Causes Of Wetland Loss Research Articles

Quantitative assessment of the key drives shaping the long-term dynamics of geographically isolated wetlands: A case study within the Nenjiang River Basin, Northeast China.

Geographically isolated wetlands (GIWs) offer a diverse array of ecosystem services and contribute largely to landscape functions. Numerous studies have documented the substantial pressures on wetland ecosystems from both natural changes and human activities worldwide. However, the quantification of these impacts on GIWs remains scarce. This study presents an assessment of the spatiotemporal dynamics of GIWs in the downstream portion of the Nenjiang River Basin, Northeast China, over a 38-year period (1978-2015). We quantitatively evaluated the impacts of anthropogenic activities and natural changes using a five-stage wetland dataset (1978, 1990, 2000, 2008, and 2015) and four-stage (1990, 2000, 2010, and 2015) land use datasets. Our findings indicate that 86% of the GIWs in the study area have vanished, primarily replaced by unused land (28.39%) and farmland (54.90%). Anthropogenic activities were identified as the main cause of wetland loss from 1978 to 2008, whereas natural changes have played a more significant role in recent years of GIWs. Considering the ongoing regional trends of warming and drying, it is imperative to conserve and restore GIWs to maintain their ecosystem services for a broad spectrum of beneficiaries.

Multi-scale spatiotemporal wetland loss and its critical influencing factors in China determined using innovative grid-based GWR

Wetlands serve as a critical habitat for many plants and animals. However, with urban expansion and other processes, the wetlands in China are lost at an alarming rate in recent decades. This study quantifies the pace of wetland loss in the past two decades and investigates the hidden mechanisms of wetland loss via a proposed innovative grid-based geographically weighted regression computing unified device architecture (Grid-GWR-CUDA) method. Also assessed in this study is the relative importance of four natural factors (precipitation, digital elevation model (DEM), slope, evaporation), and four human related factors (distance to city, distance to roads, population, and gross domestic product (GDP)) in wetland loss at both the national and regional levels. The importance of some critical factors is compared across different regions. The results indicated that GDP, population size and DEM are the three most significant factors impacting on the rate of wetland loss at the national level. They are still the most influential factors for most regions at the sub-national level while precipitation is an important factor only in the eastern regions. Therefore, the main causes of wetland loss in China are attributed to human socioeconomic activities. Compared with the traditional geographically weighted regression (GWR) method, the proposed Grid-GWR-CUDA method is innovative enough to handle large data volumes efficiently while retaining all data samples at a fine (e.g., 30 m) spatial resolution because the computational efficiency is significantly improved via graphics processing unit (GPU) acceleration. It improves the accuracy of regression by several folds over traditional ordinary least square and GWR. It has the potential to predict future wetland loss if supplied with the latest land cover data.

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.

Spatiotemporal dynamics of wetlands and their driving factors based on PLS-SEM: A case study in Wuhan

Globally, wetlands have been severely damaged due to natural environment and human activities. Understanding the spatiotemporal dynamics of wetlands and their driving forces is essential for their effective protection. This study proposes a research framework to explore the interaction between the natural environment and human activities and its impact on wetland changes, by introducing Partial Least Squares Structural Equation Modeling (PLS-SEM) and Geographically Weighted Regression (GWR) model, then applying the methodology in Wuhan, a typical wetland city in China. The validity and reliability evaluation indicated that the PLS-SEM model is reasonable. The results showed that the area of wetlands in Wuhan decreased by 10.98% in 1990–2018 and four obvious direct pathways of influence were found. Positive soil and terrain conditions are conducive to maintaining wetlands, while rapid urbanization drastically reduce the distribution of wetlands. It is remarkable that the impact of climate on wetlands is gradually shifting from positive to negative. Furthermore, four potential indirect impact pathways affecting wetland distribution shown that urbanization and climate enhance the negative impact of terrain on wetland distribution, while their impacts on soil weaken soil's direct positive impact. This study provides a quantitative methodology for determining the causes of wetland loss; it can also be applied to other cities or regions, which is essential for applying more effective measures to protect wetlands.

Tracking Historical Wetland Changes in the China Side of the Amur River Basin Based on Landsat Imagery and Training Samples Migration

In the recent decades, development of agricultural and human settlements have severely affected wetlands on the China-side of the Amur River Basin (CARB). A long-term holistic view of spatio-temporal variations of the wetlands on the CARB is essential for supporting sustainable conservation of wetlands in this region. In this study, a training sample migration method along with Random Forest classifier were adopted to map wetland and other land covers from two key seasons image collections. The proposed classification method was applied to Landsat images, and a 30-m resolution dataset was obtained, which reflected the dynamic changes of historical wetland distribution on the CARB region from 1990 to 2010. As the accuracy assessments showed, land cover maps of the CARB had high accuracies. The classification results indicated that the wetland area decreased from 89,432 km2 to 75,061 km2 between 1990 and 2010, with a net loss of 16%, which was mainly converted to paddy field and dry farmland, and the changes were most obvious in Sanjiang Plain and Songnen Plain. This suggests that agricultural activities are the main cause of wetland loss. The results can provide reliable information for the research on wetland management and sustainable development of the society and economy in the CARB.

Wetland changes in the Amur River Basin: Differing trends and proximate causes on the Chinese and Russian sides

According to the United Nations Sustainable Development Goals (SDGs), understanding the extent of wetlands, their change trends and the proximate causes is important for the conservation of wetlands and endangered waterfowls. Here we studied the world's ninth largest river basin, the Amur River Basin (ARB), with a land area of 2.08 million km2. Our objectives were to address the information deficiencies of spatially explicit wetland distributions and their changes and to quantify the proximate causes of these changes in various periods in the ARB. A hybrid approach combining object-based and hierarchical decision-trees classification (HOHC) was applied to Landsat series images to obtain multitemporal land cover datasets from 1980 to 2016. Further quantitative analysis revealed that the ARB held 184,561 km2 of wetlands in 2016, accounting for 9% of the whole basin area. Among these, 59% of the wetlands were identified on the Russian side, while 40% were on the Chinese side, and 1% were on the Mongolian side. The ARB lost 22% of its wetland (52,246 km2) from 1980 to 2016, with a consistent net loss from 1980 to 2010 but an area gain from 2010 to 2016. Human activities dominated the consistent wetland losses on the Chinese side of the ARB, of which cropland expansion was the primary proximate cause of wetland loss (69%). Conversely, the wetlands on the Russian side had consistent losses from 1980 to 2010 followed by a gain from 2010 to 2016, which could be attributed to climate change. These quantified data will inform decision-making on wetland conservation and benefit scientific studies depending on spatially explicit wetland information.

Saltmarsh grass supports fishery food webs in subtropical Australian estuaries

All fishery food webs are ultimately underpinned by organic matter produced by algae and plants, some of it supplied by primary producers at the fringes of fish habitats. This is no different in tropical and subtropical estuaries where secondary production by crustaceans and finfish may depend on coastal wetlands (e.g. mangroves, seagrass, saltmarshes) abutting channels. Coastal urbanisation is a major cause of wetland loss globally. Hypothetically, reduced wetland area may propagate to less fisheries production if wetland contributions to food webs are substantial – this is the prime question addressed here. We sampled key fisheries species in subtropical estuaries in reaches of moderate urbanisation (18–33% of shoreline hardened) and in reference locations dominated by wetlands, on the east coast of Australia. We used triple stable isotopes (C, N, S) to estimate (using mixing models) the trophic contributions of the key primary producers to regional fisheries species. Organic matter from wetland plants, particularly saltmarsh grass (Sporobolus virginicus), underpinned fishery food webs in most cases (with median contributions ranging from 18 to 88% for saltmarsh grass, followed by 6–70% for C3 wetland plants (e.g. mangroves, phragmites) and 3–36% by benthic algae). Moderate levels of urban transformation of estuarine margins did not change the dominance of wetland carbon for fish and crustaceans in settings without significant seagrass meadows. Given the demonstrated importance of saltmarshes, and other coastal wetlands, to regional fisheries production, conservation of these habitats is necessary in the face of multiple anthropogenic threats.

Canals, backfilling and wetland loss in the Mississippi Delta

Canals and spoil banks have contributed significantly to high rates of wetland loss in the Mississippi Delta. There has been relatively little research on management of canals and spoil banks and this needs to be a significant component of restoration of the delta. We analyze research on the role of backfilling canals in the context of delta restoration with special reference to Turner and McClenachan (2018) who state that if all canals were backfilled, it could significantly reduce or even reverse wetland loss and that most wetland loss is caused by canals. We agree with Turner and McClenachan that canals have been a significant cause of wetland loss in the Mississippi Delta and that removing spoil banks and backfilling canals should be an integral part of delta restoration. However, a number of factors need to be considered when choosing which canals to backfill including possible enhanced erosion due to exposure to wave action for newly created and remnant marsh, the current and future production history of oil and natural gas wells associated with canals, and other restoration activities in oil and gas fields. Turner and McClenachan's analysis using wetland loss patterns in 15-min quadrangles suggesting that canal density can explain most wetland loss in coastal Louisiana is flawed because of scale problems and other impacts of oil and gas activity. These impacts include subsurface induced subsidence and the impact of produced water and toxins on wetlands that are largely unrelated to surface alteration due to canals and spoil banks.

Urban development versus wetland loss in a coastal Latin American city: Lessons for sustainable land use planning

Urbanization is a primary cause of wetland loss in coastal metropolitan regions. Therefore, it challenges the preservation of biodiversity and the provision of key ecosystem services for urban settlements. These services include leisure and recreation, climate and water regulation, water purification, and especially alleviation of natural hazards. Tsunami flood mitigation is a particularly valuable regulating service provided by these wetlands, as recently evidenced during the 2010 tsunami that hit the central coast of Chile.The Concepción Metropolitan Area (CMA), located on the central coast of Chile, has experienced noticeable wetland loss in recent decades. Our study focused on the Rocuant-Andalién wetland, which has been particularly affected by urbanization. This wetland strongly contributes to flood control, and has provided effective protection against the CMA’s latest tsunamis (1835 and 2010). Based on Strategic Environmental Assessment (SEA), we have quantified urban growth over the wetland, both executed and projected under the Metropolitan Urban Plan of Concepción (MUPC). Recent loss in wetland area by urban growth has been quantified using land use and cover change (LUCC) maps from 2004 to 2014, obtained from the classification of Landsat images. Prospective changes (considering the complete MUPC deployment) have been inferred by combining the MUPC with the 2014 land cover map. In addition, we quantified the observed effect and planned urban growth on the wetland protected area, geoforms and potential flooding based on the area affected by the last Tsunami. Results show that urban areas have increased by 28% between 2004 and 2014, while future increase is expected to reach 238%. In contrast, wetland area has decreased by 10% from 2004 to 2014 and is expected to decrease by up to 32 %. Thus, the MUPC is not contributing to the mitigation of wetland loss nor the preservation of its biodiversity and ecosystem services. Implications for coastal planning are discussed.

Spatial Association of Wetlands over Physical Variants in Barind Tract of West Bengal, India.

<p><strong>Abstract: </strong>Barind tract of west Bengal is an uplifted old alluvial plain area where only <1 percent area is covered by wetland. Present paper concentrates on general understanding of wetland association with different geographical settings like geological, geomorphological lithological structure and altitudinal gradations. Detail investigation reveals that geological and morphological structure do not have deep influence on wetland formation and their distribution in particular favourable sub-region. But altitudinal control on wetland is noticeable. An irregular distribution of wetland is found throughout the region because of multi parametric influence on it. In recent decades wetlands in barind tract has been undergoing into rapid loss. Continuous encroachment of agricultural field and newly built-up area to wetland are considered as main causes of wetland loss in barind tract. </p>

Anthropogenic causes of wetland loss and degradation in the lower Kłodnica valley (southern Poland)

Abstract Loss and degradation of wetlands is now one of the most important environmental issues on a global scale. Previous research based on analyses of cartographic materials allow for quantification of changes in wetland area in recent centuries. The results of lithological research of peat cores, reported in this publication, have established that the processes of anthropogenic loss of wetlands can be much older and in the Kłodnica valley were initiated in the first millennium BC. As a result of increased mineral sedimentation accompanying soil erosion some peatlands have been fossilized whilst the area of others has been reduced. In total, the surface area of peat-forming wetlands in the bottom of the Kłodnica valley decreased by over 60% between the time of the Lusatian Culture settlement and the Middle Ages. Post-peatland habitats are recently used for agricultural or colonized by non-peat forming vegetation. These processes have played a more important role in the degradation of peatland ecosystems than the direct human impact in historic times. Changes in hydrographic networks, land drainage and regulation of water levels in rivers and canals in the last century have contributed to further reducing the wetland areas by almost 50% compared to the 1880s. These processes, however, have mainly affected ephemeral non-peat forming wetlands.

Wetland Loss and Research Orientation

The literature analysis method used in this paper outlines variations in research topics. We tested whether research on wetlands is topic-centered, comparative of different wetland classes, or aimed at wetland loss. We analyzed research papers to identify clusters of research activity and interpreted these clusters relative to wetland function and type. Furthermore, a case study on 61 papers was conducted in order to find a critical path of wetland loss induced by different causes. From this case study, it was determined that agriculture is regarded as a root cause of wetland loss.

Hurricanes, Floods, Levees, and Nutria: Vegetation Responses to Interacting Disturbance and Fertility Regimes with Implications for Coastal Wetland Restoration

A primary cause of wetland loss in the Louisiana coastal zone has been the construction of flood control levees along the Mississippi River. These levees restrict the inputs of freshwater, nutrients, and sediment that historically replenished these wetlands. Wetland loss is compounded by other factors such as storms, introduced herbivores, and saltwater intrusion. How do such simultaneous changes in fertility and disturbance regimes affect the vegetation of coastal wetlands? Will proposed restoration strategies, such as freshwater diversions and protection from herbivores, increase the productivity and accretion rates of coastal wetlands without sacrificing plant species diversity? During this 2-year study, we applied five disturbance treatments (control, fire, herbivory, single vegetation removal, and double vegetation removal) and four fertility treatments (control, sediment addition, fertilizer addition, and sediment fertilizer addition), using a split-plot factorial design with herbivory exclosures as main plots and species richness and total aboveground biomass as dependent variables. We found that nutria, the principal vertebrate herbivore of the marsh, limited biomass production. Other disturbances decreased biomass, but only to a limited extent in the absence of herbivores. The sediment fertilizer treatment, which simulated the additional nutrients and substrate material that a freshwater diversion might deliver, significantly increased biomass production. Fertilizer significantly increased the biomass only in the absence of herbivores. We had limited success in predicting species richness after 2 years. Only the most severe disturbance decreased species richness, whereas fertilizer addition seemed to have a minor effect (p = 0.08). Sediment- and nutrient-rich waters from freshwater diversions will likely mitigate negative impacts of nutria grazing on biomass and have no effect on species richness. However, it should be noted that freshwater diversions will have the most impact if nutria populations are reduced.

Louisiana’s Wetlands: A Lesson in Nature Appreciation

Hurricane Katrina’s disastrous flooding of the Gulf Coast confirmed three decades of warnings by scientists. Most of New Orleans is below sea level, and South Louisiana’s coastal wetlands, which once helped buffer the city from giant storms, have been disappearing at a spectacularly swift pace. Now some researchers are calling for restoration of wetlands and barrier islands to help protect New Orleans the next time a hurricane strikes. An average of 34 square miles of South Louisiana land, mostly marsh, has disappeared each year for the past five decades, according to the U.S. Geological Survey (USGS). As much as 80% of the nation’s coastal wetland loss in this time occurred in Louisiana. From 1932 to 2000, the state lost 1,900 square miles of land to the Gulf of Mexico. By 2050, if nothing is done to stop this process, the state could lose another 700 square miles, and one-third of 1930s coastal Louisiana will have vanished. Importantly, New Orleans and surrounding areas will become ever more vulnerable to future storms. “New Orleans can’t be restored unless we also address coastal and wetland restoration too,” says Craig E. Colten, a geographer at Louisiana State University (LSU).

Assessing cumulative loss of wetland functions in the Nanticoke River watershed using enhanced National Wetlands Inventory data

The coterminous U.S. has lost more than 50% of its wetlands since colonial times. Today, wet- lands are highly valued for many functions including temporary storage of surface water, streamflow main- tenance, nutrient transformation, sediment retention, shoreline stabilization, and provision of fish and wildlife habitat. Government agencies and other organizations are actively developing plans to help protect, conserve, and restore wetlands in watersheds. The U.S. Fish and Wildlife Service's National Wetlands Inventory Program (NWI) has produced wetland maps, digital geospatial data, and wetland trends data to aid these and other conservation efforts. Most recently, the NWI has developed procedures to expand the amount of information contained within its digital databases to characterize wetlands better. It has also developed techniques to use these data to predict wetland functions at the watershed level. Working with the states of Delaware and Maryland, the NWI applied these techniques to the Nanticoke River watershed to aid those states in developing a watershed-wide wetland conservation strategy. Wetland databases for pre-settlement and contemporary conditions were prepared. An assessment of wetland functions was conducted for both time periods and comparisons made. Before European settlement, the Nanticoke watershed had an estimated 93,000 ha of wetlands covering 45% of the watershed. By 1998, the wetland area had been reduced to 62% of its original extent. Sea-level rise and wetland conversion to farmland were the principal causes of wetland loss. From the functional standpoint, the watershed lost over 60% of its original capacity for streamflow maintenance and over 35% for four other functions (surface-water detention, nutrient transformation, sedi- ment and particulate retention, and provision of other wildlife habitat). This study demonstrated the value of enhanced NWI data and its use for providing watershed-level information on wetland functions and for assessing the cumulative impacts to wetlands. It provides natural resource managers and planners with a tool that can be applied consistently to watersheds and large geographic areas to show the extent of wetland change and its projected effect on wetland functions.

Ecological impacts and institutional and economic drivers for water resource development—a case study of the Murrumbidgee River, Australia

Much of the world's water for humans comes from rivers for drinking, generating hydro-electricity, industry and irrigation. Dams and diversions reduce downstream flows, particularly to floodplain wetlands, and their fauna and flora. For many countries, including Australia (75% of water use), the greatest user of water is irrigated agriculture. The Murrumbidgee River in the Murray-Darling Basin is one of the most regulated major rivers in Australia. Water resource development, including the building of 26 storages, over more than 140 years on the Murrumbidgee River in southeastern Australia destroyed or degraded at least 76% of the floodplain that once covered 304,000 ha. Remaining wetland areas are also considerably altered. Water resource development in the catchment with subsequent diversion of water and recent development of the floodplain were the main causes of wetland loss. Establishment of two major irrigation areas in Australia, the Snowy Mountains Hydro-electric Scheme and Australia's capital, Canberra were all drivers for upstream development of water. The major local drivers were community values and expectations of water, reflected in Government decisions and legislation. The water and hydro-electricity agencies were primarily responsible for most of the water resource development before the 1970. After 1980, changing expectations on the Lower Murrumbidgee floodplain and Government investment produced rapid development of the floodplain for irrigation. Likely environmental costs were not adequately considered or made explicit for transparent decision-making. Such case studies need to be used when considering likely impacts of future water resource developments on other river systems.

Reasons for the loss and degradation of Australian wetlands

Wetland conservation and management in Australia is not supported by a comprehensive information base. A national inventory has not been compiled and we have very little information on the areal extent and loss of wetlands. Further, we have little information on the values and benefits (products, functions and attributes) derived from wetlands and how these have been degraded or lost. We do know, however, that in some areas at least, wetland loss and degradation has been severe and may even be still occurring. Much of the scientific attention to wetland management has been directed towards the apparent (or ecological) reasons for wetland loss and degradation – changes to the water regime, physical modification of the habitat, eutrophication and other pollution, and invasion by exotic pest species. Lists of threats to wetlands have been compiled, but these rarely address the non-ecological reasons that have resulted in so many wetlands being lost or degraded. In this paper we summarize the key points made from a number of case studies of Australian wetlands that highlight the non-ecological causes of wetland loss and degradation. From this analysis we conclude that awareness and understanding about the non-ecological causes of wetland loss and degradation need to be as well understood as the ecological causes. Foremost amongst these we highlight greater attention to the following issues: economic development in wetlands, bureaucratic obstacles, lack of information or poor access to information, and poor general awareness of the values and benefits derived from wetlands. We further conclude that wetland loss and degradation does not need to happen – our wetlands are valuable and already severely degraded. For this situation to be rectified we need to ensure that the knowledge and expertise of wetland scientists is heard and heeded by decision-makers and wetland users and owners.

Wetland degradation and loss in the rapidly urbanizing area of Portland, Oregon

An inventory was conducted of small (≤2 ha) freshwater wetlands composed of some combination of open water and emergent marsh in the metropolitan area of Portland, Oregon to (1) document changes in the wetland resource since the National Wetlands Inventory (NWI) was conducted (1981/1982 aerial photograph dates) and (2) identify patterns in wetland loss and degradation over a 10-year period in a rapidly urbanizing area. Wetlands identified on NWI maps were visited during summer 1992, and data on the location, wetland type, and surrounding land use or the cause of loss were collected. Of the 233 wetlands identified by NWI in 1981/1982, approximately 40% had been destroyed by human activities or were missing due to drought. Although conversion to urban land uses was the predominant cause of wetland loss from human activities, agricultural conversion accounted for about 31%. Drier-end wetlands (e.g., seasonally flooded) were missing from the landscape most frequently. Of the 141 wetlands still existing, 25% were severely degraded by human activities. Approximately half of those wetlands not severely degraded were affected by noise, and about 40% were disturbed, primarily by grazing and littering. We suggest that because land uses change quickly in rapidly urbanizing areas, leading to increased pressures to convert wetlands, resource agencies and urban planners should conduct similar inventories in other metropolitan areas. Then, demographic projections could be used in conjunction with information on patterns in wetland loss to identify and prioritize areas for wetland protection before development takes place.