COASTAL CHALLENGES‘A Silent Killer’: How Saltwater Intrusion is Overtaking Coastal Farmland in the U.S.
As hurricanes get stronger, storm surges are bringing saltwater to farmland—and leaving salt there once waters evaporate. And as sea level increases due to climate change, the difference between ocean water levels and soil elevation is decreasing, making post-storm water runoff more difficult. With enough flooding, the soil on farms could become so salinized that crops can no longer be grown on that land. The salt eventually makes contact with freshwater aquifers, thus salinizing them.
Eerily empty, abandoned fields stretch across the coast of the southeast United States, replacing once sprawling fields of golden wheat, corn and soybeans.
For centuries, farmers have favored the rich soil of coastal areas during the growing season. “It’s very fertile soil, especially in some areas that are called the ‘black lands.’ These are really deep organic soils that formed on the coast over millennia,” says Michael Gavazzi, coordinator of the USDA Southeast Climate Hub coordinator and natural resource specialist.
It’s a different story when the floods come in. Hurricanes and tropical storms bring torrential rain and powerful winds that cause storm surges—abnormally large waves that can tower up to 25 feet in height. The aftermath of such disasters is devastating. Crop damage and equipment loss can rack up to thousands of dollars for farmers, even with insurance. The spread of invasive species hinders future growing seasons of certain crops. And most of all, flooding risks long-term consequences to soil health and the geological makeup of farms that could force farmers to permanently abandon their land.
Take, for instance, 2018’s Hurricane Florence. The slow-moving Category 4 giant ravaged southeast coasts, with wind gusts as high as 100 miles per hour, rainfall that exceeded 10 inches in most coastal regions (Swansboro reported 34 inches of total rainfall) and $24 billion in damages—more than Category 5 Hurricane Matthew and Category 4 Hurricane Floyd combined. The initial $1.1-billion damage cost calculation was conservative, and it didn’t account for damages from soil salinization. Even worse, climate scientists say that rainfall estimations were worsened by climate change, an indication that future storms could follow similar patterns.
The storm rocked North Carolina’s agricultural industry to its core. Five of six top agricultural counties of the state were in the most storm-vulnerable areas. Most eastern farmers’ fields were obliterated; the storm came right before peak harvest season for tobacco, corn and cotton. Crop insurance didn’t cover all the damages incurred, especially not the long-term costs.
“Fresh water [non-saline] flooding from intense rainfall events can [have] short- and long-term consequences,” says Gavazzi, “but the land will usually recover.” However, ocean-driven storm surge flooding is saltwater, and crop productivity can be negatively impacted. Repeated flooding can permanently reduce forest, range and agricultural production of these coastal areas.