Everglades National Park

Saltwater intrusion in the Everglades threatens the park’s abundant biodiversity and the drinking water supply for millions of Floridians

Nathaniel Blackford, Coastal Resiliency Fellow, National Parks Conservation Association (NPCA)

June 28, 2022

Everglades National Park was the first park designated specifically for its abundant biodiversity. The extensive mosaic of coastal forests, mangroves, and wetlands that run the gamut from fresh to salt, as well as the park’s location at the boundary of the tropics and subtropics, have given rise to a biodiversity hotspot with over 1,500 identified species. In addition to the sheer number of species, the park is also home to many threatened and endemic species.

Everglades National Park is home to many threatened and endangered species, including the Cape Sable seaside sparrow, the West Indian manatee, the Florida panther, and the wood stork. Images © NPS

In addition to biodiversity conservation, the park provides many ecosystem services to nearby communities – including safeguarding the clean drinking water supply for South Florida. Water flowing through the Everglades recharges the underlying aquifers that provide drinking water for nearly nine million people.

Much of the Biscayne aquifer, which provides drinking water Palm Beach, Broward, Miami-Dade, and Monroe Counties, is recharged by water flowing through the Everglades.

Saltwater intrusion occurs when saltwater moves inland through the soil and groundwater. Graphic adapted from Davis et al. (2016).

The park’s coastal ecosystems are under significant threat of climate change impacts – including the intrusion of saltwater moving inland through the soil and groundwater. There are two primary causes of saltwater intrusion: first, sea level rise can increase the amount of saltwater coming into low-lying coastal areas; second, reduction of freshwater flowing into an ecosystem can result in greater saltwater dominance. In the case of the Everglades, both factors are happening at the same time, resulting in a dire situation for the park.

Because Everglades National Park sits barely above sea level, even a small amount of sea level rise can cause large areas of land to be inundated with saltwater. The National Oceanic and Atmospheric Administration (NOAA) estimates that the Everglades may experience four feet of sea level rise by 2100, which would inundate vast areas of existing mangrove and saltmarsh habitat. At the same time, upstream development in Florida has significantly reduced the amount of freshwater entering the Everglades. Once a vast and free flowing “River of Grass” that spanned from Lake Okeechobee to the Florida Keys, the Everglades has been significantly impacted by agricultural, urban, suburban, and highway development. Today, the Everglades has lost 70% of its historic volume of water flow and as such is even more susceptible to climate change impacts like saltwater intrusion.

Saltwater intrusion has dramatic effects on ecosystems in the Everglades. Increased salinity kills many plant species, including sawgrass, one of the most iconic plants of the Everglades. By harming plants that form the foundation of diverse ecosystems, saltwater intrusion has effects that travel throughout the food web. Saltwater can also cause peat, the main component of soil in Everglades wetlands, to break down. This causes the land surface to sink relative to sea level rise, exacerbating the problems of sea level rise and saltwater intrusion. Because peat is comprised of primarily organic matter, peat collapse also leads to the release of stored carbon, further contributing to climate change.

Saltwater can kill vegetation and cause peat collapse. Graphic adapted from Davis et al. (2016).

While some species may be able to migrate further inland to escape the increased salinity caused by saltwater intrusion, many that reside in the isolated coastal forest patches within the wetlands will not. These various types of coastal forests, including coastal woodlands, hardwood hammocks, and pine rocklands, are home to over 75% of the rarest plants in the Everglades.

NOAA estimates that the Everglades may experience four feet of sea level rise by 2100, which would inundate vast areas of existing mangrove and saltmarsh habitat and lead to increased saltwater intrusion further inland. NOAA 2022 Technical Report on Sea Level Rise. Move the slider bar back and forth to see how sea level rise could affect the park. Click the button in the bottom left corner to open the legend.

While climate change poses a significant threat to Everglades National Park, the National Parks Conservation Association (NPCA) is working hard to advance critical restoration projects to mitigate climate impacts and make South Florida more resilient. Scientists have determined that the primary way to offset climate impacts is to restore freshwater flows to the park. Increasing the amount of freshwater flowing into the Everglades can mitigate saltwater intrusion and protect inland habitats. In 2000, Congress authorized the Comprehensive Everglades Restoration Plan (CERP) with the goal of delivering more clean freshwater to Everglades National Park. While the effort has restored some water flow to the Everglades to date, chronic underfunding has slowed progress over the years.

NPCA has been tirelessly advocating for the Everglades since the 1920s. In fact, NPCA was one of the first organizations on the ground in Florida calling for the establishment of Everglades National Park. Over the years, we have worked to protect the park from development threats and advocated for restoration funding to improve water flow. In 2022, NPCA’s advocacy contributed to the announcement of $1.1 billion in funding for Everglades restoration in the bipartisan Infrastructure Investment and Jobs Act (IIJA). The funding will be used to advance key projects to improve water flow throughout the Greater Everglades, including in the northern coastal estuaries, Biscayne Bay, Florida Bay, and Everglades National Park. This announcement represents a huge step forward in Everglades restoration. The work of NPCA and our partners is helping ensure that the Everglades remains a hotspot of biodiversity and a vital drinking water source for local communities.