Shrimps and the salt wedge: a push factor

15 May 2023

What does shrimp farming have to do with the intercontinental migration of people? More than you might think.

The link may seem almost invisible, but it exists: testament to a cause and effect relationship and the profound interconnectedness of the modern world. It’s a good example that backs up a key Slow Food message: that our food choices are political acts.

We speak about shrimp with Jacopo Pasotti, geologist, journalist and speaker at a conference dedicated to the links between aquatic and terrestrial ecosystems at Slow Fish 2023.

Where the land meets the sea – June 1, at 3 p.m.

At Slow Fish 2023 we intend to broaden our horizon, to read the seas from coast to coast, and develop a holistic vision which recognizes the connections between what happens on land and at sea. We must consider these links at all levels: from the CO2 emissions produced on land to the acidification of the waters, the health of oceanic plankton and the oxygen we breathe. We explore how how the sustainability of human activities along the coasts is integral to the health of those ecosystems, as well as to our cultural identities, first and foremost the culture of fishing.

Sign up to take part in this free conference!

Mangroves, farmed shrimp, and the rising salt wedge

“In Bangladesh, one of the world’s leading shrimp exporters, the salt wedge is penetrating inland, rendering hundreds of hectares of land unsuitable for farming,” Pasoti tells us. The salt wedge is the phenomenon whereby seawater moves up through inland waterways and contaminates sources of freshwater, like rivers. This can happen for a variety of reasons, but “in Bangladesh this has happened predominantly because of the clearing of mangrove forests, once present along the coast, to make way for shrimp farming.”

There is plenty of scientific research on the subject: one paper, published in the journal Population and Environment, states that between 2006 and 2007 alone, the salt wedge along Bangladesh’s coastline moved inland by about 20 kilometers. Other studies, such as the one conducted by the Soil Resource Development Institute (part of the Bangladesh Ministry of Agriculture) show that between 2000 and 2009 the advance of salt water, in the dry season, reached up to 160km inland, partly due to the low water flow of freshwater streams.

These precious mangrove forests, which act as a dike both against monsoons and a bulwark against the rising sea levels, have sadly been destroyed over the years to make way for salt ponds where shrimp are raised for export. The encroaching salt wedge has not only changed the morphology of the coast; it has forced the inhabitants of coastal areas – who, historically, were mostly rice farmers – to leave their lands, displaced by a form of ecological collapse caused by human action. In many cases these people are forced to move to another area of the country to find a future, others venture on longer journeys, to other countries, often to the Global North.

A global issue

“The rising salt wedge is a phenomenon we see only in Bangladesh,” Pasotti continues. It’s happening in Italy, too: on May 5, the Ministry of Infrastructure and Transport announced €22 million in funding for an ‘urgent intervention to improve the anti-salt barrage at the mouth of the Adige River with stream channelization for the containment of fresh water upstream.’ In 2022, the governor of the Veneto Region, Luca Zaia, denounced “a salt wedge of more than 20 kilometers upstream in the Po River.” This means that for more than 20 kilometers inland from the sea, that the river water couldn’t be used for irrigation, causing extensive damage to crops, and creating a critical situation in terms of the availability of drinking water for local communities.

Pasotti goes further: “The sea is beginning to encroach on our agricultural plains, with an enormous impact for ecosystems, for agriculture, and for the economy. Having seen the situation along the Ganges Delta with my own eyes, and the problems caused by the salt wedge, my hair stands on end.”

The coast: an open-air dump

The advance of the salt wedge is not the only problem affecting the coasts. They’re generally densely-populated areas affected by the arrival of pollution along the waterways that flow into the seas. They’re “an exchange boundary, an irregular line that represents the border between the marine world and the terrestrial sphere, and everything that happens on land filters down to the sea. It’s kind of like when we put our garbage out in the trash bins: we don’t worry too much about where it goes afterwards. And along the coasts there is a similar phenomenon, where we wave goodbye to all the outputs of human activities, because what happens at sea is out of sight and out of mind. Yet its impact is much greater than we realize, and it is growing.”

by Marco Gritti, info.eventi@slowfood.it

Slow Fish 2023 is organized by Slow Food and the Liguria Region, with the support of the City of Genoa. We’re in the Porto Antico of Genoa from June 1-4. Sign up to the Slow Food newsletter for the latest updates. #SlowFish2023

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