'The sea has taken everything': How Italy's coast was reclaimed

Delta del Po, Italy - Only the locals are daring enough to venture into the waters of the Po Delta, where the Po River flows into the Adriatic Sea off the coast of northern Italy. That is - only those among the locals who still remember the position of the river banks and lands which have long since sunk into the water.

Subsidence - the slow and progressive sinking of the ground over time - is a phenomenon which has become very familiar to the inhabitants of the Po Delta region. It has caused the complete submergence of entire stretches of coast over the past 50 years.

The "Isola Bonelli Levante'' in Porto Tolle is among the most striking examples of segments of land which have slipped into the sea. A large rice farm, which was in use from the 1970s, has sunk almost 3 metres (nearly 10ft) below sea level and was abandoned in the 1990s.

Another example is the vanishing "Isola Batteria" along the Po della Pila, one of the smaller channels within the wider delta. Once a German military fortification built during World War II on the island which took its name, today it is mostly a lagoon, nearly completely submerged, and can only be reached with difficulty by boat. Just a few buildings remain, reduced to skeletons and semi-submerged ruins.

The murky waters covering the seabed here are shallow. For the boats and kayaks of tourists accompanied by local guides who venture here, the risk of running aground is very real.

Of the old banks of the river, only a few shy reeds break through the surface of the water, showing where until not many years ago you could walk, sow rice or go fishing for hake. Today, those reed beds which once adorned the river bank in abundance seem to be an anomaly as the sea has repossessed land labouriously removed from the waters by centuries of reclamation.

“I was born there,” says Luciano as he steers his boat safely through the waters of the Po. The retired fisherman points to the opposite bank of the river, directing his gaze towards Pila, a small village of fishermen and farmers. “There were embankments and dirt roads to reach the countryside. On Sundays, the holiday, I came here with my father by bicycle. The sea has taken everything back” he says.

Salt of the earth

At the mouth of the Po River, where the river meets the Adriatic Sea, saltwater infiltration is reaching worrying levels.

Despite being a natural phenomenon when the freshwaters of the river mingle with the saltwater of the sea, the “salt wedge” - the area in which saltwater has sunk through the subsoil beneath the surface of the land - can spread, particularly in the summer months when there is less rain to help disperse it.

In 2022, which had a particularly dry summer, this salt wedge extended more than 40km (25 miles) inland from the Adriatic Sea. Last year, when there was more rain, the salt wedge spread for 17km (10 miles).

The delta area of ​​the Po River extends for 140 square kilometres (54 square miles) between the regions of Veneto and Emilia Romagna in northeast Italy. Approximately 70 percent of the territory is made up of agricultural land.

The rising salinity of the water is causing damage to the ecosystems along the coast, and to agricultural, livestock and industrial activities, according to a recent report from ARPAE, the Emilia Romagna Agency for the Environment.

There are several factors contributing to rising salt levels in this part of the river, some linked to climate change such as reduced rainfall, drought and the over-consumption of freshwater.

Compounding these issues, the area was heavily mined for methane gas until 1961, when the Italian government halted operations because of subsidence.

Along the rice fields of Porto Tolle in Veneto, the areas damaged by salt seeping into the soil are clearly visible. It has been caused by both direct irrigation with brackish water and by saltwater rising from the subsoil.

In the Po Delta, the problem is particularly bad because the fields are below sea level - a consequence of centuries of farming, which has slowly lowered the ground level by reclaiming terrain from the sea.

The salinisation of the soil here is having a catastrophic impact on agriculture.

“The limit on salinity for distributing water is one gramme per litre,” explains Rodolfo Laurenti, deputy director of the Consorzio Bonifica Delta del Po, the regional regulator that ensures the hydraulic safety of the Veneto area hit hard by the salt wedge.

The delta territory, being a reclaimed area below sea level is a large network of communicating channels of water within which the water must be continuously drained and moved along the canals to prevent any risk of the whole territory being flooded with water.

To manage this, the regulating body carries out hydraulic defence, irrigation and environmental protection works. It oversees the embankments protecting against flooding, the irrigation network systems, the delta lagoons and the outlets merging into the sea and the canals and facilities serving the fishing valleys.

“Even in Taglio di Po, a city 30km from the Adriatic Sea, last summer the [salination] value was 10 times higher,” Laurenti explains.

This poses a serious problem for the crops - rice, corn, soya, other cereals, fodder and fruit. In two years, the area of land which can be cultivated in the district of Polesine has reduced by more than 30 percent, according to a 2022 report from Coldiretti, an agricultural producers’ association.

Last year, the production of rice fell by 20 percent in this region as a direct result of the rising salination of the water.

Rice is a typical crop in the Po Delta that has been cultivated since the Middle Ages. The rice fields cover approximately 9,000 hectares of delta territory, and the European Union has listed the rice produced here as a Protected Geographical Indication (PGI) brand to validate its flavour and important nutritional qualities.

Many rice growers are increasingly concerned about the rising saltwater and climate change. "The cultivars we grow have a different scent and flavour from those grown far from here as they breathe the air of a territory reclaimed from the sea,” says Elisa Moretto as she shows a photograph of her rice field in Porto Tolle flooded by seawater that has risen into the canals used by farmers to irrigate the fields.

“Now my greatest fear is that the sea is taking back the land," she says. In 2022, when the drought hit and the salt wedge spread, her farm’s output of rice fell from 3,600kg (7,900lbs) to just 900kg (1,980lbs).

Salt, rising

Marco Uccellatori, a young agronomist who owns a farm in Taglio di Po that has been producing rice since 1700, is similarly concerned.

To irrigate his rice fields, he takes freshwater directly from the Po della Pila. "Rice is vital for us. During the summer season, we measure the salinity level of the river water so as not to damage the soil and not to lose the harvest," he says as he leans out from a small wooden pier to measure the salinity level of the river through a conductivity metre.

To protect agricultural and industrial areas in Volta Vaccari, in the municipality of Porto Tolle, the Consorzio Bonifica Delta del Po has installed a dam capable of collecting freshwater in a dead branch of the river - a curved lake formed where the main stream of the river has cut across the narrow end of the oxbow and no longer flows around the loop of the bend.

“It is an automated barrier that is activated when the sea current hits it and guarantees one million cubic metres of freshwater for local farms during the most critical periods,” says Laurenti.

Salt intrusion has reached particularly worrying levels in this region in recent years but the phenomenon has been known since the 1990s, when the Consorzio di Bonifica Delta del Po began installing barriers to limit the spread of salt into the various tributaries.

These are complex installations made up of poles driven into the riverbed perpendicular to the current to which unidirectional mobile fins are anchored. They remain open to accommodate the flow of water towards the sea and close, automatically forming a barrier, when the water from the sea ​​advances towards the river.

The barriers have worked well in the past, but today they run into an insurmountable obstacle: they were calibrated with the minimum flow values ​​of the Po at the time - 450 cubic metres per second - in mind.

Today, lower rainfall means the flow of the river has slowed to around 113 cubic metres per second. This has caused the barriers to be much less efficient - and less able to counteract the incoming flow of seawater, Laurenti explains.

The regulator has now submitted a proposal to the government for a new barrier in the Po della Pila, the main branch of the river that flows into the Adriatic Sea, which would help farmers across the entire delta area.

“It would guarantee in the remaining branches of the Po freshwater flow three times higher than that which would pass without the barrier,” says Laurenti.

In Emilia Romagna, scientists are monitoring rising salt levels through the analysis of water samples taken from the underground aquifer - the layer of flowing water beneath the soil and the main source of freshwater.

“The monitoring is carried out through the measurement of the groundwater level and through the analysis of the electrical conductivity and temperature of the samples taken from different depths of the surface coastal aquifer,” explains geologist Manuela Mengoni of ARPAE.

Mengoni is currently working in Bosco Mesola, a protected wooded area in the province of Ferrara about 2km inland from the sea.

By testing these samples, ARPAE researchers can determine the quantity of salt dissolved in freshwater and the variations at different depths underground, where fresh and saltwater are mixing.

They are trying to ascertain how quickly the sea water is rising in the aquifer.

“In recent years, we have detected an increase in salinisation even in the most superficial part of the aquifer and there is a statistically significant increasing trend towards the ingression of the salt wedge,” says Mengoni.