A “world-first” local study has found regional Victorian dams produce the same daily emissions as 385,000 cars, according to Deakin University.
“While our data was gathered in Victoria, this is certainly a nationally-relevant issue and likely a global one too,” said Quinn Ollivier, the study’s lead author.
Mr Ollivier, a PhD candidate at Deakin’s Blue Carbon Lab at Queensclif, sampled 77 small agricultural dams between Ballarat and Geelong during the study.
Extrapolating this data led Mr Ollivier to estimate farm dams produced emissions three times higher than reservoirs in Victoria.
Victoria has 375,000 farm dams, with a combined volume of 1.5 times the Sydney Harbour.
The study found farm dams had one of the highest emissions per square metre of all freshwater ecosystems, Mr Ollivier said.
The study linked dissolved nitrate concentrations to greenhouse emissions, which were significantly higher in livestock farm dams than crop farm dams, he said.
Reducing nitrate nutrient levels by a quarter, through activities like minimising excess fertilisation and containing animal effluent, could cut the emissions of some dams by half, Mr Ollivier estimated.
Planting native vegetation around dam edges could also cut emissions, he said.
Farm dams created a unique environment for microbes that contribute to greenhouse emissions through the breakdown of organic material, Mr Ollivier said.
“When all these little microbes munch on the plant and animal matter coming into the dams, they breathe out potent greenhouse gases, such as carbon dioxide, methane and nitrous oxide.”
Emissions from small-scale agricultural dams had remained relatively unknown until now, especially compared to similar natural water ecosystems, Mr Ollivier said.
“Global satellite networks have only made it possible to correctly assess the distribution of farm dams in the last decade.
“I think their small size has helped them stay under the radar, both figuratively and literally.”
