An oxygen-deprived “dead zone” in the Gulf of Mexico would take decades to reverse, according to a study from the University of Waterloo in Canada.
The so-called dead zones form when water doesn’t have enough oxygen for fish and other marine life to survive, which researchers attribute to agricultural runoff along the Mississippi River – namely industrial fertilizers – that makes its way into the Gulf.
Released last month, the study says, even if farmers were to completely stop the flow of runoff right now, it would take at least 30 years to dissipate.
After the runoff makes its way into oceans, it causes overgrowths of algae. When the algae dies and decomposes, oxygen in the water gets absorbed along with it, forming so-called hypoxic zones, says Kim Van Meter, a postdoctoral fellow at the University of Waterloo and co-author of the study.
“Fish can’t live there, and you can just end up with a massive die-off of the ecosystem,” Van Meter says.
The dead zone in the Gulf of Mexico is the largest one ever recorded in the U.S. At nearly 9,000 square miles, it’s roughly the size of New Jersey. But, even though it shrinks in the winter months, researchers say it still seems to be coming back stronger every summer – which causes a lot of problems.
Despite that winter reprieve, the Gulf's dead zone still causes irreversible damage to ecosystems, and there's also a more lasting economic concern, Van Meter says.
“Many communities around the Gulf Coast are dependent on both commercial and recreational fishing,” she says. “When you have these large dead zones, you’re really disrupting that industry.”
Van Meter and her colleagues conducted the determine just how long it would take to fix the damage already done, finding it would still take at least 30 years to recover – even if 100 percent of fertilizer chemicals stopped flowing into the Gulf right now.
But researchers say there is plenty the agriculture industry can do to significantly reduce the amount of chemical runoff. For one, farmers could start applying fertilizers more carefully or plant certain trees and shrubs to absorb chemicals before they get into waterways.
Both authors say that, even if it does take decades to see results, it shouldn’t discourage attempts to fix the problem.
“Like, when you go on a diet, if you’re doing all the right things and it’s staying the same, that’s very disheartening,” Van Meter says. “But if you understand it’s a long term proposition, I think it makes it a little easier to stay with the program.”
Last year, a federal task force set a goal of shrinking the Gulf’s dead zone to fewer than 2,000 square miles by 2035, but unless major changes are made quickly, it isn’t likely that goal will be met.