Why does our environment change
Both natural systems and humans can change our environment. How does this happen?
Natural systems transform the sun's energy into living matter and cause changes by cycling materials through geological, biological, oceanic and atmospheric processes known as bio-geochemical cycles.
Through these natural influences (in the absence of any human input), the Earth has experienced 5 mass extinctions, during which more than 75% of species disappeared, followed by an explosion of new species. This happened generally during periods of rapid climate change.
Some scientists believe a 6th mass extinction extinction is currently in progress. This time, humans are playing a role by altering the carbon cycle and releasing large quantities of carbon through burning fossil fuels.
Humans, until recently, have had a relatively small impact on changes to materials and energy flows. Today, however, human activities are altering these cycles and flows at unprecedented rates. Humans now fix almost as much nitrogen and sulfur in the environment as nature does. World food production depends on 80 million tonnes of nitrogen produced industrially each year, which has long-term impacts on our waterways and the species living in them.
Human release of trace elements, such as lead, exceeds natural flows by a factor of 17. The human contribution of other metals such as cadmium, zinc, mercury, nickel, arsenic and vanadium is twice or more than that of natural sources.
Most striking is the increasing volume of waste generated when we transform materials into consumer goods. In 2003, each South Australian, on average, generated 2,160 kg of waste per year. By 2017, this was 3,060 kg per year, an increase of 40%. Of this, about 80% is recycled, with 20% going to landfill.
Our physical landscape has also been unmistakably modified by humans. In SA, only about a quarter of native vegetation remains in the state’s southern temperate areas, where much of the land has been cleared for agriculture, industry, transport and human settlements. In the state’s more arid north, more than 90% of native vegetation remains, but is subject to grazing pressure and pest plants and animals.
South Australia is rich in minerals and mining operations since the 1840s have further modified our landscape.