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Andrew From

Publications and source records attributed to Andrew From.

18 recordsLinked to original sources
USGS2026

Excessive phosphorus loading contributes to future vulnerability of mangrove ecosystems by reducing net ecosystem exchange of carbon

J.N. “Ding” Darling National Wildlife Refuge (DDNWR) is located on Sanibel Island along the southwestern coast of Florida, USA. There, eutrophication attributed to agricultural discharge along the Caloosahatchee River has affected the area’s aquatic habitat. In anticipation of additional nutrient loading, we experimentally fertilized mangrove forests with nitrogen (+N; NH4) and phosphorus (+P; P2O5) for 3 years, and monitored soil and pneumatophore CO2 fluxes and tree sap flow from two mangrove species. Furthermore, we modeled individual tree and stand water use, from which we developed carbon (C) budgets for +N and + P vs. control simulations based on a novel application of water use efficiency conversion. Many of the measured response variables provided hints of subtle changes in response to +P rather than +N, which were enhanced when scaled. From this, we found that additional P loading is expected to reduce both gross and net primary productivity as well as CO2 uptake via net ecosystem exchange of C, likely pressing the system beyond metabolic capacity and leading to a 48–62% decrease in projected lateral C export. Greater eutrophication will likely compound vulnerabilities to sea-level rise submergence, especially where P concentrations are high and already reducing soil surface elevations.

Florida↗
USGS2024

Interactive effects of salinity and hydrology on radial growth of bald cypress (Taxodium distichum (L.) Rich.) in coastal Louisiana, USA

Tidal freshwater forests are usually located at or above the level of mean high water. Some Louisiana coastal forests are below mean high water, especially bald cypress ( Taxodium distichum (L.) Rich.) forests because flooding has increased due to the combined effects of global sea level rise and local subsidence. In addition, constructed channels from the coast inland act as conduits for saltwater. As a result, saltwater intrusion affects the productivity of Louisiana’s coastal bald cypress forests. To study the long-term effects of hydrology and salinity on the health of these systems, we fitted dendrometer bands on selected trees to record basal area increment as a measure of growth in permanent forest productivity plots established within six bald cypress stands. Three stands were in freshwater sites with low salinity rooting zone groundwater (0.1–1.3 ppt), while the other three had higher salinity rooting zone groundwater (0.2–4.9 ppt). Water level was logged continuously, and salinity was measured monthly to quarterly on the surface and in groundwater wells. Higher groundwater salinity levels were related to decreased bald cypress radial growth, while higher freshwater flooding increased radial growth. With these data, coastal managers can model rates of bald cypress forest change as a function of salinity and flooding.

Louisiana↗
USGS2023

Temperature thresholds for leaf damage from two extreme freeze events (2018 and 2021) near the northern range limit of black mangroves (Avicennia germinans) in southeastern North America

Extreme winter temperatures govern the northern range limit of black mangroves ( Avicennia germinans ) in southeastern North America. There is a pressing need for studies that advance our understanding of how extreme cold temperature events affect mangroves near their range limits. However, such events are infrequent and challenging to study at regional scales. Here, we compared the damage to mangroves from extreme freeze events in 2018 and 2021, using local data from sites in USA (Florida, Louisiana, and Texas) and northeastern Mexico (Tamaulipas). In 2018, mangrove damage was concentrated in Louisiana and the upper Texas coast, where minimum temperatures ranged from -4 °C to -7 °C. In 2021, damage from a more severe freeze event was concentrated along the central to northern coasts of Texas, where minimum temperatures ranged from -4 °C to -10 °C. We used regional temperature and vegetation data from these events to quantify temperature thresholds for A. germinans leaf damage. Our results indicate that A. germinans leaf damage is likely to occur when temperatures are between -4 °C and -6 °C. These findings help refine temperature thresholds for A. germinans leaf damage and advance understanding of the effects of extreme freeze events on mangrove range expansion. This information is valuable for anticipating future range dynamics in a warming world.

Atlantic Ocean, Gulf of Mexico↗
USGS2023

Integrating remote sensing with ground-based observations to quantify the effects of an extreme freeze event on black mangroves (Avicennia germinans) at the landscape scale

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 °C 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. Our results show a negative, nonlinear threshold relationship between A. germinans leaf damage and minimum temperature, with a temperature threshold for leaf damage near − 6 °C. Satellite-based analyses indicate that, at the landscape scale, damage was particularly severe along the central Texas coast, where the freeze event affected > 2000 ha of A. germinans -dominated coastal wetlands. Our analyses highlight the value of pairing remotely sensed data with regional, ground-based observations for quantifying and extrapolating the effects of extreme freeze events on mangroves and other tropical, cold-sensitive plants. The results also demonstrate how extreme freeze events govern the expansion and contraction of mangroves near northern range limits in North America.

Gulf of Mexico↗
USGS2023

Presence of hummock and hollow microtopography reflects shifting balances of shallow subsidence and root zone expansion along forested wetland river gradients

Tidal freshwater forested wetlands (TFFWs) are in an active phase of transition to tidal marsh with sea level rise and salinity incursion along the Atlantic and Gulf Coasts of the United States (U.S.). A prominent feature of TFFWs is hummock/hollow microtopography where hollows represent the flat, base-elevation of the floodplain where inundation occurs relatively frequently, while hummocks provide elevated soil surfaces that often harbor relatively greater numbers and species of trees and shrubs. Hummocks appear at the landscape river boundary just seaward of bottomland hardwoods as tides reach those positions, persist for many years, and disappear as TFFWs eventually transition to marsh. We studied TFFW surface elevation processes along four Atlantic coastal landscape river gradients by using surface elevation tables and marker horizons. Shallow subsidence between trees, equating to as much as 5.5 mm/year, was an important process in hollow maintenance as roots held hummock elevations relatively more stable. However, hummocks were actively subsiding on all sites with little sign of root zone expansion within hummocks, despite hummock elevation gain on some sites. For down-river transitions, hollow infilling through increasing sediment accretion and root zone expansion were predominant processes driving loss of microtopography as marshes replaced TFFWs closer to the estuarine interface; hollows gained elevations to meet hummocks. While these results do not preclude the importance of healthy root zone processes to the maintenance (and formation) of hummocks, our results indicate that reductions in critical sediment supplies to offset natural shallow subsidence explain persistence and eventual loss of hummock and hollow microtopography in TFFWs.

Estuaries and Coasts↗
USGS2023

Framework for facilitating mangrove recovery after hurricanes on Caribbean islands

Mangrove ecosystems in the Caribbean are frequently exposed to hurricanes, leading to structural and regenerative change that elicit calls for recovery action. For those mangroves unaffected by human modifications, recovery can occur naturally. Indeed, observable natural recovery after hurricanes is the genesis of the “disturbance adaptation” classification for mangroves; while structural legacies exist, unaltered stands often regenerate and persist. However, among the >7,000 islands, islets, and cays that make up the Caribbean archipelago, coastal alterations to support development affect mechanisms for regeneration, sediment distribution, tidal water conveyance, and intertidal mangrove transgression, imposing sometimes insurmountable barriers to natural post-hurricane recovery. We use a case study approach to suggest that actions to facilitate recovery of mangroves on Caribbean islands (and similar settings globally) may be more effective when focusing on ameliorating pre-existing anthropogenic stressors. Actions to clean debris, collect mangrove propagules, and plant seedlings are noble endeavors, but can be costly and fall short of achieving recovery goals in isolation without careful consideration of pre-hurricane stress. We update a procedural framework that considers six steps to implementing “Ecological Mangrove Restoration” (EMR), and we apply them specifically to hurricane recovery. If followed, EMR may expedite actions by suggesting immediate damage assessment focused on hydrogeomorphic mangrove type, hydrology, and previous anthropogenic (or natural) influence. Application of EMR may help to improve mangrove recovery success following catastrophic storms, and reduce guesswork, delays, and monetary inefficiencies.

Restoration Ecology↗
USGS2023

Mangrove habitat persistence and carbon vulnerability associated with increased nutrient loading and sea-level rise at Ding Darling National Wildlife Refuge (Sanibel Island, Florida, USA)

J.N. “Ding” Darling National Wildlife Refuge (DDNWR) is located on Sanibel Island along the southwestern coast of Florida, USA. Sanibel Island is heavily developed, but DDNWR provides protection for a large mangrove area that supports biodiversity and recreational opportunity. However, nitrogen (N) and phosphorus (P) eutrophication attributed to agriculture discharge along the Caloosahatchee River has affected the area’s aquatic habitat with algal blooms and may be causing untimely degradation of Sanibel’s mangrove forests. We launched a series of studies to understand how additional nutrient loading to the levels expected in the future might affect DDNWR’s mangrove resource. We experimentally fertilized selected mangrove forest areas with N fertilizer (+N; NH4) and P fertilizer (+P; P 2 O 5 ) for three years, and monitored soil surface elevation change, soil and pneumatophore CO 2 fluxes from respiration, mangrove tree sap flow from two species ( Avicennia germinans , Rhizophora mangle ), and individual tree and stand water use, from which we developed carbon (C) budgets for +N and +P vs. control simulations as applied to DDNWR’s 1112 ha mangrove area. Many of the measured response variables provided hints of subtle changes in response to +P rather than +N, which were compounded when scaled. From this, we found that additional P loading is expected to stimulate CO 2 uptake via net ecosystem exchange of C, likely pressing the system beyond metabolic capacity and leading to a projected 41% increase in lateral C export to the estuary. Additional lateral C export is concomitant to a reduction in vertical soil surface elevation with +P. Furthermore, an inability of DDNWR’s mangroves to bury additional P and a release of P-bound ions to lateral export may exacerbate estuarine eutrophication. We also modelled the effect of sea-level rise influences on DDNWR’s mangroves through 2100 using a soil cohort model (WARMER-Mangroves) and found that the mangroves may be resilient to current rates of sea-level rise into the future but may also be susceptible to moderate accelerations. Greater eutrophication could create additional vulnerabilities to mangrove submergence, especially to basin mangroves where P concentrations are high and already reducing soil surface elevations in some mangroves. Our results suggest that amelioration of current P concentrations and avoidance of additional P loading to Sanibel Island’s mangroves are management options to consider.

Florida↗
USGS2022

Soil elevation change in mangrove forests and marshes of the greater Everglades: A regional synthesis of surface elevation table-marker horizon (SET-MH) data

Coastal wetlands adapt to rising seas via feedbacks that build soil elevation, which lead to wetland stability. However, accelerated rates of sea-level rise can exceed soil elevation gain, leading to wetland instability and loss. Thus, there is a pressing need to better understand regional and landscape variability in rates of wetland soil elevation change. Here, we conducted a regional synthesis of surface elevation change data from mangrove forests and coastal marshes in the iconic Greater Everglades region of south Florida (USA). We integrated data from 51 sites in which a total of 122 surface elevation table-marker horizon (SET-MH) stations were installed. Several of these sites have been periodically monitored since the 1990s and are among the oldest SET-MH datasets in the world. Rates of surface elevation change ranged from −9.8 to 15.2 mm year −1 , indicating some wetlands are keeping pace with sea-level rise while others are at risk of submergence and conversion to open water. Vertical accretion rates ranged from 0.6 to 12.9 mm year −1 , and subsurface change rates ranged from −13.5 to 8.6 mm year −1 . Rates of surface elevation change were positively related to subsurface change but not vertical accretion. There were no significant relationships between rates of surface elevation change and elevation (NAVD 88) or rates of sea-level rise. Site-specific examples indicate that hurricanes, plant productivity, hydrologic exchange, and proximity to sediment and nutrient inputs are critical but confounding drivers of surface elevation change dynamics in the Greater Everglades region. Collectively, our results reinforce the value of long-term SET-MH data that incorporate spatial variability for advancing understanding of surface elevation change dynamics in coastal wetlands.

Florida↗
USGS2021

Potential for carbon and nitrogen sequestration by restoring tidal connectivity and enhancing soil surface elevations in denuded and degraded south Florida mangrove ecosystems

Mangroves are tidally dependent wetlands that are influenced often by alterations in hydrology associated with coastal developments that impact their distribution, health, and function. Alteration in frequency, depth, duration, and seasonality of tidal inundation can lead to changes in forest condition, although these stress-adapted ecosystems may persist for many years before succumbing to mortality. However, arresting this decline through hydrological restoration can significantly improve ecosystem condition and the provision of ecosystem services. Much of the mangrove resource on Marco Island, Florida, USA, is unhealthy if not already dead or dying due to soil structural shifts, permanent flooding, and peat compression resulting from road construction, tidal restriction, and delays in restoration actions. In order to determine the impact of restricted hydrology on these mangrove forests, we examined soil surface elevation change and soil carbon (C) and nitrogen (N) content along a degradation gradient and within a small-scale, community-driven restoration area. Using a space-for-time substitution approach, we found that the restoration of regular tidal inundation to Marco Island mangroves has the potential to increase C sequestration in surface soils alone from 0 to 360 g C/m 2 /yr (3.60 Mg C/ha/yr) and increase N sequestration from 0 to 24 g N/m2/yr (0.24 Mg N/ha/yr). Additional sequestration benefits would be realized with aboveground forest recovery. Successful mangrove restoration trials and small community-based projects such as those on Marco Island could serve as a model for larger efforts and empower stakeholders and policy makers to restore other wetlands and better manage coastal carbon.

Florida↗
USGS2021

Belowground productivity varies by assessment technique, vegetation type, and nutrient availability in tidal freshwater forested wetlands transitioning to marsh

Wetlands along upper estuaries are characterized by dynamic transitions between forested and herbaceous communities (marsh) as salinity, hydroperiod, and nutrients change. The importance of belowground net primary productivity (BNPP) associated with fine and coarse root growth also changes but remains the dominant component of overall productivity in these important blue carbon wetlands. Appropriate BNPP assessment techniques to use in various tidal wetlands are not well-defined, and could make a difference in BNPP estimation. We hypothesized that different BNPP techniques applied among tidal wetlands differ in estimation of BNPP and possibly also correlate differently with porewater nutrient concentrations. We compare 6-month and 12-month root ingrowth, serial soil coring techniques utilizing two different calculations, and a mass balance approach (TBCA, Total Belowground Carbon Allocation) among four tidal wetland types along each of two river systems transitioning from freshwater forest to marsh. Median values of BNPP were 266 to 2946 g/m 2 /year among all techniques used, with lower BNPP estimation from root ingrowth cores and TBCA (266–416 g/m 2 /year), and higher BNPP estimation from serial coring of standing crop root biomass (using Smalley and Max-Min calculation methods) (2336–2946 g/m 2 /year). Root turnover (or longevity) to a soil depth of 30 cm was 2.2/year (1.3 years), 2.7/year (1.1 years), 4.5/year (0.9 years), and 1.2/year (2.6 years), respectively, for Upper Forest, Middle Forest, Lower Forest, and Marsh. Marsh had greater root biomass and BNPP, with slower root turnover (greater root longevity) versus forested wetlands. Soil porewater concentrations of NH 3 and reactive phosphorus stimulated BNPP in the marsh when assessed with short-deployment BNPP techniques, indicating that pulses of mineralized nutrients may stimulate BNPP to facilitate marsh replacement of forested wetlands. Overall, ingrowth techniques appeared to represent forested wetland BNPP adequately, while serial coring may be necessary to represent herbaceous plant BNPP from rhizomes as marshes replace forested wetlands.

Georgia, South Carolina↗
USGS2020

Salinity, water level, and forest structure contribute to baldcypress (Taxodium distichum) rhizosphere and endosphere community structure

As rising sea levels alter coastal ecosystems, there is a pressing need to examine the effects of saltwater intrusion on coastal communities. Using 16S Illumina profiling, we characterized the communities of baldcypress tree ( Taxodium distichum ) root endosphere and rhizosphere soil bacteria. Our study utilized established sites along salinity and flooding gradients in the United States of Georgia, Louisiana, and South Carolina. We hypothesized that environmental variables, namely salinity and water level, as well as distance between sites would be correlated with baldcypress-associated rhizosphere and root endosphere bacterial communities. We found that geographic distance correlated with rhizosphere but not root endosphere bacterial communities, suggesting that the trees may have stabilized their endosphere communities via recruitment of a more specific suite of taxa from the surrounding soil. Mean water level, mean salinity, and the volume of woody debris were associated with both endosphere and rhizosphere bacterial communities in baldcypress trees. The density of host trees was also associated with endosphere community composition. Our study is the first to use 16S Illumina sequencing to characterize bacterial communities in baldcypress trees— a key restoration species in coastal swamp ecosystems under threat from rising sea levels.

Louisiana, Georgia, South Carolina↗
USGS2020

Structural impacts, carbon losses, and regeneration in mangrove wetlands after two hurricanes on St. John, U.S. Virgin Islands

Hurricanes Irma and Maria ravaged the mangroves of St. John, U.S. Virgin Islands, in 2017. Basal area losses were large (63–100%) and storm losses of carbon associated with aboveground biomass amounted to 11.9–43.5 Mg C/ha. Carbon biomass of dead standing trees increased 8.1–18.3 Mg C/ha among sites, and carbon in coarse woody debris on the forest floor increased 1.9–18.2 Mg C/ha, with effects varying by mangrove typology. While St. John has only ~45 ha of mangroves, they exist as isolated basins, salt ponds, and fringe mangroves; the latter sometimes support diverse marine communities. Salt pond and fringe mangroves had proportionately more organic carbon (46.3 Mg C/ha) than inorganic carbon (1.1 Mg C/ha) in soils than isolated basins. Soil organic carbon was also appreciable in isolated basins (30.8 Mg C/ha) but was matched by inorganic C (36.7 Mg C/ha), possibly due to adjacent land use history (e.g., road construction), previous storm overwash, or geomorphology. Soil nitrogen stocks were low across all typologies. Mangroves had limited regeneration 26 months after the storms, and recovery on St. John may be hindered by pre-storm hydrologic change in some stands, and potential genetic bottlenecks and lack of propagule sources for expedient recovery in all stands.

St Johns↗
USGS2020

Rapid peat development beneath created, maturing mangrove forests: Ecosystem changes across a 25-year chronosequence

Mangrove forests are among the world’s most productive and carbon‐rich ecosystems. Despite growing understanding of factors controlling mangrove forest soil carbon stocks, there is a need to advance understanding of the speed of peat development beneath maturing mangrove forests— especially in created and restored mangrove forests that are intended to compensate for ecosystem functions lost during mangrove forest conversion to other land uses. To better quantify the rate of soil organic matter development beneath created, maturing mangrove forests, we measured ecosystem changes across a 25‐year chronosequence. We compared ecosystem properties in created, maturing mangrove forests to adjacent natural mangrove forests. We also quantified site‐specific changes that occurred between 2010 and 2016. Soil organic matter accumulated rapidly beneath maturing mangrove forests as sandy soils transitioned to organic‐rich soils (peat). Within 25 years, a 20‐cm deep peat layer developed. The time required for created mangrove forests to reach equivalency with natural mangrove forests was estimated as: (1) < 15 years for herbaceous and juvenile vegetation; (2) ~55 years for adult trees; (3) ~25 years for the upper soil layer (0‐10 cm); and (4) ~45‐80 years for the lower soil layer (10‐30 cm). For soil elevation change, the created mangrove forests were equivalent to or surpassed natural mangrove forests within the first five years. A comparison to chronosequence studies from other ecosystems indicates that the rate of soil organic matter accumulation beneath maturing mangrove forests may be among the fastest globally. In most peatland ecosystems, soil organic matter formation occurs slowly (centuries, millennia); however, these results show that mangrove peat formation can occur within decades. Peat development, primarily due to sub‐surface root accumulation, enables mangrove forests to sequester carbon, adjust their elevation relative to sea level, and adapt to changing conditions at the dynamic land‐ocean interface. In the face of climate change and rising sea levels, coastal managers are increasingly concerned with the longevity and functionality of coastal restoration efforts. Our results advance understanding of the pace of ecosystem development in created, maturing mangrove forests, which can improve predictions of mangrove forest responses to global change and ecosystem restoration.

Florida↗
USGS2020

Soil surface elevation dynamics in a mangrove-to-marsh ecotone characterized by vegetation shifts

Mangrove forest encroachment into coastal marsh habitats has been described in subtropical regions worldwide in recent decades. To better understand how soil processes may influence vegetation change, we studied soil surface elevation change, accretion rates, and soil subsurface change across a coastal salinity gradient in Florida, USA, an area with documented mangrove encroachment into saline marshes. Our aim was to identify if variations in the soil variables studied exist and to document any associated vegetation shifts. We used surface elevation tables and marker horizons to document the soil variables over 5 years in a mangrove-to-marsh transition zone or ecotone. Study sites were located in three marsh types (brackish, salt, and transition) and in riverine mangrove forests. Mangrove forest sites had significantly higher accretion rates than marsh sites and were the only locations where elevation gain occurred. Significant loss in surface elevation occurred at transition and salt marsh sites. Transition marshes, which had a significantly higher rate of shallow subsidence compared to other wetland types, appear to be most vulnerable to submergence or to a shift to mangrove forest. Submergence can result in herbaceous vegetation mortality and conversion to open water, with severe implications to the quantity and quality of wetland services provided.

Florida↗
USGS2018

Ghost forests of Marco Island: Mangrove mortality driven by belowground soil structural shifts during tidal hydrologic alteration

Land use changes often create in situ stress and eventual mortality in mangroves as unsuitable hydroperiods are created through tidal flow alterations. Here, we document mangrove forest and soil structural changes within transects established in tidally restricted areas on Marco Island (Collier County, Florida, USA), which has broad swaths of dead-standing or unhealthy mangroves (“ghost forests”). Transects (N = 4) were arranged to include full canopy, transitional, and open canopy (dead) forests, and compared to nearby reference forests. Aboveground and belowground carbon (C) stocks (Total C) ranged from 288 to 304 Mg C ha −1 on full canopy, transitional, and reference sites, which did not differ from each other. However, Total C was lower for dead sites (233 Mg C ha −1 ) dictated entirely by differences in aboveground C (live and dead trees, downed wood); no differences were found among forest condition in belowground C stocks. This belowground C has been persistent in the soil for 85 years since initial tidal restriction. Nevertheless, hydrologic rehabilitation has the potential to increase total C stocks on dead sites by 70–110 Mg C ha −1 . Collapse of the soil surface by 6–8 cm just under the active root zone in chronically stressed mangroves was evident within the bulk density profiles from transitional versus dead sites, suggesting that surface elevation loss as root turnover ceases may work correlatively with chronic stressors (anoxia, P limitation) to affect rapid mortality of forests over short periods of time many years after stress initiation. Hydrologic rehabilitation of stressed or denuded mangroves must also include an understanding of how these soil processes might be re-established.

Florida↗
USGS2017

Created mangrove wetlands store belowground carbon and surface elevation change enables them to adjust to sea-level rise

Mangrove wetlands provide ecosystem services for millions of people, most prominently by providing storm protection, food and fodder. Mangrove wetlands are also valuable ecosystems for promoting carbon (C) sequestration and storage. However, loss of mangrove wetlands and these ecosystem services are a global concern, prompting the restoration and creation of mangrove wetlands as a potential solution. Here, we investigate soil surface elevation change, and its components, in created mangrove wetlands over a 25 year developmental gradient. All created mangrove wetlands were exceeding current relative sea-level rise rates (2.6 mm yr −1 ), with surface elevation change of 4.2–11.0 mm yr −1 compared with 1.5–7.2 mm yr −1 for nearby reference mangroves. While mangrove wetlands store C persistently in roots/soils, storage capacity is most valuable if maintained with future sea-level rise. Through empirical modeling, we discovered that properly designed creation projects may not only yield enhanced C storage, but also can facilitate wetland persistence perennially under current rates of sea-level rise and, for most sites, for over a century with projected medium accelerations in sea-level rise (IPCC RCP 6.0). Only the fastest projected accelerations in sea-level rise (IPCC RCP 8.5) led to widespread submergence and potential loss of stored C for created mangrove wetlands before 2100.

Scientific Reports↗
USGS2017

Macroclimatic change expected to transform coastal wetland ecosystems this century

Coastal wetlands, existing at the interface between land and sea, are highly vulnerable to climate change. Macroclimate (for example, temperature and precipitation regimes) greatly influences coastal wetland ecosystem structure and function. However, research on climate change impacts in coastal wetlands has concentrated primarily on sea-level rise and largely ignored macroclimatic drivers, despite their power to transform plant community structure and modify ecosystem goods and services. Here, we model wetland plant community structure based on macroclimate using field data collected across broad temperature and precipitation gradients along the northern Gulf of Mexico coast. Our analyses quantify strongly nonlinear temperature thresholds regulating the potential for marsh-to-mangrove conversion. We also identify precipitation thresholds for dominance by various functional groups, including succulent plants and unvegetated mudflats. Macroclimate-driven shifts in foundation plant species abundance will have large effects on certain ecosystem goods and services. Based on current and projected climatic conditions, we project that transformative ecological changes are probable throughout the region this century, even under conservative climate scenarios. Coastal wetland ecosystems are functionally similar worldwide, so changes in this region are indicative of potential future changes in climatically similar regions globally.

Nature Climate Change↗