Wetland Loss Research Articles

Functional Wetland Loss Drives Emerging Risks to Waterbird Migration Networks

Migratory waterbirds (i.e., shorebirds, wading birds, and waterfowl) rely on a diffuse continental network of wetland habitats to support annual life cycle needs. Emerging threats of climate and land-use change raise new concerns over the sustainability of these habitat networks as water scarcity triggers cascading ecological effects impacting wetland habitat availability. Here we use important waterbird regions in Oregon and California, United States, as a model system to examine patterns of landscape change impacting wetland habitat networks in western North America. Wetland hydrology and flooded agricultural habitats were monitored monthly from 1988 to 2020 using satellite imagery to quantify the timing and duration of inundation—a key delimiter of habitat niche values associated with waterbird use. Trends were binned by management practice and wetland hydroperiods (semi-permanent, seasonal, and temporary) to identify differences in their climate and land-use change sensitivity. Wetland results were assessed using 33 waterbird species to detect non-linear effects of network change across a diversity of life cycle and habitat needs. Pervasive loss of semi-permanent wetlands was an indicator of systemic functional decline. Shortened hydroperiods caused by excessive drying transitioned semi-permanent wetlands to seasonal and temporary hydrologies—a process that in part counterbalanced concurrent seasonal and temporary wetland losses. Expansion of seasonal and temporary wetlands associated with closed-basin lakes offset wetland declines on other public and private lands, including wildlife refuges. Diving ducks, black terns, and grebes exhibited the most significant risk of habitat decline due to semi-permanent wetland loss that overlapped important migration, breeding, molting, and wintering periods. Shorebirds and dabbling ducks were beneficiaries of stable agricultural practices and top-down processes of functional wetland declines that operated collectively to maintain habitat needs. Outcomes from this work provide a novel perspective of wetland ecosystem change affecting waterbirds and their migration networks. Understanding the complexity of these relationships will become increasingly important as water scarcity continues to restructure the timing and availability of wetland resources.

Surface water temperature impacts on coastal wetland denitrification: Implications for river reconnection

Louisiana, located in the southeast United States, is home to 40% of the continental US's coastal wetlands yet accounts for 80% of the nation's coastal wetland loss. This loss is generally attributed to decreased sediment supply, hydrologic alteration from levees, channelization, subsidence, sea-level rise, and wave and tidal induced marsh edge erosion. The Mid-Barataria Sediment Diversion is a US $1.3 billion coastal restoration project that will divert up to 2100 m3 s−1 of sediment-laden Mississippi River water directly into Barataria Basin. The influx of colder, nutrient-rich, springtime river water could negatively impact water quality of the receiving basin. We quantified the effects of colder, surface water temperature on the nitrate (NO3−) reduction rate in vegetated marsh and open water bay sediments. Colder water limited NO3− removal processes averaging 17.1 mg N m−2 d−1 in the range of 5–14 °C, before increasing almost 3-fold in the 20 °C treatments at 50.6 mg N m−2 d−1. Low N removal rates, especially near the project inflow where temperatures will be coldest will favor transport of NO3− further into Barataria Basin where eutrophic conditions could become expressed. These results will inform coastal managers around the world of the potential ecosystem response to coastal restoration aimed at river reconnection where colder waters enter warmer, shallow basins.

Recent Developments in Sea-Level Rise and Its Related Geological Disasters Mitigation: A Review

With the rapid development of urbanization around the world, the sea-level-rise problem is gaining more and more attention in the 21st century. Sea-level rise is the result of a combination of climate-related factors, structural factors and human activities. Recent studies related to the contributions of these factors to sea-level rise are reviewed and analyzed in this paper. The results suggest that the melting of glaciers and ice sheets have contributed the most to sea-level rise and will continue to be the dominant factor in sea-level rise for the following decades. As sea-level rise becomes an increasingly serious problem, geological disasters related to sea-level rise are also gaining more attention. To better understand the effect of sea-level rise on geological disasters, relevant issues including storm surges, seawater intrusion, the loss of coastal wetland, seismicity, seismic liquefaction and submarine mass failure are further reviewed and highlighted. In response to the risks of those disasters caused by sea-level rise, some disaster mitigation measures are proposed, and in the end, the quantitative disaster assessment concept based on resilience is introduced to the coastal urban system, to assess its ability to resist and recover from geological disasters due to the sea-level rise.

Global land use extent and dispersion within natural land cover using Landsat data

The conversion of natural land cover into human-dominated land use systems has significant impacts on the environment. Global mapping and monitoring of human-dominated land use extent via satellites provides an empirical basis for assessing land use pressures. Here, we present a novel 2019 global land cover, land use, and ecozone map derived from Landsat satellite imagery and topographical data using derived image feature spaces and algorithms suited per theme. From the map, we estimate the spatial extent and dispersion of land use disaggregated by climate domain and ecozone, where dispersion is the mean distance of land use to all land within a subregion. We find that percent of area under land use and distance to land use follow a power law that depicts an increasingly random spatial distribution of land use as it extends across lands of comparable development potential. For highly developed climate/ecozones, such as temperate and sub-tropical terra firma vegetation on low slopes, area under land use is contiguous and remnant natural land cover have low areal extent and high fragmentation. The tropics generally have the greatest potential for land use expansion, particularly in South America. An exception is Asian humid tropical terra firma vegetated lowland, which has land use intensities comparable to that of temperate breadbaskets such as the United States’ corn belt. Wetland extent is inversely proportional to land use extent within climate domains, indicating historical wetland loss for temperate, sub-tropical, and dry tropical biomes. Results highlight the need for planning efforts to preserve natural systems and associated ecosystem services. The demonstrated methods will be implemented operationally in quantifying global land change, enabling a monitoring framework for systematic assessments of the appropriation and restoration of natural land cover.

Trends and predictors of wetland conversion in urbanizing environments

Wetlands provide critical ecosystem services including flood mitigation and habitat for diverse species, but globally, many wetlands have been destroyed. In urban areas and surrounding urban-rural fringes, many lost wetlands have been indirectly replaced with stormwater management (SWM) ponds. SWM ponds are designed to manage urban stormwater and contaminants, but only provide limited ecosystem services. In our study area, historic extent of wetland loss is partially documented, while more recent losses and SWM pond creation have not been fully reported. We examine wetland loss and SWM pond creation in seven southern Ontario (Canada) municipalities from 2002 to 2010. We then apply a Markov model to project future extent of wetland losses and SWM pond creation, with and without effects of specific land use and land cover types. We find that from 2002 to 2010, 95.5 ha of wetlands were lost, with most being smaller than 2 ha in size. A total area of 111.6 ha of SWM ponds was created, but on average, created SWM ponds were smaller than lost wetlands. Our projections to 2026 suggest wetland losses of 438.1 ha and SWM pond creation of 293.8 ha. We suggest a need for more stringent wetland protection policies to conserve wetlands that still exist in growing municipalities, especially smaller wetlands. Lack of such protection will weaken provisioning of wetland-related ecosystem services, which are more critical than ever in a changing climate.

Realistic River Image Synthesis Using Deep Generative Adversarial Networks

In this paper, we demonstrated a practical application of realistic river image generation using deep learning. Specifically, we explored a generative adversarial network (GAN) model capable of generating high-resolution and realistic river images that can be used to support modeling and analysis in surface water estimation, river meandering, wetland loss, and other hydrological research studies. First, we have created an extensive repository of overhead river images to be used in training. Second, we incorporated the Progressive Growing GAN (PGGAN), a network architecture that iteratively trains smaller-resolution GANs to gradually build up to a very high resolution to generate high quality (i.e., 1,024 × 1,024) synthetic river imagery. With simpler GAN architectures, difficulties arose in terms of exponential increase of training time and vanishing/exploding gradient issues, which the PGGAN implementation seemed to significantly reduce. The results presented in this study show great promise in generating high-quality images and capturing the details of river structure and flow to support hydrological modeling and research.

Development of a Landscape-Based Multi-Metric Index to Assess Wetland Health of the Poyang Lake

Human-induced changes in landscapes are one of the major drivers of wetland loss and degradation. The Poyang Lake wetland in China has been experiencing severe degradation due to human disturbance and landscape modification. Indicators to assess the condition of this wetland are thus needed urgently. Here, a landscape-based multi-metric index (LMI) is developed to evaluate the condition of the Poyang Lake wetland. Twenty-three candidate metrics that have been applied to wetland health assessment in published studies were tested. Metrics that show strong discriminative power to identify reference and impaired sites, having significant correlations with either benthic macroinvertebrate- or vegetation-based indices of biotic integrity (B-IBI or V-IBI), were chosen to form the LMI index. Five of these metrics (largest patch index, modified normalized differential built-up index, Shannon’s diversity index, connectance index, and cultivated land stress index) were selected as our LMI metrics. A 2 km buffer zone around sample sites had the strongest explanatory power of any spatial scale on IBIs, suggesting that protecting landscapes at local scales is essential for wetland conservation. The LMI scores ranged between 1.05 and 5.00, with a mean of 3.25, suggesting that the condition of the Poyang Lake wetland is currently in the “fair” category. The areas along lakeshores were mainly in poor or very poor conditions, while the less accessible inner areas were in better conditions. This study demonstrates significant links between landscape characteristics and wetland biotic integrity, which validates the utility of satellite imagery-derived data in assessing wetland health. The LMI method developed in this study can be used by land managers to quickly assess broad regions of the Poyang Lake wetland.

Detecting wetland encroachment and urban agriculture land classification in Uganda using hyper-temporal remote sensing.

Background: Urbanization is an important indicator of economic growth and social change but is associated with environmental degradation, which threatens the sustainable growth of African cities. One of the most vulnerable ecosystems in urban areas are wetlands. In Uganda, wetlands cover an area of 11% of the country's land area. Half of the wetland areas in Ugandan cities have been converted to industrial and residential areas, and urban agriculture. There is limited information on the extent of wetland conversion or utilization for urban agriculture. The objective of this study was to investigate the extent of wetlands lost in two Ugandan cities, Wakiso and Kampala, in the last 30 years. Secondly, we extracted crop agriculture in the wetlands of Kampala and Wakiso from hyper-temporal satellite image analysis in an attempt to produce a spatial detail of wetland encroachment maps of urban agriculture using a reproducible mapmaking method. Methods: Using a field survey and free remote sensing data from Landsat TM 1986 and Landsat ETM 2016 we classified the rate of wetland loss and encroachment between the years 1986 and 2016. We used MODIS NDVI 16-day composites at a 500-meter spatial resolution to broaden the analysis to distinguish distinctive crops and crop mixtures in the encroached wetlands for urban agriculture using the ISODATA clustering algorithm. Results: Over 30 years, 72,828 ha (73%) of the Wakiso-Kampala wetlands have been lost meanwhile agriculture areas have doubled. Of this 16,488 ha (23%) were converted from wetlands. All cultivated agriculture in Kampala was in the wetlands while in Wakiso, 73% of crop agriculture was in the wetlands. The major crops grown in these urban wetlands were banana (20%), sugarcane (22%), maize (17%), Eucalyptus trees (12%), sweet potatoes (10%), while ornamental nurseries, pine trees, vegetables, and passion fruits were each at 5%.

Resilient Responses to Urban Wetland Loss: Experiences from Port Harcourt Municipality

Wetlands globally contribute to valuable ecosystem services to both natural species habitat and human tourist attractions in any location including those found in Port Harcourt Municipality. Wetlands are also beneficial and significant serving as breeding regions for wildlife and safe spaces for sea creatures, support a diversity of species and provide some climate restraining components, characteristic of any natural habitat. This study highlights some resilient responses residents put up in the aftermath of wetland reclamation and conversion in neighbourhoods. The study aims to ascertain the environmental and physical challenges of wetland loss on the wetland dwellers and subsequently identify resilient paradigms adopted to cope with such associated stress. Forty-one wetland settlements were identified within the Port Harcourt municipality and three out of those settlements were chosen purposively. A total of 293 questionnaires were distributed and SPSS was used to analyse the data. ERDAS Imagine 2014 version was used to show spatial changes between the years 1986 to 2000, and 2000 to 2016. The study shows that from 1986 to 2000, Port Harcourt municipality lost a total of 1,255,500m2. This translates to a 5% loss with an average rate of 89,678.57m2 per annum. Between 2000 and 2016, the rate of loss was 108,956.25m2 per annum, and approximately 7.69% of wetlands totalling 1,743,300m2 were lost to urbanisation and other activities. The result indicates that some of the challenges of wetland loss include flooding, poor refuse disposal system, and unplanned settlements. Indigenous knowledge, social capital and symbolic power are some of the resilient responses displayed by the vulnerable population to build resilience capacities. The study recommends periodic mapping of all wetlands and an effective development control framework to monitor incursions into existing wetlands.

Mass removal efficiencies in water and consequences after a river diversion into coastal wetlands: second thoughts

Salinity control, nutrient additions, and sediment supply were directly or indirectly the rationale for a $220 million coastal wetland restoration project (Davis Pond River Diversion) that began in 2002. We sampled Mississippi River water going in and out of the receiving basin from 1999 to 2018 to understand why wetland loss increased after it began. There was a reduction in inorganic sediments, nitrogen (N), and phosphorus (P) concentrations within the ponding area of 77%, 39% and 34%, respectively, which is similar to that in other wetlands. But the average sediment accumulation of 0.6 mm year−1 inadequately balances the present-day 5.6 mm year−1 sea level rise or the 7.9 ± 0.13 mm year−1 accretion rates in these organic soils. Nutrients added likely reduced live belowground biomass and soil strength, and increased decomposition of the organic matter necessary to sustain elevations. The eutrophication of the downstream aquatic system from the diversion, principally by P additions, increased Chl a concentrations to a category of ‘poor’ water quality. We conclude that this diversion, if continued, will be a negative influence on wetland area and will eutrophy the estuary. It is a case history example for understanding the potential effects arising from proposed river diversions.

Invasive water chestnut hinders tidal wetland development

AbstractConsistent shoreline development and urbanization have historically resulted in the loss of wetlands. However, some construction activities have inadvertently resulted in the emergence of new tidal wetlands, with prominent examples of such anthropogenic wetlands found within the Hudson River Estuary. Here, we utilize two of these anthropogenically created tidal wetlands to explore the sedimentary and hydrologic conditions driving wetland development from a restoration perspective. Tivoli North is an emergent freshwater tidal marsh, while Tivoli South is an intertidal mudflat with vegetation restricted to the seasonal growth of invasive water chestnut during summer months. Using a combination of sediment traps, cores, and tidal flux measurements, we present highly resolved sediment budgets from these two protected bays and parameterize trapping processes responsible for their divergent wetland evolution. Utilizing a 16‐year tidal flux dataset, we observe net sediment trapping in Tivoli North for most years, with consistent trapping throughout the year. Conversely, flux measurements at Tivoli South reveal net sediment loss over the study period, with trapping constrained to the summer months. Here, we explore potential mechanisms responsible for these contrasting accumulation regimes, including initial geological differences, sediment loading, and human land use changes, with a focus on the invasion of emergent aquatic vegetation. Results suggest that water chestnut is contributing to these divergent morphologies by inhibiting sediment trapping and facilitating erosion, thereby preventing marsh nucleation in Tivoli South. The longevity of this dataset highlights the capacity of aquatic vegetation to regulate sediment exchange and geomorphology in enclosed bays when provided with an opportunity to colonize. The results of this project provide evidence to inform the management of restoration projects in river systems with tidal wetlands, especially those affected by invasive species of aquatic vegetation.

Nutrient Retention and Release in Eroding Chesapeake Bay Tidal Wetlands

AbstractThe worldwide loss of coastal wetlands has traditionally been addressed as the loss of ongoing nutrient retention ecosystem services. However, nutrient remineralization from eroded particles may further exacerbate water quality degradation. Using data on nutrient burial and denitrification from northern Chesapeake Bay, along with estimates of the bioavailability of eroded marsh particulates, the changing role of wetlands as an important sink for nutrients is examined. Although the erosion of wetlands results in the reintroduction of nitrogen and phosphorus into open‐water habitats, the potential for exacerbating eutrophication is highly diminished by the low lability of wetland organic matter. The impact of such erosion on the cycling of Fe‐bound phosphorus from marsh soils is highly dependent on both the amount of inorganic P, its solid phase association with Fe, and its potential remobilization from the estuarine sediments into which it is deposited. Although nutrient sequestration in newly constructed wetlands built from dredged materials suggested a rapid development of nutrient sequestration, a better understanding of nutrient ecosystem services provided by marshes created by transgression into uplands is necessary for understanding the long‐term nutrient retention value of coastal wetlands.

城市化背景下小微湿地景观动态变化及其驱动因素

PDF HTML阅读 XML下载 导出引用 引用提醒 城市化背景下小微湿地景观动态变化及其驱动因素 DOI: 10.5846/stxb202107061800 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（32171530,31472020） Dynamic changes in small wetland landscapes and their driving factors under the background of urbanization Author: Affiliation: Fund Project: The National Natural Science Foundation of China (32171530, 31472020) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:小微湿地是指自然界在长期演变过程中形成的小型湿地。城市发展导致小微湿地大量消失，了解小微湿地景观动态变化特征及驱动因素是保护与管理小微湿地的重要基础。以合肥市包河区为研究区域，选取2006-2018年4期遥感影像，利用空间分析方法确定2006-2010年、2010-2014年、2014-2018年、2006-2018年4个时期小微湿地景观动态变化，基于300m×300m的网格单元，结合增强回归树和地理加权逻辑回归模型，分析13个预测变量与小微湿地损失之间的关系。结果表明：2006-2018年，小微湿地在整个研究区大范围减少，总面积下降了60.8%，斑块数量减少了60.5%，同时，小微湿地边缘复杂度降低，小微湿地间的空间距离增加，聚集程度降低。增强回归树模型显示，城市发展初期(2006-2010年)，周边用地类型(建设用地、旱地、林地和草地)变化是导致小微湿地损失的主要因素，中后期(2010-2018年)各类型土地利用变化的相对影响有不同程度的下降，斑块面积和坡度对小微湿地损失的驱动作用逐渐凸显。2006-2018年，建设用地变化(14.4%)、斑块面积(13.5%)、旱地变化(11.1%)、坡度(10.1%)、林地变化(8.5%)、草地变化(7.0%)是导致小微湿地损失的高重要性变量。地理加权逻辑回归模型揭示了高重要性变量对小微湿地损失影响的空间非平稳性特征，结果显示，除斑块面积系数的空间可视化无解释意义，其余高重要性变量对小微湿地损失的影响随地点的变化，贡献的大小和方向也有所不同。研究方法和结果可以为城市快速发展地区小微湿地的保护与管理提供理论支持。 Abstract:The term "small wetland" refers to wetlands of small scale, which can stabilize ecological systems in the process of long-term development. Against the backdrop of rapid urbanization, many small wetlands have been disappearing, often in groups in cities. Understanding the dynamic changes and their driving factors in small wetlands provides an important basis for the effective protection and management of small wetlands. In this study, we took Baohe District in Hefei City as the research area and analyzed the landscape pattern characteristics by interpreting remote sensing data through time (2006, 2010, 2014, and 2018). The spatial analysis method was used to determine the dynamic changes in small wetland landscapes over four study periods of 2006-2010, 2010-2014, 2014-2018, and 2006-2018. Based on a 300 m×300 m grid unit, boosted regression tree and geographically weighted logistic regression models were employed to identify the relationships between 13 predictive variables and the loss of small wetlands. The results showed that the total area of small wetlands decreased by 60.8% and the number of patches decreased by 60.5% during the period from 2006 to 2018. At the same time, the extent and complexity of the perimeter of the small wetlands decreased, the spatial distance between the small wetlands increased, and the distribution tended towards more discrete. The boosted regression tree model quantified the relative influences of the predictive variables and determined high-importance variables to further analyze the nonlinear relationships between the variables and the decline in small wetlands. In the early stage of urbanization, changes in the surrounding land-use type were the major driving factors in the loss of small wetlands. In the middle and late stages of urbanization, both the trend in large-scale urban sprawl slowed down, and the relative importance of other land-use type changes also declined to varying extents. The driving factors of patch area and slope on the loss of small wetlands gradually increased in importance. Construction land changes (14.4%), patch area of small wetlands (13.5%), dryland changes (11.1%), slope (10.1%), forestland changes (8.5%), and grassland changes (7.0%) were high-importance variables of small wetland losses from 2006 to 2018. The local and spatial influences of these high-importance variables were analyzed further by geographically weighted logistic regression using coefficients determined at each sample point. With the exception that the spatial visualization of the small wetland patch areas had no explanatory significance, the influences of the remaining variables varied with location, and their contributions also differed in magnitude and direction. This study provides a reference for the protection and management of small wetlands in rapidly developing urban areas. 参考文献 相似文献 引证文献

A Review on Wetlands – Threats, Conservation, Strategies and Policies

Globally 64% of the wetlands have disappeared since 1970 and the loss is higher in Asia, about 5000 km2 annually due to agriculture, dam construction and other uses. In India, the loss is about 38% with the disappearance rate of 2-3% per year. Further dependence on these wetlands leads to either extinction or threatened the species including 21% of bird species, 37% of mammal species and 20% fresh water fish species. Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water level. According to Ramsar convention the wetlands are classified as three types via., coastal/ marine wetlands, inland wetlands and human made wetlands. Worldwide, the freshwater wetland ecosystems are among the mostly heavily used, depended upon and exploited ecosystems for sustainability and well-being. The main causes of wetland loss have been classified into two types namely acute and chronic wetland loss. This loss in wetland area results in adverse impact on the key functions performed by wetlands. Hence, we have to conserve these wetlands by implementing effective legal framework and management strategies. In this context Ramsar convention is an important International Treaty for the Conservation and Sustainable use of Wetlands which was signed at a city of Iran (Ramsar) in 1971. There are currently over 2,400 Ramsar sites on the territories of 171 Ramsar Contracting Parties across the world. They cover over 2.5 million square kilometers, an area larger than Mexico.

Wading into the debate on section 2(4)(r) of the National Environmental Management Act 107/1998 and its impact on policy formulation for the protection of South African wetlands

The loss and degradation of wetlands is an international dilemma and measures are put in place to ensure their conservation. In South Africa, the Department of Water and Sanitation’s Revised Strategic Plan 2015/2016 to 2019/2020 submitted that, of the 792 wetland ecosystems, 65 per cent have been identified as threatened and 48 per cent as critically endangered. A later revised plan provides that 50 per cent of South Africa’s wetlands have been lost.3 This is worrisome considering the all-important functions they fulfil and the benefits they provide.

Land Use/Cover Changes and Surface Temperature Dynamics Over Abaminus Watershed, Northwest Ethiopia

The study investigates the impact of land use/cover changes on the dynamics of surface temperature in the Abaminus watershed, Northwest Ethiopia. Landsat-5 images of 1987, 1999, and 2010, and the Landsat-8 image of 2018 were used as the sources of data. The land use/cover changes were calculated using a land-use transition matrix. Data generated from household surveys were presented using percentage values to identify the driving forces of land use/cover changes. The land surface temperature (LST) result was quantified using the respective index equation. Results indicated that wetland, forest, shrublands, and grasslands declined by 96.6%, 72%, 77.7%, and 89.4% respectively over the analysis period. The encroachment of cultivation and overgrazing to marginal lands, weak institutional arrangement, sedimentation, high drainage of wetlands for crop production, and recurrent drought were the major driving forces behind the land use/cover change. Within this effect, the average land surface temperature was increased by 11.5°C, 3.22°C, and 2.02°C due to wetland loss, clearing of the forest, and decline of shrublands respectively for the last 31 years. LSTs had correspondingly decreased by 5.42°C and 3.77°C on the afforested barren surfaces and planted shrublands. Hence, there should be an improved institutional arrangement for managing open access resources through the participation of local people in the management for minimizing the increase of land surface temperature in the study watershed. Moreover, enclosure management and plantation of multipurpose species on degraded communal lands shall be scaled-up to significantly reduce land surface temperatures.

Plant communities in wetland mitigation banks surpass the quality of those in the most degraded, naturally occurring wetlands, but fall short of high-quality wetlands

The U.S. Clean Water Act requires that development projects causing negative impacts to wetlands must provide compensation for wetland losses through the wetland mitigation process. Compensation can be achieved through the purchase of credits from wetland mitigation banks, which are large wetland restoration projects constructed by third-party bank sponsors. To evaluate how effectively wetland mitigation banks have achieved the goal of “no net loss” of wetland resources, we compared mitigation banks to natural wetlands in the Chicago (Illinois, USA) region. We surveyed vegetation plots in 20 mitigation banks to compare vegetation metrics and composition between banks and 114 natural wetlands, representing a gradient of ecological quality, in northern Illinois. Based on metrics of species richness and floristic quality, mitigation banks possessed wetland plant communities of greater conservation value than the lowest quality, degraded, natural wetlands, but banks were not close to reaching equivalence with high-quality, reference, natural wetlands. Overall, the plant communities in banks were distinct from those of natural wetlands, a condition that appears to be driven by the abundance of the non-native species Typha angustifolia and Phragmites australis in mitigation banks. We found some evidence that dominance by native species may be lower in older banks, but otherwise did not find evidence for a relationship between vegetation metrics and bank age. These results will help those involved with wetland mitigation and similar offsetting programs assess whether compensation sites meet no-net-loss goals, informing goal setting, monitoring, and offsetting policies.

Using community-based interviews to determine population size, distribution and nest site characteristics of Pallas's fish eagle in north-east Bangladesh

AbstractPallas's fish eagle Haliaeetus leucoryphus was recategorized from Vulnerable to Endangered on the IUCN Red List in 2017 because of evidence that there is only a single population, which is declining as a result of continuous, widespread loss and degradation of freshwater wetlands. To determine the species’ status in Bangladesh, we conducted a large-scale community-based interview survey in north-east Bangladesh in 2017–2020. We also examined nest site habitat characteristics through field surveys and remotely sensed data. We conducted a total of 955 interviews in an area of 4,150 km2, through which we were able to determine the presence of 53 breeding pairs at a mean density of 1.2 nests per 100 km2. There was a higher nest density (3.7–4.8 nests per 100 km2) in some locations, which we identify as priority conservation areas. The majority of nests (62.2%) were close together and on tall trees with an open canopy structure. Nests were located within or close to (< 100 m) human settlements, and within 500 m of wetlands and rivers. Felling of nest trees, removal of nests by local people and loss of permanent wetlands (14.6% during 2010–2020) appeared to be the main threats. High nesting density in our study area suggests that the freshwater wetlands in north-east Bangladesh possibly hold the largest population of Pallas's fish eagle globally.

Comparing the Yangtze and Mississippi River Deltas in the light of coupled natural-human dynamics: Lessons learned and implications for management

The Yangtze River Delta (YRD) and Mississippi River Delta (MRD) are two of the largest deltas in the world. Despite similar forcing conditions of fluvial sediment reduction and relative sea-level rise, there are significant differences in deltaic change caused by hydrodynamics and human activities. In this review, we compare the morphological changes of the two deltas at multiple spatial and temporal scales and identify the lessons learned from past engineering and management strategies. While the YRD has seen an increase of subaerial land of ~1500 km2 since 1950, the MRD has lost approximately 5000 km2 of land since the early 1930s. Extensive land reclamation and coastal shoreline embankment in the YRD have led to land gain at the expense of tidal wetland shrinkage. In contrast, flood control, waterway transportation, and petroleum industry in the MRD have resulted in levee construction and canal building, which together with subsidence and sea-level rise, have led to significant wetland loss in the MRD. The tidal forcing in the YRD is much stronger than that in the MRD, which has played a role in redistributing subaqueous sediment back into the delta plain, offsetting the negative effect of fluvial sediment reduction. In contrast with continuous population increase on the YRD, wetland loss and exposure to flooding hazards have resulted in population loss on the MRD. These comparative analyses reveal that nature and human interventions have acted together in shaping the modern deltaic morphology. Using the Driver-Pressure-State-Impact-Response (DPSIR) analysis framework, we propose a conceptual model to provide holistic understanding of the natural-human coupled delta system and management strategies, which could yield broad implications for coping with the future challenges in global deltas.

Increasing fragmentation and squeezing of coastal wetlands: Status, drivers, and sustainable protection from the perspective of remote sensing

Coastal wetlands are of great ecological and economic value but face significant degradation and losses because of human activities. Nevertheless, the changes in spatiotemporal landscape patterns, which have occurred as a result of coastal wetland losses, have not been well documented under the rapid urbanization in coastal zones. In this study, an algorithm based on periodic tidal inundations and full time-series indices was developed to map the detailed status and trends in the coastal wetlands in Fujian Province from 1994 to 2018 by using more than archived 5000 Landsat images. The results showed that in 2018, there were 1136.56 km2 of coastal wetlands along the coast of Fujian with an overall accuracy of 95.63%, which were mainly distributed in estuaries and bays. These coastal wetlands consisted of tidal flats, low marshes, and high marshes with proportions of 84.91%, 13.05%, and 2.04%, respectively. An unprecedented loss of coastal wetlands has occurred in Fujian Province, with an annual rate of 15.44 km2/a from 1994 to 2018. Many coastal wetlands were reclaimed, dredged, and converted into inland areas for aquaculture ponds, ports, and built-up areas in different urbanization periods, which has led to a great loss of coastal spaces with an area of 476.87 km2. The interplay between the loss of coastal wetlands and seaward urbanization will lead to severe fragmentation and squeezing effects in the coastal zone and will weaken the coastal protection from marine disasters that is provided by coastal wetlands. Therefore, we conceived two conceptional frameworks for sustainable coastal protection based on the current situations of the coastal communities to provide a trade-off between economic development and the protection of coastal developing countries in the world.