A new study says that even in the "unrealistic" case of a total cessation of the flow of agricultural chemicals, the damage will persist for 30 years.
The huge "dead zone" in the Gulf of Mexico will take decades to recover, even if the flow of agricultural chemicals that is causing the damage is completely stopped, new research warned.
Intensive agriculture near the Mississippi has led to the discharge of fertilizers into the river and eventually into the Gulf of Mexico, through soils and waterways. This has resulted in a large oxygen-deprived dead zone in the Gulf that is now at its greatest extent, covering an area larger than the state of New Jersey.
A new study found that even if nitrogen runoff, a chemical fertilizer, were completely stopped, it would take about 30 years for the Gulf to recover. Even this scenario "is considered not only unrealistic, but also inherently unsustainable," the researchers claimed in the work, published in Science.
"We have been accumulating nitrogen for the past 50 years and it will take time to pass through the system," said Nandita Basu, associate professor of environmental science at the University of Waterloo in Canada and a co-author of the study.
“Money is spent on the landscape in an ad hoc way. We need to focus better. If we make the right changes, it will have an impact, it's just that it will take a few decades. It's like when you go on a diet: you can't expect results right away. "
The battered Gulf of Mexico is emblematic of a global suffocation of the oceans caused by modern agriculture, sewage and climate change, which is causing waters to heat up and contain less oxygen. At least 500 sites experiencing hypoxia, or oxygen deprivation, have been reported near coasts worldwide, compared to just 50 in 1950. The true number may, in fact, be much higher, according to experts.
Fertilizers that spill into the oceans promote the growth of algae, which can trigger toxic blooms harmful to fish, shellfish, marine mammals, and birds. These shoots can discolor the water and befoul beaches. It also depletes oxygen in the water, causing further damage to sea creatures and diminishing supplies for the people who depend on them for food.
In the US, a federal government-led task force set a goal of reducing the Gulf dead zone to less than 5,000 square kilometers by 2015. However, the hypoxic area was three times greater for the target year, which caused the deadline to be pushed back to 2035.
There is also an interim goal of reducing nitrogen flow to the Gulf by 20% by 2025, but that too appears to be in jeopardy.
"That short-term goal of 2025, based on the course we're on now, is not really possible," said Kim Van Meter, Basu's colleague and co-author. “It would take an immediate change and it takes time for that to happen. The legacy of nitrogen in the system means it will take decades. "
Nitrogen pollution can be curbed with more careful application of fertilizers, planting certain grasses, trees and shrubs that can stop chemicals from entering waterways and reduce the amount of soil tillage to prevent soil erosion. soil and runoff.
Some American farmers receive government support for these efforts, although environmentalists argue that funds have been wasted on projects that simply help farms increase crop and meat production, rather than combat pollution.
"This study shows that we need a scientific strategy and we cannot expect immediate results, but we do know what needs to be done to improve things," said Denise Breitburg, a marine scientist at the Smithsonian Environmental Research Center who was not involved in the report.
Original article (in English)