forest. Aquifer drawdown and permanent landform change (a backfilled or remaining void) are not truly undone. Acid mine drainage may require treatment indefinitely.
- Judgement
- Rehabilitation is effective at restoring landform stability and ground cover relatively quickly, but only partially effective at restoring biodiversity and function. This justifies prioritising minimising disturbance and progressive rehabilitation over relying on after-the-fact restoration.
Markers reward a balanced evaluation distinguishing recoverable from hard-to-reverse impacts, with a clear judgement.