A network model framework for prioritizing wetland conservation in the Great Plains

Context

Playa wetlands are the primary habitat for numerous wetland-dependent species in the Southern Great Plains of North America. Plant and wildlife populations that inhabit these wetlands are reciprocally linked through the dispersal of individuals, propagules and ultimately genes among local populations.

Objective

To develop and implement a framework using network models for conceptualizing, representing and analyzing potential biological flows among 48,981 spatially discrete playa wetlands in the Southern Great Plains.

Methods

We examined changes in connectivity patterns and assessed the relative importance of wetlands to maintaining these patterns by targeting wetlands for removal based on network centrality metrics weighted by estimates of habitat quality and probability of inundation.

Results

We identified several distinct, broad-scale sub networks and phase transitions among playa wetlands in the Southern Plains. In particular, for organisms that can disperse >2 km a dense and expansive wetland sub network emerges in the Southern High Plains. This network was characterized by localized, densely connected wetland clusters at link distances (h) >2 km but <5 km and was most sensitive to changes in wetland availability (p) and configuration when h = 4 km, and p = 0.2–0.4. It transitioned to a single, large connected wetland system at broader spatial scales even when the proportion of inundated wetland was relatively low (p = 0.2).

Conclusions

Our findings suggest that redundancy in the potential for broad and fine-scale movements insulates this system from damage and facilitates system-wide connectivity among populations with different dispersal capacities.

     

Importance of agricultural landscapes to nesting burrowing owls in the Northern Great Plains, USA

Anthropogenic habitat loss and fragmentation are the principle factors causing declines of grassland birds. Declines in burrowing owl (Athene cunicularia) populations have been extensive and have been linked to habitat loss, primarily the decline of black-tailed prairie dog (Cynomys ludovicianus) colonies. Development of habitat use models is a research priority and will aid conservation of owls inhabiting human-altered landscapes. From 2001 to 2004 we located 160 burrowing owl nests on prairie dog colonies on the Little Missouri National Grassland in North Dakota. We used multiple linear regression and Akaike’s Information Criterion to estimate the relationship between cover type characteristics surrounding prairie dog colonies and (1) number of owl pairs per colony and (2) reproductive success. Models were developed for two spatial scales, within 600 m and 2,000 m radii of nests for cropland, crested wheatgrass (Agropyron cristatum), grassland, and prairie dog colonies. We also included number of patches as a metric of landscape fragmentation. Annually, fewer than 30% of prairie dog colonies were occupied by owls. None of the models at the 600 m scale explained variation in number of owl pairs or reproductive success. However, models at the 2,000 m scale did explain number of owl pairs and reproductive success. Models included cropland, crested wheatgrass, and prairie dog colonies. Grasslands were not included in any of the models and had low importance values, although percentage grassland surrounding colonies was high. Management that protects prairie dog colonies bordering cropland and crested wheatgrass should be implemented to maintain nesting habitat of burrowing owls.     

Effects of large-scale wetland loss on network connectivity of the Rainwater Basin,Nebraska

Context

The Rainwater Basin region in south-central Nebraska supports a complex network of spatially-isolated wetlands that harbor diverse floral and faunal communities. Since European settlement, many wetlands have been lost from the network, which has increased distances among remaining wetlands. As a result, populations of wildlife species with limited dispersal capabilities may have become isolated and face greater local extinction risks.

Objectives

We compared the pre-European settlement and current extent of the Rainwater Basin network to assess the effects of wetland losses on network connectivity for a range of maximum dispersal distances.

Methods

We constructed network models for a range of maximum dispersal distances and calculated network metrics to assess changes in network connectivity and the relative importance of individual wetlands in regulating flow.

Results

Since European settlement, the number of wetlands in the Rainwater Basin has decreased by?>?90%. The average distance to the nearest neighboring wetland has increased by 150% to ~?1.2 km, and the dispersal distance necessary to travel throughout the whole network has increased from 3.5 to 10.0 km. Last, relative importance of individual wetlands depended on the maximum dispersal distance. Which wetlands to preserve to maintain connectivity might therefore depend on the dispersal capabilities of the species or taxa of interest.

Conclusions

To preserve a broad range of biodiversity, conservation efforts should focus on preserving dense clusters of wetlands at fine spatial scales to maintain current levels of network connectivity, and restoring connections between clusters to facilitate long-range dispersal of species with limited dispersal capabilities.

     

Measuring urban habitat fragmentation: an example from the Black Country,UK

The processes of urbanisation have left a fragmented mosaic of habitat patches of varying size, shape and character with the result that from location to location the number and quality of contacts between patches varies considerably. Traditional measurements of this habitat fragmentation, and its converse, connectivity, have rarely looked at the landscape as a whole but instead have simplified it to specific landscape subsets, or else have looked at area-to-area relationships through generalising the landscape into homogeneous pixels or grids. In this paper the character of the whole landscape is examined at scales appropriate to the spatial variability of the urban environment. Using a direct measurement of patch-to-patch contact all contacts between all patches are examined and the relationship between all contiguous and connecting habitats is quantified. This is further refined to look at connections between patches of different quality, a measure that highlights the adverse effects of urbanisation as a whole on landscape connections between quality habitats.     

A mathematical approach to simulate spatio-temporal patterns of an insect-pest,the corn rootworm Diabrotica speciosa (Coleoptera: Chrysomelidae) in intercropping systems

We report on the use of a spatially explicit model and clustering analysis in order to investigate habitat manipulation as a strategy to regulate natural population densities of the insect-pest Diabrotica speciosa. Habitat manipulation involved four major agricultural plants used as hosts by this herbivore to compose intercropping landscapes. Available biological parameters for D. speciosa on bean, soybean, potato and corn obtained under laboratory conditions were used to group the homogeneous landscapes, composed by each host plant, by a similarity measure of host suitability either for larval survival and development, and adult survival and fecundity. The results pointed corn as the most dissimilar culture. Therefore, intercropping corn with any other crop system tested could reduce insect spread through landscape. This was proved using a cellular automata model which simulate the physiological and behavioural traits of this insect, and also different spatial configurations of the intercropping. Spatio-temporal patterns obtained by simulations demonstrated that the availability of corn bordering the field edge, which are areas more likely to invasion, is key for insect population control.     

Growth rates of common urban trees in five cities in Great Britain: A dendrochronological evaluation with an emphasis on the impact of climate

The knowledge of the rate at which trees grow in urban areas is an important aspect to consider as it can influence our quantification and valuation of the ecosystem services provided by an urban forest. This study investigates growth variations in diameter and height for four common urban tree species (Acer pseudoplatanus, Betula pendula, Fraxinus excelsior and Quercus robur) across five cities in Great Britain (GB) and how the typical radial growth of two of those species (F. excelsior and Q. robur) changes with climate. Dendrochronology was used to identify tree age and changes in ring width and diameter at breast height (DBH) and tree height were measured in-situ at the time of coring. Results indicate a substantial variation in the mean annual growth rates and the relationships between DBH and age or height and age of each species across different cities. However, the multiple factors affecting tree growth seem to influence different species in different ways, with for example A. pseudoplatanus trees showing overall the fastest growth in Peterborough but B. pendula ones showing the slowest. Precipitation and temperature had an effect on radial growth of F. excelsior and Q. robur trees in GB, but the strength and direction of influence varied with time of year, species and city. In particular, low precipitation at the start or during the growing season was found to be a significant factor limiting radial growth. A trend towards a reduction in ring width increment was therefore identified in hot and dry years, primarily in south-eastern cities but in other cities too. This highlights the risk that a changing climate may have on the growth and, consequently, on the ecosystem service provision of healthy urban trees.     

Toward estimating the value of stewardship volunteers: A cost-based valuation approach in King County,Washington, USA

Urban forestry professionals are increasingly challenged to find cost-effective strategies for resource conservation and management. Many organizations partner with citizen groups to host events that enlist volunteers to perform stewardship tasks like tree planting and trail maintenance. These volunteer programs incur costs to both the managing agency and partners, such as staffing, tools, and transportation. Volunteers contribute uncompensated time and expertise. Little is known about these contributions, yet citizen stewards and host groups represent an important human dimension of urban forest management. Using a survey administered to volunteers and host organizations at restoration events in King County Parks, WA, USA, we developed a cost-based approach to estimate the value of stewardship activities that occurred in the spring field season of 2011. Expenditures included volunteer and event host time and direct cost of traveling to and from events, on-site labor, equipment, and preparation costs. Results suggest that contributions made by volunteers and hosts are significant; the combined costs associated with the 17 sampled events was approximately $35,700. These efforts represent a small subset of the more than 1000 volunteer environmental stewardship activities that take place annually in King County.     

Underestimating the effects of spatial heterogeneity due to individual movement and spatial scale: infectious disease as an example

Many ecological and epidemiological studies occur in systems with mobile individuals and heterogeneous landscapes. Using a simulation model, we show that the accuracy of inferring an underlying biological process from observational data depends on movement and spatial scale of the analysis. As an example, we focused on estimating the relationship between host density and pathogen transmission. Observational data can result in highly biased inference about the underlying process when individuals move among sampling areas. Even without sampling error, the effect of host density on disease transmission is underestimated by approximately 50 % when one in ten hosts move among sampling areas per lifetime. Aggregating data across larger regions causes minimal bias when host movement is low, and results in less biased inference when movement rates are high. However, increasing data aggregation reduces the observed spatial variation, which would lead to the misperception that a spatially targeted control effort may not be very effective. In addition, averaging over the local heterogeneity will result in underestimating the importance of spatial covariates. Minimizing the bias due to movement is not just about choosing the best spatial scale for analysis, but also about reducing the error associated with using the sampling location as a proxy for an individual’s spatial history. This error associated with the exposure covariate can be reduced by choosing sampling regions with less movement, including longitudinal information of individuals’ movements, or reducing the window of exposure by using repeated sampling or younger individuals.

     

A new approach to varietal identification in plants by microsatellite high resolution melting analysis: application to the verification of grapevine and olive cultivars

Background  

Microsatellites are popular molecular markers in many plant species due to their stable and highly polymorphic nature. A number of analysis methods have been described but analyses of these markers are typically performed on cumbersome polyacrylamide gels or more conveniently by capillary electrophoresis on automated sequencers. However post-PCR handling steps are still required. High resolution melting can now combine detailed sequence analysis with the closed-tube benefits of real-time PCR and is described here as a novel way to verify the identity of plant varieties such as grapevine and olive.     

Barriers to the effective planning and management of residential encroachment within urban forest edges: A Southern Ontario,Canada case study

Studies document degradation and loss of publicly owned urban woodland area following adjacent residential development due to residential encroachment. Residential encroachment is the negative impacts of housing land uses within both rural and urban green infrastructure networks. Prevailing planning, design and management approaches in Southern Ontario municipalities in Canada indicate planning and management tools have been developed to remove and impede encroachment impacts; however, many are infrequently implemented. This lack of implementation contributes to a high prevalence and spatial area of encroachment within Southern Ontario municipal woodland edges with adjacent housing. Long interviews were conducted with the planners, landscape architects, woodland managers and bylaw enforcement staff of six Southern Ontario municipalities to determine the barriers to implementation of municipal encroachment tools. Results indicate key barriers to policy implementation that reflect a lack of awareness of, and priority placed on addressing, residential encroachment impacts, and impacts following the point of development in general. Barriers include: (1) insufficient community and municipal access to information regarding residential encroachment and their significance relative to other development impacts; (2) lack of clarity of goals by municipalities and between departments; (3) insufficient municipal leadership and commitment to limiting encroachment; (4) lack of sufficient means within municipal departments to prevent and address encroachment; and (5) ineffectual dynamics of enforcement. Recommendations for overcoming barriers to the development and implementation of effective approaches for addressing encroachment are provided.     

Role of green roofs in urban connectivity,an exploratory approach using landscape graphs in the city of Paris,France

Green roofs provide many ecosystem services, but little is known about the way they contribute to urban functional connectivity. This paper has the following four objectives: (1) to compare the potential green roofs’ role to connectivity in relation to other urban green spaces, (2) to specify the green roofs contribution’s type, (3) to explore the influence of building height integration method and finally (4) to assess the impact on connectivity of simulated greening new roofs. Using a landscape graph approach, we modeled ecological networks of three species groups with different dispersion capacities in the Paris region (France). Then, we computed several connectivity metrics to assess the potential contribution of green roofs to functional connectivity. At a large scale (metropole scale), our results show that green roofs can slightly improve the global connectivity largely through the connections rather than the addition of habitat area. More than a stepping stone function, green roofs would have a dispersion flux function at a local scale. Furthermore, when the difficulty of crossing movement is exponential to the height of buildings, green roofs over 20 m high are mostly disconnected from the ecological networks. In addition to the green roof’s height, our analysis highlights the very strong role played by buildings’ configuration. This study raises promising directions for the integration of building height into the analysis of urban connectivity. Detailed research and long-term biological data from green roofs and green spaces are needed to confirm our results.     

Consequences of less intensive farming on the landscape: an example of vegetation dominance by Chaerophyllum aureum in the meadows of a Pyrenean valley in France

The impact of agricultural practices on the dynamics of weed invasion in a rural landscape was studied by describing the spatial distribution of Chaerophyllum aureum populations colonising less intensive managed hay meadows. Polyphenol compounds were used as individual markers to identify the structure of C. aureum diversity, in terms of its scale and patterns, within and between fields along the bottom of a Pyrenean valley. The results revealed, firstly, the existence of a dominant `genotype' successfully colonising the entire area, and secondly, the maintenance of high levels of polyphenol diversity within five different populations. This spatial arrangement of `genetic' population diversity was obviously not related to the natural reproduction and dispersal patterns of this species, but to human practices of hay production, the principal effect of which is to mix seeds of different genetic origin and thus accelerate and amplify the colonisation process of adapted `genotypes'.     

How one tree can change the future of a neighbourhood: The process behind the creation of the Boerenhof Park as an example for tactical urban planning

In this paper, the process behind the making of the Boerenhof Park on an urban Waiting Space in Ghent (Belgium) is discussed. We are highlighting how in this case ‘tactical urbanism’ actions, such as planting a tree, turned out to have a long-term impact and as such can inform a ‘tactical urban planning’ approach. Through a learning by reflection method, the Boerenhof Park case has been re-analysed using a conceptual framework built up around the concepts of ‘scratch’, ‘scar’ and ‘score’. The focus was on discerning the transgressional elements for moving from short-term interventions to long-term change. Three key aspects are brought to light: the incremental approach, a desire-driven program, and a transversal collaboration. We argue that these are key aspects for the operationalisation of a tactical urban planning approach.     

Influence of tree crown characteristics on the local PM10 distribution inside an urban street canyon in Antwerp (Belgium): A model and experimental approach

Apart from influencing the amount of leaf-deposited particles, tree crown morphology will influence the local distribution of atmospheric particles. Nevertheless, tree crowns are often represented very rudimentary in three-dimensional air quality models. Therefore, the influence of tree crown representation on the local ambient PM₁₀ concentration and resulting leaf-deposited PM₁₀ mass was evaluated, using the three-dimensional computational fluid dynamics (CFD) model ENVI-met^® and ground-based LiDAR imaging. The modelled leaf-deposited PM₁₀ mass was compared to gravimetric results within three different particle size fractions (0.2–3, 3–10 and >10 μm), obtained at 20 locations within the tree crown. Modelling of the LiDAR-derived tree crown resulted in altered atmospheric PM₁₀ concentrations in the vicinity of the tree crown. Although this model study was limited to a single tree and model configuration, our results demonstrate that improving tree crown characteristics (shape, dimensions and LAD) affects the resulting local PM₁₀ distribution in ENVI-met. An accurate tree crown representation seems, therefore, of great importance when aiming at modelling the local PM distribution.     

Contextualising landscape perceptions: the role of urban landscape,ecosystem and water system in formation of mental models of a stormwater wetland in Brisbane

Landscape Ecology - Ecological design used for stormwater management—referred to as Water Sensitive Urban Design (WSUD)—exemplifies how urban environments can benefit from mimicking...     

Quantifying the speed, growth modes, and landscape pattern changes of urbanization: a hierarchical patch dynamics approach

Urbanization transforms landscape structure and profoundly affects biodiversity and ecological processes. To understand and solve these ecological problems, at least three aspects of spatiotemporal patterns of urbanization need to be quantified: the speed, urban growth modes, and resultant changes in landscape pattern. In this study, we quantified these spatiotemporal patterns of urbanization in the central Yangtze River Delta region, China from 1979 to 2008, based on a hierarchical patch dynamics framework that guided the research design and the analysis with landscape metrics. Our results show that the urbanized area in the study region increased exponentially during the 30 years at the county, prefectural, and regional levels, with increasing speed down the urban hierarchy. Three growth modes—infilling, edge-expanding, and leapfrogging—operated concurrently and their relative dominance shifted over time. As urbanization progressed, patch density and edge density generally increased, and the connectivity of urban patches in terms of the average nearest neighbor distance also increased. While landscape-level structural complexity also tended to increase, the shape of individual patches became increasingly regular. Our results suggest that whether urban landscapes are becoming more homogenous or heterogeneous may be dependent on scale in time and space as well as landscape metrics used. The speed, growth modes, and landscape pattern are related to each other in complicated fashions. This complex relationship can be better understood by conceptualizing urbanization not simply as a dichotomous diffusion-coalescence switching process, but as a spiraling process of shifting dominance among multiple growth modes: the wax and wane of infilling, edge-expansion, and leapfrog across the landscape.     

Native plant enthusiasm reaches new heights: Perceptions,evidence, and the future of green roofs

The use of native plants on green roofs has attracted considerable attention in recent years. With this comes the implicit assumptions that native plants are better adapted, provide greater environmental benefit, and are more aesthetically pleasing than non-native plants. We examined papers published in scholarly journals and papers presented at the annual North American green roof conference to identify who is promoting the use of native plants on green roofs, their rationale for doing so, and the scientific evidence to support the assertion that natives are better adapted. Architects, landscape architects, and biologists were the most likely to promote native plants and engineers were the least likely. Many of the reasons for using native plants on green roofs originate from ground-level landscaping and have simply been transplanted to the roof, without regard for the fact that the rooftop is a fundamentally different environment than the ground. Nearly half of all pro-native papers used the term “native” without definition. This review highlights the need for greater rigor and transparency when promoting the use of native plants and further demonstrates how misconceptions can result in sub-optimal green roof design and performance.     

Greening plans as (re)presentation of the city: Toward an inclusive and gender-sensitive approach to urban greenspaces

Cities around the world are increasingly expanding their sustainability agendas and adopting urban green and blue infrastructure planning as a strategy to become more resilient, healthy and sustainable. However, the development of urban greening governance often lacks a holistic vision that considers social inequities within the planning, implementation and management of green and blue spaces. Further, gender inequities have been a specific dimension particularly overlooked in urban greening planning, despite gender concerns gaining increasing political relevance in recent years. In this research, we assessed the extento to which social and gender equity are being considered in urban greening plans and projects at the local level. We chose Barcelona (Spain) as main case study due to its pioneering role in implementing crosscutting equity and gender policies at the municipal level. Building on document analysis and semi-structured interviews with key stakeholders, we examined how social justice and gender are understood and operationalized in practice, from the design phase to implementation and maintenance of greening projects. Our findings suggest a shift in the role of urban greening which evolved from an ornamental role to a multifunctional vision of greening and is recently incorporating equity and inclusivity concerns. We identified three action areas of inclusive, gender-sensitive urban green planning practices: first, the incorporation of inclusivity and care as guiding visible values to recognize multiple needs of city residents; second, urban design for different uses and perceptions of greenspaces, particularly in relation to accessibility and autonomy; and third, the awareness and expertise from municipal staff vis-à-vis the consideration of social and gender equity in green planning and participatory approaches. Finally, we provide practical examples of the strategies that the City of Barcelona is implementing in each area and discuss some challenges and limitations, including what we identify as ad hoc intersectional greening.