Quick questions on Human modification of biophysical processes: HSC Geography

Australia has cleared around 50 percent of its original woodland and forest since 1788. Queensland alone cleared 7.7 million hectares between 2000 and 2020, mostly for cattle grazing. The Bureau of Statistics records continued woody vegetation clearing at around 400,000 ha per year nationally.

Around 86 percent of Australians live in urban areas. Sydney, Melbourne, and Brisbane between them cover roughly 30,000 km2 of formerly natural or agricultural land. Greater Sydney is projected to grow by another 1.7 million people to 2041.

Around 60 percent of the Australian landmass is used for agriculture, mostly extensive grazing. Cropping covers around 6 percent of the continent. Irrigated agriculture extracts around 9,000 GL of water per year, around 65 percent of total Australian water use.

Australia produced 480 Mt of black coal, 900 Mt of iron ore, 30 Mt of bauxite, and significant gold, copper, zinc, and uranium in 2023. Open-cut mines disturb large surface areas; underground mining causes subsidence that alters drainage patterns.

Industrial and consumer pollution adds chemicals, plastics, nutrients, and noise to natural systems. Australian beach surveys find around 7,000 pieces of plastic per square kilometre of beach. PFAS chemicals from defence and industrial sites have contaminated groundwater across multiple sites (Williamtown NSW, Oakey QLD).

The cumulative effect of all human activity is anthropogenic climate change, which now alters every other biophysical process. Australian average temperatures have risen 1.5 degrees C since 1910. Sea level has risen around 22 cm globally since 1900. Ocean pH has fallen 0.1 units, with measurable acidification on the Great Barrier Reef.

Reduced evapotranspiration alters local moisture and rainfall. Removed root systems destabilise soils, increasing erosion and sediment loads. Lost canopy interception increases stormflow peaks.