Wetland Inventory Research Articles

Mapping Geographically Isolated Wetlands in the Dougherty Plain, Georgia, USA

Increasing interest in isolated wetlands requires an understanding of the location, spatial extent, and configuration of the resource. The National Wetlands Inventory (NWI) is the most commonly used data source for this information; however, the accuracy is limited in some contexts, e.g., agricultural, seasonally-ponded, or forested wetlands. This study sought to improve isolated wetland mapping accuracy by integrating currently available NWI maps with other geospatial data sources (i.e., Soil Survey Geographic Database [SSURGO], Digital Raster Graphics [DRGs], and Digital Elevation Models [DEMs]). Relative to NWI, the optimal model (combining data derived from NWI, SSURGO, and DRGs) identified 1,874 additional isolated wetlands and 19,737-ha of additional isolated wetland area. A remote accuracy assessment indicated a high degree of accuracy for the optimal model (Kappa = 0.88, Sensitivity = 90%, and Specificity = 98%), as compared to NWI maps (Kappa = 0.70, Sensitivity = 68%, and Specificity = 99%). Small wetlands (< 4-ha) dominated the wetland population and reduced nearest neighbor distances between wetlands. Isolated wetlands were clustered and clustering was strongest among larger wetlands. This study identified a framework for improving the accuracy of wetland maps and serves as a foundation for ongoing wetland studies within the Dougherty Plain.

A multi-temporal remote sensing approach for monitoring changes in spatial extent of freshwater lake of Deepor Beel Ramsar Site, a major wetland of Assam

Sustainability of wetland ecosystem is necessary for various important functions such as food storage, water quality continuation and providing habitat for different species of flora and fauna. Hence, an inventory of wetlands of any region is a pre-requisite for their conservation and management. This study has been carried out to delineate the change in freshwater lake of ‘Deepor Beel’ wetland of Assam, India, using LANDSAT TM data. Field observation shows that the ecosystem is facing both natural as well as anthropogenic threats. Rapid urbanization, Illegal settlements, industries, invasive species (Eichhornia crassipes) are the major cause of this wetland decline. It has been found that massive decline occurred between the period 1991 to 2001 i.e., 1.891 sq.km which was at the rate of -0.171 per year where as the decline between the period 2001 to 2010 was found to be 1.013 sq. km which was at a rate of -0.101. The total area of open water bodies has decreased by 2.904 sq. km from 1991 to 2010 i.e. 59.19%. Thus the overall rate of change in the water bodies from 1991 to 2010 to other land use categories was found to be -0.145. Hence the study reveals the potentiality of Landsat TM data mapping the change in the wetland ecosystem. It is further hoped that the study will have high utility in preparing management plan for conservation of this ecosystem. Keywords: Wetland; Landsat TM; Thresholding; density sliceDOI: http://dx.doi.org/10.3126/jowe.v5i0.4696 J Wet Eco 2011 (5): 40-47

Ecosystem services delivered by small-scale wetlands

The benefits of small-scale wetlands have been largely overlooked, primarily because (a) such areas are considered problematic to manage, and (b) small wetlands fall outside the remit of most wetland inventories. The subsequent paucity of information prevents a comprehensive investigation of their properties and this must be addressed. Here we examine the evidence for the potential significance of small wetlands with regard to delivery of ecosystem services (ESs) and conclude that small wetlands often have a positive effect on their delivery, especially water quality, water regulation and biodiversity conservation. However these benefits can be offset by the emission of greenhouse gases. We suggest that, in future, wetlands should not be assessed on size alone, but rather in the context of both their location in the landscape and interaction with hydrological pathways. Furthermore, tools need to be developed to assess the type and efficiency of ESs delivered from all wetlands. Editor Z.W. Kundzewicz; Guest editor M.C. Acreman Citation Blackwell, M.S.A. and Pilgrim, E.S., 2011. Ecosystem services delivered by small-scale wetlands. Hydrological Sciences Journal, 56 (8), 1467–1484.

Wetland hydrologic class change from prior to European settlement to present on the Des Moines Lobe, Iowa

It has been hypothesized that wetland restoration policies have favored the restoration of the wettest classes of wetlands on the Des Moines Lobe of the prairie pothole region. To test this hypothesis we compared pre-drainage wetland distributions based on soils data and National Wetland Inventory (NWI) estimates of contemporary wetland distributions on the Des Moines Lobe. Based on the NWI data, the Des Moines Lobe today has only 3–4% of the wetland area that it had prior to the onset of drainage. On the basis of their soils, pre-drainage wetlands were predominantly temporarily flooded to saturated wetlands (84%), with only about 6% of the wetlands with water regimes classified as semi-permanently to permanently flooded. Depending on the interpretation of wetland modifiers on NWI maps, wetlands classified by the NWI as semi-permanent to permanently flooded make up more than 41% of the wetland area while wetlands with temporarily flooded to saturated water regimes account for 45–58% of the Lobe’s wetland area. The water regimes of contemporary wetlands when compared to their historic regimes suggest that many of today’s wetlands have different water regimes than they did prior to the onset of drainage. Because of the regional lowering of the groundwater table, many of today’s wetlands have drier water regimes, but some have wetter water regimes because they receive drainage tile inputs. Our results indicate that restoration has favored the wettest classes of wetlands and that temporarily to saturated wetland classes have not been restored in proportion to their relative abundance in the pre-drainage landscape.

Developing a Hydrogeomorphic Wetland Inventory: Reclassifying National Wetlands Inventory Polygons in Geographic Information Systems

The National Wetlands Inventory (NWI) is the most extensive inventory of wetland resources in the U.S., but it has limited ability to contribute to characterizations of wetland functions. We provide a methodology for reclassifying NWI polygons into Hydrogeomorphic (HGM) classes to facilitate monitoring wetland functions. We conducted this reclassification using spatial and attribute queries within Geographic Information Systems (GIS) for wetlands in central Oklahoma. Once classified, 149 randomly selected wetlands in four HGM classes (depressional, lacustrine fringe, riverine, and impounded depressional) were field verified. The overall accuracy of the GIS classification was 60%. Inherent issues with NWI due to attribute accuracy, spatial accuracy, and map age accounted for >50% of the misclassified sites in this analysis. The results from this analysis were also used to provide an inventory of wetlands in each HGM class and subclass based on user’s accuracy metrics. Reclassifying NWI polygons into HGM classes can assist with determining the spatial distribution and relative abundance of specific wetland classes which allows for more focused wetland restoration and monitoring efforts. However, the error rate associated with reclassification should be calculated to ensure that incorrect conclusions are not drawn regarding the abundance of HGM wetland classes and their associated functions.

How wetland type and area differ through scale: A GEOBIA case study in Alberta's Boreal Plains

It is estimated that Canada comprises approximately 28% of the world's wetlands (~ 1.5 million km 2) providing essential ecological services such as purifying water, nutrient cycling, reducing flooding, recharging ground water supplies, and protecting shorelines. In order to better understand how wetland type and area differ over a range of spatial and thematic scales, this paper introduces a multi-scale geographic object-based image analysis (GEOBIA) approach that incorporates new object-based texture measures ( geotex) and a decision-tree classifier ( See5), to assess wetland differences through five common spatial resolutions (5, 10, 15, 20 and 30 m) and two different thematic classification schemes. Themes are based on (i) a Ducks Unlimited (DU: 15 class) regional classification system for wetlands in the Boreal Plain Ecosystem and (ii) the Canadian Wetland Inventory (CWI: 5 classes). Results reveal that the highest overall accuracies (67.9% and 82.2%) were achieved at the 10 m spatial resolution for both the DU and CWI classification schemes respectively. It was also found that the DU wetland types experienced greater area differences through scale with the largest differences for both classification schemes occurring in classes with a large treed component. Results further show that the inclusion of geotex channels (generated from dynamically sized and shaped window that measures the spatial variability of the wetland components composing a scene, rather than of individual pixels within a fixed sized window) improved wetland classification.

The integration of optical, topographic, and radar data for wetland mapping in northern Minnesota

Accurate and current wetland maps are critical tools for water resources management, however, many existing wetland maps were created by manual interpretation of one aerial image for each area of interest. As such, these maps do not inherently contain information about the intra- and interannual hydrologic cycles of wetlands, which is important for effective wetland mapping. In this paper, several sources of remotely sensed data will be integrated and evaluated for their suitability to map wetlands in a forested region of northern Minnesota. These data include: aerial photographs from two different times of a growing season, National Elevation Dataset and topographical derivatives such as slope and curvature, and multitemporal satellite-based synthetic aperture radar (SAR) imagery and polarimetric decompositions. We identified the variables that are most important to accurately classify wetland from upland areas and discriminate between wetland types for a forested region of northern Minnesota using the decision-tree classifier randomForest. The classifier was able to differentiate wetland from upland and water with 75% accuracy using optical, topographic, and SAR data combined, compared with 72% using optical and topographical data alone. Classifying wetland type proved to be more challenging; however, the results were significantly improved over the original National Wetland Inventory classification of only 49% compared with 63% using optical, topographic, and SAR data combined. This paper illustrates that integration of remotely sensed data from multiple sensor platforms and over multiple periods during a growing season improved wetland mapping and wetland type classification in northern Minnesota.

Visualizing Plant Community Change Using Historical Records

Ecological data from land surveys from 1811 for the 100,000-acre Connecticut Tract in western New York were transcribed and then analyzed using ArcGIS and IDRISI GIS software. The surveys contained both witness tree data and line descriptions, which were analyzed for species composition and community type. Results illustrate that many changes have occurred in species composition. Possible causes of these changes to the mature forests may include introduced pests and diseases or anthropogenic land-use change. Comparisons to the National Wetlands Inventory Database reveal that while some of the wetlands that were present in 1811 still exist today, particularly in the Byron-Bergen Swamp and in the wetlands along the Lake Ontario shoreline, other original wetlands have been lost while new wetlands have replaced some upland forests. This study helps elucidate past causes of temporal and spatial variability, and it provides a reference point for land managers who need to understand the effects of land-use history for ongoing restoration efforts.

Risk of Inundation to Coastal Wetlands and Soil Organic Carbon and Organic Nitrogen Accounting in Louisiana, USA

Exceeding 1.2 million acres (4856 km(2)) since the 1930s, coastal wetland loss has been the most threatening environmental problem in Louisiana, United States. This study utilized high-resolution LiDAR (Light Detection and Ranging) and DEM (Digital Elevation Model) data sets to assess the risk of potential wetland loss due to future sea level rises, their spatial distribution, and the associated loss of soil organic carbon (SOC) and organic nitrogen (SON) estimated from the State Soil Geographic (STATSGO) Database and National Wetlands Inventory (NWI) digital data. Potential inundation areas were divided into five elevation scales: < 0 cm, 0-50 cm, 50-100 cm, 100-150 cm, and 150-200 cm above mean sea level. The study found that southeastern Louisiana on the Mississippi River Delta, specifically the Pontchartrain and Barataria Basins, are most vulnerable to sea-level rise induced inundation. Accordingly, approximately 42,264,600 t of SOC and 2,817,640 t of SON would be inundated by 2050 using an average wetland SOC density (203 t per hectare) for the inundation areas between 0 and 50 cm. The estimated annual SOC and SON loss from Louisiana's coast is 17% of annual organic carbon and 6-8% of annual organic nitrogen inputs from the Mississippi River.

A field based statistical approach for validating a remotely sensed mangrove forest classification scheme

Amongst the most threatened ecosystems on Earth, mangrove forests are also one of the more difficult to work in due to their growth in mud and open water coastal zones and their dense tangled stems, branches and prop roots. Consequently, there has been an impetus to employ remotely sensed imagery as a means for rapid inventory of these coastal wetlands. To date, the majority of mangrove maps derived from satellite imagery utilize a simple mangrove classification scheme which does not distinguish mangrove species and may not be useful for conservation and management purposes. Although more elaborate satellite based mangrove classification schemes are being developed, given their enhanced complexity they deserve additional justification for end users. The purpose of this study was to statistically examine the appropriateness of one such classification scheme based on an inventory of field data. In January of 2007 and May of 2008, 61 field sample plots were selected in a stratified random fashion based on a previous classification of a degraded mangrove forest of the Isla La Palma (Sinaloa, Mexico) using Landsat TM5 data. Unlike other previous Landsat TM based classifications of this region, which simply identified the mangrove forests as one class, the mangroves were classified (i.e. mapped) according to four conditions; healthy tall, healthy dwarf, poor condition, and dead mangroves. Within each sample plot, all mangroves of diameter of breast height (dbh) greater than 2.5 cm were identified and their height, condition and dbh recorded. An estimated Leaf Area Index (LAI) value also was obtained for each sample and the shortest distance from the center of each sample plot to open flowing water was determined using a geographic information system (GIS) overlay procedure. These data were then used to calculate mean values for the four classes as well as to determine stem densities, basal areas, and the Shannon–Wiener diversity index. In order to assess the appropriateness of this mangrove classification scheme a discriminant analysis approach was then applied to these field data. The results indicate this forest has undergone severe degradation, with decreasing mean tree heights, mean dbh and species diversity. In regards to the discriminant analysis procedure, further classification of these field plots and cross-validation based on these significant variables provided high classification accuracy thus validating the appropriateness of the satellite based image classification scheme. Moreover, the discriminant analysis indicated that the estimated LAI, mean height, and mean dbh are significant in the separation of the classification of mangrove forest condition along these field sample plots.

A Classification of Major Naturally-Occurring Amazonian Lowland Wetlands

Our estimates indicate that about 30% of the seven million square kilometers that make up the Amazon basin comply with international criteria for wetland definition. Most countries sharing the Amazon basin have signed the Ramsar Convention on Wetlands of International Importance but still lack complete wetland inventories, classification systems, and management plans. Amazonian wetlands vary considerably with respect to hydrology, water and soil fertility, vegetation cover, diversity of plant and animal species, and primary and secondary productivity. They also play important roles in the hydrology and biogeochemical cycles of the basin. Here, we propose a classification system for large Amazonian wetland types based on climatic, hydrological, hydrochemical, and botanical parameters. The classification scheme divides natural wetlands into one group with rather stable water levels and another with oscillating water levels. These groups are subdivided into 14 major wetland types. The types are characterized and their distributions and extents are mapped.

Insight to Ecosystem Based Approach (EBA) at Landscape Level Using a Geospatial Medium

Ecosystem based approach (EBA) for resource management is a concerted, environmentally tuned and an integrated framework that holistically addresses the ecological character of the natural resource, its societal benefit spectrum and its environmental functions. In this paper, the EBA concept is closely linked with the emerging concept of multiple use systems (MUS) while taking account of environmental, economic, and social factors that govern the ecosystems services and benefits. We elucidate a multi-scalar approach and multiple case studies to understand EBA particularly in context of a wetlandscape. At the global scale, Ramsar sites of international importance are geospatially analyzed with reference to their agro-ecology and biodiversity. At regional scale, the agrarian use of inland wetlands in India was re-evaluated taking account of database from a recent inland wetland inventory. At the local scale, drawing on the landscape characterization and the ecological economics for fresh water Lake Kolleru in India and the Muthurajawela Marsh-Negombo Lagoon coastal marsh in Sri Lanka, we illustrate some of the practical challenges in balancing wetland conservation, development needs and the overall well-being of local people. We also discuss how variability in the scale, geophysical characteristics of the site and the data availability confines the ability to simplify a single complete approach to address issues in complex ecosystem such as wetlands. All levels of the study are supported by a variety of earth observation data and the geographical information system (GIS) tools. The site level analysis also draws on socio-economic assessment tools.

A hydrogeomorphic inventory of coastal wetlands of the Manitoba Great Lakes: Lakes Winnipeg, Manitoba, and Winnipegosis

We compiled an GIS-based inventory of coastal wetlands associated with the Manitoba Great Lakes—Lakes Winnipeg, Manitoba, and Winnipegosis—using a hydrogeomorphic classification system, orthophotography, satellite imagery, and digital habitat maps. The lakes have six times more wetlands per km of shoreline than the Laurentian Great Lakes: Lake Winnipeg has 1404km2 (0.8km2/km), Lake Manitoba has 564km2 (0.6km2/km), and Lake Winnipegosis has 742km2 (0.8km2/km). Riverine wetlands are the most common class on Lakes Winnipeg and Winnipegosis whereas barrier-protected wetlands are the most common class on Lake Manitoba. The totals for Lakes Winnipeg and Winnipegosis are greater by 548% and 273%, respectively, if Treed Muskeg habitat in the northern regions of the watersheds is included in the inventory, whereas the total for more southerly Lake Manitoba is greater by only 18%. Netley-Libau Marsh (222km2) on Lake Winnipeg and Delta Marsh (139km2) on Lake Manitoba are among the largest coastal wetlands on the North American continent. These baseline data can be used to identify ecologically important wetlands warranting further study or remediation.

Demonstration of a conceptual model for using LiDAR to improve the estimation of floodwater mitigation potential of Prairie Pothole Region wetlands

Recent flood events in the Prairie Pothole Region of North America have stimulated interest in modeling water storage capacities of wetlands and their surrounding catchments to facilitate flood mitigation efforts. Accurate estimates of basin storage capacities have been hampered by a lack of high-resolution elevation data. In this paper, we developed a 0.5 m bare-earth model from Light Detection And Ranging (LiDAR) data and, in combination with National Wetlands Inventory data, delineated wetland catchments and their spilling points within a 196 km(2) study area. We then calculated the maximum water storage capacity of individual basins and modeled the connectivity among these basins. When compared to field survey results, catchment and spilling point delineations from the LiDAR bare-earth model captured subtle landscape features very well. Of the 11 modeled spilling points, 10 matched field survey spilling points. The comparison between observed and modeled maximum water storage had an R(2) of 0.87 with mean absolute error of 5564 m(3). Since maximum water storage capacity of basins does not translate into floodwater regulation capability, we further developed a Basin Floodwater Regulation Index. Based upon this index, the absolute and relative water that could be held by wetlands over a landscape could be modeled. This conceptual model of floodwater downstream contribution was demonstrated with water level data from 17 May 2008. Published by Elsevier B.V.

Groundwater Quality Degradation in the Buyuk Menderes River Coastal Wetland

A baseline hydrogeochemical investigation was carried out as a contribution to the inventory of wetlands in Buyuk Menderes River (BMR) coastal wetland which is the most important wetland in Turkey that is protected as “Natural Park” by government. In addition to the wetland values, agricultural activities are also important at this delta. From inland to coastal zone, the groundwater type is changed from Ca–HCO3 to Na–Cl. Perfect correlation of Cl with Na and SO4 indicated the mixing process between saline and fresh water. The seawater intrusion and “winter-leaching” is the main causes of salinization. Minor ions as B, Br, and Li versus Cl relationship also showed the marine influence at the BMR coastal wetland. The δ18O and δD composition of the waters are range between −8.11‰ and −1.65‰ and −49.2‰ and 8.1‰, respectively. Isotope values show the seawater mixing line and also dissolution of salts in the BMR coastal wetland. Weathering of aluminosilicates in the Paleozoic schist and clays resulted in the release of silica to the water. Due to the organic activity, iron concentrations reached to the tolerance limits. On the other hand, the use of phosphate fertilizers increases the phosphorus content in the water. The high value of As (from 0.6 to 134 μg/l) can be resulted as an evaporation process in the study area.

SALINE WETLANDS' FATE IN INLAND DESERTS: AN EXAMPLE OF 80 YEARS' DECLINE IN MONEGROS, SPAIN

ABSTRACTWetlands inventory is one of the goals of conservation plans on a national scale and a global scale. Inventories are needed for long‐term monitoring or for identifying lost wetlands and those where restoration is feasible. In this article, we present an updated inventory of the saline wetlands of Southern Monegros, Spain. We depicted the evolution of these saline wetlands, locally named saladas with a unique long‐term retrospective study based on aerial photographs from 1927. Their inventory has been accomplished through a map analysis based on a geographical information system using aerial photographs and orthophotographs, topographic maps, unpublished local studies and field surveys. Remaining vegetation, changes in soil moisture and colour, and geomorphology have been the key features in identifying the saladas. Their changes in number, size and shape have been driven by human pressure, the main modifier of landscape in the last 80 years. The information gathered will contribute to the awareness of stakeholders and decision makers for their conservation as natural resources. Moreover, our large retrospective approach is a consistent base from which to propose the inclusion of the saladas of Monegros in the Ramsar list of Wetlands of International Importance. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Wetland habitat selection by woodland caribou as characterized using the Alberta Wetland Inventory

We examined habitat selection by woodland caribou (Rangifer tarandus caribou) in northwestern Alberta based on a wetland classification system developed for the Alberta Vegetation Inventory. Our two objectives were to describe caribou habitat use, and to assess the utility of the wetland classification system in land-use planning on caribou range. We used a geographical information system to overlay the locations of radio-collared caribou on the habitat map. Using a "moving-window" analysis of habitat availability, we examined patterns of habitat selection by 16 individual female caribou during five seasons annually over two years. We did not detect significant differences in habitat selection patterns among seasons. Caribou showed significant preferences for both bogs and fens with low to moderate tree cover relative to marshes, uplands, heavily forested wetlands, water, and areas of human use. The wetland classification system appears to have value for broad-scale planning of industrial activity on caribou range. More-detailed descriptions of vegetation, especially understory species, are required to refine this system for operational-level forest harvest planning.

Proposed Hydrogeomorphic Classification for Wetlands of the Mid-Atlantic Region, USA

We propose a regional classification for wetlands of the Mid-Atlantic region, USA. It combines functional characteristics recognized by the hydrogeomorphic (HGM) approach with the established classification of the National Wetland Inventory (NWI). The HGM approach supplements the NWI classification by recognizing the importance of geomorphic setting, water sources, and flow dynamics that are key to functioning wetlands. Both NWI and HGM share at their highest levels the Marine, Estuarine, and Lacustrine classes. This classification departs from the NWI system by subdividing the Palustrine system into HGM classes of Slope, Depression, and Flat. Further, the Riverine class expands to include associated Palustrine wetlands, thus recognizing the interdependency between channel and floodplain. Deepwater habitats of NWI are not included because they differ functionally. Mid-Atlantic regional subclasses recognize two subclasses each for Flat, Slope, and Marine Tidal Fringe; three subclasses for Depression; four subclasses for Lacustrine Fringe and Estuarine Tidal Fringe, and five subclasses for Riverine. Taking a similar approach in other geographic regions will better characterize wetlands for assessment and restoration. This approach was applied successfully during a regional wetlands condition assessment. We encourage additional testing by others to confirm its utility in the region.

Spatial and Temporal Variation in Wet Area of Wetlands in the Prairie Pothole Region of North Dakota and South Dakota

Because of their sensitivity to temperature and precipitation, wetlands in the Prairie Pothole Region (PPR) are predicted to undergo changes in number, wet area, and hydroperiod as a result of climate change. However, existing PPR wetland monitoring programs are insufficient to accurately describe broad-scale variation in hydrology that might obscure signals of climate change. We assessed spatial and temporal patterns in wet area of ~40,000 wetland basins sampled each May from 1988–2007 in the U.S. PPR. The percentage of basins containing water, the wet area of basins relative to a baseline, the coefficient of variation of wet area of basins, and correlations of wet area values with values from previous years all varied temporally, spatially, and among water regimes that characterized annual duration of surface inundation. High variability in wetness suggests that monitoring programs designed to detect changes in PPR wetlands due to climate change must be implemented over broad spatiotemporal scales and consider natural and anthropogenic factors that influence water levels to be able to distinguish directional change from natural variation. Ancillary information such as annual indices of water conditions can greatly enhance the value of wetland classification schemes such as that used in the National Wetlands Inventory.

Assessing Wetland Changes in the Prairie Pothole Region of Minnesota From 1980 to 2007

Abstract Wetlands in the Minnesota Prairie Pothole Region are critical landscape elements because of their unmatched importance to breeding waterfowl, and other wildlife. They provide vast benefits to store runoff or act as nutrient sinks and offer other environmental and socio-economic returns. Data on location, extent and types of wetlands collected by the U.S. Fish and Wildlife Service National Wetlands Inventory is used for developing conservation strategies and evaluating net landscape changes affecting fish and wildlife populations. Minnesota wetlands were mapped 27 y ago by the National Wetlands Inventory. We examined 176 10.2-km2 (4-mi2) sample plots in the Minnesota Prairie Pothole Region, using aerial photo interpretation techniques, to determine the current accuracy of the National Wetlands Inventory data used in the eastern Prairie Pothole Region for conservation planning and evaluation. We stratified our analysis by Bailey's (1995) Ecological Subsections. We estimated that across the entire Minnesota Prairie Pothole Region 4.3% of wetland area has been lost since 1980 with losses varying from 0 to 15% among Ecological Subsections. Implications of these findings suggest that National Wetlands Inventory data should be regularly updated in areas subject to rapid wetland change.