Human Activities Introduced Degenerations of Wetlands (1975–2013) across the Sanjiang Plain North of the Wandashan Mountain, China

Human-induced dramatic loss and fragmentation of wetlands need further understanding through historical backtracking analysis at a geographical landscape scale. In this study, we investigated time-series wetlands maps from 1975, 1983, 1989, 2000, 2006, and 2013 derived from Landsat images based on the object-oriented classification of wetlands across the Sanjiang Plain north of the Wandashan Mountains. The spatial and temporal changes in the wetlands that occurred at different time periods and the Euclidean distances between artificial land-use types and natural land-cover areas were evaluated for their impact. Our results showed that wetland was the dominant landscape in 1975; however, arable land became the main land coverage in 2013 owing to severe changes in agricultural development over the past decades. The closer to arable land, the greater the wetland loss during the entire investigated period; agriculture activities were the dominant driving force for the degradation of wetlands based on landscape changes; secondary was the rapid expansion in building land use (i.e., human settlement, transportation, and establishment of irrigation canals). More specifically, the rapid loss of wetland areas over 1975–2000 was mainly owing to extensive agricultural reclamation. The mitigated loss of wetland areas over 2000–2013 was because of the protection and restored implementation of wetlands under governmental policies. The wetlands of the study area suffered severe human disturbance, and our analysis may help explain the loss process of wetlands, but more effective management and administration is still needed to address the issues around the balance between agricultural production and wetland protection for further sustainable development.

Bamboo Fences as a Nature-Based Measure for Coastal Wetland Protection in Vietnam

Climate change has induced sea-level rise and a high intensity of storms, which create high nearshore waves. These caused severe mangrove degradation and erosion along the coastal wetland areas in the Mekong Delta in Vietnam. Mangroves in the coastal wetland foreshore can withstand only some certain design storm waves and grow under several certain submerged conditions. Therefore, reducing waves and shallowing wetland elevation for recovering mangroves and protecting them in an early birth state is important. Bamboo or melaleuca fences have been used as a nature-based solution to reduce waves and currents approaching the shore for these above purposes along Vietnamese Mekong deltaic coasts. This paper investigates wave transmission through the bamboo fence system and assesses its effectiveness in protecting the mangroves. Waves were simultaneously measured at two locations for comparison: in front of and behind the fences. The result shows that the wave reduction by the fences is considerable, and sedimentation occurs rapidly in the shelter areas behind the fences, which is highly favorable for the recovery and growth of mangroves. Next, the empirical formulae have been proposed for relationships between the wave transmission coefficient of the fence and the dimensionless wave-structures parameters, such as the relative water depth, the wave steepness, and the fence freeboard. The findings create a basic technical reference for designing a naturally friendly-based solution by using bamboo and/or wooden fences in coastal protection generally and protecting mangroves specifically. The outcome of the research contributes to narrowing an existing gap in Vietnamese design guidelines for coastal wetland protection and also facilitates the use of locally available eco-friendly materials for coastal management along the Vietnamese Mekong delta coasts.

Estimating residents' willingness to pay for wetland conservation using contingent valuation: the case of Van Long Ramsar Protected Area, Vietnam

Truong DD. 2021. Estimating residents' willingness to pay for wetland conservation using contingent valuation: the case of Van Long Ramsar Protected Area, Vietnam. Biodiversitas 22: 4784-4793. Willingness to pay (WTP) for wetland conservation is an important basis for designing market-based wetland protection strategies and sustainable wetland management. The main objective of this study is to estimate villagers' WTP for wetland conservation in Van Long Wetland Protected Area, Vietnam, and analyze factors influencing WTP. A questionnaire survey based on the dichotomous contingent valuation method (CVM) was conducted at seven communes surrounding Van Long Ramsar Protected Area (VLPA). The results showed that the local people in the studied area appreciate the roles of the wetland in preserving landscape values, supporting livelihoods, and transmitting values ??to future generations. The value of biodiversity conservation and the value of water filtration and regulation are perceived to a lesser extent in terms of the importance of conservation. Of the 384 respondents, 96% are WTP for wetland conservation at different levels. With the parametric model, the average value of WTP ranges from 300,000 to VND 328,000 VND /family/year. In the non-parametric model, the average of WTP is from 338,000 to 359,000 VND/family/year. The probability of environmental response' that willing to pay for conservation is closely related to their awareness, family income and payment amount. The results also showed optimistic points that the local people are willing to contribute to improving wetland quality. In a general sense, the results of this study make good contributions to the literature related to WTP for wetland conservation in developing countries.

Land Use Change and Driving Force Analysis of Wetland in Poyang Lake Based on Remote Sensing

As an important wetland in the world, Poyang Lake wetland is constantly changing its land use mode due to economic development and human activities, thus affecting the ecological environment of wetland.Landsat remote sensing images from 1986 to 2020 are utilized to obtain land use information data through supervised classification and interpretation. Combined with ENVI and ArcGIS software, five land use type maps are generated by taking 8 years or so as the interval period. Land use transfer matrix and land use dynamic attitude are adopted.This paper analyzes the wetland land use change in Poyang Lake and explores the driving factors of wetland land use change in Poyang Lake.The results show that the wetland land use types in Poyang Lake will change greatly from 1985 to 2020, and the change range of construction land, mudflat, paddy field and dry land is relatively large and shows an increasing trend.The area of water and grassland decreased on the whole, and the transferred area was large, which was mainly transferred to construction land, paddy field and dry land.The woodland area increased slowly, but the change range was not large from the perspective of dynamic attitude.The change of wetland area of reed flat decreased first and then increased, and the overall land use change was relatively gentle.According to the grey correlation analysis, the total population and annual precipitation are the main driving factors of land use change in Poyang Lake wetland.Through the above research, it provides important reference for wetland protection and land resource management of Poyang Lake.

Remote Sensing Approach for Monitoring Coastal Wetland in the Mekong Delta, Vietnam: Change Trends and Their Driving Forces

Coastal wetlands in the Mekong Delta (MD), Vietnam, provide various vital ecosystem services for the region. These wetlands have experienced critical changes due to the increase in regional anthropogenic activities, global climate change, and the associated sea level rise (SLR). However, documented information and research on the dynamics and drivers of these important wetland areas remain limited for the region. The present study aims to determine the long-term dynamics of wetlands in the south-west coast of the MD using remote sensing approaches, and analyse the potential factors driving these dynamics. Wetland maps from the years 1995, 2002, 2013, and 2020 at a 15 m spatial resolution were derived from Landsat images with the aid of a hybrid classification approach. The accuracy of the wetland maps was relatively high, with overall accuracies ranging from 86–93%. The findings showed that the critical changes over the period 1995/2020 included the expansion of marine water into coastal lands, showing 129% shoreline erosion; a remarkable increase of 345% in aquaculture ponds; and a reduction of forested wetlands and rice fields/other crops by 32% and 73%, respectively. Although mangrove forests slightly increased for the period 2013/2020, the overall trend was also a reduction of 5%. Our findings show that the substantial increase in aquaculture ponds is at the expense of mangroves, forested wetlands, and rice fields/other crops, while shoreline erosion significantly affected coastal lands, especially mangrove forests. The interaction of a set of environmental and socioeconomic factors were responsible for the dynamics. In particular, SLR was identified as one of the main underlying drivers; however, the rapid changes were directly driven by policies on land-use for economic development in the region. The trends of wetland changes and SLR implicate their significant effects on environment, natural resources, food security, and likelihood of communities in the region sustaining for the long-term. These findings can assist in developing and planning appropriate management strategies and policies for wetland protection and conservation, and for sustainable development in the region.

Signatures of Wetland Impact: Spatial Distribution of Forest Aboveground Biomass in Tumen River Basin

The Tumen River Basin, located in the cross-border region of China, North Korea, and Russia, constitutes an important ecological barrier in China. Forest here is mainly distributed around wetland, with the distribution of wetland having the potential to regulate regional forest carbon storage. However, the spatially explicit map of forest aboveground biomass (AGB) and potential impact of drivers, i.e., wetland distribution and climate, is still lacking. We thus use a deep neural network and multi-source remote sensing data to quantify forest AGB in the Tumen River Basin. Our results show the mean forest AGB is 103.43 Mg ha−1, with divergent spatial variation along its distance to wetland. The results of correlation analysis showed that with sufficient soil moisture supply, temperature dominant spatial variation of forest aboveground biomass. Noted that using the space for time substitution, we find when wetland decreased by less than 11.1%, the forest AGB decreased by more than 8%. Our result highlight the signatures of wetland impact on its nearby forest carbon storage, and urge the wetland protection, especially under the warming and drying future.

Wetland Changes and Their Relation to Climate Change in the Pumqu Basin, Tibetan Plateau

Wetland ecosystems play one of the most crucial roles in the world. Wetlands have the functions of ecological water storage, water supply, and climate regulation, which plays an indispensable role in global environmental security. The Pumqu River Basin (PRB) is located in an area with extremely vulnerable ecological environment, where climate change is obvious. Understanding wetland distribution, changes and causes in the PRB are of great importance to the rational management and protection of wetlands. Using the Landsat series satellite images, wetlands of this area in 2000, 2010, and 2018 were extracted. The results showed that (1) there were obvious regional differences in wetland types and their distribution patterns in the basin. Wetlands were mainly distributed in areas with slopes less than 12° and at elevations between 4000 m and 5500 m. (2) During the past 20 years, the wetland area in the basin decreased, and the changing trend of wetlands was different. Palustrine wetlands decreased tremendously, riverine and lacustrine wetlands first decreased and then increased, while floodplain wetlands first increased and then decreased. Palustrine wetlands were reclaimed to cultivated land, but the proportion of reclamation is small. (3) Climate dominated wetland changes in the PRB. The changes in riverine and lacustrine wetlands were mainly affected by the warm-season average temperature, the change in palustrine wetlands was mainly related to the annual precipitation and the warm-season average temperature, and the change in floodplain wetlands was related to the warm-season precipitation. To achieve sustainable development, the government plays a guiding role and actively formulates and implements wetland protection policies, such as restricting or prohibiting grazing on wetlands, which play an important role in wetland protection and restoration.

Emerging water scarcity risks in tropical Andean glacier-fed river basins

<p>In the tropical Andes and adjacent lowlands, human and natural systems often rely on high-mountain water resources. Glaciated headwaters play an essential role in safeguarding water security for downstream water use. However, there is mounting concern particularly about long-term water supply as the timing and magnitude of glacier meltwater contribution to river streamflow become less reliable with rapid glacier shrinkage. This concern matches an increase in water demand from growing irrigation, population and hydropower capacity in combination with high social-ecological vulnerabilities threatening sustained water security. Despite important progress in assessing the impacts of glacier shrinkage and consequences for meltwater availability, little is known about the associated hydrological risks and how they propagate downstream. Therefore, integrated approaches are needed that combine a detailed picture of the meltwater propagation through the terrestrial water cycle with human vulnerabilities and exposure to water scarcity. However, the complex topographic and sociocultural setting including scarce data, limited local capacities and frequent water conflicts hamper a more thorough process understanding and water security assessment at a basin scale.</p><p>Under high complexity and uncertainty, we propose a coupled risk framework combining water scarcity hazards, exposed people and multiple human vulnerabilities to address these limitations. An important aspect of the framework is the recognition of knowledge from indigenous and rural communities that can potentially be integrated into current scientific baselines and innovative adaptation debates. Our framework interlinks a broad set of hydroclimatic, socioeconomic and water management variables at unprecedented detail. We put particular emphasis on the quantification and understanding of multidimensional vulnerabilities as a key element for evaluating the enabling effects of these impacts in social-environmental systems. However, the assessment of corresponding vulnerabilities might not be relevant if the degree of the systems’ exposure is not sufficiently addressed. Therefore, we further analyse the interplay of the diverse variables and critical system thresholds that determine the dimensions and spatiotemporal patterns which enable meaningful assessments of cascading processes and interconnected risks to water scarcity.</p><p>Our risk framework provides a thorough baseline to support assessments of future water availability for guiding climate change adaptation, water management, and governance in rapidly changing mountain basins. Nonetheless, remaining uncertainties and limited understanding relate to the availability of local data and highlight the need for additional data collection. Lastly, we identify specific opportunities to explore the use of nature-based solutions, such as source water and wetland protection, in combination with a strong engagement of local communities and policy makers as an efficient pathway to cope with emerging risks to water scarcity in glacier-fed river basins.</p>

Ecological adaptability and population growth tolerance characteristics of Carex cinerascens in response to water level changes in Poyang Lake, China

Water level conditions are the key factors that affect the growth and distribution of wetland plants. Using Carex cinerascens (C. cinerascens) as the study species, we employ indoor simulations and field surveys. Our results show that C. cinerascens can adapt to rhythmic changes in the water level through different adaptation strategies. Compared to that of the control group, plant growth was better with a 0–0.4 cm/d water level rate, and plant growth was in the 42–56 cm range to that a 1.0–1.4 cm/d water level rate. Furthermore, it was observed that 0–0.4 cm/d was the most suitable growth rate, with 0.6–1.0 cm/d and 0–32 cm being the ideal plant tolerance ranges, and increasing to 1.0–1.4 cm/d and 32–56 cm exceeds the plant tolerance threshold. In the middle and late period of the experiment (25–45 d), the ecological characteristics of the plants changed significantly. For example, the root-to-shoot ratio of the plant in the stable water level reached 26.1. In our field observations, plant biomass can be influenced by a variety of environmental factors. The frequency of the species was the largest at an elevation of 15 m, and the growth status of the dominant and companion species of C. cinerascens was weakened with an increase in soil moisture content. The suitable water content for C. cinerascens growth was 27.6–57.3%, the distribution elevation was 12.54–16.59 m, and the optimum elevation was 13.56–15.54 m. The study is expected to provide a reference for wetland ecology research and wetland protection and restoration, a theoretical reference for the coordination of water resource development and utilization of Poyang Lake and ecological protection of important lakes and wetlands, and an important scientific basis for wetland hydrologic regulation, ecological restoration and biodiversity conservation.