Impacts of section 404 permits requiring compensatory mitigation on wetlands in California (USA)

We analyzed data from Section 404 permits issued in California from January 1971 through November 1987 that involved impacts to wetlands and required compensatory mitigation (wetland creation, restoration, or preservation). The purpose of this study was to determine patterns and trends in permitting activity and to document cumulative effects of associated management decisions on the California wetland resource. The 324 permits examined documented that 387 compensatory wetlands (1255.9 ha) were required as mitigation for impacts to 368 wetlands (1176.3 ha). The utility of the data on wetland area was limited, however, since 38.0% of the impacted wetlands and 41.6% of the compensatory wetlands lacked acreage data. The wetland type most frequently impacted (37.8% of impacted wetlands) and used in compensation (38.2% of compensatory wetlands) was palustrine forested wetlands. Estuarine intertidal emergent wetlands had the most area impacted (52.3%) and compensated (62.5%). The majority of the wetlands were small (less than or equal to 4.0 ha in size). Wildlife habitat was the most frequently listed function of impacted wetlands (90.7% of the permits) and objective of compensatory wetlands (83.3%). Endangered species were listed as affected in 20.4% of impacted and 21.0% of compensatory projects. The number of permits requiring compensatory mitigation and the number of impacted and compensatory wetlands increased from 1971 to 1986.Documentation of the details of Section 404 permit decisions was inadequate for the permits we examined. Area information and specific locations of impacted and compensatory wetlands were lacking or of poor quality. Follow-up information was also inadequate. For example, project completion dates were specified in the permit for only 2.2% of compensatory wetlands. Furthermore, less than one-third (31.5%) of the permits required the compensatory wetland to be monitored by at least one site visit. We recommend improved documentation, regular reporting, and increased monitoring for better evaluation of the Section 404 permitting system.     

Carbon storage dynamics of temperate freshwater wetlands in Pennsylvania

Healthy wetlands play a significant role in climate change mitigation by storing carbon that would otherwise contribute to global warming, leading to the reduction of water and food resources as well as more extreme weather phenomena. Investigating the magnitude of carbon storage potential of different freshwater wetland systems using multiple ecological indicators at varying spatial scales provides insight and justification for selective wetland restoration and conservation initiatives. We provide a holistic accounting of total carbon values for 193 wetland sites, integrating existing carbon algorithms to rapidly assess each of the following carbon pools: above-ground, below-ground, soil, woody debris, shrub cover, and herbaceous cover. Aspects of soil, vegetation, and ecosystem characteristics and stressors were measured to obtain an overall understanding of the ecosystems ability to store carbon (long-term) along a gradient of human disturbance. Based on a review of the literature, methods were prioritized based on the initial data available from field measurements as well as their practicality and ease in replicating the process in the future. Lacustrine human impounded (88.7?±?18.0 tC/ha), riverine beaver impounded (116.2?±?29.4 tC/ha), riverine upper perennial (163.3?±?11.8 tC/ha), riverine lower perennial (199.2?±?24.7 tC/ha), riverine headwater complex (159.5?±?22.2 tC/ha), perennial/seasonal depression (269.6?±?42.4 tC/ha), and slope (162.2?±?14.6 tC/ha) wetland types were compared. Overall results showed moderate variability (9.33–835.95 tC/ha) for total carbon storage values across the wetland types, with an average total carbon storage of 174.6?±?8.8 tC/ha for all wetlands. Results show that carbon storage was significantly higher (p?=?0.002) in least disturbed wetland sites. Apart from perennial/seasonal depression wetlands, all reference standard wetlands had greater carbon storage, less disturbance impact, and a greater extent of forest cover than non-reference wetlands. Carbon storage values calculated were comparable to published literature.     

Simulated environmental effects of wetland restoration scenarios in a typical Canadian prairie watershed

Wetland conservation and restoration contribute to improved watershed functions through providing both water quantity benefits in terms of flood attenuation and water quality benefits such as retention of sediment and nutrients. However, it is important to quantify these environmental benefits for informed decision making. This study uses a “hydrologic equivalent wetland” concept in the Soil and Water Assessment Tool to examine the effects of various wetland restoration scenarios on stream flow and sediment at a watershed scale. The modeling system was applied to the 25,139 ha Broughton’s Creek watershed in western Manitoba in Canada. As a representative prairie watershed, the Broughton’s Creek watershed experienced historic wetland losses from 2,998 ha in 1968 to 2,379 ha in 2005. Modeling results showed that if wetlands in the Broughton’s Creek watershed can be restored to the 1968 level, the peak discharge and average sediment loading can be reduced by 23.4 and 16.9%, respectively at the watershed outlet. Based on wetland and stream drainage areas estimated by the model and empirical nutrient export coefficients, the corresponding water quality benefits in terms of reductions in total phosphorus and nitrogen loadings were estimated at 23.4%. The modeling results are helpful for designing effective watershed restoration strategies in the Broughton’s Creek watershed. The developed methodology can be also applied to other study areas for examining the environmental effects of wetland restoration scenarios.     

Seasonal wetlands on the Lake Wales Ridge, Florida: does a relict seed bank persist despite long term disturbance?

Wetlands maintain biodiversity and provide numerous ecosystem services, so the pressure to perform successful restoration consequently is high. However, restoration projects rarely include an in-depth assessment of wetland potential for recovery, and restoration techniques may not be tailored to site-specific concerns. This study examined the seed bank of disturbed wetlands slotted for hydrologic, but not vegetation, restoration to determine if a seed bank comparable to that of nearby undisturbed wetlands persisted despite long-term anthropogenic disturbance. We compared the aboveground vegetation and seed bank compositions under drained, drawdown, and flooded conditions between undisturbed and historically ditched (“disturbed”) wetlands. Disturbed and undisturbed wetlands shared fewer than 30 % of total aboveground species. While undisturbed wetlands were dominated by graminoids, disturbed wetlands had greater cover of forbs. The seed banks of disturbed wetlands had high species diversity, but their composition was dissimilar to that of nearby undisturbed wetlands. In total, the seed banks of both disturbance histories germinated 56 species; drained conditions had the fewest germinants while flooded conditions had the most. Germinant richness was significantly affected by disturbance, moisture, and their interaction; evenness was significantly affected by moisture, and Shannon diversity by disturbance. Because the seed bank of disturbed wetlands included many fast-growing wetland plants, passive vegetation restoration and active hydrologic restoration may result in wetlands overgrown with weedy species and with fewer conservative wetland plants. An understanding of the capacity for seed banks to re-vegetate wetlands post-restoration and approximate undisturbed wetlands is crucial to the overall success of restoration projects.     

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.     

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.     

Vegetation Similarity and Avifaunal Food Value of Restored and Natural Marshes in Northern New York

Measuring the success of wetland restoration efforts requires an assessment of the wetland plant community as it changes following restoration. But analyses of restored wetlands often include plant community data from only one time period. We studied the development of plant communities at 13 restored marshes in northern New York for 4 years, including 1 year prior to restoration and 3 years afterwards. Restored wetlands ranged in size from 0.23 to 1.70 ha. Four reference wetlands of similar basin morphology, soil type, and size (0.29–0.48 ha) that occurred naturally in the same area were studied as comparisons. Dike construction to restore hydrology disturbed the existing vegetation in some parts of the restored sites, and vegetation was monitored in both disturbed and undisturbed areas. Undisturbed areas within the restored sites, which were dominated by upland field grasses before restoration, developed wetland plant communities with lower wetland index values but comparable numbers of wetland plant species than the reference wetlands, and they lagged behind the reference sites in terms of total wetland plant cover. There were significantly more plant species valuable as food sources for wetland birds, and a significantly higher percent cover of these species, at the undisturbed areas of the restored sites than at the reference wetlands. Areas of the restored sites that were disturbed by dike construction, however, often developed dense, monospecific cattail stands. In general, the plant communities at restored sites became increasingly similar to those at the reference wetlands over time, but higher numbers of herbaceous plants developed at the restored sites, including food plants for waterfowl, rails, and songbirds. Differences in shrub cover will probably lessen as natural recolonization increases shrub cover at the restored sites. Natural recolonization appears to be an effective technique for restoring wetlands on abandoned agricultural fields with established plant cover, but it is less successful in areas where soil has been exposed by construction activity.     

Where is the avoidance in the implementation of wetland law and policy?

Many jurisdictions in North America use a “mitigation sequence” to protect wetlands: First, avoid impacts; second, minimize unavoidable impacts; and third, compensate for irreducible impacts through the use of wetland restoration, enhancement, creation, or protection. Despite the continued reliance on this sequence in wetland decision-making, there is broad agreement among scholars, scientists, policymakers, regulators, and the regulated community that the first and most important step in the mitigation sequence, avoidance, is ignored more often than it is implemented. This paper draws on literature published between 1989 and 2010, as well as 33 semi-structured, key-informant interviews carried out in 2009 and 2010 with actors intimately involved with wetland policy in Alberta, Canada, to address key reasons why “avoidance” as a policy directive is seldom effective. Five key factors emerged from the literature, and were supported by interview data, as being central to the failure of decision-makers to prioritize wetland avoidance and minimization above compensation in the mitigation sequence: (1) a lack of agreement on what constitutes avoidance; (2) current approaches to land-use planning do not identify high-priority wetlands in advance of development; (3) wetlands are economically undervalued; (4) there is a “techno-arrogance” associated with wetland creation and restoration that results in increased wetland loss, and; (5) compensation requirements are inadequately enforced. Largely untested but proactive ways to re-institute avoidance as a workable option in wetland management include: watershed-based planning; comprehensive economic and social valuation of wetlands; and long-term citizen-based monitoring schemes.     

Analysis of multi-decadal wetland changes,and cumulative impact of multiple storms 1984 to 2017

Land-cover classification analysis using Landsat satellite imagery acquired between 1984 and 2017 quantified short- (post-Hurricane Sandy) and long-term wetland-change trends along the Maryland and Virginia coasts between Metompkin Bay, VA and Ocean City, MD. Although there are limited options for upland migration of wetlands in the study area, regression analysis showed that wetland area increased slightly between 1984 and 2011, indicating that marsh aggradation rates were sufficient to maintain wetland elevation relative to mean sea level. Following Hurricane Irene (August 2011), the Halloween Nor’Easter (October 2011), and Hurricane Sandy (October 2012), wetland area decreased by more than 7 km² compared with average pre-storm extents. We assume that Hurricane Sandy had the greatest impact due to the size and intensity of the storm. However, the cumulative effects of multiple storms within a short time period likely contributed to the greater observed losses in coastal wetlands relative to earlier periods. Five years after Hurricane Sandy, wetland area had not significantly recovered, but more time may be necessary to assess if the observed wetland losses will persist or if new growth within flooded marsh areas will be sufficient for the wetlands to recover to pre-storm extents. Comparisons of long-term and storm-driven wetland changes can lead to improved accuracy of habitat vulnerability models and greater understanding of potential impacts of future storms and SLR to coastal wetlands.     

Functional equivalency of created and natural wetlands: diet composition of red-spotted newts (Notophthalmus viridescens viridescens)

Evaluating the adequacy of created wetlands to replace functions of lost natural wetlands is important because wetland mitigation is a major tool used to offset wetland losses. However, measurements such as vegetative cover and wildlife presence may not be evidence enough that created wetlands are functioning properly and thus, examining the ecology of wetland biota such as amphibians may be a more useful surrogate for function. Our objectives were to measure the diet composition of adult red-spotted newts (Notophthalmus viridescens viridescens) and compare the selection of prey by newts between created and natural wetlands. Newts were trapped during the spring and summer of 2009 and 2010, and the stomach contents of 149 newts were obtained with gastric lavage. Invertebrate prey availability was obtained within a 5 m radius of each captured newt. Selection of prey by newts was nonrandom, but was only minimally affected by wetland type. Both dietary breadth and prey selection were affected primarily by time of year, likely driven by temporal variation in invertebrate abundance. Our results suggest that the function of providing an adequate prey base for a generalist wetland predator such as the red-spotted newt is being fulfilled for the created wetlands that we examined.     

Detecting soil and plant community changes in restored wetlands using a chronosequence approach

Wetland restoration aims to recreate or enhance valuable ecosystem services lost during wetland destruction. Regaining wetland ecosystem services depends on restarting basic wetland functions, like carbon (C) storage, which are unmeasured in many Wetlands Reserve Program (WRP) restoration sites. We collected soil and plant data from 17 WRP sites in western New York that were used for tillage or non-tillage agriculture and then actively restored as isolated depressional wetlands by excavating basins and disabling drainage systems. Sites had been restored for 0–15 years when sampled in August-October 2010. We analyzed data as chronosequences and tested whether soil and vegetation parameters in restored wetlands, over time, (1) departed from pre-restoration baselines, estimated using active agricultural fields paired to each WRP site, and (2) converged towards “natural” benchmarks, estimated from four naturally-occurring wetlands. Restored WRP soils remained similar to agricultural soils in organic matter, density, moisture, and belowground plant biomass across chronosequences, indicating negligible C storage and belowground development for 15 years following restoration. Soil changes were limited in sites restored after both tillage and non-tillage agriculture and throughout the upland meadow, emergent shoreline, and open-water habitat zones that characterize these sites. Many plant metrics like aboveground biomass matched natural wetlands within 15 years, but recovered inconsistently among tilled and untilled sites and across all habitat zones, suggesting land-use history impacts and/or zonation effects. Disparities in recovery times exists between vegetation, which can respond quickly to wetland restoration, and underlying soils, which show limited signs of recovery 15 years after being restored.     

Microbial ecoenzyme stoichiometry,nutrient limitation,and organic matter decomposition in wetlands of the conterminous United States

Microbial respiration (R_m) and ecoenzyme activities (EEA) related to microbial carbon, nitrogen, and phosphorus acquisition were measured in 792 freshwater and estuarine wetlands (representing a cumulative area of 217,480 km²) across the continental United States as part of the US EPA’s 2011 National Wetland Condition Assessment. EEA stoichiometry was used to construct models for and assess nutrient limitation, carbon use efficiency (CUE), and organic matter decomposition (? k). The wetlands were classified into ten groups based on aggregated ecoregion and wetland type. The wetlands were also assigned to least, intermediate, and most disturbed classes, based on the extent of human influences. Ecoenzyme activity related to C, N and P acquisition, R_m, CUE, and ? k differed among ecoregion–wetland types and, with the exception of C acquisition and ? k, among disturbance classes. R_m and EEA were positively correlated with soil C, N and P content (r = 0.15–0.64) and stoichiometry (r = 0.15–0.48), and negatively correlated with an index of carbon quality (r = ? 0.22 to ? 0.39). EEA stoichiometry revealed that wetlands were more often P- than N-limited, and that P-limitation increases with increasing disturbance. Our enzyme-based approach for modeling C, N, and P acquisition, and organic matter decomposition, all rooted in stoichiometric theory, provides a mechanism for modeling resource limitations of microbial metabolism and biogeochemical cycling in wetlands. Given the ease of collecting and analyzing soil EEA and their response to wetland disturbance gradients, enzyme stoichiometry models are a cost-effective tool for monitoring ecosystem responses to resource availability and the environmental drivers of microbial metabolism, including those related to global climate changes.     

Long-term development of tidal mitigation wetlands in Florida

Monitoring periods for compensatory wetland mitigation projects are relatively short, typically 3 to 5 years. Although forested wetlands may require decades to develop structural characteristics similar to those of natural systems, studies that describe long-term trends in site development are rare. Eighteen mitigation sites in Florida that had originally been sampled in 1988 were re-visited in 2005. Changes in mangrove community composition and stand structure occurring over this timeframe at ten of these sites are described and compared with other mangrove wetlands in Florida. Factors limiting development of the remaining sites are discussed. The continued persistence and development of the majority of these mitigation sites indicates that the mitigation process can be successful, at least in terms of compliance with the typical permit requirements. Basal area and height had increased at most sites, and some were difficult to visually distinguish from adjacent natural stands of mangroves. However, even after 13–25 years, stand structure in mangrove mitigation wetlands in Florida still differed from that of natural sites. Although the number of mangrove species was similar, mitigation sites had lower basal area and height than natural sites, and were more dense and complex than natural sites.     

Estimating phosphorus retention of existing and restored coastal wetlands in a tributary watershed of the Laurentian Great Lakes in Michigan,USA

Simulation modeling with uncertainty analysis was applied to the question of nonpoint source pollution control through extensive wetland restoration. The model was applied to the Quanicassee River basin, a tributary stream to Saginaw Bay on Lake Huron in northeastern Michigan, USA. An estimate of the role of the existing 695 ha of riverside and lake-side wetlands in the lower Quanicassee River basin suggests that they retain 1.2 metric tons of phosphorus per year (mt P/yr), or 2.5% of the total phosphorus load from the basin. A simple Vollenweider-type model of phosphorus retention by created wetlands, calibrated with 3-years of data from two wetland sites in Midwestern USA, was used to estimate the effect of major wetland restoration in the basin. For a wetland restoration project involving 15% of the Quanicassee River basin or 3,120 ha of wetlands, an estimated 33 mt P/yr could be retained, assuming a proper hydrologic connection between the wetlands and the river. This would represent a reduction of two-thirds of the existing phosphorus load to the Bay from the Quanicassee River basin. Large-scale wetland restoration appears to be a viable management practice for controlling phosphorus and other nonpoint source pollution from entering Saginaw Bay. It is an alternative that meets two major resource goals – developing wetland habitat and controlling pollution to the Great Lakes.     

Compensating for wetland losses in the United States

Impacts of climate change on US wetlands will add to those of historical impacts due to other causes. In the US, wetland losses and degradation result from drainage for agriculture, filling for urbanization and road construction. States that rely heavily on agriculture (California, Iowa, Illinois, Missouri, Ohio, Indiana) have lost over 80% of their historical area of wetlands, and large cities, such as Los Angeles and New York City, have retained only tiny remnants of wetlands, all of which are highly disturbed. The cumulative effects of historical and future degradation will be difficult to abate. A recent review of mitigation efforts in the US shows a net loss of wetland area and function, even though 'no net loss' is the national policy and compensatory measures are mandatory. US policy does not include mitigation of losses due to climate change. Extrapolating from the regulatory experience, one can expect additional losses in wetland areas and in highly valued functions. Coastal wetlands will be hardest hit due to sea-level rise. As wetlands are increasingly inundated, both quantity and quality will decline. Recognition of historical, current and future losses of wetland invokes the precautionary principal: avoid all deliberate loss of coastal wetland area in order to reduce overall net loss. Failing that, our ability to restore and sustain wetlands must be improved substantially.     

湿地生态系统设计的一些基本问题探讨

湿地生态系统设计是恢复、调整湿地的重要手段,本文3从湿地生态系统设计概念入手,阐述了设计的基本原则。较详细地讨论了设计中的指标（水文指标、化学指标、基质指标和生物指标）要求,根据湿地生态系统设计的用途不同,探讨了3种主要的湿地生态系统设计类型,即作为废水处理湿地的设计,作为调整湿地的系统设计和作为洪水及非点源污染控制的湿地设计。     

Wetland restoration to enhance biodiversity in urban areas: a comparative analysis

Wetlands mitigation for any activity can be applied to avoid or minimize damage and restore, enhance, or create wetlands as well. New tools for mitigating and creating wetlands are available, including the Wetland Impact Assessment. This article explores many current issues in wetland mitigation and mitigation strategies, using case studies for illustration. We include some general guidelines for successful wetland mitigation based primarily on existing literature review in several cities. We use comparison and analyses on biodiversity improvement and various wetland functions, including flood-risk management, linking people to nature through urban regeneration, and connecting with the natural environment. Also, restoration, enhancement, mitigation, and creation analyses are included.     

Nestedness and successional trajectories of macroinvertebrate assemblages in man-made wetlands

Current successional models, primarily those based on floral succession, propose several distinct trajectories based on the integration of two key hypotheses from succession theory: convergence versus divergence in species composition among successional sites, and progression towards versus deviation from a desired reference state. We applied this framework to faunal succession, including differential colonization between active and passive dispersers, and the nested patterns generated as a consequence of this peculiarity. Nine man-made wetlands located in three different areas, from 0–3 years from wetland creation, were assessed. In addition, 91 wetlands distributed throughout the region were used as references for natural macroinvertebrate communities. We predicted the following: (1) highly nested structures in pioneering assemblages will decrease to lower mid-term values due to a shift from active pioneering taxa to passive disperser ones; (2) passive idiosyncratic taxa will elicit divergent successional trajectories among areas; (3) the divergent trajectories will provoke lower local and higher regional diversity values in the mid-term assemblages than in pioneer assemblages. Our results were largely congruent with hypotheses (1) and (2), diverging from the anticipated patterns only in the case of the temporary wetlands area. However, overall diversity trends based on hypothesis (3) did not follow the expected pattern. The divergent successional trajectories did not compensate for regional biodiversity losses that occurred as a consequence of pioneering colonizer decline over time. Consequently, we suggest reconsidering wetland construction for mitigation purposes within mid-term time frames (≤3 years). Wetlands may not offset, within this temporal scenario, regional biodiversity loss because the ecosystem may not support idiosyncratic taxa from natural wetlands.     

Waterbird Response to Wetlands Restored Through the Conservation Reserve Enhancement Program

Abstract: Conservation programs that facilitate restoration of natural areas on private land are one of the best strategies for recovery of valuable wetland acreage in critical ecoregions of the United States. Wetlands enrolled in the Conservation Reserve Enhancement Program (CREP) provide many ecological functions but may be particularly important as habitat for migrant and resident waterbirds; however, use of, and factors associated with use of, CREP wetlands as stopover and breeding sites have not been evaluated. We surveyed a random sample of CREP wetlands in the Illinois River watershed in 2004 and 2005 to quantify use of restored wetlands by spring migrating and breeding waterbirds. Waterbirds used 75% of wetlands during spring migration. Total use-day abundance for the entire spring migration ranged from 0 to 49,633 per wetland and averaged 6,437 ± 1,887 (SE). Semipermanent wetlands supported the greatest total number of use-days and the greatest number of use-days relative to wetland area. Species richness ranged from 0 to 42 (x̄ = 10.0 ± 1.5 [SE]), and 5 of these species were classified as endangered in Illinois. Density of waterfowl breeding pairs ranged from 0.0 pairs/ha to 16.6 pairs/ha (x̄ = 1.9 ± 0.5 [SE] pairs/ha), and 16 species of wetland birds were identified as local breeders. Density of waterfowl broods ranged from 0.0 broods/ha to 3.6 broods/ha and averaged 0.5 ± 0.1 (SE) broods/ha. We also modeled spring stopover use, waterbird species richness, and waterfowl reproduction in relation to spatial, physical, and floristic characteristics of CREP wetlands. The best approximating models to explain variation in all 3 dependent variables included only the covariate accounting for level of hydrologic management (i.e., none, passive, or active). Active management was associated with 858% greater use-days during spring than sites with only passive water management. Sites where hydrology was passively managed also averaged 402% greater species richness than sites where no hydrologic management was possible. Density of waterfowl broods was 120% greater on passively managed sites than on sites without water management but was 29% less on sites with active compared to passive hydrologic management. Densities of waterfowl broods also were greatest when ratios of open water to cover were 70:30. Models that accounted for vegetation quality and landscape variables ranked lower than models based solely on hydrologic management or vegetation cover in all candidate sets. Although placement and clustering of sites may be critical for maintaining populations of some wetland bird species, these factors appeared to be less important for attracting migrant waterbirds in our study area. In the context of restored CREP wetlands, we suggest the greatest gains in waterbird use and reproduction may be accomplished by emphasizing site-specific restoration efforts related to hydrology and floristic structure. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):654–664; 2008)     

Influence of the Leeuwin Current on the epipelagic euphausiid assemblages of the south-east Indian Ocean

Ecosystem services provided by wetland systems presently play a pivotal role in intensive cropland as water purification from agricultural pollution. A field trial was conducted in 2014 to evaluate herbicide runoff reduction and retention using a 0.32 ha constructed surface flow wetland (CSFW) at the outlet of a 6 ha agricultural basin. To simulate an extreme pulse contamination, the CSFW was flooded with a runoff contaminated with metolachlor, and terbuthylazine and two other subsequent floods with pure water were applied 21 and 65 days later. Results show that the CSFW can reduce runoff concentration of metolachlor and terbuthylazine by a factor of 45–80 even in extreme flooding conditions. Herbicides retention in the CSFW was reversible, and the second and third floods mobilized 14–31 and 3.5–7.0% respectively, of the amount detected in the first flood. The CSFW performs a high buffer capacity for herbicides, capable to provide water purification service, protecting downstream surface water. Moreover, mitigation capacity of a CSFW for a heavy runoff from a 10 ha basin is 90% for every 50 m in length of a 15 m wide wetland. This confirms that the implementation of CSFWs in agro-systems can improve the sustainability of agricultural production.