Evaluating wetlands within an urban context

Coastal regions are among the most rapidly urbanizing places on earth. The numerous effects of urbanization on hydrology, geomorphology, and ecology make wetlands in urban regions likely to function differently from wetlands in non-urban lands. Furthermore, wetlands in urban regions may take on human-related values that they lack in non-urban areas, as they provide some contact with nature, and some opportunities for recrea-tions that are otherwise rare in the urban landscape. Evaluations of the success of restorations in urban regions require that criteria first determine the kinds and intensities of urban influence on the site, and then secondly assess functional performance. The development of success criteria, at both levels of assessment, depends on the proper definition of a reference domain (the set of wetlands to which success criteria will apply), and the documentation of a set of reference sites within the domain; both must be based within the urban context appropriate for the region of interest. An example is presented from a study of urban wetlands in New Jersey of a procedure for establishing the reference domain, the reference set of wetlands, and criteria for the assessment of urban influence.     

Emergy evaluation of food production in urban residential landscapes

To transform cities from heterotrophic into sustainable ecosystems many authors have called for increased food production, including home gardening, in urban areas. We conducted an emergy analysis of four model backyard landscape plots—a conventional ornamental landscape, an intensive organic garden, an edible landscape, and a forest garden—to assess the yield and sustainability of these systems. Data were collected during the 2001 growing season and extrapolated to make a five year projection. In the 2001 season, all plots had low Emergy Yield Ratios (EYR) of between 0.0003 and 0.17 and extremely low Emergy Sustainability Indices (SI). In the five year projection, all plots still had low EYRs of between 0.0008 and 0.33 and very low SIs. These low indices are due primarily to the high levels of economic inputs required for the installation and maintenance of these plots in an urban context. Analyses performed on larger systems (households, neighborhoods and cities) containing productive landscapes such as those studied here may produce different results. Installing food-producing landscapes in urban areas without altering the networks by which such landscapes are supplied, however, may not substantially alter the heterotrophic nature of cities.     

Common factors influence bee foraging in urban and wildland landscapes

Bees are important flower-visiting insects that display differential occurrences at food resources throughout urban and wildland landscapes. This study examined the visitation rates and foraging patterns of eight taxonomic groups of bees that are common to California poppies, Eschscholzia californica, in both landscape types. Bee occurrence was documented in relation to floral resource characteristics (patch area, poppy coverage, and poppy density), local landscape characteristics (distance to the wildland-urban interface, distance to riparian areas, distance to green space, and land use), and regional landscape context (urban versus wildland). Similar abundance and richness measures were recorded at both urban and wildland poppy patches, but community composition varied in each landscape. Bumble bees were more abundant at poppies in the wildland whereas species in the family Halictidae (sweat bees) were more abundant at poppies within the urban landscape. Resource patch size and density consistently correlated with increased bee presence for all bee types foraging in the wildland. Individual patterns of occurrence in the urban landscape were somewhat divergent; the foraging dynamics of larger bodied-bees (Bombus vosnesenskii and Megachile species) correlated significantly with resource patch size and density, whereas smaller-bodied bees (family Halictidae and Andrena species) were influenced by landscape characteristics such as distance to the wildland-urban interface and distance to riparian areas. In summary, the surrounding landscape had an influence on community composition, but the magnitude of the floral resource present at a site and factors relating to foraging energetics were dominant drivers of local occurrence. These results suggest that management strategies that provide dense and abundant floral resources should be successful in attracting bees, irrespective of their location within the urban matrix.     

Large body size for metamorphic wood frogs in urban stormwater wetlands

Constructed wetlands in urban environments may be used by urban amphibian populations for breeding. Yet, few studies have examined the performance of young-of-the-year from created wetlands even though the success of terrestrial life stages is directly linked to the performance of individuals at the egg and larval stage. We assessed how early-stage amphibians developing within constructed stormwater wetlands compared in body size (one metric of performance) to those in nearby natural wetlands. We conducted surveys for wood frog, Lithobates sylvaticus, larvae and young-of-the-year metamorphs at 13 wetlands located in the City of Edmonton, Alberta, Canada and compared metamorph size (a useful metric for fitness and reproductive success) between constructed stormwater and two types of natural wetlands. We related body size to within-wetland parameters (reflecting water chemistry, thermal regimes and physical characteristics) and used an information-theoretic approach to identify predictors of metamorph body size. Abundances of egg masses, larvae and metamorphs were generally lower at stormwater than natural wetlands. Metamorphs exhibited larger body size in stormwater wetlands compared to natural wetlands. Low metamorph abundances and cool, stable water temperatures best explained large body size in stormwater metamorphs. We propose that with increasing urbanization and associated construction of artificial wetlands, size benefits in early developmental stages may help individuals cope with reduced habitat suitability in the terrestrial environment.     

Amphibian use of constructed and remnant wetlands in an urban landscape

Urban areas are increasing in number, extent, and human population density worldwide. There is potential to mitigate negative impacts of urbanization to native pond-breeding amphibians by providing habitat in both remnant natural and constructed wetlands. This study examines amphibian use of potential breeding sites in natural and constructed ponds in a large metropolitan area to investigate habitat characteristics that are associated with successful breeding. I surveyed 62 ponds over three breeding seasons in Portland, Oregon, measuring eleven habitat characteristics that may influence their successful breeding: pond depth, nitrate level, aquatic refugia, aquatic vegetation, surrounding vegetation, pond permanence, presence of fish and of introduced bullfrogs, surrounding road density and forest cover, and whether they were constructed or remnant natural ponds. Five of the six native pond-breeding species that occur in the region were regularly found breeding in city ponds. Surrounding forest cover and amount of aquatic vegetation were highly associated with breeding, indicating that preserving and planting vegetation likely benefits urban amphibians. Non-native bullfrogs were not associated with native species richness. Surprisingly, whether a pond was natural or constructed was also only weakly associated with native species breeding, and the trend was towards higher presence for all species in constructed ponds. This indicates that novel, human-dominated areas can provide habitat for these species. Consideration of habitat characteristics associated with breeding success in urban pond management will likely benefit native amphibians in these rapidly expanding landscapes.     

Detecting the scales at which birds respond to structure in urban landscapes

Little empirical information exists about how birds respond to urban landscape structure across multiple scales. We explored how the variation in percent tree canopy cover, at four different scales, affected the abundance of bird species across various urban sites in North America. Bird counts were derived from previous studies, and tree patches were measured from aerial photographs that represented areas of 0.2 km², 1.5 km², 25.0 km², and 85.0 km². At each of the four areas, we conducted regressions between bird counts and percent cover of various tree patch sizes. From these analyses, we determined the area (called the best prediction area—BPA) and the patch size (called the best patch size—BPS) that accounted for a significant amount of the variation in bird counts, beyond the variation accounted for by these parameters measured at other scales. BPA and BPS were calculated primarily to take into account the high degree of collinearity that existed among the amount of tree canopy cover measured across the four scales.We calculated BPA and BPS values for a variety of bird species and ascertained whether larger species had relatively larger BPS and BPA values. In the spring, middle-sized to large birds (16.6 g–184.0 g) had relatively larger BPS values than did smaller birds (3.2 g–16.5 g), but in the summer, the largest birds (61.7 g–576.0 g) had small BPS values. Spring BPA values showed a similar result but summer BPA values did not. A majority of birds of all sizes had summer BPA values at the finer scales of 0.2 km² and 1.5 km². Overall, body size was an approximate predictor of the area and patch size at which a species responds to trees in a landscape, but many exceptions did occur. These exceptions could be related to a variety of factors, one being the difficulty in relating human-biased measurements to avian measurements of a landscape. The method described in this study will help researchers design multi-scale studies to address the effect of landscape pattern on different animal species.     

Indiana bat roosting behavior differs between urban and rural landscapes

Urban Ecosystems - Urbanization may negatively affect forest obligate bat species. We compared the roosting behavior of federally endangered Indiana bats (Myotis sodalis) in a fragmented site,...     

Developing habitat models for waterbirds in urban wetlands: a log-linear approach

Up to 95% of wetlands in southwestern Ontario, Canada, have been drained and converted to other land uses since the mid-1800s. Remaining wetlands now exist within a mosaic of urban and agriculture land cover and may resemble “islands” from the point of view of species that need this habitat. We investigated the relationships between waterbirds and wetland size, isolation, and adjacent forest cover and roads in 19 wetlands within and adjacent to London, Ontario. Waterbirds were grouped into resource-based guilds: Dabblers, Divers, Waders, and Gulls and Terns (because of small samples, the Passerine and Raptor guilds were dropped from the statistical analyses). Because of the high degree of multicollinearity between variables, we used log-linear analysis to develop models that explained variations in species richness in the waterbird guilds. The log-linear technique provided quantification of environmental effects in a richer way than previous research as the interplay between biophysical factors found in reality are partially captured by the inclusion of interaction in the habitat models. All of the models incorporated the biophysical variables of wetland size and adjacent wetland area, forest cover, and roads. Waterbirds in these urban and near-urban landscapes appear to be using all wetlands available to them, no matter how small or how disjunct the wetland. This has implications for wetland evaluations that may not rate wetlands in human-dominated landscapes highly enough to be protected from development.     

Dialogic landscapes: Toward a nuanced understanding of globalization in urban Indonesian signage

This article shows that a perspective rooted in Bakhtin's dialogism between the fixed centripetal and fluid centrifugal forces of language and culture is useful in achieving a nuanced understanding of globalization in general and semiotic landscapes in Indonesia in particular. Drawing on data from Indonesia, this article shows dialogic interconnections between fixed and fluid notions of languages and cultures through a multimodal and indexical analysis of governmental and commercial signage in the urban center of Semarang, the provincial capital of Central Java. The analysis highlights the nuanced localizing and globalizing strategies in signage and how dialogicity helps shape the semiotic landscape.     

Flight initiation distance changes across landscapes and habitats in a successful urban coloniser

Urban Ecosystems - Urbanisation is a major land use change that introduces novel sources of disturbance and risk into an ecosystem. Successful urban species modify their fear behaviour in response...     

Exotic plant invasions in forested wetlands: effects of adjacent urban land use type

There are a variety of land use types in urbanized areas that may have different effects on the ecological characteristics of patches of natural vegetation. In particular, residential housing and industrial land-use may have different effects on adjacent forest communities. We tested this hypothesis by examining the vegetation of forested wetlands in a densely urban region, northeastern New Jersey. Wetlands embedded in industrial areas were much less invaded by exotic plant species than were wetlands embedded in residential areas, as reflected in the number of exotic species, the fraction of the total flora that was exotic, and their frequencies of occurrence. Few other structural characteristics of the vegetation differed between the two types of urban areas. We suggest that the management of land adjacent to forest edges may explain this surprising result. The low rate of invasion of wetlands within industrial areas suggests they could have high conservation value in urban ecosystems.     

Factors affecting the perceived value of coins

Subjects were asked to judge the relative values or assign absolute values to coins similar to the proposed new UK 20p and £1 coins along with other metal blanks, prior to the announcement of the new coins. Preliminary studies indicated that while a ‘yellow’ (gold-coloured) coin would not normally be rated higher in value than the blank 5p coin, the addition of extra thickness and an elaborate edge enhanced its apparent relative value. It was also shown that seven-sided ‘white’ (silver-coloured) coins were rated as more valuable than 12-sided or circular coins of about the same diameter. The absolute values assigned to such coins followed a similar trend to the relative values. Seven-sided white coins were assigned higher values than 12-sided white coins, and thicker yellow coins were assigned higher value characteristics and colour were examined independently. For smooth circular, milled circular and seven-sided coins, ‘red’ (cooper-coloured) coins were perceived as least valuable, and white and yellow coins were equally often assigned to intermediate and high values. For red, white and yellow coins, smooth circular coins were rated least valuable and seven-sided coins as most valuable. It appears that people assign learned ‘rules’ about features indicating value in a systematic and independent manner.     

Factors affecting member perceptions of coalition impact

The purpose of this study was to identify attributes of communitybased coalitions associated with member perceptions of greater impact. Based on Hackman's model of work group effectiveness, we hypothesized that member effort, knowledge and skill, and performance strategies would affect their perceptions of coalition impact. Findings from a lagged regression on a sample of forty‐five youth‐oriented coalitions indicated that two aspects of member effort were associated with subsequent perceived impact, as were performance strategies for both coalition governance and community interventions. There were no associations, however, between member knowledge and skill and perceived impact. These results suggest that leaders may improve perceived coalition impact by encouraging member participation in discussions and interventions and by developing effective strategies for both governance and implementation.     

Managing urban wetlands for multiple use: research,restoration, and recreation

Conservation of urban wetland habitat is challenging, because multiple uses must coexist. We use examples from California and Wisconsin to describe potential synergies among recreation, restoration and research activities (the 3 R's). Allowing passive recreation is often essential to garner public support for habitat protection, restoration, and research. In turn, restoration activities can improve the appearance of degraded sites, and designing the work as a research experiment can serve the scientific community. Two projects at Tijuana Estuary support the 3 R's. (1) Oneonta Tidal Linkage is a 0.7-ha tidal channel and salt marsh that was excavated from disturbed upland to bring wetland habitat closer to the Visitor Center (thereby reducing visitor intrusion into natural marsh habitat, where endangered species would be disturbed). It supports an ambitious field experiment that is testing the importance of species diversity in restoration; it also includes a bridge that serves the interpretive program, and it adds 0.7 ha of wetland habitat that helps restore regional biodiversity. (2) A larger excavation (8 ha) of former tidal wetland will soon add wetland habitat, while testing the importance of tidal creek networks in ecosystem functioning and offering views and interpretive opportunities. A third situation, at the 485-ha University of Wisconsin–Madison Arboretum, concerns restored wet prairies, which provide habitat for native species and serve many hikers. Urban stormwater flows into and degrades the Henry Greene Prairie, allowing aggressive plants to invade. Research and restoration efforts are planned to sustain the habitat and recreation functions. These three models suggest that recreation, restoration, and research are compatible uses of urban wetland habitats.     

Demographic drivers of Norway rat populations from urban slums in Brazil

Urban Ecosystems - The Norway rat is a globally distributed pest, known for its resilience to eradication and control programs. Efficient population control, especially in urban settings, is...