Butterfly species’ responses to urbanization: differing effects of human population density and built-up area

Abstract

Good knowledge on how increasing urbanization affects biodiversity is essential in order to preserve biodiversity in urban green spaces. We examined how urban development affects species richness and total abundance of butterflies as well as the occurrence and abundance of individual species within the Helsinki metropolitan area in Northern Europe. Repeated butterfly counts in 167 separate 1-km-long transects within Helsinki covered the entire urbanization gradient, quantified by human population density and the proportion of built-up area (within a 50-m buffer surrounding each butterfly transect). We found consistently negative effects of both human population density and built-up area on all studied butterfly variables, though butterflies responded markedly more negatively to increasing human population density than to built-up area. Responses in butterfly species richness and total abundance showed higher variability in relation to proportion of built-up area than to human density, especially in areas of high human density. Increasing human density negatively affected both the abundance and the occurrence of 47% of the 19 most abundant species, whereas, for the proportion of built-up area, the corresponding percentages were 32% and 32%, respectively. Species with high habitat specificity and low mobility showed higher sensitivity to urbanization (especially high human population density) than habitat generalists and mobile species that dominated the urban butterfly communities. Our results suggest that human population density provides a better indicator of urbanization effects on butterflies compared to the proportion of built-up area. The generality of this finding should be verified in other contexts and taxonomic groups.

Supporting Bees in Cities: How Bees Are Influenced by Local and Landscape Features

“…Inconsistencies in the classification methods may affect results in such a way that over or underestimates the actual urban impact on pollinators. Regardless, species richness and abundance generally appear to decrease in association with increased proportions of impervious surfaces [ 6 , 72 ]. Intensification of impervious surfaces has also been associated with shifts in pollinator community structure where greater proportions of impervious surface generally possess a higher abundance of cavity-nesting bees compared to ground-nesting bees [ 11 , 72 , 73 ].…”

“…Regardless, species richness and abundance generally appear to decrease in association with increased proportions of impervious surfaces [ 6 , 72 ]. Intensification of impervious surfaces has also been associated with shifts in pollinator community structure where greater proportions of impervious surface generally possess a higher abundance of cavity-nesting bees compared to ground-nesting bees [ 11 , 72 , 73 ]. Such results appear intuitive, given that impervious surfaces diminish the amount of available nesting space that can be utilized by ground-nesting insects; however, such trends are not entirely generalizable as city compositions may vary uniquely to affect bees differently.…”

Mammalian body size is determined by interactions between climate, urbanization, and ecological traits

“…1 , S 1 , Supplemental Data 1 ). Our overarching question is how climate and human population density, a proxy for the human built environment (i.e., urbanization; e.g., 34 ), impact mammal body size. We first addressed the relationship between body mass and head-body length, as each is commonly used as a body size metric but the former can vary seasonally due to age, reproductive status, or food availability 35 , potentially weakening mass-length allometries at range-wide scales 36 .…”

Nature-Based Solutions in Cities—Contribution of the Portuguese National Association of Green Roofs to Urban Circularity

“…1 as a relevant NBS real case implementation). Understanding cities as novel ecosystems and implementing approaches that use NBS would support the environmental, social and economic costs of inaction that would lead to ecosystem collapse considering how the special urban conditions affect biodiversity in green spaces [16,17].…”

“…Effective knowledge and engagement to assist mechanisms and instruments on legal and stakeholder level, involving communication and interdisciplinary research programmes and activities, provide constructive information and valuable transdisciplinary networks on NBS proper designs, implementation and performance-based assessment tools and techniques, and methods and analyses for socio-economic benefits and preferences based on nature [17,27,28]. The following sections highlight specific and/or combined NBS initiatives and actions that support an urban circular thinking; and, provide an overview of the current existing EU policies and regulations aimed at a systematic development, consideration and implementation of NBS, which would be promoted by citizens, researchers, investors/funders, policy-makers Fig.…”