Conversion Of Wetlands Research Articles

Soil carbon pools and microbial network stability depletion associated with wetland conversion into aquaculture ponds in Southeast China

Wetlands, which are ecosystems with the highest soil surface carbon density, have been severely degraded and replaced by artificial reclamation for fish and shrimp ponds in recent years. This transformation is causing intricate shifts in soil carbon pools and microbial stability. In this study, we examined natural wetlands and reclaimed aquaculture ponds in Southeast China to analyze the structure and network stability of soil microbial communities following the reclamation of estuarine wetlands and to elucidate the microbial-mediated mechanisms for regulating soil organic carbon (SOC). The aquaculture ponds presented significantly less average SOC content than the natural wetlands (p < 0.05). ACE, Chao1, and Shannon's indices of bacteria and fungi were decreased in aquaculture ponds. Less numbers of nodes and edge links in the co-occurrence network of soil fungi and bacteria in aquaculture ponds. This suggests reduced correlation and stability within the microbial network of aquaculture ponds. Decomposers in soil fungi (e.g. Dung Saprotroph) reduced. Reduced proportions of key phyla Ascomycota, Basidiomycota and Rozellomycota in the soil fungal network. Reduced proportions of key phyla Proteobacteria, Chloroflexi and Desulfobacterota in the soil bacterial network. In conclusion, our results suggest that converting wetland paddocks to intensive aquaculture ponds results in carbon pool loss and reduces soil microbial network stability. The results highlight the importance of protecting or moderately restoring mangrove wetlands along the coast of southeastern China. It is also predicted that such measures may enhance the storage capacity of soil carbon pools and improve the stability of carbon sequestration by soil microorganisms, thus offering a potential solution for mitigating global climate change.

Endemic and Threatened: The Conservation Value of the Philippine Duck

The Philippine duck (Anas luzonica) is a vulnerable species, endemic to the Philippines. The need of local people for food and land has led to the endangerment of the Philippine duck populations through illegal hunting and the conversion of wetlands to aquaculture and farmland. This study was conducted to determine the willingness to pay (WTP) of residents (n = 500) in Maguindanao provinces for the conservation of the Philippine duck and the effects of conservation attitude and knowledge toward the Philippine duck, as well as sociodemographic characteristics, on WTP. The mean annual WTP for Philippine duck conservation was USD 0.60, and the total estimated annual amount that could be collected was USD 134 thousand when projected based on the number of households in the Maguindanao provinces. A positive conservation attitude and high knowledge increased the WTP for Philippine duck conservation. Females, pet owners, and those with higher income pledged a higher WTP than males, non-pet owners, and those with lower income. This study revealed that local residents are supportive of the conservation of the vulnerable duck populations by paying a considerable amount. These results are critical for designing and implementing outreach programs for increasing awareness and the acquisition of funds urgently needed for the protection and conservation of the remaining Philippine duck population in the area.

Land use conversion to uplands significantly increased the risk of antibiotic resistance genes in estuary area

Land use conversion in estuary wetlands may affect the transmission of antibiotic resistance genes (ARGs), while the risk rank of the ARGs and the change of clinically relevant ARGs under various land-use types are not well understood. This study used metagenomics to reveal the diversity and abundance of ARGs across five distinct land uses: reed wetland, tidal flat, grassland, agricultural land and fallow land, as well as their distribution and potential health risks. Results showed that high numbers of ARG subtypes and classes were detected irrespective of land-use types, notably higher in agricultural land (144 ARG subtypes). The most shared ARG subtypes were multidrug resistance genes across all the land uses (29 subtypes, 4.7 × 10−2-1.5 × 10−1 copies per 16S rRNA gene copy). Proteobacteria and Actinobacteria were primary ARG hosts, with 18 and 15 ARGs were found in both of them, respectively. The ARG subtype mdtB was the most dominant clinical ARG detected with 90 % amino acid identity. The change of ARGs exhibited a consistent trend across land uses in terms of health risk ranks, with the highest observed in fallow land and the lowest in reed wetland. This study reveals the distribution pattern of ARGs across various land-use types, and enhances our understanding of the potential health risks associated with ARGs in the context of coastal wetland conversion in estuary areas.

Patterns of Urban Sprawl and Agricultural Land Loss in Sub-Saharan Africa: The Cases of the Ugandan Cities of Kampala and Mbarara

Sub-Saharan Africa (SSA) is undergoing rapid urbanization, yet research comparing urban expansion and agricultural land loss in peri-urban areas is scarce. This study utilizes multi-temporal Landsat imagery to examine the impact of urban growth on agricultural land and fragile ecosystems in Kampala (a mega city) and Mbarara (a regional urban center) in Uganda. We distinguish between random and systematic land-use and land-cover (LULC) transitions in the landscape. The results reveal substantial urban expansion. Kampala’s urban area surged from 7.14% in 1989 to 55.10% in 2015, while Mbarara increased from 6.37% in 2002 to 30.95% in 2016. Correspondingly, agricultural land decreased, from 48.02% to 16.69% in Kampala, and from 39.92% to 32.08% in Mbarara. Notably, a significant proportion of urban growth in both cities encroached upon agricultural land (66.7% in Kampala and 57.8% in Mbarara). The transition from agricultural to built-up areas accounted for 14.72% to 28.45% of the landscapes. Additionally, unsustainable practices led to the conversion of wetlands and forests to agricultural land, with approximately 13% of wetlands and 23% of Savannah and forests being converted between 2001 and 2015. These findings underscore the necessity of monitoring LULC changes for sustainable urban growth management, emphasizing the importance of preserving agricultural land and ecosystems to ensure present and future food security. This research contributes to the understanding of urbanization’s impact on peri-urban agricultural land and ecosystems in SSA, providing insights that are crucial for informed urban planning and policy formulation aimed at sustainable development in the region.

Phylogenetics of Asian Small-Clawed Otters (Aonyx cinereus) in West Sumatra.

&lt;b&gt;Background and Objective:&lt;/b&gt; The presence of Asian small-clawed otters (&lt;i&gt;Aonyx cinereus&lt;/i&gt;) in West Sumatra has been reported from ecological data in the form of footprints and feces, while its genetic information has not been reported yet. This genetic information needs to be reported along with the determination of &lt;i&gt;A. cinereus&lt;/i&gt; as a vulnerable species and is experiencing population decline by the International Union for Conservation of Nature (IUCN). This study aimed to determine the phylogenetic relationship of &lt;i&gt;A. cinereus&lt;/i&gt; found in West Sumatra with other regions. &lt;b&gt;Materials and Methods:&lt;/b&gt; The samples used were &lt;i&gt;A. cinereus&lt;/i&gt; stool collected from several wetland locations in West Sumatra. &lt;i&gt;Aonyx cinereus&lt;/i&gt; DNA was extracted from stool samples following the QIAamp Fast DNA Stool Mini Kit protocol (Qiagen). Amplification was performed using the CO1 gene. The IQTree was used to provide phylogenetic information on &lt;i&gt;A. cinereus&lt;/i&gt; and MEGA 7 was used to determine the uncorrected genetic distance of &lt;i&gt;A. cinereus&lt;/i&gt;. &lt;b&gt;Results:&lt;/b&gt; &lt;i&gt;Aonyx cinereus&lt;/i&gt; clustered to form three sub-clusters namely &lt;i&gt;A. cinereus&lt;/i&gt; Sundaland, Laos lineage and unknown lineage. &lt;i&gt;Aonyx cinereus&lt;/i&gt; Sundaland consists of &lt;i&gt;A. cinereus&lt;/i&gt; West Sumatra and &lt;i&gt;A. cinereus&lt;/i&gt; Sarawak, Malaysia which are closely related with a genetic distance of 0.68%. Moreover, compared to &lt;i&gt;A. cinereus&lt;/i&gt; from unknown lineage (including Captive Copenhagen Zoo) and Laos lineage, &lt;i&gt;A. cinereus&lt;/i&gt; of West Sumatra had a genetic distance of 0.68-1.20 and 4.18%, respectively. &lt;b&gt;Conclusion:&lt;/b&gt; Wetland conversion and the role of humans have influenced the obstacle to connectivity among populations that cause genetic variation.

Coastal conversion alters topsoil carbon, nitrogen and phosphorus stocks and stoichiometric balances in subtropical coastal wetlands

The extensive conversion of coastal wetlands into agricultural and aquaculture areas has significant repercussions on soil nutrient balance. However, how coastal conversion specifically influences the dynamics and stoichiometry of topsoil carbon (C), nitrogen (N), and phosphorus (P) remains limited due to the considerable spatial variability and a lack of comprehensive field data. Here, we investigated the concentration and distribution of total C (TC), N (TN) and P (TP), along with their stoichiometric balance in four distinct coastal landscapes, including natural marshes and tidal flats, as well as converted agricultural croplands and ponds. The results revealed that converted croplands and ponds exhibited significantly higher concentrations of soil C, N and P, particularly in comparison to tidal flats. Furthermore, croplands and ponds have higher topsoil C stocks than tidal flats, but little difference or even lose stored C compared to marshes. Cropland soils showed considerably higher levels of available N (NH4+-N and NO3−-N) and available P compared to those in natural marshes and tidal flats. The distribution of soil TC, TN, and TP demonstrated greater spatial heterogeneity in natural marshes and tidal flats, while the converted areas were more uniform and became hotspots for N and P accumulation. Coastal conversion altered soil C:N:P stoichiometry, with cropland soils exhibiting a lower N:P ratio (2.9 ± 1.1), indicating that long-term application of N and P fertilizers could decrease the N:P ratio, as P is more retained in the soil than N. Furthermore, it was observed that the dynamics of C, N and P, as well as their stoichiometry, are closely linked to soil physicochemical properties, especially soil organic matter and texture. These findings highlight that coastal conversion and associated management practices markedly affected soil C, N and P dynamics in a representative wetland area of the subtropical regions, leading to a reshaping of their stoichiometric balances, particularly in the topsoil layer.

Linking carbon storage with land use dynamics in a coastal Ramsar wetland

Coastal wetland ecosystems make an important contribution to the global carbon pool, yet their extent is declining due to aquaculture-related land use changes. We conducted an extensive investigation into the carbon stock and area coverage of macrophytes in a tropical coastal Ramsar wetland, Kolleru in Andhra Pradesh, India. A total of 72 quadrats of size 1 × 1 m2 were laid in the wetland, 19 species of macrophytes were collected and analyzed for carbon content using a CNHS analyzer. To assess changes in the wetland macrophytes, Normalized Difference Vegetation Index (NDVI) was estimated using Landsat time series data from 1975 to 2023. The importance value index (IVI) of macrophytes scored highest for the Ipomoea aquatica (41.4) and the lowest for Ottelia alismoides (1.9). Non-metric multidimensional scaling (NMDS) significantly (r = 0.1905, p = 0.0361) revealed a clear separation of macrophytes in ordination space. ANOVA indicated highly significant (p < 0.0001) variations in the carbon content of aboveground and belowground components of macrophytes. Among the different macrophytes, the highest carbon content was found in Phragmites karka (0.6 g. g−1) and the lowest was recorded in Utricularia stellaris (0.2 g. g−1). On an average, emergents in the Kolleru wetland sequester 1525 ± 181 g C m−2 yr−1, rooted floating species sequester 858 ± 101 g C m−2 yr−1, submerged macrophytes sequester 480 ± 60 g C m−2 yr−1, and free-floating macrophytes sequester 221 ± 90 g C m−2 yr−1. Land cover mapping revealed a decrease in spread of aquatic vegetation from 225.2 km2 in 1975 to 100.6 km2 in 2023. Although macrophytes are vital carbon sinks, the wetland conversion into fishponds has resulted in a loss of 55.3 % of carbon storage. Therefore, immediate restoration of macrophyte cover is vital for the proper functioning of carbon sequestration and mitigation of climate change impacts.

Unveiling the landscape predictors of resilient vegetation in coastal wetlands to inform conservation in the face of climate extremes.

Unveiling spatial variation in vegetation resilience to climate extremes can inform effective conservation planning under climate change. Although many conservation efforts are implemented on landscape scales, they often remain blind to landscape variation in vegetation resilience. We explored the distribution of drought-resilient vegetation (i.e., vegetation that could withstand and quickly recover from drought) and its predictors across a heterogeneous coastal landscape under long-term wetland conversion, through a series of high-resolution satellite image interpretations, spatial analyses, and nonlinear modelling. We found that vegetation varied greatly in drought resilience across the coastal wetland landscape and that drought-resilient vegetation could be predicted with distances to coastline and tidal channel. Specifically, drought-resilient vegetation exhibited a nearly bimodal distribution and had a seaward optimum at ~2 km from coastline (corresponding to an inundation frequency of ~30%), a pattern particularly pronounced in areas further away from tidal channels. Furthermore, we found that areas with drought-resilient vegetation were more likely to be eliminated by wetland conversion. Even in protected areas where wetland conversion was slowed, drought-resilient vegetation was increasingly lost to wetland conversion at its landward optimum in combination with rapid plant invasions at its seaward optimum. Our study highlights that the distribution of drought-resilient vegetation can be predicted using landscape features but without incorporating this predictive understanding, conservation efforts may risk failing in the face of climate extremes.

Leveraging Reed Bed Burnings as Indicators of Wetland Conversion in Modern Greece

This study explores the historical occurrence of wetland ecosystems in Greece by using recurring Phragmites australis (common reed) burnings as an indicator. Phragmites australis, a plant closely associated with wetlands, provides excellent insights into wetland distribution. We establish a substantial association between reed fires and historical wetland existence in Greece using geographical and statistical analysis, with these fires exhibiting remarkable constancy across time. Using Corine land-cover (CLC) data, we extend our analysis into land-use dynamics, demonstrating that places with the highest reed-bed-fire rates were originally wetlands, particularly those converted into permanent irrigated land and areas with complex agriculture patterns. We find spatial commonalities between reed fires and past wetland existence by analyzing fire occurrence across three main categories: reed fires, agricultural land fires, and grassland fires. Historical records of wetland conversion into agricultural land (or land reclamation works) in locations such as Yianitsa and Kopaida give context to our findings. Visualizations confirm the clustering of reed fires around these converted agricultural regions. In summary, our study offers a unique indicator based on Phragmites australis burnings that can be used to identify previous wetland-type ecosystems, with Mediterranean-wide implications. Despite data constraints, this study adds to the conversation about wetland preservation and sustainable land-use management.

Land use changes and edaphic properties control contents and isotopic compositions of soil organic carbon and nitrogen in wetlands

Land use change in wetlands leads to significant losses of soil organic matter (SOM). Stable carbon (C) and nitrogen (N) isotopes offer insights into changes in C3/C4 vegetation, SOM sources, and decomposition processes. Yet, predicting the spatial–temporal dynamics of SOM contents and isotopes under land use changes remains challenging. This study delves into the effects of land use changes on soil organic carbon (SOC), total nitrogen (TN), δ13C and δ15N values, and soil physico-chemical properties and lignin phenols. Our results highlight the significance of soil water content (SWC) in determining the outcomes of land use changes. The conversion of wetland to cropland, forestland and construction land, led to notable reductions in SOC contents (8.71–56.33 %), and TN contents (7.87–37.12 %). Wetland conversion resulted in an enrichment of 13C and 15N abundance, with wetlands exhibiting the lowest δ13C (−25.57 to –22.89 ‰) and δ15N (2.66 to 6.67 ‰) values. A significant correlation occurred between δ13C and δ15N values in wetlands, but underwent considerable changes after wetland conversion. Key parameters, including bulk density (BD), C:N, the acid-to-aldehyde of vanillyl ((Ad/Al)v), lignin content (Λ8), and total phosphorus (TP), were identified as influencing factors for both SOC and TN contents. When evaluating δ13C values, the most influential factors included silt, C:N, SOC, sand, and BD. These indicate the importance of soil chemical group (from 41 % to 21 %) in elucidating δ13C values declined, while lignin group’s (from 9 % to 28 %) importance increased from topsoil to subsoil. The acid-to-aldehyde of syringyl ((Ad/Al)s), Λ8, C:N, BD and the cinnamyl-to-vanillyl ratio (C/V) were identified as the primary factors influencing δ15N values, with chemical group accounting for 36 % and lignin group for 48 % in topsoil, while physical group dominated 42 % in subsoil. Our findings underscore the shifts in SOM sources and distinct mechanisms of degradation/preservation of SOM following land use changes.

Evaluation of Effects of Wetland Conversion on Quantitative Soil Properties and Water Quality in Namutumba District, Uganda

Evaluation of Effects of Wetland Conversion on Quantitative Soil Properties and Water Quality in Namutumba District, Uganda

Response of the Stability of Soil Aggregates and Erodibility to Land Use Patterns in Wetland Ecosystems of Karst Plateau

The world’s natural wetlands, which have important ecological functions, are being lost at an alarming rate. The erosion and deposition of soil on wetlands is a major cause of wetland conversion to agriculture. An urgent problem to be solved is how to slow down the erosion and deposition of wetlands resulting from land use. Land use patterns affect soil properties, thereby affecting soil aggregate stability and erodibility. Evaluating the effects of land use patterns on soil aggregate stability and erodibility in small watersheds of wetland ecosystems of karst plateau is of great importance. Thus, we compared the soil properties, aggregate stability indicators and soil erodibility of shrubland, grassland, artificial forest land and sloping farmland for evaluating the impact of various land use patterns on soil aggregate stability and erodibility in typical karst plateau wetland ecosystems. Our results showed that the mass fraction of soil aggregates &gt; 0.25 mm was the main component in the four land uses, with greater variation in aggregates &gt; 5 mm; overall, MWD, GMD and WSA0.25 were higher in grassland and shrubland than in sloping farmland and artificial forest land, while K values, PAD and SCAI showed the opposite trend. Correlation analysis showed that effective soil nutrients had a positive effect on soil aggregate stability. In conclusion, the stability of soil aggregates and resistance to soil erosion were strongest under the influence of shrubland. Our study showed that shrubland can better improve soil aggregate stability and erosion resistance, which may provide a guide for protecting and restoring karst plateau wetland ecosystems.

Dynamics of Wetland Conversion and Its Implications for Socio-Cultural Aspects of Communities in Banjar District, Indonesia

The massive conversion of wetlands has implications not only for social aspects but also for cultural aspects of society. This research aims to analyze the dynamics of wetland conversion and its implications for the socio-cultural aspects of society in Banjar Regency. The research method is a qualitative method with data collection methods through observation, literature studies, and in-depth interviews. The research results show that the process of changing the function of wetlands in Banjar Regency is carried out through hierarchy 1 which occurs in the first stage of wetland conversion, with characteristics that are still passive and social changes that emerge to the surface or are manifest only in the individual realm (not collective), and is closely related to the direct impact of spatial changes. Hierarchy 2 occurs when hierarchy 1 experiences a value addition process, namely the infiltration of capitalistic values into the socio-cultural values that exist in society. This process occurred when the private sector (companies the warehousing industry and housing developers) emerged as actors driving the conversion of wetland functions who made concrete efforts to encourage change. In hierarchical dynamics 2, a transformation process occurs in socio-cultural society, which is characterized by a process of internalizing a "new perspective" regarding employment status, or economic accumulation, and tends to ignore and even erase the "old perspective" namely the community's traditional life as farmers in a wetland environment.

Faster cycling but lower efficiency: A microbial metabolic perspective on carbon loss after wetland conversion to cropland

Natural wetlands store 20–30% of soil organic carbon (C) in terrestrial ecosystems. Wetlands conversion to croplands has caused a massive loss of soil organic C; however, the microbial contribution to this C loss remains elusive. In this study, we took 24 soil cores from a natural wetland and a 23-year cultivated cropland over four seasons to compare the abundance of functional genes encoding 138 enzymes for ten C-cycling pathways classified as organic C degradation, catabolic and anabolic processes. We found that land use-induced C loss was primarily driven by enhanced organic C degradation (∼24% increase) but suppressed microbial C assimilation efficiency, represented by shifted catabolism and declined anabolism (∼22% decrease). The enhanced organic C degradation was advocated by the enriched genes encoding organic C degradation enzymes; the suppressed microbial C assimilation efficiency was upheld by the shifted catabolic processes and inhibited anabolic processes. Compared with natural wetlands, the croplands showed substantial shifts in catabolic processes - 22% suppression of the Embden-Meyerhof-Parnas pathway, 27% decline in the Citrate Cycle, 22% increase in Entner-Doudoroff, and 25% stimulation in pentose phosphate pathways. Meanwhile, the anabolic process, especially the Wood-Ljungdahl pathway, was significantly suppressed (∼55%) in the cropland. The shifts in organic C degradation, catabolism, and anabolism were stronger in spring and summer than in winter and autumn. At the ecosystem level, microbial metabolic quotient was suppressed by 44%, while microbial biomass carbon was boosted by 5% after wetland conversion to cropland, indicating a faster microbial growth rate but lower C use efficiency. Differentiating microbial metabolic processes explained the C loss after wetland cultivation, indicating an urgency to represent microbial metabolism in soil C models.

Drone Lidar Deep Learning for Fine-Scale Bare Earth Surface and 3D Marsh Mapping in Intertidal Estuaries

Tidal marshes are dynamic environments providing important ecological and economic services in coastal regions. With accelerating climate change and sea level rise (SLR), marsh mortality and wetland conversion have been observed on global coasts. For sustainable coastal management, accurate projection of SLR-induced tidal inundation and flooding requires fine-scale 3D terrain of the intertidal zones. The airborne Lidar systems, although successful in extracting terrestrial topography, suffer from high vertical uncertainties in coastal wetlands due to tidal effects. This study tests the feasibility of drone Lidar leveraging deep learning of point clouds on 3D marsh mapping. In an ocean-front, pristine estuary dominated by Spartina alterniflora, drone Lidar point clouds, and in-field marsh samples were collected. The RandLA-Net deep learning model was applied to classify the Lidar point cloud to ground, low vegetation, and high vegetation with an overall accuracy of around 0.84. With the extracted digital terrain model and digital surface model, the cm-level bare earth surfaces and marsh heights were mapped. The bare earth terrain reached a vertical accuracy (root-mean-square error, or RMSE) of 5.55 cm. At the 65 marsh samples, the drone Lidar-extracted marsh height was lower than the in-field height measurements. However, their strongly significantly linear relationship (Pearson’s r = 0.93) reflects the validity of the drone Lidar for measuring marsh canopy height. The adjusted Lidar-extracted marsh height had an RMSE of 0.12 m. This experiment demonstrates a multi-step operational procedure to deploy drone Lidar for accurate, fine-scale terrain and 3D marsh mapping, which provides essential base layers for projecting wetland inundation in various climate change and SLR scenarios.

Land use change analysis and modeling of its future trajectories in Morogoro Region, Tanzania: Implication for conservation

In Sub-Saharan Africa, where people's livelihoods depend largely on natural resources, understanding land use change dynamics and its implications for the sustainability of social-ecological systems is critical. This study analyzed both historic land use and land cover (LULC) change and trajectories for future change in the Morogoro Region, Tanzania. We mapped LULC in the study area for 1994, 2007 and 2020 using Random Forest in Google Earth Engine and projected future LULC in 2033 using Land Change Modeler. Results revealed that conversion of natural vegetation and wetlands has occurred at a high rate due to cropland expansion and will likely continue over the next decade. Conversion to cropland occurred on the edges of protected areas, in remnant forests and near existing cropland, and was associated with slope, elevation, proximity to settlements and variation in annual precipitation. In landscapes where wildlife shares areas with humans, converting natural vegetation into crop production increases tension and human-wildlife conflicts. Given compounding impacts of a growing human population in Tanzania, and reduced crop yields due to unpredictable rains and prolonged droughts, both human wellbeing and biodiversity conservation require understanding the resulting pressure on land and ecosystems.

Socio-economic impacts of wetland conversion on residents of Port Harcourt municipality, Rivers State, Nigeria

Increased demand for land space in most urban areas often triggers the conversion of wetlands resulting in their total disappearance with attendant implications on man’s survival. This study examined the socio-economic impacts of wetland conversion on residents of Port Harcourt municipality. Data were sourced from both primary and secondary sources. Four (4) out of the twenty-four (24) reclaimed wetland sites were purposively selected for the study. The cross-sectional research design was used since there was no manipulation of the variables under investigation. A sample size comprised 280 heads of households from the eight proximate communities within the four selected reclaimed sites. The study revealed that wetland conversions have both positive impacts on residents of the study area. On a positive note, wetland conversion is a means of increasing land space for needed physical development and the provision of urban goods and services. The negative impacts of wetland conversion include the destruction of sources of livelihood for the people, the destruction of natural heritage and aesthetic areas and the destruction of conservation areas among others. The study advocates for the adoption of a sustainable wetland management strategy with an emphasis on the wise use of wetland resources to ensure the continued existence of wetlands in their pristine state, as this is the only way we can preserve the services that wetland provides to the survival of the human environment.

Planning for sustainability: Historical data and remote sensing-based analyses aid landscape design in one of the largest remnant European floodplains

Large floodplain rivers are among the most threatened ecosystems on Earth and their utilization is expected to grow. Here, we integrated historical data and remote sensing-based landscape analyses and applied stakeholder evaluation of present-day utilization of different river–floodplain habitat types to understand the process of landscape development and provide a basis for sustainable landscape design in one of the largest remnant floodplains of the Danube River, Hungary. Temporal trajectories indicated drastic transformation of the landscape over almost four centuries as a result of river regulation works. Of these, the most substantial were the canalization of the main channel of the Danube into its largest side arm and cutting of large meandering segments, which resulted in the conversion of wetlands to other land uses, particularly agricultural land. The total area of aquatic habitats decreased by more than five-fold, and substantial changes occurred in the extent and composition of river–floodplain habitat types. Evaluation of present-day land use indicated that protected areas are under less human influence and have higher potential for the maintenance of aquatic biodiversity than unprotected ones. Although the protected area network still includes representatives of all floodplain habitat types, past changes and present-day utilization of the landscape limit conservation and restoration possibilities. We provide implications for management and conclude that the joint analyses of historical landscape conditions and present-day evaluation of human utilization can be fruitful to aid the sustainability design and management of river–floodplain ecosystems.

Effects of Temporal and Spatial Changes in Wetlands on Regional Carbon Storage in the Naoli River Basin, Sanjiang Plain, China

The Naoli River (NLR) Basin is a crucial distribution area for wetlands in China. Investigating the link between land use changes and carbon storage in this basin is of significant importance for protecting regional ecosystems and promoting the sustainable development of the social economy. This paper uses long-term Landsat satellite images provided on the GEE (Google Earth Engine) platform and the random forest classification algorithm to create spatial distribution maps of land use in the NLR Basin from 1993 to 2022. The study analyzes the dynamic changes in wetlands in the basin over the past 30 years and employs the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model to explore the temporal and spatial evolution characteristics of carbon storage. The results reveal that the wetland area of the NLR Basin showed a downward trend from 1993 to 2022, with a total decrease of 1507.18 hm2 over 30 years. During this period, the carbon storage in the NLR Basin decreased, with a cumulative loss of 1.98 × 107 t, mainly due to the continuous reductions in wetland and forest land. Additionally, the change in carbon storage in the basin has a strong spatial and temporal relationship with the changes in land use/cover area. The total carbon storage is positively associated with the areas of wetland, forest land, and water bodies. The conversion of wetlands into any other land type results in the reduction in carbon storage. These findings can improve our understanding of the spatial and temporal dynamics of wetlands in the NLR Basin over the past 30 years and enable us to analyze the relationship between land use changes and regional carbon storage. The results of this study have great significance for protecting the wetland ecology and regional carbon balance in the NLR Basin.

Conversion of natural coastal wetlands to mariculture ponds dramatically decreased methane production by reducing substrate availability

Coastal wetlands are increasingly being converted into aquaculture ponds to meet growing global demand for fish protein. Coastal wetlands conversion has been predicted to result in significant carbon (C) emissions; however, a mechanistic understanding of the effects of coastal wetland conversion on soil’s capacity to produce greenhouse gases remains lacking. Here, integrated biogeochemical investigations on methanogenic substrates, community structures, and activities were conducted in a coastal Spartina alterniflora saltmarsh and three saltmarsh-converted mariculture ponds aged 6, 13, and 20 years. Saltmarsh conversion into mariculture ponds decreased CH4 production potential from 353 to 16.3–78.3 µg CH4 kg−1 d−1. The concentrations of dissolved organic C and non-competitive methanogenic substrate, trimethylamine, were reduced by 84.8% and 79.7%, respectively, whereas methanogens abundance decreased by 43.7%, probably due to the decreased C input following conversion. Among the ponds, CH4 production potential, methanogenic substrates (acetate and trimethylamine), and methanogen abundance decreased with conversion chronosequence. However, the dominant methanogen group did not shift after land conversion, and the potential methylamine-utilizing Methanosarcinaceae accounted for 86.5% and 85.3–89.7% of the total populations in the S. alterniflora saltmarsh and mariculture ponds, respectively, implying that methylotrophic methanogenesis was the predominant pathway of CH4 production in both ecosystems. The results indicated that the conversion of natural coastal saltmarsh to mariculture ponds decreased CH4 production by reducing substrate availability and methanogen abundance, and CH4 production potential in mariculture ponds was more efficiently suppressed with conversion chronosequence.