Perda de diversidade taxonômica e funcional de aves em área urbana no sul do Brasil

Abstract

ABSTRACT. Reduction in taxonomic and functional bird diversity in an urban area in Southern Brazil. Urbanization is a globally process studied and considered one of the most drastic environmental disturb on biodiversity. This study aimed to evaluate how different intensities of urbanization act in the structure of birds in a medium size city inserted in a wetland area. In addition to the traditional metrics richness, abundance and taxonomic composition, it was found as the functional diversity and redundancy of birds are influenced by urban gradient. The urban area studied was the Pelotas city (31°46''S, 52°20'W) situated at the southernmost part of Brazil in a humid region of Pampa biome. A total of 216 fixed observation points along an urbanization gradient were used to sample the avifauna and four independent variables: number of trees, number of buildings with two or more floors, presence of aquatic habitat, and presence of open habitat. Functional traits of species characterized the biomass, diet, forage substrate and nesting substrate. The richness, abundance and functional diversity of avifauna were negatively related to the increase of urban intensity while the redundancy, different from the expected, did not respond to the urban gradient. The traits related to the areas with more intense urbanization (building with two or more floors) were: preference for foraging in the air, omnivory and cavity nesting. Areas with less intense urbanization (more trees and open habitats) were related to the preference for nesting on vegetation and in lower sites, and carnivory. The study showed the importance of the presence of open and aquatic habitats for the avifauna, landscape features typically not cited in urban studies, which highlight the need to adequate the mitigation actions for conservation efforts inside urban habitats according to the regional pool of species.KEYWORDS. Biotic homogenization, Rao's functional diversity, wetlands, Pampa biome. RESUMO.A urbanização é um processo globalmente estudado e considerado um dos distúrbios mais drásticos sobre a biodiversidade. Este estudo teve como objetivo avaliar como diferentes intensidades de urbanização atuam na estruturação da avifauna em uma cidade de tamanho médio e inserida em região de área úmida. Além das métricas tradicionais de riqueza, abundância e composição taxonômica, verificou-se como a diversidade e redundâncias funcionais das aves são influenciadas pelo gradiente urbano. A área urbana estudada foi a cidade de Pelotas (31°46'S, 52°20'W), extremo sul do Brasil, que está inserida em uma área úmida do bioma Pampa. A amostragem das aves e a medida das variáveis urbanas (número de árvores, número de construções de até dois andares ou de mais de dois andares, presença de ambiente aquático e presença de ambiente aberto) foram realizadas em 216 pontos fixos de observação que foram marcados em diferentes intensidades de urbanização. Os atributos funcionais utilizados para caracterizar as espécies foram os relacionados à massa, dieta, substrato de forrageame...

Bird diversity in an urban ecosystem: the role of local habitats in understanding the effects of urbanization

“…Although some effects of urbanization on the bird species assemblage were not so clear, the regression models nonetheless showed well known effects of urbanization. The proportion of arboreal vegetation cover was the most important variable predicting an increase in species richness in Canoas, corroborating the known role of green areas as biodiversity enhancers in urban centers (Chace & Walsh, 2006;Evans et al, 2009;Fontana et al, 2011;Ortega-Álvarez & MacGregor-Fors, 2011;Toledo et al, 2012;Njoroge et al, 2013;Aronson et al, 2014;Beninde et al, 2015;Sacco et al, 2015). Open landscapes prevail in the Canoas region, and the arboreal component is characterized by gardens, squares and parks in the urban area; this contrasts with cities with large forested areas on the borders, for instance around Porto Alegre (Fontana et al, 2011).…”

“…On the other hand, the negative effects of urbanization upon bird diversity are clearly showed in the relationships between species richness and the level of noise and the density of houses. Noise is a striking feature of urban centers, usually related to low species richness and abundance (Fontana et al, 2011;Pickett et al, 2011;Sacco et al, 2015). Together with other human activities, noise may constrain species' ability settle in urban centers, which leads to loss of diversity and differentiation in bird species assemblages (Francis et al, 2009;Fontana et al, 2011;Rolando et al, 1997;Slabbekoorn & Peet, 2003;Bisson et al, 2011;Pickett et al, 2011;Chávez-Zichinelli et al, 2013).…”

“…The availability of green areas and the level of noise are two of the most important features affecting urban avian species assemblages (Chace & Walsh, 2006;Evans et al, 2009;Fontana et al, 2011;Toledo et al, 2012;Njoroge et al, 2013, Beninde et al, 2015Sacco et al, 2015). High bird diversity in urban landscapes has been associated with high densities of trees and the presence of large green spaces connected or near to each other (i.e., not fragmented, but connected by corridors or acting as stepping stones) (Evans et al, 2009;Aronson et al, 2014, Beninde et al, 2015.…”

“…Birds' responses to living in urban centers and the effects of disturbance in these areas have been studied for decades in the northern hemisphere (e.g., Marzluff et al, 2001;Chace & Walsh, 2006;Evans et al, 2009;Pickett et al, 2011;Davis et al, 2012;Taylor et al, 2013;Aronson et al, 2014;Sol et al, 2014;Beninde et al, 2015), but are a relatively new research focus in South America (e.g., Fontana et al, 2011;Ortega-Álvarez & MacGregor-Fors, 2011;Toledo et al, 2012;Njoroge et al, 2013;Puga-Caballero et al, 2014;Leveau et al, 2015;Sacco et al, 2015). Although urban species assemblages in South and North America show similar patterns, still there are several gaps to be filled (e.g., demographic patterns, physiological responses, behavioral ecology, biotic homogenization; Ortega-Álvarez & MacGregor-Fors, 2011).…”

Diagnóstico ambiental do estuário do rio Tramandaí, litoral norte do Rio Grande do Sul, Brasil

“…Duas espécies exóticas invasoras foram observadas: o pardal (Passer domesticus) e o pombo doméstico (Columba livia). A presença dessas aves está relacionada com o aumento da urbanização das áreas adjacentes à faixa de praia (Sacco et al, 2015). Em todos os meses, foi registrada a presença de cães e veículos automotores na faixa de praia, o que configura infração do Código Ambiental do Município de Tramandaí (Tramandaí, 2017).…”