Species and functional diversity - A better understanding of the impact of urbanization on bee communities

Urban environments increase generalization of hummingbird-plant networks across climate gradients

Urbanization has reshaped the distribution of biodiversity on Earth, but we are only beginning to understand its effects on ecological communities. While urbanization may have homogenization effects strong enough to blur the large-scale patterns in interaction networks, urban community patterns may still be associated with climate gradients reflecting large-scale biogeographical processes. Using 103 hummingbird-plant mutualistic networks across continental Americas, including 176 hummingbird and 1,180 plant species, we asked how urbanization affects species interactions over large climate gradients. Urban networks were more generalized, exhibiting greater interaction overlap. Higher generalization was also associated with lower precipitation in both urban and natural areas, indicating that climate affects networks irrespective of habitat type. Urban habitats also showed lower hummingbird functional trait diversity and over/underrepresentation of specific clades. From the plant side, urban communities had a higher prevalence of nonnative nectar plants, which were more frequently visited by the hummingbird species occurring in both urban and natural areas. Therefore, urbanization affected hummingbird-plant interactions through both the composition of species and traits, as well as floral resource availability. Taken together, we show that urbanization consistently modifies ecological communities and their interactions, but climate still plays a role in affecting the structure of these novel communities over the scale of continents.

Identifying the coupling coordination relationship between urbanization and forest ecological security and its impact mechanism: Case study of the Yangtze River Economic Belt, China

Boosting the coordination and symbiosis of urbanization and forest ecological security is notably critical for promoting regional green and sustainable development and achieving emission peak and carbon neutrality goals. However, there was still a lack of in-depth analysis of the coupling coordination relationship between urbanization and forest ecological security and its impact mechanism. On the basis of the data from 844 counties in the Yangtze River Economic Belt, this paper explored the spatial differences and influencing factors of the coupling coordination degree of urbanization and forest ecological security. The results manifested that: i) There were apparent spatial disparities in the urbanization index, forest ecological security index, comprehensive index, coupling degree and coupling coordination degree of the Yangtze River Economic Belt. Among them, the spatial pattern of coupling coordination degree had a strong consistency with urbanization index, that is, areas with higher urbanization index also had higher coupling coordination degree. ii) Based on coupling feature identification, it was found that 249 'problem areas' were mainly located in Yunnan Province, southeastern Guizhou Province, central Anhui Province, and central and eastern Jiangsu Province. The main factor for the formation was due to the lag of urbanization in coordinated development. iii) Among the socioeconomic indicators, population structure (0.136), per capita year-end financial institutions loan balance (0.409) and per capita fixed asset investment (0.202) all had a positive impact on coupling coordination degree, while location conditions (-0.126) had a negative impact. Among the natural indicators, soil organic matter (-0.212) and temperature (-0.094) had a negative impact on coupling coordination degree. iv) During the process of coordinated development, it was necessary to increase financial investment and financial support, actively formulate policies to attract talents, enhance the education and publicity of ecological civilization, and develop a green circular economy. The above measures can promote the harmonious development of urbanization and forest ecological security in the Yangtze River Economic Belt.

Urban insect bioarks of the 21st century

Insects exhibit divergent biodiversity responses to cities. Many urban populations are not at equilibrium: biodiversity decline or recovery from environmental perturbation is often still in progress. Substantial variation in urban biodiversity patterns suggests the need to understand its mechanistic basis. In addition, current urban infrastructure decisions might profoundly influence future biodiversity trends. Although many nature-based solutions to urban climate problems also support urban insect biodiversity, trade-offs are possible and should be avoided to maximize biodiversity-climate cobenefits. Because insects are coping with the dual threats of urbanization and climate change, there is an urgent need to design cities that facilitate persistence within the city footprint or facilitate compensatory responses to global climate change as species transit through the city footprint.

Diversity of greenspace design and management impacts pollinator communities in a densely urbanized landscape: the city of Paris, France

The response of insect pollinator communities to increasing urbanization is shaped by landscape and local factors. But what about habitats that are already highly artificial? We investigated the drivers of pollinator diversity in a dense urban matrix, the city of Paris. We monitored insect pollinator communities monthly (March-October) for two consecutive years in 12 green spaces that differed in their management practices, focusing on four insect orders (Hymenoptera, Diptera, Lepidoptera, Coleoptera). Pollinator abundance and species richness were both positively tied to green space size and flowering plant species richness, but negatively linked to surrounding impervious surfaces. In addition, environmental features at both the local and landscape scales influenced the composition and functional diversity of wild bee communities. Indeed, small and large bees responded differently, with the occurrence of large-bodied species being impaired by the proportion of impervious surfaces but strongly enhanced by plant species richness. Also, sites with a majority of spontaneous plant species had more functionally diverse bee communities, with oligolectic species more likely to be found.

These results, consistent with the literature, can guide the design and management practices of urban green spaces to promote pollinator diversity and pollination function, even in dense urban environments.

Phylogenetic, functional and taxonomic responses of wild bee communities along urbanisation gradients

Increasing urbanisation is one of the primary drivers of land-use change that threaten biodiversity. Wild bee communities have been reported with contrasting responses to urbanisation, with varying effects on abundance and taxonomical diversity. The suite of functional traits exhibited by wild bee species might determine their persistence in urban areas. Urbanisation thus can impose an environmental filter with potential consequences on the functional and phylogenetical diversity of wild bee communities. Here, we sampled 2944 wild bee specimens from 156 species in 29 sites located along an urbanisation gradient using a replicated design in three mid-sized cities in the Loire valley (France). We show that urban landscape cover has a negative effect on overall species richness and taxonomical diversity indices, while total abundance remains constant. Species loss was taxon dependent, mainly driven by Andrenidae and Halictidae. Only a few species, especially of the genus Lasioglossum, were positively affected by the urban landscape cover. Urban and peri-urban areas differed in their composition of bee assemblages. Species turnover was the main component of beta diversity, driving community dissimilarities through the urban gradient. Urbanisation favours bees with small body sizes, social structure and extended flight periods but did not affect the phylogenetic or the functional diversity of communities. Our findings have implications for understanding the factors involved in the environmental filter exerted through the urban gradient on bee communities helping to implement conservation measures and managing urban spaces for bees.

Suburbanization within City Limits in Hungary—A Challenge for Environmental and Social Sustainability

Suburbanization is one of the most prominent processes of post-socialist urban development, leading to the deconcentration of people, capital, as well as productive and non-productive activities within the functional urban area. This phenomenon also has a significant impact on the traditional rural landscape and leads to environmental and social sustainability challenges. Outmigration from the city center to the rural municipalities of the agglomeration ring is already a thoroughly studied topic. However, less attention is given to migration processes not crossing municipal borders. In Hungary, a significant fraction of them is driven by similar motivations as “traditional” suburbanization. Such movements include flows to built-up residential areas that are physically separated from the urban core. Due to their peculiar development path, the inhabited outskirts can also become destinations for within-city migration. This kind of mobility can be considered suburbanization within the city limits. Because of the general lack of data, this phenomenon is seldom researched. However, this study attempts to address this gap. The prevalence of this process in Hungary is explored by analyzing national statistical data sources. Four case studies are selected for detailed examination—Győr, Zalaegerszeg, Kecskemét, and Szeged. GIS methods, field examinations, surveys, and expert interviews are used to get a detailed picture of the demographic and land cover change processes, as well as the distinctions between the destination areas of the case studies. A comparison of the results drawn from the different methods reveals that land use change in the study area is more widespread than what the land cover datasets indicate. The findings indicate that the Corine Land Cover categories describing mixed land use—especially complex cultivation patterns—are not able to capture the drastic function shift caused by intense suburbanization. Different environmental and social sustainability issues are identified depending on the economic status of the outmigrants. This paper also sheds some light on the urban planning considerations of this emerging challenge.

Functional diversity and habitat preferences of native grassland plants and ground-dwelling invertebrates in private gardens along an urbanization gradient

Urbanization is occurring around the globe, changing environmental conditions and influencing biodiversity and ecosystem functions. Urban domestic gardens represent a small-grained mosaic of diverse habitats for numerous species. The challenging conditions in urban gardens support species possessing certain traits, and exclude other species. Functional diversity is therefore often altered in urban gardens. By using a multi-taxa approach focused on native grassland plants and ground-dwelling invertebrates with overall low mobility (snails, slugs, spiders, millipedes, woodlice, ants, rove beetles), we examined the effects of urbanization (distance to city center, percentage of sealed area) and garden characteristics on functional dispersion, functional evenness, habitat preferences and body size. We conducted a field survey in 35 domestic gardens along a rural-urban gradient in Basel, Switzerland. The various groups showed different responses to urbanization. Functional dispersion of native grassland plants decreased with increasing distance to the city center, while functional dispersion of ants decreased with increasing percentage of sealed area. Functional evenness of ants increased with increasing distance to the city center and that of rove beetles decreased with increasing percentage of sealed area. Contrary to our expectation, in rove beetles, the proportion of generalists decreased with increasing percentage of sealed area in the surroundings, and the proportion of species preferring dry conditions increased with increasing distance to the city center. Body size of species increased with distance to city center for slugs, spiders, millipedes, ants, and rove beetles. Local garden characteristics had few effects on functional diversity and habitat preferences of the groups examined. Our study supports the importance of using multi-taxa approaches when examining effects of environmental change on biodiversity. Considering only a single group may result in misleading findings for overall biodiversity. The ground-dwelling invertebrates investigated may be affected in different ways from the more often-studied flying pollinators or birds.