Wetland Loss Research Articles

Hydrologic variability and plant composition drive relative abundance of marsh birds at created and reference marshes in southeastern Louisiana, U.S.A.

Coastal marsh loss occurs at an alarming pace globally, with extremely high rates along the northern Gulf of Mexico, particularly in Louisiana. In Louisiana, marsh creation projects combat wetland loss; however, biotic responses of vegetation and wildlife receive little to no consideration during and after construction. Habitat characteristics such as hydrologic processes, plant composition, and habitat structure affect the abundance of marsh birds, and understanding these features is important when creating suitable habitat for marsh birds. Our study compared hydrologic characteristics, plant composition, and habitat structure between created (n = 10) and reference (n = 9) sites across southeastern Louisiana and determined the relationship of these habitat characteristics to marsh bird relative abundance. We performed bird surveys (n = 766), including call‐back surveys for secretive marsh birds, at all sites across three breeding seasons (2021–2023). We used drone imagery to determine plant composition and used water level recording devices to assess hydrologic characteristics. Our results indicate that hydrologic variation and plant composition are drivers of marsh bird relative abundance regardless of whether a marsh is created or not. While some habitat features differed between created and reference sites, our results indicated that created marshes can support similar abundances of marsh birds as reference sites, depending on what habitat features are present at the site. Our study demonstrates the importance of creating marshes that promote hydrologic connectivity and water level variability, which in turn supports diverse emergent vegetation communities and provides suitable habitat for a variety of marsh bird species.

Impact of urbanization on mangrove wetland at Eagle Island, Rivers State, Nigeria

Urbanization has destroyed wetlands globally, and in the Niger Delta area surge in human population has led to increased encroachment into wetlands area resulting in habitat destruction. This research aims to determine the impact of urbanization on selected wetland areas at Eagle Island, Rivers State. The study was carried out between April 2023 and January 2024. Physico-chemical parameters were assessed using standard procedures. The results of the water quality assessment show the range of temperature, dissolved oxygen, and pH to be within acceptable limits for tropical waters as recommended by WHO, while others, including total dissolved solids and electrical conductivity (µS/cm), were not within acceptable limit as stipulated by WHO. The mean concentration of heavy metals, nitrates, and phosphate in surface water was within the NUPRC permissible limits. The mean concentrations of cadmium, chromium, and lead in sediment were higher than the NUPRC permissible limits, while nickel, iron, nitrate, and phosphate were within the NUPRC permissible limits. The concentration of metals in surface water were: Cd= 0.014 µg/l, Cr = 0.219 µg/l, Ni = 0.651 µg/l, Pb = 0.160 µg/l, Fe = 1.881 µg/l, in the order of Fe>Ni>Cr>Pb>Cd. The result implies that there is a gradual deterioration of environmental quality as a result of human-mediated activities. The soil and water quality in wetland areas are facing degradation because of the unprotected intrusion of private individuals and organizations who enter to carry out the sand filling, swamp reclamation, and construction activities, leading to the loss of wetlands and river systems.

Assessment of urban wetlands loss and fragmentation using land use and land cover change and guidostoolbox: A study of Chorrillos district, Lima.

The coastal landscape of the Chorrillos district is an ecosystem characterized by hosting the largest population of migratory and resident bird species in Lima, including the Protected Natural Area of the Pantanos de Villa Wildlife Refuge (RVSPV). In response to wetland loss, this study aims to explore the process of natural landscape fragmentation in the Chorrillos district, including the RVSPV, from 1985 to 2021 to identify the impact of anthropogenic agents on structural connectivity. The methodology involves (i) an analysis of land cover and land use (LULC) using the MapBiomas Peru Collection 1.0 Platform, (ii) a patch accounting analysis, (iii) an analysis of Area Density in the Foreground (FAD), and (iv) an analysis of Morphological Spatial Patterns (MSPA) using the GuidosToolbox (Graphic User Interface for Image Object Description and Shapes-GTB) Version 3.304. The results indicate a hierarchy of disturbed patches, with the largest patch (RVSPV) displaying specific spatial processes that contribute to landscape transformation and persistence. The ecological function of the patches and habitat links demonstrate the benefits of connectivity and environmental exchange between fragments, aiming to counteract landscape loss.

The trajectory of wetland change in China between 1980 and 2020: hidden losses and restoration effects.

Understanding wetland change is critical to establishing and implementing international conservation and management conventions. With such knowledge, supporting sustainable development, making management decisions, improving policies, and conducting scientific research become possible. However, consistent information on changes in Chinese wetlands has been unavailable. We applied the hybrid object-based and hierarchical classification approach to ∼53,000 scenes of Landsat images acquired between 1980 and 2020 and created a national wetland mapping product (China_Wetlands) for six periods (e.g., 1980, 1990, 2000, 2010, 2015, and 2020). China_Wetlands revealed diverse changes in Chinese wetlands and their trajectories in response to climate change and human impacts over the past four decades. Specifically, there was a substantial shrinkage in wetland area before 2015, with a small rebound between 2015 and 2020. The net loss was ∼60.9×103km2, which represents 12% of the area in 1980. However, the loss of natural wetlands was hidden by human-made wetland gain with an offset of 15.6×103km2. Additionally, the expansion of surface water extent approximately 14.0×103km2 obscured the loss of vegetated wetlands. Wetland loss in hotspot areas (e.g., Sanjiang Plain and Yangtze River Delta) should not be neglected. The sustainable management and effective conservation of wetlands in China should target wetland areas, landscape structures, and small wetlands delivering important ecosystem services. Moreover, the conversion of wetland types and the invasion of alien species need to be monitored and regulated. China_Wetlands will be a critical wetland dataset for ecological research and the assessment of national and global environmental objectives (e.g., the United Nation's sustainable development goals).

Carbon dioxide fluxes and the dominant role of vegetation in recently created and reference Gulf Coast marshes

AbstractCoastal wetlands are one of the most productive ecosystems on Earth with the capacity to sequester large amounts of carbon dioxide (CO2). Wetland loss due to anthropogenic and natural causes reduces the carbon (C) storage capacity and potentially releases previously fixed C in biomass and soil to the water column and atmosphere through decomposition. Coastal wetland restoration has the potential to mitigate some of the C losses depending on the balance of C fluxes. However, the role of vegetation and environmental conditions in governing rates of C accumulation in restoration sites is not well resolved. The purpose of this study was to examine seasonal C fluxes, specifically, gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem exchange (NEE) of CO2 in unvegetated and vegetated (Spartina alterniflora) areas of a 2‐year old created marsh, and S. alterniflora and Spartina patens communities in a “natural” reference brackish marsh. S. alterniflora‐dominated areas were sinks for CO2 in both the newly created and reference marsh with an average CO2 uptake rate of 7.0 ± 1.0 μmol m−2 s−1. The unvegetated areas in the newly created marsh and S. patens areas in the reference marsh had approximately net neutral CO2 fluxes. S. alterniflora areas of the created marsh had similar carbon fluxes to that in the reference marsh, despite a much lower soil organic matter content. Because vegetation develops much faster than soil properties, restored marshes can be a C sink equivalent to natural marshes as soon as the marsh is vegetated. Ecosystem productivity and C assimilation in S. alterniflora areas of the reference marsh were enhanced by lower elevations (up to 6 cm) and higher soil bulk density (up to 0.28 g cm−3). At similar elevations, S. alterniflora in both the created and reference marshes was a greater C sink than S. patens areas of the reference marsh. Our findings illustrate that establishment of vegetation is critical to promoting C sink functions in created marshes and, notably, species do matter.

Impacts of Sea Level Rise on Danish Coastal Wetlands - a GIS-based Analysis.

Intergovernmental Panel on Climate Change (IPCC) scenarios run by an ensemble of models developed by the Coupled Model Intercomparison Project (CMIP) projects an average sea level rise (SLRs) of 0.6 to 1.2 m for the low and high emission scenarios (SSP1-1.9, SSP5-8.5), during the next century (IPCC 2021). The coastal zone will experience an increase in the flooding of terrestrial habitats and the depth of marine productive areas, with potential negative consequences for these ecosystems. The coast in Denmark is highly modified due to anthropogenic uses. Dikes, dams, and other coastal infrastructure are widespread, causing a coastal squeeze that prevents natural coastal development and inland migration of coastlines. We performed a national-scale analysis on the impacts of mean sea level rise (MSLR) in 2070 and 2120, and a 1 in 10-year storm surge water level (10SS) in 2120 MSLR for the Danish coast. Our study shows extensive permanent flooding of coastal habitats (~14%), whereas only 1.6% of urban areas will be flooded. Finally, very large agricultural areas (~191,000 ha) will be frequently flooded by 10SS if no extra protective measures are planned. With the present coastal protection structures, key habitats will be affected by permanent flooding or coastal squeeze while even larger extents will be subjected to intermittent marine flooding. About 45% (199 km2) of all Danish coastal wetlands will be permanently flooded by 2120, while areas occupied by forest, lakes and freshwater wetlands will be more frequently flooded by marine water. This study highlights the importance of including coastal habitats as dynamic elements in climate adaptation plans. Conservation and restoration of key habitats such as coastal wetlands should be prioritized in management plans. If Denmark does not change its current priorities, it may face the complete loss of coastal wetlands habitat in the 22nd century.

Effects of Surrounding Landscape Context on Threatened Wetland Bird Diversity at the Global Scale

Wetland birds are undergoing severe population declines globally, primarily attributed to extensive wetland loss and degradation. The attributes of the landscape surrounding a focal locality, referred to as ‘landscape context’, have been shown to influence the diversity of wetland birds living in the given area. At a global scale, however, the landscape context effects on wetland birds have not been assessed. Here, we assessed the effect of landscape context on the richness of threatened bird species recorded in 334 inland Ramsar wetland sites across the globe. Generalized linear mixed models were used to quantify the relationship between the richness of these bird species and the landscape context of the Ramsar sites. Variation partitioning was used to quantify the independent explanatory power of landscape context for comparison between migratory and non-migratory species. The overall and independent explanatory power of landscape context for the global-scale richness pattern of threatened avifauna reached ca. 17% and 3%, respectively, with the scale of peak explanatory power being 5 times the area of a focal Ramsar site. The independent explanatory power of landscape context was significantly higher for migratory species (ca. 30%) than for non-migratory ones (ca. 3%). Among the landscape context metrics, wetland habitat loss and fragmentation were most strongly associated with the global-scale richness of threatened migrant species at Ramsar sites. Our results suggest that even at macroecological scales, landscape context contributes to shaping the richness pattern of threatened bird species, especially for migrants. These findings provide useful insight for managing landscapes surrounding Ramsar sites, in order to improve conservation effectiveness for wetland birds worldwide.

Satellite-Based Assessment of Rocket Launch and Coastal Change Impacts on Cape Canaveral Barrier Island, Florida, USA

The Cape Canaveral Barrier Island, home to the National Aeronautics and Space Administration (NASA)’s Kennedy Space Center and the United States (U.S.) Space Force’s Cape Canaveral Space Force Station, is situated in a unique ecological transition zone that supports diverse wildlife. This study evaluates the recent changes in vegetation cover (2016–2023) and dune elevation (2007–2017) within the Cape Canaveral Barrier Island using high-resolution optical satellite and light detection and ranging (LiDAR) data. The study period was chosen to depict the time period of a recent increase in rocket launches. The study objectives include assessing changes in vegetation communities, identifying detectable impacts of liquid propellant launches on nearby vegetation, and evaluating dune elevation and tide level shifts near launchpads. The results indicate vegetation cover changes, including mangrove expansion in wetland areas and the conversion of coastal strands to denser scrubs and hardwood forests, which were likely influenced by mild winters and fire management. While detectable impacts of rocket launches on nearby vegetation were observed, they were less severe than those caused by solid rocket motors. Compounding challenges, such as rising tide levels, beach erosion, and wetland loss, potentially threaten the resilience of launch operations and the surrounding habitats. The volume and scale of launches continue to increase, and a balance between space exploration and ecological conservation is required in this biodiverse region. This study focuses on the assessment of barrier islands’ shorelines.

Plant and soil responses to sediment deposition and nutrient‐enrichment in healthy, deteriorating, and newly created coastal marshes of the Mississippi River Delta

Coastal marshes vulnerable to sea‐level rise may benefit from sediment amendments to increase elevation. However, nutrient‐loading to estuaries may counter elevation gain through reduced root production and/or increased decomposition. Here, we test if belowground plant productivity, root decomposition, and marsh accretion response to nutrient‐loading differs with sediment addition in three marsh types: a healthy intermediate salinity marsh, a deteriorating brackish marsh, and a created marsh in Barataria Basin, Louisiana, United States. In this region, wetland loss is rapid, and a major restoration project is underway to introduce Mississippi River water, sediment, and nutrients to offset marsh loss. Porewater nutrient concentrations, vegetation structure, belowground productivity and decomposition, and accretion rates were measured over 450 days. Experimental nitrate additions yielded high porewater ammonium‐N concentrations in the Deteriorating marsh but had a smaller effect in Healthy and Created marshes. Belowground productivity in the Deteriorating marsh was neutral to negatively affected by nutrient and sediment treatments, whereas positive effects occurred in Healthy and Created marshes. Despite elevation increase from sediment treatments, and substantial effects of nutrient treatments on porewater nutrient concentrations, belowground decomposition and surface accretion rates were not affected by treatments. Sediment deposition increased species richness in the Healthy marsh and added sediment and added nutrients with sediment increased plant height in the Created and Deteriorating marshes, respectively. Over the timescale measured, experimental sedimentation and pulsed nutrient input had few consistent effects on belowground ingrowth, decomposition, or surface accretion. Our findings highlight that response to nutrient pulses are complex and depend on baseline marsh conditions.

Assessing cost-effectiveness of dissuasion techniques targeting waterbirds in rice fields

In a scenario of global wetland loss, rice fields are becoming vital habitats for waterbirds, often offering abundant and predictable food resources. However, the increasing presence of waterbirds in rice fields is exacerbating human-wildlife conflicts, as birds are seen as pests by farmers due to the damage they perceive the birds inflict to the crops. To tackle this situation, farmers use dissuasion methods like propane gas cannons, but its effectiveness in reducing damage is often not quantified. In this study we evaluate the cost-effectiveness of propane gas cannons in deterring waterbirds from rice fields and test if there is a correlation between bird abundance in a given field during rice growth and rice yield in the same field. Waterbird counts were conducted before and after dissuasion actions targeting Glossy ibis and White stork in a major rice production area in Portugal. To assess the potential magnitude of damage reduction gained through dissuasion, we estimated the time elapsed between dissuasion events and the reestablishment of bird numbers in the disturbed fields. The economic cost of dissuasion was compared with the estimated gains from reduced damage. Results showed that on average, waterbird numbers recovered ca. 30min after dissuasion, leading to an estimated 0.78% reduction in crop damage. The final yield of rice production was modelled considering all gains and costs involved in dissuasion actions in relation to an increase in dissuasion efforts for 11 scenarios of potential waterbird damage (0-20%). For dissuasion to be cost-effective, waterbirds would need to destroy at least 17% of the crops, far more than any damage previously recorded in Europe. Also, we found that the abundance of waterbirds in a rice field does not affect rice yield. We suggest that efforts to reduce damage should shift to more cost-effective and environmentally friendly methods, such as diversionary fields or economic compensations to farmers. This can enhance the economies of rice-dependent countries and reduce conflicts, ultimately reconciling rice agriculture with biodiversity conservation.

Multi-temporal image analysis of wetland dynamics using machine learning algorithms

Wetlands play a crucial role in enhancing groundwater quality, mitigating natural hazards, controlling erosion, and providing essential habitats for unique flora and wildlife. Despite their significance, wetlands are facing decline in various global locations, underscoring the need for effective mapping, monitoring, and predictive modeling approaches. Recent advances in machine learning, time series earth observation data, and cloud computing have opened up new possibilities to address the challenges of large-scale wetlands mapping and dynamics forecasting. This research conducts a comprehensive analysis of wetland dynamics in the Thatta region, encompassing Haleji & Kinjhar Lake in Pakistan, and evaluates the efficacy of different classification systems. Leveraging Google Earth Engine, Landsat imagery, and various spectral indices, we assess four classification techniques to derive accurate wetland mapping results. Our findings demonstrate that Random Forest emerged as the most efficient and accurate method, achieving 87% accuracy across all time periods. Change detection analysis reveals a significant and alarming decline in Haleji & Kinjhar Lake wetlands over 1990-2020, primarily driven by agricultural expansion, urbanization, groundwater extraction, and climate change impacts like rising temperatures and reduced precipitation. If left unaddressed, this continued wetland loss could have severe implications for aquatic and terrestrial species, water and soil quality, wildlife populations, and local livelihoods. The study predicts future wetland dynamics under different scenarios - enhancing drainage for farmland conversion (10-20% increase), increasing urbanization (10-20% expansion), escalating groundwater extraction (7.2m annual decline), and climate change (up to 5°C warming and 54% precipitation deficit by 2050). These scenarios forecast sustained long-term wetland deterioration driven by anthropogenic pressures and climate change. To guide conservation strategies, the research integrates satellite data analytics, machine learning algorithms, and spatial modeling to generate actionable insights into multifaceted wetland vulnerabilities. Findings provide a robust baseline to inform policies ensuring sustainable management and preservation of these vital ecosystems amidst escalating human and climate threats. Over 1990-2020, the Thatta region witnessed a 352.8 sq.km loss of wetlands, necessitating urgent restoration efforts to safeguard their invaluable ecosystem services.

The Spatiotemporal Evolution of the Mudflat Wetland in the Yellow Sea Using Landsat Time Series

Mudflat wetland, one of the 27 surface elements identified by the International Geographic Data Committee, has undergone substantial transformations with the rapid growth of the social economy and marine hazards, resulting in significant changes in its area and distribution. Quick identification of mudflat wetland evolution is vital to improve the mudflat ecological service value. We employed object-oriented and decision tree classification methods to map the mudflat wetland in the Yellow Sea using the Landsat time series from 1983 to 2020. The Improved Spectral Water Index (IWI) was established by combining the characteristics of many ratio indices and using ratio operation and quadratic power operation. The coefficient of variation (CV) of the IWI was calculated, and the range of the intertidal zone in 1983, 1990, 2000, 2010, and 2020 was obtained by using a threshold method. The results indicate that the mudflat wetland area decreased continuously from 1983 to 2020, with a reduction of 337.38 km2/10a. Among the total area, the natural wetland experienced a decline of 446.9 km2/10a, with the most drastic changes occurring between 2000 and 2010. In contrast, the area of the human-made wetland increased by 109.56 km2/10a. Over the 38 years, the tidal flat has undergone the most drastic reduction, with an average of 157.45 km2/10a. From 1983 to 2020, the intertidal zone area decreased, with a reduction of 429.02 km2/10a. Human activities were the key factors causing mudflat wetland loss. Based on these findings, we propose several policy suggestions. This study provides a scientific basis for understanding the synergetic evolution mechanism of coastal resources utilization and mudflat wetland protection under global change.

A blue–green ratio of urban wetlands as an ecosystem health indicator: the case of urban sprawl in Nagpur, India

ABSTRACT Rampant urban sprawl has affected the structure and function of existing urban green and blue spaces, exposing developing cities to unexpected disaster events. Drawing on a mixture of secondary information supported by GIS and field-based studies, we assessed the impact of growing impervious surfaces on the dynamic zones of urban wetlands in Nagpur, India. We compared decadal data (2000-2020) to understand the pattern of wetland loss and its drivers in the region. Our findings reveal a significant loss of wetland structure and area over the past two decades, raising alarming concerns regarding ecological and economic repercussions. To address these issues, we propose a blue–green buffer-based assessment approach that incorporates local knowledge and observations along with proactive monitoring of ecosystem health. Our study highlights the urgency of reducing the spatial complexity of landscape patches, restoring wetland buffers, declaring wetland buffers as no-go zones, and promoting corridor connectivity to urban wetlands to improve urban blue infrastructure health. Multi-sectoral and stakeholder cooperation, involvement, and strict enforcement of the Wetland Rules (2017) by local governing bodies can help build urban resilience by protecting urban blue–green infrastructure.

Nutrients, isolation and lack of grazing limit plant diversity in restored wetlands

Abstract Agricultural intensification has led to the loss of most natural wetlands from human‐dominated landscapes but, in recent decades, wetland restoration has gained traction worldwide. Restoration of suitable habitat conditions is hampered by nutrient residues from decades of high‐input farming, by continued input of nutrients from surrounding farmland and by incomplete restoration of natural hydrology. We assessed the effect of wetland restoration and disturbance (grazing) on vascular plant and bryophyte diversity in restored wetlands in Denmark at plot and landscape scales. Compared to near‐natural wetlands, we found a lower species richness and community uniqueness in restored wetlands, but we also found that grazing had a positive effect on vascular plant richness in restored wetlands. The size of the local species pool, presence of near‐natural habitat prior to restoration and near‐natural restored hydrology all had positive effects on plant diversity, whereas high soil iron and nitrogen had negative effects. Synthesis and applications: Restoration of plant diversity in wetlands is challenging, but our results point to potential remedies: plan restoration areas near colonisation sources of the target biota, restore hydrology to near‐natural conditions, discontinue nutrient loads from surrounding arable land and restore near‐natural grazing regimes. Bryophytes may be particularly useful as indicators for successful restoration of wetlands.

Stopover habitat use of coastal Pied Avocet revealed by satellite tracking and remote sensing technology

Stopover habitat use of coastal Pied Avocet revealed by satellite tracking and remote sensing technology

Assessment of wetland loss through industrialization and community expansion: a case study of the greater amanzule wetland in the Ellembelle district of Ghana

Wetland ecosystems provide numerous services to humanity and the biosphere at large. However, these services are constantly dwindling due to the massive wetland loss caused by urbanization. Urbanization-induced wetland loss is a global problem, with most developing countries experiencing it currently. Several studies on wetland loss have been conducted. However, there is a dearth of studies integrating GIS and other ecological models to estimate the periodic deterioration of wetlands in rural settings in underdeveloped nations. As a result, this study aims to determine wetland loss in a developing country’s countryside, using the Greater Amanzule Wetland in the Ellembelle District of Ghana as a case study. The study used the GIS and Remote Sensing dataset, the Normalization Difference Vegetation Index, and the InVEST-Habitat Quality model to analyze the spatial pattern of wetland loss and habitat quality variations caused by industrialization and community expansions between 2000 and 2020. Our results indicate that, from 2000 to 2015, community built-up and industrial land areas grew from 25.19 ha to 84.21 ha and 0–4.71 ha respectively, causing a wetland loss of −39.64 ha (−31.10%). Between 2015 and 2020, community built-up land grew to 78.65 ha while industrial land slightly reduced to 2.54 ha, leading to the wetland degradation of approximately −69.06 ha (−42.53%). Wetland habitat quality steadily declined, from 0.97 in 2000 to 0.93 in 2015 and 0.93 in 2020. The study findings led to policy recommendations to reduce wetland encroachment and enhance sustainability. These recommendations included conducting effective land-use plan inspections before issuing permits, coordinating effective management, and promoting the recovery of natural and artificial vegetation to sustain the wetland.

Assessing the contribution of super-resolution in satellite derived bathymetry in the Antarctic

Assessing the contribution of super-resolution in satellite derived bathymetry in the Antarctic

Muskrat occurrence in Rhode Island shows little evidence of land use change driving declines

AbstractMuskrat (Ondatra zibethicus) populations have been in apparent decline across their native range in North America for decades. Several hypotheses exist for the causes of these declines, including loss of wetlands. We used time‐to‐detection data from 925 surveys from 276 sites across Rhode Island, USA, between 2021–2023 to fit an occupancy model that related the probability of muskrat occupancy at a site to land cover classification. We found that muskrat occupancy was higher in areas with more open water, urban land cover, or a second‐order or larger stream, and lower in areas with salt water. We estimated changes in wetland area throughout Rhode Island using the National Land Cover Database classifications from 2001 and 2019 and found a net loss in wetland cover of 219 ha. We calculated the distance between wetland patches in each of these periods and found that patches were closer together than the dispersal distance of muskrats, suggesting isolation is unlikely to be driving muskrat declines. Additionally, when we used our model to predict changes in muskrat occupancy between 2001 and 2019, both mean and median predicted occupancy changed by <0.005. These results indicate that muskrat declines are not driven by habitat loss, and suggest future research is needed that focuses on other hypothesized mechanisms of muskrat declines such as disease, declining habitat quality, predation, and competition.

Biodiversity conservation and restoration of wetlands in suburban areas: challenges and prospects

Context Wetland loss threatens global biodiversity. Peri-urban wetlands face acute pressures from urban expansion. Aims Investigate biodiversity and land-cover changes in two wetlands undergoing suburbanisation near Hangzhou, China. Methods Seasonal field surveys of birds, fish and amphibians, coupled with remote-sensing analysis of land-cover changes from 2009 to 2020. Key results Suburban wetlands exhibited unique degradation patterns, including reduced species diversity, simplified community structures and proliferation of invasive species, with 91 bird species being recorded, dominated by common residents, 25 still-water fish species with few carnivores and migratory species, and 5 ubiquitous amphibian species detected. Species richness was lower than in nearby conserved wetlands. From 2009 to 2020, 6–7% of the wetlands were lost to urban expansion and converted to artificial vegetation or infrastructure. Conclusions Ecological degradation is driven by rapid urbanisation, with habitats being fragmented by roads and converted to artificial land covers. Water pollution from insufficient treatment and abandoned aquaculture further impairs habitats. Implications Innovative integrated-management framework was proposed for wetlands biodiversity restoration in suburban area. Key strategies include (1) modernising traditional circular economies to sustain wise use, (2) wildlife-friendly infrastructure design, (3) targeted invasive species control, and (4) adaptive co-management informed by ongoing monitoring. This socio-ecological systems approach aims to harmonise biodiversity conservation, cultural heritage and sustainable development in threatened suburban wetlands.

Dredged Canals, Wetland Loss, and Legacy

AbstractThe direct effects of converting coastal wetlands to open water by dredging them can be magnified by indirect effects. For example, dredged canals allow for recovery of mineral fluids 1000 s of m belowground which may induce geological subsidence or faulting; the dredged material deposited at the surface creates levees that redirect overland water flows. These indirect factors may stress wetland plants enough so that additional wetland habitat is converted to open water as a result of longer intervals of wetland soil waterlogging and drying, sulfide toxicity, less organic matter and sediment accumulation, and greater erosion. We quantified the indirect effects by demonstrating a robust dose–response relationship between coastal land loss and canal density in the Mississippi and Niger river deltas over 5 decades. Importantly, the ratio of land loss to canal area increases with time—a legacy effect. Surface impediments to water movements rather than belowground subsidence are the dominant causal factor. We also found that flood protection levees on the main river channel did not significantly magnify the effect of dredging on wetland loss. The cumulative effect of these direct and indirect consequences in coastal Louisiana is enormous and continuing, equaling many tens of billions dollars annually. Understanding these effects supports the rejection of a hypothesis that regional river channel flood protection levees or fluid withdrawal is of greater importance than the local changes in wetland hydrology. Wetland restoration/mitigation of dredging impacts on these two coasts can be implemented at a relatively low cost and quickly if this paradigm of the causes of coastal wetland losses is adopted.