We have all seen the news items over the last couple of years on the 'Blue-Green Algae' and 'Toxic Algae' scares. The Murray-Darling system’s fish life has been battered by introduced competition (European Carp and others), reduced breeding opportunity (loss of access to traditional flood-plain spawning sites) and overfishing. The algae was just another 'nail in the coffin'.
Who do we blame? The media was full of suggestions. Was it 'The Farmers' and their superphosphate? Was it 'The Townies' and their overflowing sewerage works? Or was it just the great rivers themselves, finally laying down to die?
The answer was a little of all three, yet actually none of the above. The Murray-Darling River Commission put out a report titled "Investigation of nutrient pollution in the Murray-Darling River System" (Gutteridge, Haskins and Davey, January 1992). one review of the report reads as follows:
The above report states that the total nutrient loads in feedlot wastes from 180,000 cattle (number in the Murray-Darling Basin) was calculated to be about 1620 tonnes/year of phosphorus and 7200 of total nitrogen. Fish farms in NSW and Victoria contribute roughly 120 tonnes/year of total nitrogen and 17 tonnes/year of phosphorus. 11 and "The 180,000 cattle and more than 1 million pigs reared under intensive conditions in the Murray-Darling Basin represent in total the equivalent of human populations of 4.7 million and 3.6 million in terms of their capacity for the generation of phosphorus and nitrogen. This compares with an existing human population of 1.8 million in the basin.
Interestingly enough, those among us who condemn the New Guinean government for allowing cyanide from gold mine tailings to leach Into the Ok Tedi and thence the Fly Rivers are partly responsible for the damage by nutrient pollution of Australia’s biggest river system. Maybe we should clean up our own act first.