Opinion | Soils ain't soils | Tim Roberts

Channelling the brilliant Castrol GTX ads ‘soils ain’t soils, Sol’:  pre-1788 Australian soils were carbon rich with levels some five to 10 times higher than current levels, as reported by the explorer Strzelecki in 1845.  A return to such stored carbon levels across Australia would be equivalent to a massive capture of atmospheric carbon. 

Soil carbon is the key to soil health and productivity. In a few short decades of European settlement the Australian soils moved from being soft and spongy and absorbent to being hard and impervious with water flowing rapidly across the surface. 

One of the key contributors to this change was the introduction of hard-hoofed grazing animals such as sheep and cattle. The initial uncontrolled grazing by cattle, and then the huge expansion of herds with the advent of farming, rapidly led to the eating out of the native grasses and the compaction of the soil, water runoff then leading to massive loss of fertile topsoil through erosion. 

Governor Arthur Phillip reported in 1788 of the escape of some seven head of cattle into the hinterland near Sydney Cove. Seven years later the cattle were located on the floodplains of the Nepean River and by 1802 the herd numbered at least 400 animals.

Grasslands were aplenty because the all-conquering eucalypt which had been held in check for thousands of years by regular burning were yet to colonise and sterilise the landscape. The following decades saw a huge expansion in the number of hard-hoofed sheep, cattle, and goats across Australia, the clearing of the land, the loss due to foxes and cats of those small marsupials that, by foraging for truffles, made the land pervious to rain. Australia is in urgent need of an active program to address the legacy of our degraded lands.  Soils without carbon ain’t soils.

Professor Tim Roberts is the director of the Tom Farrell Institute for the Environment, University of Newcastle