Saltwater Intrusion on Coastal Forests and Farms

Farmland showing areas where crop yield is decreasing or disappearing

Salinity and Salinization Impacts

Coastal forests and farmlands in parts of the Southeast are being negatively affected by saltwater intrusion and salinization. Elevated salinity levels cause crop yield declines, coastal forest loss, salt-tolerant invasive species takeover, eutrophication and marsh migration. Vegetation stressed by salinization impacts are also more susceptible to mortality by events such as drought, hurricanes, and fires. Other impacts from salinity and salinization include clay dispersion that reduces the hydraulic conductivity of soils and drainage capacity, nutrient release that can lead to algal blooms and cause fish death, and degraded groundwater for irrigation.

 Contributing Factors

Factors that contribute to the vulnerability of lands to saltwater intrusion and salinization include the elevation of the land and its rate of subsidence, in addition to the following drivers: 

  • Sea level rise: Rise relative to land and water table elevation. Higher sea levels increase the reach of tidal influences and king tides, and pushes the salt water/fresh water interface inland.
  • Storms and Tides: Tides and wind can push saltwater far inland. Storm surge inundates land with salt water.
  • Drought: Frequent and long droughts can lead to saltwater incursion and reduced the ability to leach salts from soils.
  • Water management: Ground and surface water extraction for human use and reduced freshwater discharge can increase the risk of saltwater intrusion.
  • Connectivity: Water control structures (e.g., tide gates, levees, canals, ditches) and tidal creek

Outlook

Salinization is expected to increase in vulnerable areas as sea levels continue to rise. Rising sea levels will inundate lands, increase tide and storm surge levels, and push salt water farther inland through ditches and tidal creeks. Natural leaching of salts from soils is expected to decrease as precipitation patterns change to greater periods of drought along with more frequent and intense storms. Working land profitability is expected to decline with increasing salinity. Areas with high rates of sea level rise are expected to see salt water pushed farther inland. For example, the North Carolina Albemarle-Pamlico Peninsula has a high rate of sea level rise and is projected to lose about half of its land area to open water with a 3-foot rise in sea level.
 
What are we doing to help?
 
The USDA Southeast Climate Hub is working with federal, state and Extension groups to better understand the current and projected rate and extent of saltwater intrusion, monitor salinity levels and impacts on crops and forests, and develop adaptation practices to help producers remain productive and resilient to saltwater intrusion and make climate-informed decisions. Current adaptation options include growing alternative crops/trees, developing salt-tolerant crops/trees, planting salt-tolerant plant buffers, or applying for wetland easements.
 
View our factsheet on salinity and salinization impacts to learn more.