It is renowned for its beaches and its seafood, but the Adriatic Sea is also at grave risk from pollution.
Each year between late August and early September, a part of the marine environment dies, becoming a biological dead zone; a result of the agricultural run-off that flows down the River Po, Italy’s longest river, and into the Adriatic.
The nitrate – and phosphorous-rich effluent comes largely from pig, cattle and chicken farms. The Po valley accounts for 35% of Italy’s agricultural production and 55% of its livestock – that’s four million cattle, five million pigs and 46 million chicken.
They produce some of Italy’s most renowned food products, from prosciutto ham to cheeses such as Parmigiano Reggiano and Grana Padano. Nitrogen and phosphorus encourage the growth of plant life which sucks oxygen from the sea and kills marine organisms.
“Among these plants there are algae on the rocks and on the seashore, but we are mostly talking about phytoplankton, small microscopic plants, floating in the water”, said Michael Stachowitsch, an expert in marine ecology at the University of Vienna.
“Organisms on the seafloor start to die, because there is no oxygen. And when they die, they also need to be broken down by bacteria, which require even more oxygen. Large organisms may be able to escape, by swimming away, but most of the organisms are sitting on the seafloor where they are growing on seashells, and they can’t move”.
Pierluigi Viaroli, a biologist at the University of Parma, says the problem has got more serious in the last two decades. “In the last 20 years both cattle and pig densities have risen in a relatively small area south-east of Milan,” he said.
The EU has strict controls on how much livestock manure can be applied to farmland but farmers frequently exceed the limits, and also dump effluent illegally in streams and rivers. There are too many farms in too small an area, and transporting manure to other regions would be too expensive.
The levels of nitrogen that are being dumped into the Adriatic must be brought under control in order to avoid “catastrophic events” in the future, according to Rossano Bolpagni, a biologist at the University of Parma.