Everglades National Park Research Articles

Interactions between the imperiled West Indian manatee, Trichechus manatus, and mosquitoes (Diptera: Culicidae) in Everglades National Park, Florida, USA

Arthropod-borne viruses (arboviruses), including those vectored by mosquitoes, have recently been cited as potential emerging health threats to marine mammals. Despite the fully aquatic habits of cetaceans, immunologic exposure to arboviruses including West Nile virus and Eastern equine encephalitis virus has been detected in wild Atlantic bottlenose dolphins, and captive orcas have been killed by West Nile virus and St. Louis encephalitis virus. Currently, there is no evidence of direct interactions between mosquitoes and marine mammals in nature, and it remains unknown how wild cetaceans are exposed to mosquito-vectored pathogens. Here, we report the first evidence of direct interactions between an aquatic mammal, the West Indian manatee, a federally threatened species, and mosquitoes in nature. Observations of manatees in Everglades National Park, Florida, USA, indicate that mosquitoes of three genera, Aedes, Anopheles, and Culex are able to locate and land on surface-active manatees, and at minimum, penetrate and probe manatee epidermis with their mouthparts. Whether mosquitoes can successfully take a blood meal is not known; however, an arbovirus-infected mosquito can inoculate extravascular host tissues with virus-infected saliva during probing. These observations suggest that it is possible for marine mammals to be exposed to mosquito-vectored pathogens through direct interactions with mosquitoes.

Scientific Note: Insects associated with Guettarda scabra in Everglades National Park, Florida

Scientific Note: Insects associated with Guettarda scabra in Everglades National Park, Florida

The Impact of Hurricane Irma on Our Community and the Collier Mosquito Control District's Mission.

The Collier Mosquito Control District, located in southwest Florida, is uniquely positioned in a subtropical environment between the Gulf of Mexico and Everglades National Park. The District's mission is focused on the control of disease vector and nuisance mosquitoes in Collier County, which is accomplished through integrated mosquito management. Hurricane Irma made landfall in the county on September 10, 2017, leaving in its wake tremendous property and infrastructure damage, and it also disrupted communications and airport operations. These factors greatly affected the District's operations and its ability to meet its mission. In addition, the lengthy loss of electrical power forced most residents outdoors, increasing their exposure to mosquitoes. From challenges in completing poststorm treatments to outdated policies that caught us off-guard, the event prompted a new hurricane policy and plan to ensure improved preparedness for the next natural disaster. The poststorm environment also provided a rich foundation for research into mosquito populations after tropical disturbances of this scale. Here we report the impact on the District's aerial mosquito control operations, changes to internal policies, and mosquito population abundance following Hurricane Irma.

A Tropical Cyclone-Induced Ecological Regime Shift: Mangrove Forest Conversion to Mudflat in Everglades National Park (Florida, USA)

The ecological effects of tropical cyclones on mangrove forests are diverse and highly location- and cyclone-dependent. Ecological resistance, resilience, and enhancement are terms that describe most mangrove forest responses to tropical cyclones. However, in the most extreme cases, tropical cyclones can trigger abrupt and irreversible ecological transformations (i.e., ecological regime shifts). Here, we examine a cyclone-induced ecological regime shift that occurred in Everglades National Park (USA), where forest mortality and peat collapse due to a powerful tropical cyclone (the 1935 Labor Day Hurricane) led to the conversion of mangrove forests to mudflats and an estimated elevation loss of approximately 75 cm. We investigated soil elevation change measured in these mangrove forests and adjacent mudflats during a twenty-year period [1998–2018] using Surface Elevation Table-Marker Horizon (SET-MH) methods. This period encompasses the effects of Hurricanes Wilma (2005) and Irma (2017). We also used historical sea-level rise rates and future sea-level rise scenarios to estimate surface elevation changes in the past (1930–1998) and to illustrate elevation gains needed for these ecosystems to adapt to future change. Collectively, our findings advance understanding of the long-term effects of cyclone-induced ecological regime shifts due to forest mortality, peat collapse, and conversion of mangrove forests to mudflats.

Visualizing When, Where, and How Fires Happen in U.S. Parks and Protected Areas

Fire management in protected areas faces mounting obstacles as climate change alters disturbance regimes, resources are diverted to fighting wildfires, and more people live along the boundaries of parks. Evidence-based prescribed fire management and improved communication with stakeholders is vital to reducing fire risk while maintaining public trust. Numerous national fire databases document when and where natural, prescribed, and human-caused fires have occurred on public lands in the United States. However, these databases are incongruous and non-standardized, making it difficult to visualize spatiotemporal patterns of fire and engage stakeholders in decision-making. We created interactive decision analytics (“VISTAFiRe”) that transform fire history data into clear visualizations of the spatial and temporal dimensions of fire and its management. We demonstrate the utility of our approach using Big Cypress National Preserve and Everglades National Park as examples of protected areas experiencing fire regime change between 1980 and 2017. Our open source visualizations may be applied to any data from the National Park Service Wildland Fire Events Geodatabase, with flexibility to communicate shifts in fire regimes over time, such as the type of ignition, duration and magnitude, and changes in seasonal occurrence. Application of the tool to Everglades and Big Cypress revealed that natural wildfires are occurring earlier in the wildfire season, while human-caused and prescribed wildfires are becoming less and more common, respectively. These new avenues of stakeholder communication are allowing the National Park Service to devise research plans to prepare for environmental change, guide resource allocation, and support decision-making in a clear and timely manner.

Human-caused climate change in United States national parks and solutions for the future

Author(s): Gonzalez, Patrick | Abstract: Human-caused climate change has exposed the US national park area to more severe increases in heat and aridity than the country as a whole and caused widespread impacts on ecosystems and resources. Reducing carbon dioxide emissions from cars, power plants, and other human sources would reduce future risks. Since 1895, annual average temperature of the area of the 419 national parks has increased at a rate of 1.0 ± 0.2oC (1.8 ± 0.4oF) per century, double the rate of the US as a whole, while precipitation has declined significantly on 12% of national park area, compared with 3% of the US. This occurs because extensive areas of national parks are located in extreme environments. Scientific research in national parks has detected numerous changes that analyses have attributed primarily to human-caused climate change. These include a doubling of the area burned by wildfire across the western US, including Yosemite National Park, melting of glaciers in Glacier Bay National Park, a doubling of tree mortality across the western US, including Sequoia National Park, a loss of bird species from Death Valley National Park, a shift of trees onto tundra in Noatak National Preserve, sea level rise of 42 cm (17 in.) near the Statue of Liberty National Monument, and other impacts. Without emissions reductions, climate change could increase temperatures across the national parks, up to 9oC (16oF) by 2100 in parks in Alaska. This could melt all glaciers from Glacier National Park, raise sea level enough to inundate half of Everglades National Park, dissolve coral reefs in Virgin Islands National Park through ocean acidification, and damage many other natural and cultural resources. Adaptation measures, including conservation of refugia in Joshua Tree National Park and raising heat-resistant local corals in Biscayne National Park, can strengthen ecosystem integrity. Yet, reducing greenhouse gas emissions from human activities is the only solution that prevents the pollution that causes climate change. Energy conservation and efficiency improvements, renewable energy, public transit, and other actions could lower projected heating by two-thirds, reducing risks to our national parks.

The Importance of the Northeastern Gulf of Mexico to Foraging Loggerhead Sea Turtles

Identification of high-use foraging sites where imperiled sea turtles are resident remains a globally-recognized conservation priority. In the biodiverse Gulf of Mexico (GoM), recent telemetry studies highlighted post-nesting foraging sites for federally threatened loggerhead turtles (Caretta caretta). Our aim here was to discern loggerhead use of additional northern GoM regions that may serve as high-use foraging sites. Thus, we used satellite tracking and switching state-space modeling to show that the Big Bend region off the northwest Florida coast is a coastal foraging area that supports imperiled adult female loggerhead turtles tracked from different nesting subpopulations. From 2011 – 2016, we satellite-tagged 15 loggerheads that nested on four distinct beaches around the GoM: Dry Tortugas National Park, FL; Everglades National Park, FL; St. Joseph Peninsula, FL; and Gulf Shores, AL. Turtles arrived at their foraging ground in the Big Bend region between June and September and remained resident in their respective foraging sites for an average of 198 tracking days, where they established mean home ranges (95% kernel density estimate) 232.7 km2. Larger home ranges were in deeper water; 50% kernel density estimate centroid values were a mean 26.4 m deep and 52.7 km from shore. The Big Bend region provides a wide area of suitable year-round foraging habitat for loggerheads from at least 3 different nesting subpopulations. Understanding where and when threatened loggerheads forage and remain resident is key for designing both surveys of foraging resources and additional protection strategies that can impact population recovery trajectories for this imperiled species.

Stakeholders’ perceptions of social and environmental changes affecting Everglades National Park in South Florida

Urban sprawl and population growth have altered the landscape in the U.S in recent decades. Protected areas and development are compatible lenses, yet stakeholders’ involvement in decision-making is often missing from environmental governance. Knowing how managers and stakeholders work together is also necessary to capture the meanings and feelings that local communities and various groups might have about a park and its ecosystem. The purpose of this study was to examine how stakeholders living and working in proximity to Everglades National Park (EVER) perceive environmental and social changes to the park and community relations. Data collection involved 41 interviews with stakeholders who have interacted with EVER, e.g., consumers, NGOs, federal agencies, state/local governments, businesses, and scientists. The in-person, semi-structured interviews were conducted using snowball sampling. These data were generated using three methods: field notes, audio recordings, and transcripts. An analysis of the interview data generated six research themes: loss of native species, urban development, a shortage and contamination of water, hurricanes, climate change, and increased recreation use. The results of this study add to the literature by providing a better understanding of the relationships stakeholders have with national parks. The results will provide useable knowledge that may help stakeholders and public land managers design strategies for sustainable plans for the park and its surrounding communities.

Using historical information and data to strengthen planning for environmental protection and management at Everglades National Park, South Florida

The early environmental conditions in many national parks fit the favorable description given to Everglades National Park (ENP) at the time of its founding that the park’s wilderness and ecological resources were “superlative in value.” With the understanding that wilderness does not mean complete human exclusion, this study examines the possibilities, interests, and difficulties associated with establishing the historical superlative state of the park’s resources as a target for current restoration efforts. The focus is specifically on ENP, as the park’s existence was considered justified only if its superlative and pristine wilderness conditions could be retained in the future. Data were gathered from 18 historical documents obtained from the ENP museum and the online archives of the library shared by Florida International University and the University of Miami. The 1979 Master Plan, 2000 Comprehensive Everglades Restoration Plan (CERP) and other literature provided planning information. Qualitative data analysis was performed using NVivo 11. The findings indicate that the current restoration targets are heavily influenced by shifting baseline syndrome and that outcomes fall short of no net loss of environmental resources. Therefore, the restoration targets not based on the region’s resources during the predrainage period are technically achievable but cannot produce a restored ecosystem in the long term. This study concludes that that planning initiatives should go beyond pollution reduction strategies to include historical conditions and acquisitions of conservation lands as targets for ongoing restoration efforts.

Conservation Strategies for a Globally Imperiled and Hyper-Fragmented Ecosystem: Acquisition, Regulations, Incentives and Outreach in Miami Dade County

Pine rocklands are a globally critically imperiled ecosystem with limited geographic range, characterized by a high biodiversity of endemic herbaceous plants and frequent fire intervals (2-5 years). In Miami-Dade County, approximately 2% of the forest outside Everglades National Park (ENP) remains. The County adopted a forest property tax program in 1979, passed a forest preservation ordinance in 1984, and created a land acquisition program in 1991. Outreach and filling in the gaps between preservation areas are critical for the survival of a number of species.

Variation in movement behavior of alligators after a major hurricane

BackgroundHurricanes can have catastrophic effects on coastal ecosystems. To minimize negative impacts of storms, animals may seek shelter in place, move to a nearby refuge, or evacuate long-distances. Crocodilians can be important predators in estuarine habitats, but little is known about how they respond to extreme weather events. We investigated the movement behaviors of eight acoustically tracked American alligators (Alligator mississippiensis) before, during, and after Hurricane Irma in 2017 within the Shark River Estuary of Everglades National Park, USA. Using tracking data, we compared their movements and habitat use before and after the hurricane to similar timeframes in other years without major storms.ResultsWe observed considerable variation in movement tactics and responses to the hurricane. Of eight animals that we tracked, two showed no changes in movement or habitat use throughout the study. Two animals ceased upstream excursions that they were regularly making before the hurricane with one of these animals reducing the distance ranged across the river system. Another animal moved upstream from the lower river to the mid-estuary immediately after the hurricane despite having not done this in the 60 days prior. Two other animals moved from the marsh and mangrove forest habitats to river channels several days after the hurricane. One animal shifted to commuting downstream from its upstream habitat shortly before the storm and continued this behavior for the rest of the 2017 and 2018 wet seasons.ConclusionsWe found considerable variability in behavioral responses to the hurricane, ranging from no discernable changes in movements to one animal exhibiting a complete shift in movement tactics not observed by any animal in the long-term tracking of this population. Our research provides insight into alligator movement behavior and ecology in the context of a major hurricane disturbance.

Effects of Saltwater Pulses on Soil Microbial Enzymes and Organic Matter Breakdown in Freshwater and Brackish Coastal Wetlands

Coastal freshwater and brackish wetlands are exposed to pulses of saltwater during times of reduced freshwater flows (i.e., dry seasons, droughts), periodic storm surges, and increased tidal extent associated with rising seas. The effects of saltwater pulses on belowground processing rates of detrital organic matter as mediated by microbial activities are uncertain. Our objectives were to quantify whether and how pulses of saltwater (i) change soil porewater physicochemistry, (ii) change soil microbial extracellular enzyme activities, and (iii) change root litter breakdown over time in freshwater and brackish marshes. From 2014 to 2016, we simulated saltwater intrusion as monthly in situ pulsed additions of artificial seawater in experimental dosing chambers (1.4 m diameter) within freshwater and brackish marshes of Everglades National Park. At monthly intervals, we collected soil porewater chemistry, and measured microbial extracellular enzymes, elemental stoichiometric ratios, and breakdown rates (k) of incubated (0–30 cm depth) root litter and compared these responses over time. Saltwater pulses increased sulfate and nitrogen concentrations in porewater at the freshwater site. However, saltwater pulses generally decreased porewater constituents (e.g., dissolved organic carbon, dissolved nitrogen and phosphorus species) at the brackish site. One saltwater pulse increased root litter k by 1.25-fold in the brackish marsh. However, long-term (740 days) k in brackish wetlands, and both short- and long-term k in freshwater wetlands, were not affected by 24 monthly pulses of saltwater. Enzyme activities fluctuated with time and did not respond to multiple saltwater pulses. Our results suggest that detrital organic matter stocks and associated soil microbial activities are relatively resistant to single and multiple (n = 24) pulses of saltwater.

Shifts in hatching date of American crocodile (Crocodylus acutus) in southern Florida.

Globally temperature of marine environments is on the rise and temperature plays an important role in the life-history of reptiles. In this study, we examined the relationship between sea surface temperature and average date of hatching for American crocodiles (Crocodylus acutus) over a 37-year period at two nesting sites, Everglades National Park and Florida Power and Light Turkey Point Power Plant site in southern Florida. Our results indicate that hatch dates are shifting 1.5 days earlier every two years and at half that rate for the Turkey Point site, and with every 1°C degree increase in temperature, hatching occurs about 10 days earlier in the Everglades and 6 days earlier at Turkey Point. Our results on shifting hatch dates for American crocodiles provide further details about the impacts of temperature change on crocodile life history and suggest that increased temperature may affect their phenology.

Evidence for trait‐based community assembly patterns in hardwood hammock forests

AbstractThe hardwood forests of south Florida, commonly referred to as hammocks, persist as well‐drained patches of broadleaf forest, embedded in a matrix of brackish water swamp, freshwater marsh, or pineland. Little is known about the patterns of community assembly of these subtropical forest communities in the landscape mosaic of south Florida. We used a functional trait approach to understand the composition of these communities and their responses to environmental variation across four areas of south Florida: the pine rocklands and freshwater marshes in Everglades National Park, and the lower and upper Florida Keys, where the hammocks are surrounded by halophytic swamp communities. These sites represent an environmental gradient from less‐productive, more xeric sites in the lower Florida Keys, to more‐productive, wetter sites in the Everglades marshes. We examined the patterns of trait variation at three levels (individual, population, and community) to examine the underlying processes driving assembly in these hammock communities. To understand processes governing community composition in each site, we used methods that partition variance in six traits (maximum tree height, specific leaf area, wood specific gravity, leaf nitrogen, leaf phosphorus, and leaf stable carbon isotope ratios) into internal and external filtering components. Community‐weighted mean trait values for three traits (specific leaf area, height, and leaf phosphorus) increased significantly from dry, less‐productive coastal sites in the Florida Keys to the moist, more‐productive areas on the mainland, while wood specific gravity and leaf δ13C showed the opposite pattern. For one or more traits per site, standardized effect sizes differed significantly from null expectation. Processes such as competition for resources (e.g., water, nutrients, light) and species sorting across microhabitats (i.e., within site) operate to increase local functional trait variation within communities and among species across sites. External filtering on individuals for height and leaf phosphorus differed significantly from null expectations across sites, while external filtering on species was only observed for specific leaf area, maximum tree height, and leaf phosphorus. These results are consistent with strong environmental filtering across the region, among local communities differing in freshwater accessibility or that occupy different positions along strong edaphic gradients. Our results confirm the importance of intraspecific variation among species and reflect a high degree of trait plasticity across the environmental gradient.

Impacts of Hurricane Irma on Florida Bay Islands, Everglades National Park, USA

Hurricane Irma made landfall in south Florida, USA, on September 10, 2017 as a category 4 storm. In January 2018, fieldwork was conducted on four previously (2014) sampled islands in Florida Bay, Everglades National Park to examine changes between 2014 and 2018. The objectives were to determine if the net impact of the storm was gain or loss of island landmass and/or elevation; observe and quantify impacts to mangroves; and identify distinctive sedimentary, biochemical, and/or geochemical signatures of the storm. Storm overwash deposits were measured in the field and, in general, interior island mudflats appeared to experience deposition ranging from ~ 0.5 to ~ 6.5 cm. Elevation changes were measured using real-time kinematic positioning and satellite receivers. Comparison of 2014 to 2018 elevation measurements indicates mangrove berms and transitional areas between mudflats and berms experienced erosion and loss of elevation, whereas interior mudflats gained elevation, possibly due to Hurricane Irma. Geographic information system analysis of pre- and post-storm satellite imagery indicates the western-most island, closest to the eye of the storm, lost 32 to 42% (~ 11 to 13 m) of the width of the eastern berm, and vegetated coverage was reduced 9.3% or ~ 9700 m2. Vegetated coverage on the eastern-most island was reduced by 1.9% or ~ 9200 m2. These results are compared to previous accounts of hurricane impacts and provide a baseline for examining long-term constructive and destructive aspects of hurricanes on the islands and the role of storms in resiliency of Florida Bay islands.

Ontogenetic and Temporal Diet Shifts of the Invasive Asian Swamp Eel in South Florida

AbstractThe Asian Swamp Eel Monopterus albus is an introduced species in South Florida waters and is considered to be a potential threat to the native biota and ecosystems in the region. As a protogynous hermaphrodite that, under the right climatic conditions, can travel short distances over land and tolerate abrupt shifts in salinity, this species has strong invasive potential. In this study, our main goal was to evaluate the potential effects of the Asian Swamp Eel as a predator on native fishes and other biota. Our specific objectives were to (1) analyze the stomach contents of introduced Asian Swamp Eels from canals located near Everglades National Park and (2) assess the ontogenetic and temporal shifts in their consumption of prey. We dissected 752 Asian Swamp Eels (107–833 mm TL), and 46.4% (N = 349) of the samples had stomach contents for the analyses. The analyses indicated that amphipods, fishes, dragonfly nymphs, Hemiptera insects, and grass shrimp Palaemonetes were the most important prey items for Swamp Eels. Swamp Darters Etheostoma fusiforme, juvenile Asian Swamp Eels, and centrarchids were the most common fishes eaten by Swamp Eels. Ontogenetic shifts in diet were apparent, with amphipods and dipteran larvae most often observed in the stomachs of small‐ to medium‐sized Swamp Eels and fish, dragonfly nymphs, and Hemiptera insects more commonly identified in the stomachs of larger eels. The Swamp Eels also became increasingly piscivorous with size. Dragonfly nymphs and grass shrimp occurred more frequently in the Swamp Eel diets in May 2010, while the consumption of fish and amphipods increased in October 2010. Fish were the most important prey item that was consumed during the November–December 2009 period, although other prey items were relatively important during that collection period. As an opportunistic predator that consumes a wide range of prey, the Asian Swamp Eel likely has its greatest effects on native biota and ecosystems as a predator and competitor with native fishes for resources.

The Long-Term Effects of Hurricanes Wilma and Irma on Soil Elevation Change in Everglades Mangrove Forests

Mangrove forests in the Florida Everglades (USA) are frequently affected by hurricanes that produce high-velocity winds, storm surge, and extreme rainfall, but also provide sediment subsidies that help mangroves adjust to sea-level rise. The long-term influence of hurricane sediment inputs on soil elevation dynamics in mangrove forests is not well understood. Here, we assessed the effects of sediment deposition during Hurricanes Wilma (2005) and Irma (2017) on soil elevation change at two mangrove forests located along the Shark and Lostmans Rivers in Everglades National Park. We used surface elevation change data from a 16-year period (2002–2018), measured with the surface elevation table-marker horizon (SET-MH) approach. At the Shark River mangrove forest, we used marker horizons and a combination of deep, shallow, and original SETs to quantify the contributions of four soil zones to net soil elevation change. Rates of elevation change were greatly influenced by storm sediments. Abrupt increases in elevation due to sediment inputs and subsurface expansion during Hurricane Wilma were followed by: (1) an initial post-hurricane period of elevation loss due to erosion of hurricane sediments and subsurface contraction; (2) a secondary period of elevation gain due primarily to accretion; and (3) an abrupt elevation gain due to new sediment inputs during Hurricane Irma. Our findings suggest that elevation change in hurricane-affected mangrove forests can be cyclical or include disjunct phases, which is critical information for advancing the understanding of wetland responses to accelerated sea-level rise given the expectation of increasing storm intensity due to climate change.

Utilizing fossilized charcoal to augment the Everglades National Park Fire History Geodatabase

Everglades National Park (ENP) has been documenting fire events since 1948, and these data have been incorporated into an ESRI geodatabase. According to this geodatabase, 757,078 ha of wetlands burned from 1948 to 2011. The main type of vegetation that has burned is comprised of palustrine and estuarine wetlands. However, there are areas in ENP that are comprised of these wetlands that have no documented fire events. We examined fossil charcoal in soil cores and found evidence that fires did indeed occur in some of these areas. Sites of known fires were used to validate the fossil charcoal method. The abundance of fossil charcoal in soil cores from six locations in ENP was measured. Two of the cores were taken from areas with well-documented fire events and four cores where taken from areas with no documented fire events. Three of the cores were dated using 210Pb geochronology. The initial goal was to determine if fires had gone undetected or undocumented in the geodatabase with the ultimate goal being to demonstrate the usefulness of this approach to augment the geodatabase and therefore enhance our understanding of fire ecology in ENP.

Host Associations of Culex (Melanoconion) atratus (Diptera: Culicidae) and Culex (Melanoconion) pilosus from Florida, USA.

Characterizing the host-use patterns of mosquitoes is an essential component of understanding the transmission dynamics of mosquito-vectored pathogens. The host associations of two species of the medically important Culex subgenus Melanoconion, Culex atratus, and Culex pilosus are unknown or unclear, respectively. Both species have wide neotropical distributions. In the United States of America (USA), Culex pilosus occurs throughout the southeastern coastal plain, while Culex atratus is restricted to the southern Florida Peninsula. Using PCR-based blood meal analysis, we investigated the host associations of Culex atratus and Culex pilosus that were collected from Everglades National Park, Florida, USA We identified the host species of 208 Culex atratus and 168 Culex pilosus. Both species were narrowly associated with reptilian host species, particularly native and non-native lizards of the genus Anolis. Sampled Culex atratus exclusively fed on reptilian hosts, with >99% of blood meals derived from Anolis lizards. Culex pilosus fed predominantly from reptiles, but avian and mammalian blood meals were also detected. Of these, 92% of blood meals were derived from Anolis species. For both species, Anolis sagrei, an invasive exotic lizard in Florida, was the most frequently detected host species. These data indicate that Culex atratus and Culex pilosus are specialists of reptilian hosts, particularly Anolis lizards.

Rapid inundation of southern Florida coastline despite low relative sea-level rise rates during the late-Holocene

Sediment cores from Florida Bay, Everglades National Park were examined to determine ecosystem response to relative sea-level rise (RSLR) over the Holocene. High-resolution multiproxy analysis from four sites show freshwater wetlands transitioned to mangrove environments 4–3.6 ka, followed by estuarine environments 3.4–2.8 ka, during a period of enhanced climate variability. We calculate a RSLR rate of 0.67 ± 0.1 mm yr−1 between ~4.2–2.8 ka, 4–6 times lower than current rates. Despite low RSLR rates, the rapid mangrove to estuarine transgression was facilitated by a period of prolonged droughts and frequent storms. These findings suggest that with higher and accelerating RSLR today, enhanced climate variability could further hasten the loss of mangrove-lined coastlines, compounded by the reductions in natural flow to the coast caused by water management. Climate variability is nonlinear, and when superimposed on increases in RSLR, can complicate estimated trajectories of coastal inundation for resource management and urban planning.