Wetland Loss Research Articles

Uncovering the ecosystem service legacies of wetland loss using high‐resolution models

AbstractEcosystem services provided by contemporary landscapes are different from those of the past, and this difference is influenced by the legacies of policies that incentivized wetland drainage without considering the impact on ecosystem services. Heterogeneity in ecosystem service legacies is rarely acknowledged or documented. Even less understood is the relative role of historical wetland type (e.g., swamps, fens) and contemporary land cover in shaping these heterogeneous outcomes. Here, we contrasted contemporary ecosystem services with a scenario of no wetland drainage in the Ruamahanga Basin, New Zealand, a region historically rich in wetlands. Using the high‐resolution Land Use Capability Indicator model, we mapped nitrogen retention, phosphorous retention, sediment retention, agricultural productivity, and flood mitigation at a 5‐m spatial resolution under these two scenarios. Our work supports the broad understanding that agricultural productivity has increased in contemporary landscapes, while flood mitigation and nutrient retention have decreased. Net losses in ecosystem services occurred for the majority of historical wetlands, while net gains were less common. However, spatially heterogeneous and divergent responses of ecosystem services to land cover changes reinforced the need for high‐resolution models to untangle the range of factors affecting ecosystem service provisioning. Contemporary land cover explained very little variation in ecosystem services. Initial conditions, however, played an important role in determining ecosystem service outcomes with losses of swamps being particularly problematic for net loss of ecosystem services provisioning. The maps we produced, and the algorithms underlying them, provide tools to envision both local‐ and broad‐scale effects of historical wetland drainage.

A Methodology to Assess Land Use Development, Flooding, and Wetland Change as Indicators of Coastal Vulnerability

Coastal areas around the world are becoming increasingly urban, which has increased stress to both natural and anthropogenic systems. In the United States, 52% of the population lives along the coast, and North Carolina is in the top 10 fastest growing states. Within North Carolina, the southeastern coast is the fastest growing region in the state. Therefore, this research has developed a methodology that investigates the complex relationship between urbanization, land cover change, and potential flood risk and tested the approach in a rapidly urbanizing region. A variety of data, including satellite (PlanetScope) and airborne imagery (NAIP and Lidar) and vector data (C-CAP, FEMA floodplains, and building permits), were used to assess changes through space and time. The techniques consisted of (1) matrix change analysis, (2) a new approach to analyzing shorelines by computing adjacency statistics for changes in wetland and urban development, and (3) calculating risk using a fishnet, or tessellation, where hexagons of equal size (15 ha) were ranked into high, medium, and low risk and comparing these results with the amount of urbanization. As other research has shown, there was a significant relationship between residential development and wetland loss. Where urban development has yet to occur, most of the remaining area is at risk to flooding. Importantly, the combined methods used in this study have identified at-risk areas and places where wetlands have migrated/transgressed in relationship to urban development. The combination of techniques developed here has resulted in data that local government planners are using to evaluate current development regulations and incorporating into the new long-range plan for the County that will include smart growth and identification of risk. Additionally, results from this study area are being utilized in an application to the Federal Emergency Management Agency’s Community Response System which will provide residents with lower flood insurance costs.

Focusing on rapid urbanization areas can control the rapid loss of migratory water bird habitats in China

Over 240 migratory water bird species depend on China's 18,000 km coastline as a vital stopover area. However, the rapid loss of natural wetlands has threatened this seasonal water bird migration over the last few decades. In the present study, to improve our understanding of the pattern and amount of habitat loss in key stopover areas (KSAs) and the spatial covariance between habitat loss and economic development, we conducted a spatially explicit evaluation of coastal habitat loss in KSAs and explored its relationship with social and economic dynamics along the China coast by integrating high-spatial resolution satellite imagery with an updated coastal water bird investigation data set. The remote sensing survey detected a habitat loss percentage of 19.4% in the KSAs during 2000 and 2010. Aquaculture, urbanization, and land reclamation were responsible for the most severe disturbances to coastal habitats. These results demonstrate that the losses of wetland habitats in the KSAs in Chinese coastal areas are more severe than those in other coastal areas even though more protective measures have been implemented in these areas. Risk-based analysis showed that the risk of habitat loss was greatest in undeveloped regions with rich natural wetland and large populations, thereby demonstrating the critical importance of shifting the focus of water bird conservation to these regions to ensure the conservation of migratory water birds in the East Asian–Australasian Flyway. These findings disagree with the hypothesis that more habitats are lost when the economy is more developed. Therefore, we suggest that focusing conservation decisions on areas undergoing urbanization might improve the effectiveness of conservation measures given the pressures due to various forms of wetland exploitation.

Quantifying hydrologic controls on local- and landscape-scale indicators of coastal wetland loss.

Coastal wetlands have evolved to withstand stressful abiotic conditions through the maintenance of hydrologic feedbacks between vegetation production and flooding. However, disruption of these feedbacks can lead to ecosystem collapse, or a regime shift from vegetated wetland to open water. To prevent the loss of critical coastal wetland habitat, we must improve understanding of the abiotic-biotic linkages among flooding and wetland stability. The aim of this research was to identify characteristic landscape patterns and thresholds of wetland degradation that can be used to identify areas of vulnerability, reduce flooding threats and improve habitat quality. We measured local- and landscape-scale responses of coastal wetland vegetation to flooding stress in healthy and degrading coastal wetlands. We hypothesized that conversion of Spartina patens wetlands to open water could be defined by a distinct change in landscape configuration pattern, and that this change would occur at a discrete elevation threshold. Despite similarities in total land and water cover, we observed differences in the landscape configuration of vegetated and open water pixels in healthy and degrading wetlands. Healthy wetlands were more aggregated, and degrading wetlands were more fragmented. Generally, greater aggregation was associated with higher wetland elevation and better drainage, compared with fragmented wetlands, which had lower elevation and poor drainage. The relationship between vegetation cover and elevation was non-linear, and the conversion from vegetated wetland to open water occurred beyond an elevation threshold of hydrologic stress. The elevation threshold defined a transition zone where healthy, aggregated, wetland converted to a degrading, fragmented, wetland beyond an elevation threshold of 0.09 m [1988 North American Vertical Datum (NAVD88)] [0.27 m mean sea level (MSL)], and complete conversion to open water occurred beyond 0.03 m NAVD88 (0.21 m MSL). This work illustrates that changes in landscape configuration can be used as an indicator of wetland loss. Furthermore, in conjunction with specific elevation thresholds, these data can inform restoration and conservation planning to maximize wetland stability in anticipation of flooding threats.

Legal barriers and enablers for reintroducing tides: An Australian case study in reconverting ponded pasture for climate change mitigation

Across the globe, areas of the floodplain have been converted to agricultural use – often at the expense of natural ecosystems. In Australia, coastal wetlands have been transformed to ‘ponded pasture’ for cattle grazing which has resulted in a loss of saline wetlands, increased methane emissions, and impacts on species like fish and birds. Reconversion of these areas to saline wetlands is a potential climate change mitigation strategy, but given they occur at the intersection of private and public ownership regimes, some specific legal issues must be considered.This article provides an analysis of the legal enablers and barriers associated with reconverting ponded pastures or other hydrologically modified coastal land to saline wetlands for climate change mitigation, using Queensland, Australia as a case study. While projects are clearly possible, some of the key factors to consider in order to reduce legal risk and liability include: whether the law permits reflooding and what permits are required; clarifying land and carbon rights, which may require negotiation with the state government; and understanding the liabilities for potential impacts on adjacent land and biota.

Modeling Intersecting Processes of Wetland Shrinkage and Urban Expansion by a Time-Varying Methodology

Continuous urban expansion worldwide has resulted in significant wetland degradation and loss. A limited number of studies have addressed the coupling of wetland and urban dynamics, but this relationship remains unclear. In this study, a time-varying methodology of predicting wetland distribution was developed to support decision-making. The novelty of the methodology is its ability to dynamically simulate wetland shrinkage together with urban expansion and reveal conflicts and potential tradeoffs under different scenarios. The developed methodology consists of three modules: a historical change detection of wetland and urban areas module, a spatial urban sprawl simulation and forecasting module that can accommodate different development priorities, and a wetland distribution module with time-varying logistic regression. The methodology was applied and tested in the Tonghu Wetland as a case study. The wetland and urban extents presented a spatially intersecting shift, where wetlands lost more than 40% of their area from 1977 to 2017, while urban areas expanded by 10-fold, threatening wetlands. The increase in the relative importance metric of the time-varying regression model indicated an enhanced influence of urban expansion on the wetland. An accuracy assessment validated a robust statistical result and a good visual fit between spatially distributed wetland occurrence probabilities and the actual distribution of wetland. Incorporating the new variable of urban expansion improved modeling performance and, particularly, realized a greater ability to predict potential wetland loss than provided by the traditional method. Future wetland loss probabilities were visualized under different scenarios. The historical trend scenario predicted continuously expanding urban growth and wetland shrinkage to 2030. However, a specific urban development strategy scenario was designed interactively to control the potential wetland loss. Consideration of such scenarios can facilitate identifying tradeoffs to support wetland conservation.

Hidden Loss of Wetlands in China.

To counter their widespread loss, global aspirations are for no net loss of remaining wetlands [1]. Weexamine whether this goal alone is sufficient for managing China's wetlands, for they constitute 10%of the world's total. Analyzing wetland changes between 2000 and 2015 using 30-m-resolution satelliteimages, we show that China's wetlands expanded by 27,614km2 but lost 26,066km2-a net increase of 1,548km2 (or 0.4%). This net change hides considerable complexities in the types of wetlands created and destroyed. The area of open water surface increased by 9,110km2, but natural wetlands-henceforth "marshes"-decreased by 7,562km2. Of the expanded wetlands, restoration policies contributed 24.5% and dam construction contributed 20.8%. Climate change accounted for23.6% but is likely to involve a transient increasedue to melting glaciers. Of the lost wetlands,agricultural and urban expansion contributed 47.7% and 13.8%, respectively. The increase in wetlandsfrom conservation efforts (6,765km2) didnot offset human-caused wetland losses (16,032km2). The wetland changes may harm wildlife. The wetland loss in east China threatens bird migration across eastern Asia [2]. Open water fromdam construction flooded the original habitatsof threatened terrestrial species and affected aquatic species by fragmenting wetland habitats[3].Thus, the "no net loss" target measures totalchanges without considering changes in composition and the corresponding ecological functions.It may result in "paper offsets" and shouldbeused carefully as a target for wetland conservation.

Voluntary Restoration: Mitigation's Silent Partner in the Quest to Reverse Coastal Wetland Loss in the USA.

Coastal ecosystems are under pressure from a vast array of anthropogenic stressors, including development and climate change, resulting in significant habitat losses globally Conservation policies are often implemented with the intent of reducing habitat loss. However, losses already incurred will require restoration if ecosystem functions and services are to be recovered. The United States has a long history of wetland loss and recognizes that averting loss requires a multi-pronged approach including mitigation for regulated activities and non-mitigation (voluntary herein) restoration. The 1989 “No Net Loss” (NNL) policy stated the Federal government’s intent that losses of wetlands would be offset by at least as many gains of wetlands. However, coastal wetlands losses result from both regulated and non-regulated activities. We examined the effectiveness of Federally funded, voluntary restoration efforts in helping avert losses of coastal wetlands by assessing: (1) What are the current and past trends in coastal wetland change in the U.S.?; and (2) How much and where are voluntary restoration efforts occurring? First, we calculated palustrine and estuarine wetland change in U.S. coastal shoreline counties using data from NOAA’s Coastal Change Analysis Program, which integrates both types of potential losses and gains. We then synthesized available data on Federally funded, voluntary restoration of coastal wetlands. We found that from 1996 to 2010, the U.S. lost 139,552 acres (~565 km2) of estuarine wetlands (2.5% of 1996 area) and 336,922 acres (~1,363 km2) of palustrine wetlands (1.4%). From 2006 to 2015, restoration of 145,442 acres (~589 km2) of estuarine wetlands and 154,772 acres (~626 km2) of palustrine wetlands occurred. Further, wetland losses and restoration were not always geographically aligned, resulting in local and regional “winners” and “losers.” While these restoration efforts have been considerable, restoration and mitigation collectively have not been able to keep pace with wetland losses; thus, reversing this trend will likely require greater investment in coastal habitat conservation and restoration efforts. We further conclude that “area restored,” the most prevalent metric used to assess progress, is inadequate, as it does not necessarily equate to restoration of functions. Assessing the effectiveness of wetland restoration not just in the U.S., but globally, will require allocation of sufficient funding for long-term monitoring of restored wetland functions, as well as implementation of standardized methods for monitoring data collection, synthesis, interpretation, and application.

Drivers of Wetland Conversion in the Tropical Environment

<p>The study identified factors responsible for wetland dynamics and negative marks produced on the environment in the area. It equally suggested efforts aimed at reducing effects of the factors on the environment. The study incorporated both meta-analysis of case studies and questionnaires distribution and administration to the respondents who are mainly members of the Fadama User Group (FUG). The results showed changes in rainfall intensity as the major factor responsible for wetland loss; followed by settlement developments and loss of soil water due to river drainage. The results further revealed the effects of the factors to include siltation of drainages, destruction of ecosystem and loss of wetness, and emergent of heavy flooding. The study concluded by suggesting efforts aimed at reducing the influence of the factors on the environment.</p>

Differences exist in bird communities using restored and natural wetlands in the Parkland region, Alberta, Canada

Wetland restoration is used to compensate for historic and ongoing wetland losses. We compared bird community composition in 24 restored wetlands and 36 natural wetlands in the Parkland region of Alberta. Natural wetlands ranged in exposure to agricultural activity and were binned into three classes (low, medium, and high disturbance). Although the abundance and average species richness of birds were similar between restored and natural wetlands (analysis of variance: p > 0.22), the avian community composition differed significantly among wetland types (multiresponse permutation procedure [MRPP]: A = 0.05, p < 0.001). The avifauna using restored wetlands was distinct from the avifauna using natural wetlands spanning a range of disturbance levels (A = 0.02–0.06; p ≤ 0.006). Notably, restored wetlands were surrounded by less shrub/forest cover and more open water than low‐disturbance, natural wetlands. The majority (58%) of species using the surveyed wetlands were not classified as wetland‐dependent. Interestingly, if only wetland‐dependent species are considered, the avifauna using restored wetlands is no longer distinctive (MRPP: A < 0.01, p = 0.187), although the abundance of wetland‐dependent birds was marginally higher in restored wetlands (n = 24) than in low‐disturbance, natural wetlands (n = 10; Tukey's honestly significant difference test: p = 0.041). Overall, restored wetlands had reduced beta diversity compared to natural wetlands, regardless of whether the avifauna were restricted to wetland‐dependent species or considered comprehensively. This draws into question the legitimacy of the assumption that restoration can fully offset continued losses of natural wetlands.

Effects of Drainage for Silviculture on Wetland Hydrology

Wetland silviculture on the Southeastern Coastal Plain attempts to balance competing objectives of draining topsoils sufficiently to provide access and promote tree growth while maintaining hydric soil characteristics in compliance with the Clean Water Act. This balancing act is dynamic as soil hydraulic properties, and thus water table regimes, change over the stand rotation cycle. Previous studies have defined threshold ditch spacings that would sustain wetland hydrology on a wide range of poorly drained coastal plain soils in US southeast. There is strong evidence that the hydraulic conductivity (K) and transmissivity (T) of the soil profile increase as trees mature. Such changes increase drainage rates, lower water tables, and potentially remove wetland hydrology from drained sites. Results from a long term forested watershed study showed that T of the profile decreased from 50 m2/d under a mature loblolly pine plantation to 5.5 m2/d after harvest and site preparation for regeneration, and then increased to 34 m2/d by 8 years after replanting. Based on these results, a modeling case study was conducted to determine the effects of changes in soil properties on wetland hydrology for a pine plantation. Results showed that 90 cm deep drainage ditches would have to be more than 62 m apart in a young plantation (YP) to sustain wetland hydrology on a site with 15 cm of surface storage. Increases in K and T as the plantation matures increased the predicted threshold spacing (LT) for wetland hydrology from 62 m for YP to 290 m for a mature plantation (MP). For ditch spacings greater than LT, wetland hydrology will be sustained in a broad center section midway between ditches, with the width of the wetland section dependent on ditch depth, spacing and soil properties. Methods developed to estimate the lateral effect of a single ditch on wetland hydrology were used to determine the width of a strip adjacent to the ditch where wetland hydrology is not sustained, and, thereby the percentage of wetland loss from the plantation. Depending on ditch depth, wetland hydrology will not be sustained on 14 to 27% of the land area for a 200 m ditch spacing on the young plantation of the case study. As the plantation matures (to MP), wetland hydrology will not be sustained for normal ditch spacings (100 to 200 m) on these soils. More research is needed to determine effects of stand age and production practices on hydraulic conductivity for a wide range of drained soils. Wetland hydrology can be enhanced by limiting depth and increasing spacing of drainage ditches, by use of control structures in some cases, and by allowing field ditches to fill naturally as plantations mature.

Dynamic changes and driving factors of wetlands in Inner Mongolia Plateau, China.

Wetlands are one of the most critical resources in Inner Mongolia Plateau. However, the region has experienced severe wetland loss in the context of global change. To quantify the dynamic change and the related driving forces, we extracted wetland information using multi-temporal Landsat images between 1993 and 2013 using ArcGIS platform and man-machine interactive interpretation. Dynamically changing characteristics for the past 20 years were analyzed, including wetland types and spatial distribution patterns of the wetlands in Inner Mongolia. We also performed correlation analysis and generalized linear models to quantify the contribution of natural and human factors to the changes in natural wetland area. Our results indicated that the total area of wetlands was 42421.2 km2 in 1993, and decreased to 38912.4 km2 in 2013, a decline ratio of 8.3%. Meanwhile, all types of wetlands showed a trend of transformation into non-wetlands. Anthropogenic factors led to the loss of natural wetlands in Inner Mongolia. In grasslands, mining coal was the dominant driver for natural wetland loss, while in arable lands, agricultural encroachment and irrigation were the primary driving forces. These findings can provide meaningful information for improving sustainable wetlands management strategies according to local conditions in different sub-regions.

Insights into estuary habitat loss in the western United States using a new method for mapping maximum extent of tidal wetlands.

Effective conservation and restoration of estuarine wetlands require accurate maps of their historical and current extent, as well as estimated losses of these valued habitats. Existing coast-wide tidal wetland mapping does not explicitly map historical tidal wetlands that are now disconnected from the tides, which represent restoration opportunities; nor does it use water level models or high-resolution elevation data (e.g. lidar) to accurately identify current tidal wetlands. To better inform estuarine conservation and restoration, we generated new maps of current and historical tidal wetlands for the entire contiguous U.S. West Coast (Washington, Oregon, and California). The new maps are based on an Elevation-Based Estuary Extent Model (EBEEM) that combines lidar digital elevation models (DEMs) and water level models to establish the maximum historical extent of tidal wetlands, representing a major step forward in mapping accuracy for restoration planning and analysis of wetland loss. Building from this new base, we also developed an indirect method for mapping tidal wetland losses, and created maps of these losses for 55 estuaries on the West Coast (representing about 97% of historical West Coast vegetated tidal wetland area). Based on these new maps, we estimated that total historical estuary area for the West Coast is approximately 735,000 hectares (including vegetated and nonvegetated areas), and that about 85% of vegetated tidal wetlands have been lost from West Coast estuaries. Losses were highest for major river deltas. The new maps will help interested groups improve action plans for estuarine wetland habitat restoration and conservation, and will also provide a better baseline for understanding and predicting future changes with projected sea level rise.

Canals, backfilling and wetland loss in the Mississippi Delta

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

Diverse policies leading to contrasting impacts on land cover and ecosystem services in Northeast China

Abstract Understanding where important ecosystem services originate in space and how they change in time is essential for sustainable ecosystem management. Spatially explicit information of integrated changes in land cover and ecosystem services impacted by diverse policies has been unavailable in Northeast China, limiting the improvement of human well-being. Therefore, this study integrated remote sensing, meteorological records, and statistical data to evaluate the impacts of policies on land cover and ecosystem services from 2000 to 2015. The results reveal that diverse policies induced both notable changes in land cover, as well as geospatially varied changes in ecosystem services. Specifically, agricultural cultivation was still the dominant factor driving the losses of woodland, grassland, and wetland, while large areas of croplands have been returned to natural land cover, including a net area increase in woodland (2256 km2). Cropland expansion occurred at the expense of wetland (7121 km2), while the expansion of built-up land was converted primarily from cropland (62.8%). Marked decrease in water yield was observed, while sandstorm prevention, habitat suitability, and grain production have been enhanced on the scale of Northeast China. Moreover, soil retention and ecosystem carbon stock decreased slightly. In terms of present policies and changes in ecosystem services, it is important to rethink the emphasis on food production, reduce policy-driven natural ecosystem losses, and enhance the effectiveness of ecological projects. The findings are expected to help achieve win-win outcomes between ecological conservation and social-economic development in Northeast China.

Factors influencing blue carbon accumulation across a 32‐year chronosequence of created coastal marshes

AbstractSaline coastal marshes are blue carbon ecosystems with relatively high soil carbon (C) stocks and high rates of soil C accumulation. Loss of saline wetlands due to relative sea‐level rise, land‐use change, and hydrologic alterations liberates previously stored C and reduces the capacity for future C sequestration. Widespread wetland loss has prompted marsh restoration and creation projects around the world; however, little is known about the timescale and capacity for created marshes to function as blue C sinks and the role of environmental conditions in mediating soil C accumulation in restoration sites. Using a chronosequence of five created saline marshes ranging in age from 5 to 32 yr and two adjacent natural reference marshes in southwest Louisiana, USA, short‐ and longer‐term C accumulation rates (SCAR and LCAR, respectively) were determined using feldspar marker horizons and peat depth in cores at six locations in each marsh. Created marshes ranged in elevation from −12 to 41 cm (NAVD88) and supported assorted plant community compositions driven by local environmental conditions. SCAR ranged from 75 to 430 g C·m−2·yr−1, which were comparable in the two youngest and two oldest marshes. Longer‐term CAR ranged from 18 to 99 g C·m−2·yr−1 but did not significantly differ among marshes of different ages. Our findings indicate that LCAR in these created marshes were influenced by site‐specific environmental conditions (i.e., stem density and mineral sediment) rather than marsh age. Results suggest that conditions appropriate for the establishment of vegetation with high stem densities, such as Distichlis spicata and Spartina patens, may facilitate higher LCAR in created marshes, which may be useful for restoration project planning and mitigation of climate change.

Changes in ecosystem services from wetland loss and restoration: An ecosystem assessment of the Danube Delta (1960–2010)

Deltaic flood plains provide critically important ecosystem services, including food production, fresh water, flood control, nutrient cycling, spiritual values and opportunities for recreation. Despite growing recognition of their societal and ecological importance, deltaic flood plains are declining worldwide at alarming rates. Loss of wetland ecosystem services bears socio-environmental costs overlooked in land-use planning. Conversely, wetland restoration can deliver important long-term benefits. This paper examines effects of different land use policies on ecosystem services provided by the Danube Delta, one of Europe’s largest and most outstanding wetlands. First, we identify, characterize and measure the most important ecosystem services provided by the Danube Delta. Second, we assess trends between 1960 and 2010, contrasting periods of economic development (1960–1989) and ecological restoration (1990–2010). Our results indicate that i) the Danube Delta provides important services with benefits accrue from local communities to humanity at large, ii) that two thirds of the Delta’s ecosystem services have declined over the studied period and iii) that ongoing restoration efforts have so far been unable to reverse trends in ecosystem service decline. Benefits from ecological restoration policies are already becoming apparent, but at a scale not yet comparable to the costs from ecosystem decline incurred over previous decades.

Day and night use of habitats by northern pintails during winter in a primary rice-growing region of Iberia.

Loss of natural wetlands is a global phenomenon that has severe consequences for waterbird populations and their associated ecosystem services. Although agroecosystems can reduce the impact of natural habitat loss, drivers of use of such artificial habitats by waterbirds remain poorly understood. Using the cosmopolitan northern pintail Anas acuta as a model species, we monitored home-range and fine-scale resource selection across the agricultural landscape. Individuals were tracked using GPS-GSM transmitters, and a suite of environmental and landscape features were measured throughout the winter seasons. Spatial patterns of habitat use were analysed using generalized linear mixed effect models by integrating field-observations with GPS telemetry. All birds used rice fields as foraging grounds at night and commuted to an adjacent reservoir to roost during daylight. Home-ranges and maximum foraging distances of nocturnally foraging birds increased with decreasing availability of flooded fields, and were positively correlated with moonlight levels. Birds selected flooded rice paddies (water depth range: 9–21 cm) with standing stubble and substrate with pebbles smaller than 0.5 cm in diameter. Density of rice seeds, rice paddy size, and other environmental and landscape features did not emerge as significant predictors. Our findings indicate that nocturnal foraging of northern pintails within rice fields is driven primarily by straw manipulation, water level and substrate pebble size. Thus, the presence of standing stubble in flooded paddies with soft bottoms should be prioritized to improve foraging areas for dabbling ducks. These management procedures in themselves would not increase economic costs or affect rice production and could be applied for dabbling-duck conservation throughout the world.

Nutrient dynamics and their interaction with phytoplankton growth during autumn in Liaodong Bay, China

Discharges of domestic sewage, industrial wastewater, and runoff of agricultural fertilizer have caused severe nutrient pollution and eutrophication in many estuaries and coastal areas around the world, especially in the Bohai Sea of China and its inner bay, Liaodong Bay. Subsequent to studies of this bay during the summer of 2013, an investigation was conducted in the autumn (dry season) to better understand the interactive effects of light, temperature, and nutrient concentrations on phytoplankton growth in the bay. Analyses of long-term data showed that dissolved inorganic nitrogen concentrations had increased roughly sixfold to eightfold since the 1980s as a result of nitrogen fertilizer use, pollution from industrial wastewater and domestic sewage, and loss of wetlands and their water purification service. In contrast, phosphate and silicate concentrations have decreased by factors of 2 and 5, respectively, during the past half century because of anthropogenic reductions of sediment loads (e.g., the construction of check dams and reservoirs and large-scale vegetation restoration projects). We found no evidence that phytoplankton growth was limited by nitrogen or phosphorus. Plots of nitrate and silicate concentrations versus salinity indicated conservative mixing in both cases. Analogous plots of ammonium and phosphate revealed a net uptake and net input, respectively. Phytoplankton uptake likely accounted for the net uptake of ammonium, and desorption of phosphorus from suspended particulate matter for the net input of phosphate. The major factors controlling phytoplankton growth in this study were light availability and temperature. Nearly all incoming photosynthetically active radiation was attenuated in the water column, and less than 1% of the light energy was absorbed by phytoplankton. Comparisons of this study with previous work in Liaodong Bay during the summer and similar case studies in contrasting regions of the world revealed a general pattern of regional maxima of phytoplankton biomass (or even harmful algal blooms) and changes of community structure associated with light availability and temperature variations in the presence of growth-rate-saturating nutrient concentrations.

Spatial conservation planning under uncertainty: adapting to climate change risks using modern portfolio theory.

Climate change and urban growth impact habitats, species, and ecosystem services. To buffer against global change, an established adaptation strategy is designing protected areas to increase representation and complementarity of biodiversity features. Uncertainty regarding the scale and magnitude of landscape change complicates reserve planning and exposes decision makers to the risk of failing to meet conservation goals. Conservation planning tends to treat risk as an absolute measure, ignoring the context of the management problem and risk preferences of stakeholders. Application of risk management theory to conservation emphasizes the diversification of a portfolio of assets, with the goal of reducing the impact of system volatility on investment return. We use principles of Modern Portfolio Theory (MPT), which quantifies risk as the variance and correlation among assets, to formalize diversification as an explicit strategy for managing risk in climate-driven reserve design. We extend MPT to specify a framework that evaluates multiple conservation objectives, allows decision makers to balance management benefits and risk when preferences are contested or unknown, and includes additional decision options such as parcel divestment when evaluating candidate reserve designs. We apply an efficient search algorithm that optimizes portfolio design for large conservation problems and a game theoretic approach to evaluate portfolio trade-offs that satisfy decision makers with divergent benefit and risk tolerances, or when a single decision maker cannot resolve their own preferences. Evaluating several risk profiles for a case study in South Carolina, our results suggest that a reserve design may be somewhat robust to differences in risk attitude but that budgets will likely be important determinants of conservation planning strategies, particularly when divestment is considered a viable alternative. We identify a possible fiscal threshold where adequate resources allow protecting a sufficiently diverse portfolio of habitats such that the risk of failing to achieve conservation objectives is considerably lower. For a range of sea-level rise projections, conversion of habitat to open water (14-180%) and wetland loss (1-7%) are unable to be compensated under the current protected network. In contrast, optimal reserve design outcomes are predicted to ameliorate expected losses relative to current and future habitat protected under the existing conservation estate.