The Sanibel rice rat and mangrove forests are critical components of wetland ecosystems in J.N. “Ding” Darling National Wildlife Refuge on Sanibel Island in Florida. The rice rat is a link in the food chain; mangroves effectively store carbon and produce habitat for a wide variety of species.

Slow, methodical research and monitoring of both rice rats and mangroves will help identify changes caused by sea-level rise and whether the small mammal or sprawling mangroves already are adapting to such changes.

The most wide-ranging and long-term research is a collaboration with the U.S. Geological Survey (USGS) to assess the vulnerability of coastal mangroves to sea-level rise and climate change, understand how mangroves store carbon, and learn how valuable mangrove forests are to humans in terms of the ecosystem services they provide.

“Ding” Darling Refuge biologist Jeremy Conrad has begun setting up six to eight surface evaluation tables (SETs) at the refuge to measure the effect of mangroves on wetland elevation. Current models predicting the impact of sea-level rise do not always consider that wetland elevation can increase or decrease. “If mangroves add two millimeters of sedimentation and there is a four-millimeter sea-level rise, you have counteracted the sea-level rise to a small degree,” explains Conrad.

SETs also will be established in mangrove forests in eight to 10 other Florida refuges to determine if the trend for these wetlands is gaining elevation or subsiding, and at what rate.

Over the next three years, USGS will conduct three other strands of research at “Ding” Darling Refuge: testing soil and peat under the mangroves to determine the carbon storage rate; identifying the economic value of mangroves based on certain ecosystem services; and using satellite images to analyze changes in the distribution and abundance of mangroves over the past 30 to 40 years. Recent literature suggests that mangroves’ carbon sequestration- per-acre rate is among the highest of any habitat.

Mangroves benefit humans by providing coastal protection during storms, nurseries for bait fish for large commercial fisheries, and recreation opportunities for birdwatchers and paddlers.

Mangroves also appear to provide habitat for the Sanibel rice rat, a subspecies unique to the island.

Wesley Boone is a graduate student at the University of Florida. He tromps around “Ding” Darling Refuge setting traps for Sanibel rice rats to determine what specific refuge habitats they frequent. For the first time, says Boone, these rats have been found in saline mangrove habitat.

“Before, we thought they were restricted to freshwater habitats, and now we know they can survive in mangroves,” says Boone. “That’s a good thing. They may survive in mangroves even if we lose our freshwater habitat to sea-level rise.”

Although the rice rat and mangrove research projects were initiated independently, Conrad says “we are now discovering connections because we are finding rice rats where we didn’t think they were – in mangroves.” Boone’s research will help determine how important mangroves are to rice rat survival.

For Boone, there are practical and philosophical reasons that compel him to regularly get wet and muddy for rice rats. The rice rats are prey for owls, which also eat invasive and highly damaging black rats. Besides, “small mammals enable us to ask big questions about ecology,” says Boone, “questions that apply not only to Sanibel but to islands halfway around the world, like how to protect different species during changes in seasonal water levels, including flooding.”

Boone hopes to begin analyzing two field seasons of data later this year.

Karen Leggett is a writer-editor in the Refuge System Branch of Communications.