Urban green roofs provide habitat for migrating and breeding birds and their arthropod prey

Impacts of a herring gull colony on runoff water quality from an urban green roof

Green infrastructure (GI) strategies, including green roofs, have become a common, decentralized, nature-based strategy for reducing urban runoff and restoring ecosystem services to the urban environment. In this study, we examined the water quality of incident rainfall and runoff from a green roof installed on top of the Jacob K. Javits Convention Center in New York City. Since the 2014 installation of this green roof, one of the largest in North America, a colony of nesting herring gulls grew to approximately 100 nesting pairs in 2018 and 150 nesting pairs in 2019. Water quality monitoring took place between September 2018 and October 2019. Except for phosphorus on some occasions, we found concentrations of nitrate, nitrite, chlorine, sulfate to be below federal drinking water standards. Levels of the fecal indicator bacteria (FIB), total coliform, E. coli, and Enterococcus, were consistently higher in runoff samples than rainwater, ranging from 150 to over 20,000 CFU/100 mL for E. coli and 100 to over 140,000 CFU/100 mL for total coliform. Quantitative polymerase chain reaction (qPCR) methods were used to search for potential opportunistic pathogens, including Legionella spp., Mycobacterium spp., Campylobacter spp., and Salmonella spp. Discovery of the presence of Catellicoccus marimammalium, a gull-associated marker in runoff water indicates that herring gulls are the likely source of contamination. Due to habitat loss, herring gulls, and other Larus gull species are increasingly nesting on urban roofs, both green (such as at the Javits Center) and conventional (such as on Rikers and Governors Islands). Habitat creation is one of the target ecosystem services desired from GI systems. Although the discharge from the green roof of the Javits Center is directed to the city's sewer system, this study demonstrates the need to treat runoff from green roofs with nesting gull populations if its intended use involves reuse or human contact.

Urban rooftops near sports pitches provide a safe haven for a declining shorebird

Urbanisation has contributed to a severe decline in biodiversity worldwide. However, urban ecosystems can also play an important role in the conservation of threatened species, including ground-nesting birds such as the Eurasian Oystercatcher (Haematopus ostralegus). While the coastal populations of this shorebird have declined sharply, there is growing evidence that pairs nesting on urban flat roofs have high reproductive success. However, the reasons for rooftop nesting and the species' habitat use in urban areas remain poorly understood. In this study, we investigate the territory selection and foraging behaviour of the Eurasian Oystercatcher in the city of Münster (NW Germany). All nesting sites were located on flat roofs (N = 24), most of which were covered with gravel. Overall, reproductive success was high. This was mainly because the roofs provided protection from mammalian predators, leading to increased nest and chick survival. Moreover, breeding performance in the study area was favoured by the proximity of sports pitches. According to our observations, they provided a large amount of easily accessible prey throughout the breeding season. Overall, our study highlights that the reproductive success of the Eurasian Oystercatcher in urban environments is highly dependent on both safe nesting sites on flat roofs and the availability of suitable foraging habitats. Although our study suggests that breeding in urban areas can be beneficial for the model organism, the species' strong territory fidelity makes it very sensitive to the rapid environmental changes occurring in cities. The value of urban ecosystems for bird conservation should therefore be better integrated into urban planning and management.

Patterns in bird and pollinator occupancy and richness in a mosaic of urban office parks across scales and seasons

Urbanization is a leading cause of global biodiversity loss, yet cities can provide resources required by many species throughout the year. In recognition of this, cities around the world are adopting strategies to increase biodiversity. These efforts would benefit from a robust understanding of how natural and enhanced features in urbanized areas influence various taxa. We explored seasonal and spatial patterns in occupancy and taxonomic richness of birds and pollinators among office parks in Santa Clara County, California, USA, where natural features and commercial landscaping have generated variation in conditions across scales. We surveyed birds and insect pollinators, estimated multi-species occupancy and species richness, and found that spatial scale (local, neighborhood, and landscape scale), season, and urban sensitivity were all important for understanding how communities occupied sites. Features at the landscape (distance to streams or baylands) and local scale (tree canopy, shrub, or impervious cover) were the strongest predictors of avian occupancy in all seasons. Pollinator richness was influenced by local tree canopy and impervious cover in spring, and distance to baylands in early and late summer. We then predicted the relative contributions of different spatial scales to annual bird species richness by simulating "good" and "poor" quality sites based on influential covariates returned by the previous models. Shifting from poor to good quality conditions locally increased annual avian richness by up to 6.8 species with no predicted effect on the quality of the neighborhood. Conversely, sites of poor local and neighborhood scale quality in good-quality landscapes were predicted to harbor 11.5 more species than sites of good local- and neighborhood-scale quality in poor-quality landscapes. Finally, more urban-sensitive bird species were gained at good quality sites relative to urban tolerant species, suggesting that urban natural features at the local and landscape scales disproportionately benefited them.

Green roof development knowledge map: A review of visual analysis using CiteSpace and VOSviewer

Green roofs are generally acknowledged as environmentally sustainable roof systems with several environmental, economic, and social benefits, as well as an effective and practical strategy for mitigating the negative consequences of urbanization. In this paper, we used CiteSpace and VOSviewer bibliometric software for visual analysis, citation analysis, co-authorship network, co-citation analysis, and keyword analysis for descriptive statistics on 3986 articles on "green roofs" published in the Web of Science core database since 2000. Descriptive statistics were used for citation analysis, co-authorship network, co-citation analysis, and keyword analysis. According to a review of green roofing-related research literature, (1) Through analysis from three dimensions of country, institution, and author, it was found that China, the United States, and Italy ranked among the top three countries in terms of green roof publication volume; All but three of the top 10 institutions in terms of publications are from China and all are from developed countries; A large-scale collaborative network has not yet formed among authors. (2) Through keyword clustering analysis, it was found that "green roof," "performance," and "UHI" were the three keywords with the highest frequency. The research direction of this theme mainly includes five primary themes: rainwater management, urban biodiversity, building energy efficiency, alleviating urban heat islands and improving air quality, sustainable development, and public health. Through keyword hot words, it is found that the frequency of occurrence is relatively high, mainly involving energy conservation, alleviating urban heat islands, biodiversity, and sustainable development. The research on sustainable development, its impact on urban microclimate, and air quality remains a hot topic through keyword highlighting. (3) Co-citation analysis was used to identify the most influential journals, highly cited publications, and authors. (4) Three potential study objectives have been identified: synergistic development with other green infrastructures from an urban planning standpoint, localized research on green roofs, and photovoltaic green roofs.

Constructing urban ecological corridors to reflect local species diversity and conservation objectives

Ensuring bird diversity can secure key ecosystem services within cities. Building ecological corridors into urban planning is an effective way to protect urban birds, but existing corridor construction methods often ignore locality and diversity of species, leading to homogenization of corridor construction results and orientation. We proposed a corridor construction model that combines local bird surveys and bird threat levels. After constructing differentiated corridors for each bird species by assessing their habits and flight abilities, we used three weighted scenarios (original, weighted abundance, weighted abundance, and phylogeny) to assess the conservation priorities of birds and overlaid them to derive a comprehensive bird corridor model. Our results show significant differences in conservation priority and corridor pattern among different bird species, thus demonstrating the importance of local bird surveys and knowledge of threat levels in accurate corridor simulations. This study provides differential simulation of corridors for each bird species and the identification of important conservation species, and uses these to extend the theory of ecological corridor planning to urban bird populations. These results can be applied to guide biodiversity management, evaluate green space policies, and provide practical assistance for sustainable urban development and management.

Optimization of green infrastructure networks based on potential green roof integration in a high-density urban area-A case study of Beijing, China

Green infrastructure network (GIN) optimization is an effective measure to reduce the landscape fragmentation caused by rapid urbanization. However, there are few targeted and practical studies of GINs in high-density urban areas with a prominent contradiction between ecological construction and land scarcity, leading to insufficient feasibility of most optimization paths as they avoid practical contradictions (scarcity of land, high cost, etc.). As an effective way to economically increase green infrastructure, green roofs have been demonstrated to provide habitats and stepping stones to increase landscape connectivity for high-mobility organisms. However, few studies have applied green roofs to GIN optimization. To address this question, a new approach to optimize GINs was proposed from the perspective of integrating potential green roofs (PGRs). A complete and feasible workflow was also established to rapidly, accurately, and cost-effectively extract PGRs, scientifically evaluate the comprehensive landscape connectivity accounting for PGR isolation factors, and practically optimize GINs according to the spatial differentiation of PGRs with high landscape connectivity. This was done by integrating high-spatial-resolution remote sensing, machine learning, morphological spatial pattern analysis, landscape index method, and a minimum cumulative resistance model. A case study in a typical high-density urban area within the Beijing Fifth Ring Road, China demonstrated the applicability and implications of the workflow. The results clearly showed that the study area had a high potential for green roof retrofitting, PGRs with high landscape connectivity could effectively improve the GINs, and the spatial differentiation characteristics of the PGR network optimization benefits provided the scientific guidance for developing targeted ecological strategies. The new approach effectively improves the scientificity and implementability of GINs. It also provides a strong reference for landscape planning and ecological construction in other high-density urban areas facing the contradiction between ecological construction and land scarcity.

Do We Need More Urban Green Space to Alleviate PM2.5 Pollution? A Case Study in Wuhan, China

Urban green space can help to reduce PM2.5 concentration by absorption and deposition processes. However, few studies have focused on the historical influence of green space on PM2.5 at a fine grid scale. Taking the central city of Wuhan as an example, this study has analyzed the spatiotemporal trend and the relationship between green space and PM2.5 in the last two decades. The results have shown that: (1) PM2.5 concentration reached a maximum value (139 μg/m3) in 2010 and decreased thereafter. Moran’s I index values of PM2.5 were in a downward trend, which indicates a sparser distribution; (2) from 2000 to 2019, the total area of green space decreased by 25.83%. The reduction in larger patches, increment in land cover diversity, and less connectivity led to fragmented spatial patterns of green space; and (3) the regression results showed that large patches of green space significantly correlated with PM2.5 concentration. The land use/cover diversity negatively correlated with the PM2.5 concentration in the ordinary linear regression. In conclusion, preserving large native natural habitats can be a supplemental measure to enlarge the air purification function of the green space. For cities in the process of PM2.5 reduction, enhancing the landscape patterns of green space provides a win-win solution to handle air pollution and raise human well-being.

Small Urban Green Roof Plots Near Larger Green Spaces May Not Provide Additional Habitat for Birds

Global wildlife populations are in decline, in part, due to urbanization. However, in urban landscapes, green infrastructure such as green roofs are being created to provide habitat for wildlife. Green roof isolation, planting heterogeneity, and size can all influence wildlife biodiversity, as may the age of a green roof. When new habitat is created, wildlife use of these new habitats is expected to increase over time. To test this expectation for birds, we monitored bird activity prior to and after installation of small green roof plots on six buildings located within New York City parks. Contrary to expectations, bird activity and bird species richness did not increase after green roof plot installation, nor did they increase over a period of 4 years following installation. These unexpected results may reflect the relatively small size of the plots or the fact that the plots were on buildings located within urban parks. Bird activity and bird species richness varied widely between roofs, and the composition of rooftop bird species may have been more influenced by the characteristics of the surrounding landscapes than the presence of the green roof plots. These findings suggest that small urban green roofs within a larger and, potentially, higher quality habitat may not provide additional habitat for foraging birds. Urban green roofs have numerous ecological and environmental benefits, but the size and characteristics of landscapes surrounding a green roof need to be considered when installing green roofs as wildlife habitat.

Lessons from New York High Line Green Roof: Conserving Biodiversity and Reconnecting with Nature

The concept of sustainable urban design has appeared in different perspectives to minimize and reduce the negative impacts of urban expansion in terms of climatic and environmental drawbacks. One of the undeniable approaches of sustainable urban design is the adoption of green urban roofs. Green roofs are seen to have a substantial role in addressing and resolving environmental issues in the context of climate change. Research investigations have indicated that green roofs have a remarkable impact on decreasing rainwater runoff, reducing the heat island effect in urban spaces, and increasing biodiversity. Nevertheless, green roofs in urban spaces as a competent alternative to nature remains a standing question. To what extent can green roofs mimic the biodiversity that is seen in nature? Moreover, to what level is this approach practical for achieving a tangible reconnection with nature, or so-called biophilia? This study attempts to discuss the essence and impact of green roofs in urban spaces based on a case study approach. The study reflected lessons from the New York High Line Green Roof regarding biophilia and biodiversity in this case study. It concludes with key lessons that can be transferred to other urban spaces with similar settings.

Urban Integration of Green Roofs: Current Challenges and Perspectives

Green roofs (GRs) are a sustainable alternative to conventional roofs that provide multiple ecosystem services. Integrating GRs into urban areas is highly relevant considering the rapidly increasing built-up in cities. Therefore, this paper systematically and comprehensively reviews the recent literature from 2011 to 2019 on GRs to identify the challenges and perspectives related to the urban integration of GRs. The review suggests that the effectiveness of GRs in delivering ecosystem services is largely dependent on context-specific parameters such as weather conditions and existing construction or design-related parameters. Integrating GRs into urban areas can be challenging given the diversity of actors, functions, and conditions characterizing these areas. Although significant research has already been conducted on GRs, research covering more geographical locations and contexts is needed. The review points out the need to include future urbanization scenarios, such as tall buildings while analyzing the impact of GRs on ecological networks. Additionally, the review emphasizes the inclusion of urban morphological parameters alongside an analysis of the impact of GRs on microclimate regulation and air quality. In terms of social acceptance, this review points out the need to consider the temporal cycles of vegetation for noting users’ perspectives. Additionally, further research is required on the social impact of GRs, considering their influence on property prices. Lastly, the review stresses the need for more city-scale studies on the impact of GRs on ecosystem services.

Can Habitat Quality Index Measured Using the InVEST Model Explain Variations in Bird Diversity in an Urban Area?

Biodiversity maintenance is a crucial ecosystem service. Due to time limits and data availability, assessing biodiversity using indicators or models has become a hot topic in recent decades. However, whether some proposed indicators can explain biodiversity well at the local scale is still unclear. This study attempted to test whether the habitat quality index (HQI) as measured using the integrated valuation of ecosystem services and trade-offs (InVEST) model could explain variations in bird diversity in New Jiangwan Town, a rapidly urbanized region of Shanghai, China. The relationships from 2002 to 2013 among HQI and the two diversity indices, species richness and species abundance, were analyzed using Fisher’s exact test and gray correlation analysis. No significant association was found. Habitat connectivity was then integrated to develop a new combined indicator of habitat quality and connectivity index (HQCI). The associations between HQCI and the two diversity indices were improved significantly. The results indicated that connectivity may be an important factor explaining the diversity of certain species at a local scale. More empirical studies should be conducted to provide scientific evidence relating habitat quality to biodiversity.

Cross-tracking of faecal pollution origins, macronutrients, pharmaceuticals and personal care products in rural and urban watercourses

This study describes microbial and chemical source tracking approaches for water pollution in rural and urban catchments. Culturable faecal indicator bacteria, represented by Escherichia coli, were quantified. Microbial source tracking (MST) using host-specific DNA markers was applied to identify the origins of faecal contamination. Chemical source tracking (CST) was conducted to determine contaminants of emerging concern (CEC) of human/anthropogenic origin, including pharmaceuticals and personal care products (PPCPs) and endocrine-disrupting chemicals (EDCs). In addition, the eutrophication-causing macronutrients nitrogen and phosphorus were studied. MST tests revealed both anthropogenic and zoogenic faecal origins, with a dominance of human sources in the urban stream; non-human/environmental sources were prevalent in the rural creek. CST analyses revealed a higher number of CECs in the urban stream than in the rural watercourse. Positive correlations between PPCPs and both E. coli and the human DNA marker were uncovered in the urban stream, while in the rural creek, PPCPs were only highly correlated with the anthropogenic marker. Interestingly, macronutrients were strongly associated with primary faecal pollution origins in both watercourses. This correlation pattern determines the main pollutant contributors (anthropogenic or zoogenic) to eutrophication.

Green roof and ground-level invertebrate communities are similar and are driven by building height and landscape context

Green roofs are increasingly promoted for urban biodiversity conservation, but the value of these novel habitats is uncertain. We aimed to test two hypotheses: (i) green roofs can support comparable invertebrate family and order richness, composition and abundances to ground-level habitats and (ii) green roofs planted with native species from local habitats will support a richer invertebrate community at family and order level than other green roofs. We sampled the invertebrate community on green roofs dominated by native grassland or introduced succulent species in Melbourne, Australia, and compared these to the invertebrate community in ground-level sites close by, and sites with similar vegetation types. The only significant differences between the invertebrate communities sampled on green roofs and ground-level habitats were total abundance and fly family richness, which were higher in ground-level habitats. Second hypothesis was not supported as invertebrate communities on green roofs supporting a local vegetation community and those planted with introduced Sedum and other succulents were not detectably different at family level. The per cent cover of green space surrounding each site was consistently important in predicting the richness and abundance of the invertebrate families we focussed on, while roof height, site age and size were influential for some taxa. Our results suggest that invertebrate communities of green roofs in Melbourne are driven largely by their surrounding environment and consequently the effectiveness of green roofs as invertebrate habitat is highly dependent on location and their horizontal and vertical connection to other habitats.

Biodiversity Impact of Green Roofs and Constructed Wetlands as Progressive Eco-Technologies in Urban Areas

The total amount of sealed surfaces is increasing in many urban areas, which presents a challenge for sewerage systems and wastewater treatment plants when extreme rainfall events occur. One promising solution approach is the application of decentralized eco-technologies for water management such as green roofs and constructed wetlands, which also have the potential to improve urban biodiversity. We review the effects of these two eco-technologies on species richness, abundance and other facets of biodiversity (e.g., functional diversity). We find that while green roofs support fewer species than ground-level habitats and thus are not a substitute for the latter, the increase in green roof structural diversity supports species richness. Species abundance benefits from improved roof conditions (e.g., increased substrate depth). Few studies have investigated the functional diversity of green roofs so far, but the typical traits of green roof species have been identified. The biodiversity of animals in constructed wetlands can be improved by applying animal-aided design rather than by solely considering engineering requirements. For example, flat and barrier-free shore areas, diverse vegetation, and heterogeneous surroundings increase the attractiveness of constructed wetlands for a range of animals. We suggest that by combining and making increasing use of these two eco-technologies in urban areas, biodiversity will benefit.

Perception and Barriers to Implementation of Intensive and Extensive Green Roofs in Dhaka, Bangladesh

Buildings are one of the biggest consumers of fossil fuels, and thus, contribute largely to greenhouse gas emissions. As a result, a large number of studies have been conducted and innovative ideas or green solutions have been invented, adopted, and implemented across the globe. These solutions are often contextual and heavily dependent on local environmental and socio-economic factors. Green roofs are such an example. Green roofs (both intensive and extensive) for buildings have been successfully adopted in many countries around the world. Bangladesh, a developing country that can benefit from green roofs, seems to remain in complete darkness regarding its potential. The objective of this study is to identify the reasons why green roofs have not been widely implemented in Bangladesh, especially in the capital Dhaka, even though, theoretically, the climatic conditions of this country favor this technology. This study focuses on the perception of the construction industry to comprehend the possible obstacles they are facing towards using green roofs in their designs. A questionnaire study was conducted among architects, engineers, construction managers, contractors, and owners who are at different levels of experience in their respective fields. The results indicate a gap in knowledge and misconceptions, which are major hindrances to the implementation of green roofs.