How thin is the line between freshwater and saltwater in coastal areas? A recent study shows that this boundary is becoming increasingly fragile. Researchers have found that the delicate underground balance between freshwater and saltwater is at risk of being disrupted, with devastating consequences for coastal communities.
The dance of the underground waters
Under our coasts, a sort of aquatic dance takes place: fresh water and salt water maintain a unique balance, like two dancers who move without ever stepping on each other's feet. This delicate ballet is maintained by the pressure of the ocean towards the hinterland and by the rains that replenish the aquifers. There is even a "transition zone" where the two "partners" touch each other, but normally each one remains in its own space.
Unfortunately, the climate change is stepping in as a third wheel in this dance, giving salt water an unfair advantage. And do you know what that means for theagriculture coastal? A big problem, considering that many of our most valuable crops grow right in these areas.
Those with the fewest resources are the most affected by sea level rise and climate change
The numbers speak clearly
Il Jet Propulsion Laboratory of NASA he analysed over 60.000 coastal watersheds worldwide. The result? By 2100, 77% of these will be affected by saltwater intrusion. That's as if three-quarters of our "water boundaries" are about to be breached.
But there is more: sea level rise alone will push salt water inland in 82% of the basins studied, pushing the transition zone back as much as 200 meters by 2100. Regions such as Southeast Asia, the Gulf Coast, and parts of the East Coast of the United States are particularly at risk.
Salt water, a two-faced problem
Secondo Kyra Adams of JPL, co-author of the study published in Geophysical Research Letters (I link it here), the situation is complex but not entirely negative. In some areas, groundwater recharge will increase in as many as 42% of the remaining basins, sometimes even counteracting saltwater intrusion.
It's like a chess game on a global scale: sea level rise will influence saltwater intrusion globally, while aquifer recharge will determine the depth of intrusion locally. And as in any good game of chess, the moves are interconnected.
Salt water, a warning bell
Ben Hamlington of JPL, who co-led the study, points out that sea level rise is raising the baseline risk for significant changes in groundwater recharge. The year 2100 may seem far away, but if we want to give an effective response to these predictions, time is already running out.
The situation calls for global climate approaches that take into account local climate impacts. This is especially important for countries that do not have sufficient resources to conduct this type of research independently. As with any environmental challenge, international collaboration will be key to protecting our precious coastal water resources.
