Changes In Wetland Area Research Articles

Landsat-based monitoring of annual wetland change in the Willamette Valley of Oregon, USA from 1972 to 2012

In Oregon’s Willamette Valley, remaining wetlands are at high risk to loss and degradation from agricultural activity and urbanization. With an increased need for fine temporal-scale monitoring of sensitive wetlands, we used annual Landsat MSS and TM/ETM+ images from 1972 to 2012 to manually interpret loss, gain, and type conversion of wetland area in the floodplain of the Willamette River. By creating Tasseled Cap Brightness, Greenness, and Wetness indices for MSS data that visually match TM/ETM+ Tasseled Cap images, we were able to construct a complete and consistent, annual time series and utilize the entire Landsat archive. With an extended time series we were also able to compare annual trends of net change in wetland area before and after the no-net-loss policy established under Section 404 of the Clean Water Act in 1990 using a Theil-Sen Slope estimate analysis. Vegetated wetlands experienced a 314 ha net loss of wetland area and non-vegetated wetlands experienced a 393 ha net gain, indicating higher functioning wetlands were replaced in area by non-vegetated wetland habitats such as agricultural and quarry ponds. The majority of both gain and loss in the study area was attributed to gains and losses of agricultural land. After 1990 policy implementations, the rate of wetland area lost slowed for some wetland categories and reversed into trends of gain in wetland area for others, perhaps representative of the success of increased regulations. Overall accuracy of land use classification through manual interpretation was at 80 %. This accuracy increased to 91.1 % when land use classes were aggregated to either wetland or upland categories, indicating that our methodology was more accurate at distinguishing between general upland and wetland than finer categorical classes.

Historical trends of wetland areas in the agriculture and pasture interlaced zone: A case study of the Huangqihai Lake Basin in northern China

Wetland degradation has become a serious global environmental issue. The agriculture and pasture interlaced zone (APIZ) in China is often close to the transition zone between arid and semi-arid regions, and it is extremely ecologically sensitive and vulnerable to global change. However, reports on changes in wetland areas in such zones are rarely available. Here, we analyzed remote sensing images to quantify the historical change in the wetland area of the Huangqihai Lake Basin located in the APIZ in China. The comparison indicated an excellent agreement between the results from remote sensing images and historical records for the lake area. Our results showed that 73% of wetland area had disappeared during 1976–2010. About 86% of the lost wetland area was converted to grassland, forest, and bare fields, while 14% was converted to cropland and built-up land use types. The largest lake in this basin, the Huangqihai Lake, was in a state of contraction during this period, and it has been completely dry since 2008. A large share (54%) of the lost area of the lake has become marshes, while about 97% of the original marsh area within the basin disappeared during 1976–2010. Without substantial efforts in wetland management and protection, this trend in natural wetland degradation is likely to continue. Mapping wetland areas with remote sensing images is an effective approach to providing wetland area information in a spatially and temporarily explicit way in regions where monitoring programs are not available. Such information is useful for understanding wetland degradation processes, and is helpful for investigating the driving forces of wetland degradation.

Evidence of Diminishing Marginal Product of Wetlands for Damage Mitigation

Communities along the USA coast are highly vulnerable to coastal storms. Trends in population growth, climatic events and land use are likely to exacerbate future damages. Coastal management entities are faced with decisions about how to manage resources in a manner that improves environmental quality and provides the maximum benefit for coastal populations. This is particularly true along the USA coast of the Gulf of Mexico, where coastal storms are common, land loss is rapid and states are planning ambitious and costly coastal restoration projects. Many of these projects are intended to mitigate hurricane damages by using wetlands as storm buffers. The physical science literature shows that wetlands do provide situational protection from storm surge. However, little economic analysis has explored the effect of wetlands on economic losses. This analysis uses hurricane simulation data to estimate county- or parish-level damages based on observed damages from coastal storms making landfall along the Gulf coast. A model describing these damages as a function of wetland area, socio-economic conditions and storm intensity allows the estimation of the value of wetlands for their protective ecosystem services. This analysis finds that wetlands are valuable for storm damage mitigation and that wetland area change is most impactful where wetlands are most scarce. The implications of these finding are significant for coastal restoration decisions in a changing environment.

Evaluation of surface water dynamics for water-food security in seasonal wetlands, north-central Namibia

Abstract. Agricultural use of wetlands is important for food security in various regions. However, land-use changes in wetland areas could alter the water cycle and the ecosystem. To conserve the water environments of wetlands, care is needed when introducing new cropping systems. This study is the first attempt to evaluate the water dynamics in the case of the introduction of rice-millet mixed-cropping systems to the Cuvelai system seasonal wetlands (CSSWs) in north-central Namibia. We first investigated seasonal changes in surface water coverage by using satellite remote sensing data. We also assessed the effect of the introduction of rice-millet mixed-cropping systems on evapotranspiration in the CSSWs region. For the former investigation, we used MODIS and AMSR-E satellite remote sensing data. These data showed that at the beginning of the wet season, surface water appears from the southern (lower) part and then expands to the northern (higher) part of the CSSWs. For the latter investigation, we used data obtained by the classical Bowen ratio-energy balance (BREB) method at an experimental field site established in September 2012 on the Ogongo campus, University of Namibia. This analysis showed the importance of water and vegetation conditions when introducing mixed-cropping to the region.

Historic maps as a data source for socio-hydrology: a case study of the Lake Balaton wetland system, Hungary

Abstract. Socio-hydrology is the science of human influence on hydrology and the influence of the water cycle on human social systems. This newly emerging discipline inherently involves a historic perspective, often focusing on timescales of several centuries. While data on human history is typically available for this time frame, gathering information on the hydrological situation during such a period can prove difficult: measured hydrological data for such long periods are rare, while models and secondary data sets from geomorphology, pedology or archaeology are typically not accurate enough over such a short time. In the first part of this study, the use of historic maps in hydrology is reviewed. Major breakthroughs were the acceptance of historic map content as valid data, the use of preserved features for investigating situations earlier than the map, and the onset of digital georeferencing and data integration. Historic maps can be primary quantitative sources of hydro-geomorphological information, they can provide a context for point-based measurements over larger areas, and they can deliver time series for a better understanding of change scenarios. In the second part, a case study is presented: water level fluctuations of Lake Balaton were reconstructed from maps, levelling logs and other documents. An 18th century map system of the whole 5700 km2 catchment was georeferenced, integrated with two 19th century map systems, and wetlands, forests and open water digitized. Changes in wetland area were compared with lake water level changes in a 220 yr time series. Historic maps show that the water level of the lake was closer to present-day levels than expected, and that wetland loss pre-dates drainage of the lake. The present and future role of historic maps is discussed. Historic hydrological data has to be treated with caution: while it is possible to learn form the past, the assumption that future changes will be like past changes does not always hold. Nevertheless, old maps are relatively accessible data sets and the knowledge base for using them is rapidly growing, and it can be expected that long-term time series will be established by integrating georeferenced map systems over large areas. In the Appendix, a step-by-step guide to using historic maps in hydrology is given, starting from finding a map, through georeferencing and processing the map to publication of the results.

Tracking wetland loss to improve evidence-based wetland policy learning and decision making

At the core of any evidence-based policy analysis are accurate data and the policy analytic capacity of government agencies to use these data to develop and measure metrics of policy success. This study evaluated the government’s policy capacity to manage wetlands in Alberta, Canada, by measuring and evaluating three policy metrics: (1) no net change of wetland area; (2) permitted versus unpermitted wetland loss; and (3) an information tracking system that provides credible regulatory oversight. Using a climate-corrected wetland loss inventory, we detected the loss of 242 wetlands, totaling 71 ha, in the Beaverhill subwatershed between 1999 and 2009. The majority of the losses occurred on land that were classified as ‘developed’ (urban and industrial) or ‘agriculture’. When wetland loss was compared to government-issued wetland permit data, we found that over 80 % of the wetland area was lost without a government permit. The wetland permit data also revealed serious problems with information tracking by both government and non-government agencies responsible for policy and regulatory oversight. In order to resolve these common policy failures, governments need to commit more resources towards acquiring, effectively managing, and freely sharing information that can be used to evaluate policy outcomes to ‘open up’ wetland management and decision making to include active participation from informal institutions, local governments, and the general public as a means to drive improved regulatory oversight.

Quantifying Area Changes of Internationally Important Wetlands Due to Water Consumption in LCA

Wetlands harbor diverse species assemblages but are among the world's most threatened ecosystems. Half of their global area was lost during the last century. No approach currently exists in life cycle impact assessment that acknowledges the vulnerability and importance of wetlands globally and provides fate factors for water consumption. We use data from 1184 inland wetlands, all designated as sites of international importance under the Ramsar Convention, to develop regionalized fate factors (FF) for consumptive water use. FFs quantify the change of wetland area caused per m(3)/yr water consumed. We distinguish between surface water-fed and groundwater-fed wetlands and develop FFs for surface water and groundwater consumption. FFs vary over 8 (surface water-fed) and 6 (groundwater-fed) orders of magnitude as a function of the site characteristics, showing the importance of local conditions. Largest FFs for surface water-fed wetlands generally occur in hyper-arid zones and smallest in humid zones, highlighting the dependency on available surface water flows. FFs for groundwater-fed wetlands depend on hydrogeological conditions and vary largely with the total amount of water consumed from the aquifer. Our FFs translate water consumption into wetland area loss and thus become compatible with life cycle assessment methodologies of land use.

Effects of the introduction of rice on evapotranspiration in seasonal wetlands

AbstractLand use changes in wetland areas can alter evapotranspiration, a major component of the water balance, which eventually affects the water cycle and ecosystem. This study assessed the effect of introduced rice‐cropping on evapotranspiration in seasonal wetlands of northern Namibia. By using the Bowen ratio–energy balance method, measurements of evapotranspiration were performed over a period of 2.5 years at two wetland sites—a rice field (RF) and a natural vegetation field (NVF)—and at one upland field (UF) devoid of surface water. The mean evapotranspiration rates of RF (1.9 mm daytime−1) and NVF (1.8 mm daytime−1) were greater than that in UF (1.0 mm daytime−1). RF and NVF showed a slight difference in seasonal variations in evapotranspiration rates. During the dry season, RF evapotranspiration was less than the NVF evapotranspiration. The net radiation in RF was less in this period because of the higher albedo of the non‐vegetated surface after rice harvesting. In the early growth period of rice during the wet season, evapotranspiration in RF was higher than that in NVF, which was attributed to a difference in the evaporation efficiency and the transfer coefficient for latent heat that were both affected by leaf area index (LAI). Evapotranspiration sharply negatively responded to an increase in LAI when surface water is present according to sensitivity analysis, probably because a higher LAI over a surface suppresses evaporation. The control of LAI is therefore a key for reducing evaporation and conserving water. Copyright © 2013 John Wiley & Sons, Ltd.

Quantifying driving forces of urban wetlands change in Beijing City

The decision tree and the threshold methods have been adopted to delineate boundaries and features of water bodies from LANDSAT images. After a spatial overlay analysis and using a remote sensing technique and the wetland inventory data in Beijing, the water bodies were visually classified into different types of urban wetlands, and data on the urban wetlands of Beijing in 1986, 1991, 1996, 2000, 2002, 2004 and 2007 were obtained. Thirteen driving factors that affect wetland change were selected, and gray correlation analysis was employed to calculate the correlation between each driving factor and the total area of urban wetlands. Then, six major driving factors were selected based on the correlation coefficient, and the contribution rates of these six driving factors to the area change of various urban wetlands were calculated based on canonical correlation analysis. After that, this research analyzed the relationship and mechanism between the main driving factors and various types of wetlands. Five conclusions can be drawn. (1) The total area of surface water bodies in Beijing increased from 1986 to 1996, and gradually decreased from 1996 to 2007. (2) The areas of the river wetlands, water storage areas and pool and culture areas gradually decreased, and its variation tendency is consistent with that of the total area of wetlands. The area of the mining water areas and wastewater treatment plants slightly increased. (3) The six factors of driving forces are the annual rainfall, the evaporation, the quantity of inflow water, the volume of groundwater available, the urbanization rate and the daily average discharge of wastewater are the main factors affecting changes in the wetland areas, and they correlate well with the total area of wetlands. (4) The hydrologic indicators of water resources such as the quantity of inflow water and the volume of groundwater are the most important and direct driving forces that affect the change of the wetland area. These factors have a combined contribution rate of 43.94%. (5) Climate factors such as rainfall and evaporation are external factors that affect the changes in wetland area, and they have a contribution rate of 36.54%. (6) Human activities such as the urbanization rate and the daily average quantity of wastewater are major artificial driving factors. They have an influence rate of 19.52%.

Wetland changes and droughts in southwestern China

The five provinces of southwestern China, Sichuan, Chongqing, Guizhou, Yunnan and Guangxi, frequently suffer from droughts, especially the recent severe drought of five consecutive months from autumn 2009 to spring 2010, which caused serious water shortages, huge economic losses and adverse social consequences. With increasing human activity in the last 200 years, the wetland areas have decreased and their ecological functions such as water conservation, climate regulation have declined, which has a direct impact on climate and the ecological environment. Using satellite images, changes in wetland areas of the five provinces of southwestern China have been mapped from 1970 to 2008. Our detailed analysis shows that the wetland area in the 1970s, 1990, 2000 and 2008 occupy an area of 20822.9, 18386.16, 19904.22 and 17269.72 km2, respectively, which indicate that the wetland areas have a downtrend, at an accelerating rate, from 2000 to 2008. Considering the complexity between wetland change and drought, the correlation between spatial and temporal wetland change and drought have been analysed using monthly ground meteorological data from 1971 to 2009, obtained from the China Meteorological Data Sharing Service Network. The analysed results show that the decrease of the wetland area, damage to biological resources and decline in climate regulation function are closely related to serious drought problems in the five provinces of southwestern China. Finally the corresponding solutions are discussed by analysing the problems faced by the wetland ecological system.

长沙城市斑块湿地资源的时空演变

Wetland is one of the important ecosystems providing various ecological goods and services to human well-being.However,in urban areas,owing to rapid economic development and urban expansion,wetlands are encountering a threaten to be converting to other land uses,including resident houses,transportation facilities,and industrial buildings.Understanding the spatial-temporal changing patterns of urban wetland and their driving forces could provide valuable information for wetland conservation and urban planning toward sustainable development. Characterized by typical hilly area and subtropical monsoon climate,Changsha has abundant wetland resources.The changes in wetland area in Changsha city represent the common phenomena in south-central cities of China.In this study,the urban wetland data in Changsha were derived from topographical maps in 1955,1972 and 1990,and remote sensing image in 2007 by using the GIS tool.Then,we selected the most representative patch wetlands as our study objectives.From the viewpoints of the time and space,dynamics and static,we investigated and analyzed the dynamics and variations of elements and spatial characteristics in urban patch wetlands ecosystem during last five decades. The result indicated that total areas of urban patch wetlands in Changsha has been increased from 1955 thorough 1972 to 1990,but then decreased from 1990 to 2007.The general tendency during the last five decades exhibited an increased process.The variation amplitude of urban patch wetland area in Changsha continued to be increased and the change rate gradually speeded up.In terms of wetland size,the area of patch wetland smaller than 32ha has increased while the area of wetland larger than 32 ha showed a reversed tendency.Whether in the downtown or the suburb area,the density of urban patch wetland has been increased.The number of the reconstructed patch wetland and the remained patch wetland per land area has been increased in both the downtown and the suburb area.The ratio of reconstructed to remained patch wetland showed reversed change tendency in the downtown and the suburb area.The number of patch wetland per land area decreased in the downtown area.Our results suggested that no matter how differences in temporal scales,spatial attribute and spatial state,urban patch wetland often appear to be different and even opposite change patterns along with city expansion.In either dynamic or static space,the boundaries between downtown area and suburbs were key area of changes in urban patch wetlands. Overall,we found three key factors that mainly determined the changes in urban patch wetlands in Changsha.The first one was the size of patch wetland,with area smaller than 8 ha constituting more than 60% the total patch wetland;The second was the land use policy and urban construction,which resulted in the decline in patch wetland in the last decade;The third was location or area in the city,with increase of wetland in suburb area and decline of wetland in downtown.However,the direct relationships among these three factors mentioned above and changes in patch wetlands,as well as the effects of other natural factors(such as climate change) are not well understood and will be the further research topics.

Watershed land use and river engineering drive wetland formation and loss in the Mississippi River birdfoot delta

The Mississippi River basin was developed for agriculture at an unprecedented scale and intensity within the last 200 yr. These changes favored erosion and sediment transport, which were subsequently reduced by soil conservation practices, the trapping of sediment behind large reservoirs, and channel engineering. We discuss the relationship between sediment loading and the growth, loss, and stability of wetlands in the Mississippi River birdfoot delta (MRBD). We report an anthropogenically driven increase in mean suspended sediment concentrations in the Mississippi River below New Orleans, from a modeled 350 mg L−1 (174 × 109 kg yr−1) at the end of the 18th century to a measured maximum of 675 mg L−1 (348 × 109 kg yr−1) in the late 19th century, followed by a sharp reduction, and then a period of stabilization at 157 mg L−1 (91 × 109 kg yr−1) after 1962. Changes in wetland area of the MRBD over the past two centuries reflect variations in sediment supply during periods of increasing, decreasing, and stable sediment loading, and are distinct from wetland loss patterns in other areas of coastal Louisiana. The rapid growth of the MRBD until the 1930s, which has been used as a reference for one of the world's largest wetland restoration efforts, may not be a suitable archetype for the majority of the coast. Additionally, future variation in sediment supply to the MRBD would likely change the total wetland area of the MRBD.

Eco-compensation of wetlands in Yellow River Delta of Shandong Province, China

Wetlands play an important ecological role and provide many functions for people, yet wetlands are currently decreasing and deteriorating. The ability to calculate an economic value for the loss of wetlands is becoming increasingly important for policy makers. In this study, remote sensing, field investigations, department visits, and other methods were used to survey wetland types, assess wetland area changes, and calculate wetland economic value. Market value loss and ecological function value loss, caused by reduction of wetland area and environmental pollution were calculated using commonly accepted methods of market valuation, ecological valuation, environmental protection investment cost analysis, and outcome parameters. According to market value loss and ecological function value loss, preliminarily fund allocation for wetland and ecological compensation was calculated. This will provide an important reference for future Yellow River Delta eco-compensation studies.

Long-Term Changes in Wetland Area and Composition in the Netherlands Affecting the Carrying Capacity for Wintering Waterbirds

In The Netherlands, arising in geological time as the delta of the rivers Rhine, Meuse and Scheldt, a considerable change in landscape occurred during the Holocene period due to sea level rise. In more recent times this change was dramatically enforced by human actions. This started with the opening up of the large woods on higher soils, some 4500 years BP. It is estimated that the country was only populated then by a few thousand people. During the next 2000 years, the extensive forest clearing continued, and up to approximately 60% of the upland area changed into grazed woodland. Over-exploitation during the Middle Ages resulted in extended heathlands, which covered up to 40% of the total area of upland sands by 1500 AD. Today woodlands cover only 1 promille of the surface area it covered 7000 years ago. Wetlands remained undisturbed for a long period, but they have become seriously affected since the late Middle Ages; the construction of dikes, embankments and drainage have caused the area of wetlands to shrink dramatically. Especially when in the 19th and 20th centuries, as a result of the introduction of steam and later diesel and electric engines, large-scale projects could be realised. This led to the disappearance of many freshwater lakes and the almost complete loss of the area of brackish water, the natural link between sea water and freshwater. Although the influence of Man upon the Dutch landscape commenced some 4500 years ago, it is only during the last 600 years that wetlands have been affected. Particularly the last 100 years have been crucial with respect to drainage and cultivation. By reconstructing ancient landscapes, an attempt has been made to describe the species composition and numerical abundance of waterbirds, starting 7000 years BP. Two species have become extinct in the territory, many others show changes in abundance. The start of agriculture has caused a major change in the food provisioning of many herbivorous waterbirds. Over the last 7000 years, a sevenfold increase of the number of herbivorous waterfowl is estimated. On the other hand the number of fish-eaters, benthos-eaters and planktivorous waterbirds has declined, their available habitat now having diminished by 45%, 36% and 55% respectively with respect to the Late Subatlantic period, c. 850–1350 AD.

A Remote Sensing Investigation of Wetlands in Yellow River Basin

Based on MSS,ETM+ and 2006 satellite CBERS-2 satellite images obtained in 1975,2000 and 2006,the authors studied the changes in wetland areas of the total basin during the 31 years of 1975～2006.The survey reveals that the total area of the wetlands steadily decreased from 1975 to 2000,with the total reduced area being 1 388.50 km2.The results also show that,from 2000 to 2006,the area of the wetlands increased from 80 762.13 km2 to 81 825.15 km2.The shrinkage of Yellow River Basin wetlands year by year has led the authors to believe that the geological background and climate factors of the working area determine the overall distribution and changes of the wetlands,and that human factors also play an equally important role in the variation of the wetlands.

Nekton populations, long-term wetland loss, and the effect of recent habitat restoration in Galveston Bay, Texas, USA

We used data from 1984 samples taken approximately monthly over 11 yr (1982 to 1992) with a 2.6 m 2 drop sampler to quantify and compare nekton densities in Spartina alterniflora marsh edge and over adjacent shallow nonvegetated bottom (SNB) in Carancahua Cove, Galveston Bay estuary, Texas, USA. We also used a Geographic Information System (GIS), aerial photography, and population models to track changes in wetland area and trends in fishery populations over time. Decapod crustaceans were less speciose than fishes (35 vs. 60 species) in our samples, but this taxo- nomic group accounted for most (91%) of the animals we collected. Annual variability in animal abundance was high. Most species peaked in abundance during spring or fall, and were absent or occurred at low densities during winter. Mean densities of all abundant decapod crustaceans and several abundant fishes in our study were significantly greater in marsh vegetation than over SNB. Based on our GIS analysis, we estimated that 61% of the wetlands in the study area were converted to open water between 1982 and 1995; marsh edge (marsh within 1 m of the shoreline) was reduced by 70% during the same period. Our fishery models showed that brown shrimp Farfantepenaeus aztecus, white shrimp Litopenaeus setiferus, and blue crab Callinectes sapidus populations also declined substantially during this period as the area of wetlands and marsh edge was reduced. A marsh-terracing project in 1999 replaced some open water with marsh, and our models show that populations of these fishery species rebounded in response to this recent restoration effort.

Use of individualistic streamflow-vegetation relations along the Fremont River, Utah, USA to assess impacts of flow alteration on wetland and riparian areas

We analyzed the transverse pattern of vegetation along a reach of the Fremont River in Capitol Reef National Park, Utah, USA using models that support both delineation of wetland extent and projection of the changes in wetland area resulting from upstream hydrologic alteration. We linked stage-discharge relations developed by a hydraulic model to a flow-duration curve derived from the flow history in order to calculate the inundation duration of 361 plots (0.5 × 2 m). Logistic regression was used to relate plant species occurrence in plots to inundation duration. A weighted average of the wetland indicator values of species was used to characterize plots as Aquatic, Wetland, Transitional, or Upland. Finally, we assessed how alterations in the flow duration curve would change the relative widths of these four zones. The wetland indicator values of species and the wetland prevalence index scores of plots were strongly correlated with inundation duration. Our results support the concept that plants classified as wetland species typically occur gradient study reach of the Fremont River that satisfied the vegetation criterion for a regulatory wetland was narrow (2 m wide). Both the unvegetated Aquatic zone (7.8 m) and the Transitional zone (8 m) were substantially wider. The Transitional zone included the maxima of several species and was, therefore, not merely a combination of elements of the Wetland and Upland zones. Multiplicative increases or decreases in streamflow regime produced a wetter, or drier, bottomland vegetation, respectively. Systematic reductions in flow variability reduced the width of both the Wetland and Transitional zones and increased the width of the Upland zone. Our approach is widely applicable to inform water management decisions involving changes in flow regime.

Modeling wetland change along the United States Atlantic Coast

As an aid in waterfowl habitat conservation planning, we predicted change in wetland area between the 1950s and 1970s and the 1970s to 1990s along the United States Atlantic Coast. We developed zero-inflation models using logistic regression to predict occurrence and linear regression to predict area for six wetland classes: estuarine emergent, lacustrine, and palustrine emergent, forested, scrub-shrub, and unconsolidated bottom. A prediction grid of 10.36 km 2 cells was established for the study area. We predicted wetland class area for cells for four decades: 1950s, 1970s, 1980s, and 1990s. Wetland occurrence and area measurements from the U.S. Fish and Wildlife Service’s Wetlands Status and Trends Study (WST) sample plots served as response variables. Spatial structure in the WST data was preserved by interpolating residuals at plot locations and summing predicted residuals and predicted wetland area for each cell. Wetland changes reflect conversion both to and from upland as well as to and from other wetland classes. We predicted a 30.7 thousand ha decline in estuarine emergents in the study area from the 1950s to 1970s, but an increase of 0.9 thousand ha between the 1970s and 1990s. Predicted lacustrine area increased 161.6 thousand ha from the 1950s to 1970s, but declined 5.4 thousand ha from the 1970s to the 1990s. A loss of 731.4 thousand and 189.9 thousand ha of palustrine emergents was predicted from the 1950s to 1970s and from the 1970s to 1990s, respectively. Palustrine forested was predicted to have declined by 536.5 thousand ha between the 1950s and 1970s and 985.8 thousand ha between the 1970s and 1990s. Palustrine scrub-shrub was predicted to have declined 562.6 thousand ha between the 1950s and 1970s, but increased 119.2 thousand ha between the 1970s and 1990s. Finally, palustrine unconsolidated bottom wetlands were predicted to have increased 159.2 and 142.8 thousand ha between the 1950s and 1970s and 1970s and 1990s, respectively. Predictions were most reliable for estuarine emergent, lacustrine, and palustrine forested classes, probably due to the restricted distribution and relative constancy of the estuarine emergent and lacustrine classes. Reliable palustrine forested predictions were likely due to the association of this class with watercourses and the relationship between the predictor variables and lotic habitats. Predictor variables were likely less relevant for palustrine emergent, scrub-shrub, and unconsolidated bottom, where model fit was poorer. Human activities such as agriculture and forestry probably contributed to the poorer model fit for these classes.

Modeling wetland change along the United States Atlantic Coast

As an aid in waterfowl habitat conservation planning, we predicted change in wetland area between the 1950s and 1970s and the 1970s to 1990s along the United States Atlantic Coast. We developed zero-inflation models using logistic regression to predict occurrence and linear regression to predict area for six wetland classes: estuarine emergent, lacustrine, and palustrine emergent, forested, scrub-shrub, and unconsolidated bottom. A prediction grid of 10.36 km2 cells was established for the study area. We predicted wetland class area for cells for four decades: 1950s, 1970s, 1980s, and 1990s. Wetland occurrence and area measurements from the U.S. Fish and Wildlife Service’s Wetlands Status and Trends Study (WST) sample plots served as response variables. Spatial structure in the WST data was preserved by interpolating residuals at plot locations and summing predicted residuals and predicted wetland area for each cell. Wetland changes reflect conversion both to and from upland as well as to and from other wetland classes. We predicted a 30.7 thousand ha decline in estuarine emergents in the study area from the 1950s to 1970s, but an increase of 0.9 thousand ha between the 1970s and 1990s. Predicted lacustrine area increased 161.6 thousand ha from the 1950s to 1970s, but declined 5.4 thousand ha from the 1970s to the 1990s. A loss of 731.4 thousand and 189.9 thousand ha of palustrine emergents was predicted from the 1950s to 1970s and from the 1970s to 1990s, respectively. Palustrine forested was predicted to have declined by 536.5 thousand ha between the 1950s and 1970s and 985.8 thousand ha between the 1970s and 1990s. Palustrine scrub-shrub was predicted to have declined 562.6 thousand ha between the 1950s and 1970s, but increased 119.2 thousand ha between the 1970s and 1990s. Finally, palustrine unconsolidated bottom wetlands were predicted to have increased 159.2 and 142.8 thousand ha between the 1950s and 1970s and 1970s and 1990s, respectively. Predictions were most reliable for estuarine emergent, lacustrine, and palustrine forested classes, probably due to the restricted distribution and relative constancy of the estuarine emergent and lacustrine classes. Reliable palustrine forested predictions were likely due to the association of this class with watercourses and the relationship between the predictor variables and lotic habitats. Predictor variables were likely less relevant for palustrine emergent, scrub-shrub, and unconsolidated bottom, where model fit was poorer. Human activities such as agriculture and forestry probably contributed to the poorer model fit for these classes.

Dissolved phosphorus retention and release from a coastal plain in-stream wetland.

Dissolved phosphorus (DP) can be released from wetlands as a result of flooding or shifts in water column concentrations. Our objectives were to determine the long-term (1460 d) DP retention and release characteristics of an in-stream wetland, and to evaluate how these characteristics respond to flooding, draining, and changes in DP concentrations. The studied in-stream wetland drains an agriculturally intensive subwatershed in the North Carolina Coastal Plain region. The wetland's DP retention and release characteristics were evaluated by measuring inflow and outflow DP concentrations, DP mass balance, and DP movement across the sediment-water column interface. Phosphorus sorption isotherms were measured to determine the sediment's equilibria P concentration (EPCo), and passive samplers were used to measure sediment pore water DP concentrations. Initially, the in-stream wetland was undersized (0.31 ha) and released 1.5 kg of DP. Increasing the in-stream wetland area to 0.67 ha by flooding resulted in more DP retention (28 kg) and low outflow DP concentrations. Draining the in-stream wetland from 0.67 to 0.33 ha caused the release of stored DP (12.1 kg). Shifts both in sediment pore water DP concentrations and sediment EPCo values corroborate the release of stored DP. Reflooding the wetland from 0.33 to 0.85 ha caused additional release of stored DP into the outflowing stream (10.9 kg). We conclude that for a time period, this in-stream wetland did provide DP retention. During other time periods, DP was released due to changes in wetland area, rainfall, and DP concentrations.