Advanced Search
April 22, 2025
Key Takeaways:
Saltwater intrusion refers to the movement of saltwater into groundwater systems due to excessive groundwater pumping, sea level rise, and other factors.
Wetter soils with elevated salinity levels cannot support conventional crops, leading to declining yields, soil degradation, eutrophication (nutrient accumulation leading to oxygen deprivation), and marsh migration. This poses a direct threat to food security and local economies in low-elevation coastal agricultural states.
To combat the impacts of saltwater intrusion, farmers can employ a range of adaptation strategies, with support from entities like the U.S. Department of Agriculture’s (USDA’s) Southeast Climate Hub, to preserve the productivity of their land in the short term.
Saltwater intrusion into groundwater systems is a slow-onset climate crisis. As increasing global temperatures lead to the thermal expansion of water and melting polar ice, sea levels are rising, pushing saltwater further into coastal lands. Additionally, the over-extraction of groundwater to meet human freshwater demands depletes aquifers, allowing underground saltwater to infiltrate upwards into the soil.
Unlike sudden, extreme climate events such as wildfires, heatwaves, and hurricanes, slow-onset climate events are gradual, long-term environmental changes that include biodiversity loss, glacial retreat, ocean acidification—in addition to saltwater intrusion. The effects of these changes develop over extended periods of time, meaning they often attract less attention and prompt fewer policy responses to mitigate their impact. While significant resources are allocated to address catastrophic storms, the accumulation of under-the-radar environmental stressors can present a more complex challenge.
“We are preparing for the wrong disaster almost everywhere,” said Rob Young, director of the Program for the Study of Developed Shorelines at Western Carolina University and an EESI Advisory Board member. “These smaller changes will be a greater threat over time than the next hurricane, no question about it,” he noted during an EESI briefing.
Groundwater flow patterns in a coastal aquifer. Source: California Water Science Center.
Though slower to emerge, the impacts of slow-onset climate events are already being felt. Saltwater intrusion has already contaminated freshwater aquifers in 43 U.S. states. Beyond making water undrinkable, rising groundwater levels also mobilize contaminants from municipal and industrial waste, polluting streams, reservoirs, and agricultural land.
In the low-elevation coastal farmland of the Southeast, saltwater intrusion poses a direct threat to food security and local economies. “When salt comes into our fields, there’re places that won’t grow crops, nothing will germinate,” says Dawson Pugh, a fourth-generation farmer from Hyde County, North Carolina, in a special by PBS North Carolina. Wetter soils with elevated salinity levels cannot support conventional crops, leading to declining yields, soil degradation, eutrophication (nutrient accumulation leading to oxygen deprivation), and marsh migration. “It’s not something that just started, it’s been happening for generations, and it’s getting worse,” Pugh explains. Pugh’s farm is now only 18 inches above sea level.
Saline-saturated soils appear white in color and result in decreased crop yields. Credit: USDA
When saltwater enters soil, it disrupts water uptake in plants, stunting crop growth and reducing yields. Common crops such as soybeans, corn, and wheat are hit especially hard by high-salinity conditions. Additionally, salt mobilizes and removes essential nutrients and harms microbial communities, reducing soil fertility. These mobilized nutrients and fertilizers can then run off into nearby streams and estuaries, resulting in algal blooms followed by fish die-offs from toxicity and low oxygen levels.
The economic consequences of saltwater intrusion are severe. Lost crops and degraded land reduce farmers’ income, increase their reliance on expensive water management systems, and disrupt rural economies that depend on agriculture. Salt-degraded land in irrigated areas could be contributing to global annual economic losses of between $12 and $27.3 billion from reduced crop yields.
To combat the impacts of saltwater intrusion, farmers can employ a range of adaptation strategies to preserve the productivity of their land in the short term.
For example, farmers can use freshwater irrigation to flush salts from the soil. However, this requires access to significant freshwater sources. Adding gypsum to soils can help counteract sodium buildup, improving soil structure. Farmers can also use deep-rooted cover crops, such as rye and clover, during the off-season to aerate soil, improve water infiltration, and help salt escape down through the soil. Finally, farmers can swap out salt- and flood-intolerant crops with different, more tolerant varieties such as specially-modified cotton, barley, safflower, and alfalfa.
As sea levels continue to rise, even fields that are replanted with salt-tolerant crops will become too wet for any crops at all. At that point, farmers can convert their land to wetland habitat and enroll in conservation easement programs, like the U.S. Department of Agriculture’s (USDA’s) Agriculture Conservation Easement Program, to keep the land profitable. Salt marshes bring billions of dollars of recreational revenue to coastal states, so it can be cost-effective for states and the federal government to create incentives for farmers to build salt marshes on their flooded farmland.
The USDA’s Southeast Climate Hub is actively researching saltwater intrusion, working with farmers to develop adaptation strategies and improve soil resilience. In 2019, they hosted a workshop with select scientists to share knowledge, encourage community discussions, and develop plans for addressing regional salinization issues. USDA Senior Soil Scientist Greg Taylor presented his work predicting zones vulnerable to saltwater intrusion based on soil surveys, and Diana Rashash, then with the NC Cooperative Extension, shared her findings on the impact of salinization on soil and crops based on well sample data.
The information provided by the speakers was used to develop a soil salinization mitigation and adaptation manual for farm and forest management, allowing farmers to identify the stage, cause, and progression of salinization on their land, as well as potential response strategies. By monitoring soil salinity, developing climate-informed agricultural practices, and providing technical assistance, the Southeast Climate Hub supports communities facing the creeping threat of salinization. However, long-term solutions require collaboration between federal agencies, state agencies, and local stakeholders to scale up adaptation strategies.
While adaptation efforts provide short-term solutions, they do not address the root cause of saltwater intrusion: rising sea levels. Sea levels were at least six inches higher along the Gulf and Southeast coasts in 2023 than in 2010, and are projected to increase 36 inches along parts of the East Coast by the end of the century.
Preparing for these shifts is essential, especially for farmers. Having robust data is key, and funding is needed for salinity monitoring, updated water quality models, and sustainable land-use planning. Without swift action, the slow creep of salt water will continue to transform coastal landscapes, threaten food production, and reshape rural economies.
Author: Whitney Orloff
Advancing science-based climate solutions
Top-Rated Climate Nonprofit – 4-Star Charity