Advancing understanding of the complex nature of urban systems

Cities and urbanized regions are complex, dynamic, and highly integrated systems linking social, ecological, and technical infrastructure domains in ways that create deep challenges for good governance, policymaking, and planning. The combination of impacts from climate change in cities, air pollution, rapid population growth, multiple sources of development pressure and overall urban system complexity make it difficult for decision-makers to develop and guide development trajectories along more livable, equitable, and at the same time, more resilient pathways. Advancing urban sustainability and resilience agendas requires expanding the scope of inter- and trans-disciplinarity approaches, moving beyond the historically separate social–ecological and socio-technical approaches to jointly study social–ecological–technical infrastructure systems in cities. We take urban complexity as a given and suggest that in both research and practice we need to better capture and understand feedbacks, interdependencies, and non-linearities which create uncertainties and challenge the efficacy of governance practices to achieve normative goals for society. Here, we explore new methods, tools, and approaches to advance our understanding of urban system complexity through a series of journal special issue articles that examine urban structure–function relationships, urban sustainability transitions, green space availability, social–ecological memory, functional traits, and urban land use scenarios.     

Are all urban green spaces a favourable habitat for pollinator communities? Bees,butterflies and hoverflies in different urban green areas

1. Urban ecosystems create suitable habitats for many plant and animal species, including pollinators. However, heterogenic habitats in city centres and suburban areas have various effects on pollinators due to variations in the composition of vegetation and in landscape management by humans. 2. This study compared the abundance and species richness of three main groups of pollinators – wild bees, butterflies, and hoverflies – in Poznań, western Poland, and in three different types of urban green areas – urban grasslands, urban parks, and green infrastructure in housing estates. 3. The total abundance of pollinators was higher in urban grasslands than in housing estates and urban parks. Species composition of pollinator communities differed between the three habitat types. 4. The study results showed that species richness and abundance of butterflies varied between habitat types, whereas no such differences were found in the case of wild bees and hoverflies. Cover of green area, vegetation structure, and plant height were important for the pollinator community; however, these variables had different effects depending on habitat type. 5. These findings revealed that not all urban green areas are equally valuable in terms of local biodiversity. High‐quality urban habitats such as urban grasslands are capable of supporting rich and abundant populations of pollinators. Therefore, it is important to protect high‐value urban green areas and simultaneously strive to improve intensively managed urban habitats through effective planning and new management practices.     

Consumer‐resource interactions along urbanization gradients drive natural selection*

Urbanization is an important component of global change. Urbanization affects species interactions, but the evolutionary implications are rarely studied. We investigate the evolutionary consequences of a common pattern: the loss of high trophic‐level species in urban areas. Using a gall‐forming fly, Eurosta solidaginis, and its natural enemies that select for opposite gall sizes, we test for patterns of enemy loss, selection, and local adaptation along five urbanization gradients. Eurosta declined in urban areas, as did predation by birds, which preferentially consume gallmakers that induce large galls. These declines were linked to changes in habitat availability, namely reduced forest cover in urban areas. Conversely, a parasitoid that attacks gallmakers that induce small galls was unaffected by urbanization. Changes in patterns of attack by birds and parasitoids resulted in stronger directional selection, but loss of stabilizing selection in urban areas, a pattern which we suggest may be general. Despite divergent selective regimes, gall size did not very systematically with urbanization, suggesting but not conclusively demonstrating that environmental differences, gene flow, or drift, may have prevented the adaptive divergence of phenotypes. We argue that the evolutionary effects of urbanization will have predictable consequences for patterns of species interactions and natural selection.     

Plural cities in comparative perspective

Adopting a comparative perspective, the article focuses on ethnically heterogeneous cities as sites shaped by political economy, and asks whether varieties of the plural city can be mapped against varieties of polity. Four ideotypical configurations of city, society and polity (preindustrial-patrimonial, colonial, modern-industrial-capitalist, neoliberal-postmodern-global) are discussed in terms of their modalities of ethnicity. In preindustrial-patrimonial cities, rulers were concerned less with the ethnicity of subordinate minority populations than their ability to render tribute, taxes and labour. The colonial city was grounded in the differentiation of the population in terms of supposed 'racial' distinctions. Modern-industrial-capitalist cities sought the cultural and linguistic homogeneity of their immigrant populations through assimilation, or, where certain groups ('races') were thought unassimilable, through exclusion. In the late twentieth century such cities have shifted towards postindustrial and postmodern forms of sociality in a globalized, transnational, world espousing neoliberal economic and social policies and contested forms of 'multiculturalism'.     

A comprehensive wealth index for cities in Germany

We apply a comprehensive wealth index for the 100 largest autonomous cities in Germany to measure their endowment with environmental, energy, social, human, and economic capital stocks. We find that (i) there is no inherent trade-off between economic and environmental capital stocks; (ii) clear regional differences exist between West and East Germany and between North and South Germany; and (iii) the comprehensive wealth index is strongly correlated with housing rents, which reflect individual willingness to pay for living in a certain city.     

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 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 recreations that are otherwise rare in the urban landscape. Evaluations of the success of restorations in urban regions require criteria first to determine the kinds, and intensities of urban influence on the site, and secondly to assess functional performance. The development of success criteria, at both the 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.     

试论华南药用植物在城市及乡镇绿化中的作用

我国是“药用植物之乡”。本文概述了在华南地区约有4000种药用植物,其中约380种是城市及乡镇主要与常见的绿化用植物,这些用于绿化的药用植物不但在美化,而且还在净化环境中均起着重要的作用。本文分别列举出若干分布华南的药用植物,有作为庭园观赏或作行道树的速生乔木及配合其立体绿化用的灌木,包括藤状灌木;还有花檀用的花卉与草坪植物;另外有室内观赏的阴生植物;棚架或屋外遮阴用的木质或草质藤本;绿篱植物;护坡或护堤植物;水域或沼地观赏植物等。此外,文中还建议对若干药用,但系珍稀、濒危植物宜结合庭园绿化提供其适宜的生态环境,扩大种植面积,以保护与增加其种质资源。     

Functional sustainability indicators

Sustainability indicators (SIs) are not just traditional performance metrics but are value laden pathways to supporting urban development. This paper presents a functional classification for SIs. The following six classes are used to illustrate the various functions of SIs: (F1) Political and Operational; (F2) Problem Recognition and Awareness; (F3) Justificatory; (F4) Monitoring Control and Reporting; (F5) Normative Guidance; (F6) Communication and Opinion Forming. The Houston Sustainability Indicators (HSI) program was used as a heuristic case study of how the functional classification could be applied. F1 was illustrated by carefully choosing geographic boundaries for the study. F2 was highlighted by careful review of the socio-economics of persons in the Food Desert. F3 was demonstrated by a look at issues of calculating population growth totals and also setting standards for access to parks. F4 was illustrated by a look at Employment figures. F5 was highlighted by a look at affordability in Houston. Lastly F6 was explained by a look at income inequality. This paper is intended to strengthen the importance of sustainability in development planning, through the illustration of key functions for SIs.     

Exploring the links between functional traits and cultural ecosystem services to enhance urban ecosystem management

Functional traits have been proposed as a more mechanistic way than species data alone to connect biodiversity to ecosystem processes and function in ecological research. Recently, this framework has also been broadened to include connections of traits to ecosystem services. While many links between traits and ecosystem processes/functions are easily and logically extended to regulating, supporting, and provisioning services, connections to cultural services have not yet been dealt with in depth. We argue that addressing this gap may involve a renegotiation of what have traditionally been considered traits, and a targeted effort to include and expand upon efforts to address traits-cultural ecosystem services links in traits research. Traits may also offer a better way to explore the recognition and appreciation of biodiversity. Drawing upon examples from outside the explicit traits literature, we present a number of potential connections between functional traits and cultural ecosystem services for attention in future research. Finally, we explore considerations and implications of employing a traits approach in urban areas, and examine how connections between traits and ecosystem services could be developed as indicators in a research and management context to generate a robust and resilient supply of ecosystem services.