Urbanization is not associated with increased abundance or decreased richness of terrestrial animals - dissecting the literature through meta-analysis

Saari, Seppo; Richter, Scott J.; Higgins, Michael; Oberhofer, Martina; Jennings, Andrew James Blevins; Faeth, Stanley H.

doi:10.1007/s11252-016-0549-x

Cited by 48 publications

(50 citation statements)

References 60 publications

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“…Indeed, Saari et al. (), in a multi‐taxa meta‐analysis of terrestrial animals based on 26 studies, found weak evidence of negative effects of urbanization on species richness, and no evidence of consistent responses of abundance. Clergeau et al.…”

Section: Discussionmentioning

confidence: 99%

“…Although species loss is more marked from suburban to urban than from rural to suburban areas, our results nonetheless suggest that urbanization exerts a consistent more‐or‐less negative linear effect on bird species richness. Previous reviews have found that the universality of richness and abundance responses is unclear (Saari et al., ). Here, in the most comprehensive quantitative review of birds yet, we find linear responses for richness (which have been less commonly found in literature) and non‐linear responses for abundance (which are previously unreported).…”

Section: Discussionmentioning

confidence: 99%

“…In particular, (i) we adopted an objective definition of urban, suburban and rural areas (e.g. Clergeau et al., and Saari et al., ) in order that different gradients can be broadly comparable; (ii) we assessed bird responses across a simple urban–rural contrast, but also assessed intermediate levels of urbanization, thus allowing detection of non‐linear responses; and (iii) we assessed the responses of bird communities in relation to city size, which is assumed to be a good indicator of city‐level characteristics (as per Bettencourt & West, ). This type of analysis provides a statistical framework for integrating results of previous studies, and aids our understanding of both the ecological implications of increasing urbanization and how to mitigate its threat to biodiversity.…”

Section: Introductionmentioning

confidence: 99%

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Non‐linearities in bird responses across urbanization gradients: A meta‐analysis

Batáry

Kurucz

Suarez‐Rubio

et al. 2017

Global Change Biology

114

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Urbanisation is one of the most extreme forms of environmental alteration, posing a major threat to biodiversity. We studied the effects of urbanisation on avian communities via a systematic review using hierarchical and categorical meta-analyses. Altogether, we found 42 observations from 37 case studies for species richness and 23 observations from 20 case studies for abundance. Urbanisation had an overall strong negative effect on bird species richness, whereas abundance increased marginally with urbanisation. There was no evidence that city size played a role in influencing the relationship between urbanisation and either species richness or abundance. Studies that examined long gradients (i.e. from urban to rural) were more likely to detect negative urbanisation effects on species richness than studies that considered short gradients (i.e. urban vs. suburban or urban vs. rural areas). In contrast, we found little evidence that the effect of urbanisation on abundance was influenced by gradient length. Effects of urbanization on species richness were more negative for studies including public green spaces (parks and other amenity areas) in the sampled landscapes. In contrast, studies performed solely in the urban matrix (i.e., no green spaces) revealed a strong positive effect on bird abundance. When performing subset analyses on urban-suburban, suburbanrural and suburban-natural comparisons, species richness decreased from natural to urban areas, but with a stronger decrease at the urban-suburban interface, whereas bird abundance showed a clear intermediate peak along the urban-rural gradient, although abundance in natural areas was comparable to that in suburban areas. This suggests that species loss happens especially at the urban-suburban interface, and that the highest abundances occur in suburban areas compared to urban or rural areas. Thus, our study shows the importance of suburban areas, where the majority of birds occur with fairly high species richness.3

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Non‐linearities in bird responses across urbanization gradients: A meta‐analysis

Batáry

Kurucz

Suarez‐Rubio

et al. 2017

Global Change Biology

114

View full text Add to dashboard Cite

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“…In our study, reptile abundance rather than richness seems to be sensitive to differences in habitat structure and human impact. Reports on differential effects of human land use on different diversity indices are not uncommon in the literature (Saari et al., ). Similar results have been found for grasslands (Simons et al., ) and rainforest ecosystems (Laurance et al., ), in which species abundances significantly changed with human impact while species richness remained stable.…”

Section: Discussionmentioning

confidence: 99%

Human land use promotes the abundance and diversity of exotic species on Caribbean islands

Jesse

Behm

Helmus

et al. 2018

Global Change Biology

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Human land use causes major changes in species abundance and composition, yet native and exotic species can exhibit different responses to land use change. Native populations generally decline in human-impacted habitats while exotic species often benefit. In this study, we assessed the effects of human land use on exotic and native reptile diversity, including functional diversity, which relates to the range of habitat use strategies in biotic communities. We surveyed 114 reptile communities from localities that varied in habitat structure and human impact level on two Caribbean islands, and calculated species richness, overall abundance, and evenness for every plot. Functional diversity indices were calculated using published trait data, which enabled us to detect signs of trait filtering associated with impacted habitats. Our results show that environmental variation among sampling plots was explained by two Principal Component Analysis (PCA) ordination axes related to habitat structure (i.e., forest or nonforest) and human impact level (i.e., addition of man-made constructions such as roads and buildings). Several diversity indices were significantly correlated with the two PCA axes, but exotic and native species showed opposing responses. Native species reached the highest abundance in forests, while exotic species were absent in this habitat. Human impact was associated with an increase in exotic abundance and species richness, while native species showed no significant associations. Functional diversity was highest in nonforested environments on both islands, and further increased on St. Martin with the establishment of functionally unique exotic species in nonforested habitat. Habitat structure, rather than human impact, proved to be an important agent for environmental filtering of traits, causing divergent functional trait values across forested and nonforested environments. Our results illustrate the importance of considering various elements of land use when studying its impact on species diversity and the establishment and spread of exotic species.

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“…Earlier studies suggested that urbanization increases overall abundance even as richness declines, but recent studies suggest a more variable response (Shochat et al. ; Faeth et al., ; Aronson et al., ; Saari et al., ; Marzluff, ). Organisms have been divided into categories based on their responses to urbanization; several categories have been proposed and debated (Fischer, Schneider, Ahlers, & Miller, ; Marzluff & Rodewald, ; McKinney, ).…”

Section: Urban Effects On Consumers and Trophic Interactionsmentioning

confidence: 99%

Trophic structure in a rapidly urbanizing planet

El‐Sabaawi

2018

Functional Ecology

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The human population is rapidly urbanizing, and the negative impacts of urban cover on biodiversity and ecosystem function are expected to increase. Trophic dynamics have been hypothesized to change with urbanization, with consequences for biodiversity and function. Here, I review recent progress in this area by focusing on how urbanization affects dietary sources, trophic interactions and the functional ecology of synanthropic species. Urbanization affects primary autochthonous production in terrestrial and aquatic ecosystems by replacing and fragmenting natural areas with impervious cover, increasing nutrient supply, changing hydrological regimes, and altering the composition and seasonality of primary producers. The responses of primary production differ between climatic regions or across hydrological regimes. Urbanization can also change the availability of subsidies (autochthonous vs. allochthonous resources) because many urban species feed on human food (anthropogenic subsidies) and because of changes in the plant composition and physical characteristics of riparian zones. Urbanization can change the composition of consumers by decreasing the abundance of apex predators, releasing mesopredators, as well as the introduction of non‐native omnivores. Few direct experiments have been conducted on trophic interactions in urban ecosystems. They broadly suggest that urbanization weakens herbivory and predation, but that it might increase competition between synanthropic and urbanophobic species. However, the outcomes of these interactions are highly context‐specific. The reliance of synanthropic species on anthropogenic subsidies appears to be an important aspect of urban trophic ecology. However, more research is needed to understand how dietary flexibility, especially in relation to anthropogenic subsidies, contributes to the physiology and population dynamics of synanthropes. Urbanization can dramatically change trophic dynamics in the urban ecosystem with implications for biodiversity patterns, management and conservation. However, it is clear that a broader and more mechanistic understanding of the urban food webs is needed. This can be accomplished through inclusion of functional trophic metrics in monitoring efforts, the use of stable isotope food web metrics, the use of multi‐trophic‐level experiments and a more detailed study of the functional ecology of synanthropes. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13114/suppinfo is available for this article.

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Urbanization is not associated with increased abundance or decreased richness of terrestrial animals - dissecting the literature through meta-analysis

Cited by 48 publications

References 60 publications

Non‐linearities in bird responses across urbanization gradients: A meta‐analysis

Non‐linearities in bird responses across urbanization gradients: A meta‐analysis

Human land use promotes the abundance and diversity of exotic species on Caribbean islands

Trophic structure in a rapidly urbanizing planet

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