Global climate change is leading to large-scale shifts in species’ range limits. For example, rising winter temperatures are shifting the abundance and distributions of tropical, cold sensitive plant species towards higher latitudes. Coastal wetlands provide a prime example of such shifts, with tropical mangrove forests expanding into temperate salt marshes as winter warming alleviates past geographic limits set by cold intolerance. These rapid changes are dynamic and challenging to monitor, and uncertainty remains regarding the extent of mangrove expansion near poleward range limits. Here, we synthesized existing datasets and expert knowledge to assess the current (i.e., 2021) distribution of mangroves near dynamic range limits in eastern North America. Each grid cell has a resolution of 0.125 degrees, or approximately 14 x 16 km, within which the presence or absence of mangrove has been independently determined using existing datasets and expert knowledge.

We evaluated changes in mangrove distribution and ecosystem properties in the southeastern United States under climate change using known climate-ecological relationships, recent climate data for the period 1981-2010, and future projected climate data for the period 2071-2100 under two Shared Socio-economic Pathways (SSPs): the SSP2-4.5 and SSP5-8.5 scenarios, which correspond to intermediate and high greenhouse gas emissions scenarios, respectively. We quantified potential mangrove presence, mangrove relative abundance, coastal wetland vegetation height, and coastal wetland vegetation aboveground biomass under recent climatic conditions and under the two alternative future climate scenarios.

We evaluated changes in mangrove distribution and ecosystem properties in the southeastern United States under climate change using known climate-ecological relationships, recent climate data for the period 1981-2010, and future projected climate data for the period 2071-2100 under two Shared Socio-economic Pathways (SSPs): the SSP2-4.5 and SSP5-8.5 scenarios, which correspond to intermediate and high greenhouse gas emissions scenarios, respectively. We quantified potential mangrove presence, mangrove relative abundance, coastal wetland vegetation height, and coastal wetland vegetation aboveground biomass under recent climatic conditions and under the two alternative future climate scenarios.

Winter climate change has the potential to have a large impact on coastal wetlands in the southeastern U.S. Warmer winter temperatures and reductions in the intensity of freeze events would likely lead to mangrove forest range expansion and salt marsh displacement in parts of the U.S. Gulf of Mexico and Atlantic coast. The objective of this research was to better understand some of the ecological implications of mangrove forest migration and salt marsh displacement. The potential ecological effects of mangrove migration are diverse ranging from important biotic impacts (e.g., coastal fisheries, land bird migration; colonial nesting wading birds) to ecosystem stability (e.g., response to sea level rise and drought; habitat loss; coastal protection) to biogeochemical processes (e.g., carbon storage; water quality). In this research, our focus was on the impact of mangrove forest migration on coastal wetland soil processes and the consequent implications for coastal wetland responses to sea level rise, ecosystem resilience, and carbon storage. Our study specifically addressed the following questions: (1) How do ecological processes and ecosystem properties differ between salt marshes and mangrove forests; (2) As mangrove forests develop, how do their ecosystem properties change and how do these properties compare to salt marshes; (3) How do plant-soil interactions across mangrove forest structural gradients differ among three distinct locations that span the northern Gulf of Mexico; and (4) What are the implications of mangrove forest encroachment and development into salt marsh in terms of soil development, carbon and nitrogen storage, and soil strength? To address these questions, we utilized the salt marshes and natural mangrove forest structural gradients present at three distinct locations in the northern Gulf of Mexico: Cedar Key (Florida), Port Fourchon (Louisiana), and Port Aransas (Texas). Each of these locations represents a distinct combination of climate-driven abiotic conditions. We quantified relationships between plant community composition and structure, soil and porewater physicochemical properties, hydroperiod, and climatic conditions. The suite of measurements that we collected provide initial insights into how different geographic areas of an ecotone, with different environmental conditions, may be impacted by mangrove forest expansion and development, and how these changes may alter the supply of specific ecosystem goods and services. This file includes the scanned field notes associated with this project This work was conducted via a collaborative effort between scientists at the U.S. Geological Survey National Wetland Research Center and the Department of Biology of the University of Louisiana at Lafayette.

In coastal wetlands, one of the most striking examples of climate change is the poleward range expansion of mangrove forests in response to warming winters. In North America, the Cedar Key region has often been considered the range limit for mangroves along the western coast of Florida (USA). However, within the past several decades, robust stands of Avicennia germinans and Rhizophora mangle have been observed in the Apalachicola Bay region, which is 200 km northwest of Cedar Key. This dataset characterizes the distribution and structure of the mangroves in the Apalachicola Bay area of Florida identified via extensive ground surveys and photointerpretation of aerial imagery from 2018 to 2019.

In coastal wetlands, one of the most striking examples of climate change is the poleward range expansion of mangrove forests in response to warming winters. In North America, the Cedar Key region has often been considered the range limit for mangroves along the western coast of Florida (USA). However, within the past several decades, robust stands of Avicennia germinans and Rhizophora mangle have been observed in the Apalachicola Bay region, which is 200 km northwest of Cedar Key. This dataset characterizes the distribution and structure of the mangroves in the Apalachicola Bay area of Florida identified via extensive ground surveys and photointerpretation of aerial imagery from 2018 to 2019.

Climate change is altering the frequency and intensity of extreme weather events. Quantifying ecosystem responses to extreme events at the landscape scale is critical for understanding and responding to climate-driven change but is constrained by limited data availability. Here, we integrated remote sensing with ground-based observations to quantify landscape-scale vegetation damage from an extreme climatic event. We used ground- and satellite-based black mangrove (Avicennia germinans) leaf damage data from the northern Gulf of Mexico (USA and Mexico) to examine the effects of an extreme freeze in a region where black mangroves are expanding their range. The February 2021 event produced coastal temperatures as low as -10 ℃ in some areas, exceeding thresholds for A. germinans damage and mortality. We used Sentinel-2 surface reflectance data to assess vegetation greenness before and after the freeze, along with ground-based observations of A. germinans leaf damage.

Climate change is altering the frequency and intensity of extreme weather events. Quantifying ecosystem responses to extreme events at the landscape scale is critical for understanding and responding to climate-driven change but is constrained by limited data availability. Here, we integrated remote sensing with ground-based observations to quantify landscape-scale vegetation damage from an extreme climatic event. We used ground- and satellite-based black mangrove (Avicennia germinans) leaf damage data from the northern Gulf of Mexico (USA and Mexico) to examine the effects of an extreme freeze in a region where black mangroves are expanding their range. The February 2021 event produced coastal temperatures as low as -10 ℃ in some areas, exceeding thresholds for A. germinans damage and mortality. We used Sentinel-2 surface reflectance data to assess vegetation greenness before and after the freeze, along with ground-based observations of A. germinans leaf damage.

Winter climate change has the potential to have a large impact on coastal wetlands in the southeastern U.S. Warmer winter temperatures and reductions in the intensity of freeze events would likely lead to mangrove forest range expansion and salt marsh displacement in parts of the U.S. Gulf of Mexico and Atlantic coast. The objective of this research was to better understand some of the ecological implications of mangrove forest migration and salt marsh displacement. The potential ecological effects of mangrove migration are diverse ranging from important biotic impacts (e.g., coastal fisheries, land bird migration; colonial nesting wading birds) to ecosystem stability (e.g., response to sea level rise and drought; habitat loss; coastal protection) to biogeochemical processes (e.g., carbon storage; water quality). In this research, our focus was on the impact of mangrove forest migration on coastal wetland soil processes and the consequent implications for coastal wetland responses to sea level rise, ecosystem resilience, and carbon storage. Our study specifically addressed the following questions: (1) How do ecological processes and ecosystem properties differ between salt marshes and mangrove forests; (2) As mangrove forests develop, how do their ecosystem properties change and how do these properties compare to salt marshes; (3) How do plant-soil interactions across mangrove forest structural gradients differ among three distinct locations that span the northern Gulf of Mexico; and (4) What are the implications of mangrove forest encroachment and development into salt marsh in terms of soil development, carbon and nitrogen storage, and soil strength? To address these questions, we utilized the salt marshes and natural mangrove forest structural gradients present at three distinct locations in the northern Gulf of Mexico: Cedar Key (Florida), Port Fourchon (Louisiana), and Port Aransas (Texas). Each of these locations represents a distinct combination of climate-driven abiotic conditions. We quantified relationships between plant community composition and structure, soil and porewater physicochemical properties, hydroperiod, and climatic conditions. The suite of measurements that we collected provide initial insights into how different geographic areas of an ecotone, with different environmental conditions, may be impacted by mangrove forest expansion and development, and how these changes may alter the supply of specific ecosystem goods and services. This file includes the site-level elevation data. This work was conducted via a collaborative effort between scientists at the U.S. Geological Survey National Wetland Research Center and the Department of Biology of the University of Louisiana at Lafayette.

Black mangrove (Avicennia germinans (L.) L.) has historically occurred along the Louisiana coast in saline wetland habitats, but its distribution has been sparse. Mangroves are tropical to semi-tropical species and their distribution is limited by freezing temperatures. Black mangrove distribution and abundance has increased and decreased in the coastal zone of Louisiana according to freeze frequency and duration and concomitant freeze damage and dieback or lack thereof. In 2009, a fixed wing aircraft was used to conduct an aerial cruise census of the entire coastal area of Louisiana to document and map the total distribution of mangroves in the state.