Save Fisheries, Save Water

Caption Jon Connell

A Maldivian fishing boat

Whoever thought that eating saltwater fish could help protect freshwater?

Unlike land-based sources of protein including meat and dairy, saltwater fish production requires little to no freshwater. So, consuming fish instead of meat represents a savings of water.

In a new study, Jessica Gephart and her colleagues calculated for the first time just how much freshwater would be needed to replace fish and other marine protein in our diets with protein produced on land. It's an unusual example of how our food and water resources are closely linked.

The study finds that if everyone in the world replaced the amount of fish they currently eat with "terrestrial protein" (i.e. meat, dairy, nuts, etc.) it would require an additional 92 trillion gallons of freshwater per year. That's a lot, although it represents a relatively small 4.6 percent increase in global freshwater use. If you look at specific regions, however, the implications can be dramatic. 

If the health of its fisheries was to decline, and its citizens had to make a switch from fish to meat, the Maldives would have the most to lose of any country in the world. Right now that nation's diet of fish and other marine protein provides them with water savings of about 50 percent as compared to a more meat-based diet. The Maldives are very dependent on fish, but because they have little land to capture freshwater or to raise land-based protein, the island nation would struggle to feed its people if fish stocks declined.

Other countries face different challenges. Much of the Middle East and North Africa, and parts of Sub-Saharan Africa, have sufficient land but insufficient water to manage a shift in its citizens' diets, while other countries, including Japan and Bangladesh, have sufficient water resources but insufficient land.

So what about the role of aquaculture? It's complicated, to say the least. As the study says, "sustainable aquaculture is likely an important component of meeting the increasing protein demands of a growing population without substantially increasing the water footprint of humanity."

However fish aren’t always farmed sustainably. It's estimated that by 2030, about two-thirds of fish consumed globally will be farmed. Those raised in offshore fish farms, for example, can ultimately harm wild fisheries. Better choices like recirculating aquaculture have more promise.

Ultimately, the study provides yet another example of how water resources and food security are linked. While it might at first sound odd, it makes perfect sense that Gephart and her colleagues recommend that fisheries management and international fishing agreements start considering freshwater security. If we can better manage the world's fisheries we not only preserve fish stocks, but help make our land-based food and freshwater resources more secure.

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