Near the Royal Palm Visitor Center, a boardwalk crosses over a marsh. A sign attached to the wooden railing overlooks clumps of trees. A nearby measuring pole stands in the water and is attached to the side of the boardwalk.
The sign's title appears over an illustrated aerial view of South Florida, with two inset photographs, and an illustration of the measuring pole.
Text in English and Spanish:
"From Lake Okeechobee to Florida Bay, plentiful rains sustain the 'River of Grass' and replenish the Biscayne Aquifer held within the limestone bedrock. But rising sea level pushes salt water inland and may one day damage this wildlife sanctuary. As Earth's warming temperatures melt glaciers and expand ocean waters, it's important to curb activities that cause sea level rise, like burning fossil fuels. Can we do it?"
On the photo of an illustrated aerial view of South Florida, labels point out Lake Okeechobee in the center of the peninsula, and coastal cities West Palm Beach to the east of the lake, Miami southeast, and Naples west on the gulf coast. Arrows show freshwater flowing south from Lake Okeechobee and saltwater pushing into the southern tip of Florida. Dotted lines indicate the Salt Water / Fresh Water transition zone. The "You Are Here" arrow points to within the Salt Water / Fresh Water transition zone.
An image of an American alligator stands on the peninsula. Another image shows an anhinga — a long-necked dark-gray bird — in flight with its wings and tail feathers spread.
Two inset photos next to the pole present contrasting views of a pond. During the dry season, the area is a mud flat, and it is a filled pond in the rainy season.
"From November to May — during the dry season — fresh water levels are lower here. Because this area retains more water than surrounding lands, it is a critical watering hole for the wildlife seen here."
An illustration shows rising tides along the tall measuring pole over time. "This pole marks Royal Palm's fresh water level — and future sea levels that will drive salt water into this wildlife refuge." From bottom to top:
The blue marker identifies the Biscayne Aquifer at minus 1 foot.
The blue zero marker shows average sea level in 2000 at zero.
The next blue marker represents the average elevation of fresh water at Royal Palm: 1.5 feet.
The red three-foot marker shows projected sea level in 2100: 3 feet.
The red twelve-foot marker shows projected sea level in 2300: 12 feet.