Date Published: May 6, 2019
Publisher: Public Library of Science
Author(s): Savitha Swamy, Harini Nagendra, Soubadra Devy, Bi-Song Yue.
Cities comprise of mixed green patches that vary in size and are highly scattered and disconnected. Although small green spaces largely dominate the cityscape, they are often neglected and ignored by the naturalists and conservationists, as they do not fulfill the large green spaces criteria. The citizens on the other hand seem to have a different perception and requirements from small green spaces as they are within their neighbourhood. Bangalore, a developing city within South India, consists of a large number of newly formed residential areas which have pocket green spaces in the form of neighbourhood parks (henceforth NPs). They are maintained by the municipality and are mainly designed for recreation purposes, completely neglecting the fact that these spaces could be essential for biodiversity. Here, there is a disconnect between the requirements of the citizens, conservationists and the end product that the municipality delivers. Here, through a questionnaire survey we assess the biodiversity citizens are fond off, and use them as surrogate taxa for the not so immediately obvious taxa, insects to enumerate the biodiversity within NPs. We analyze and identify landscape characteristics around NPs which could enhance the biodiversity within NPs. Our results reveal that people are fond of Birds and Butterflies and we use them as surrogates for the inconspicuous taxa to assess biodiversity within NPs. 55 tree species, 45 species of birds, 41 species of butterflies and 68 morpho species of insects were recorded. We demonstrate that small green spaces are critical systems and help support biodiversity across three scale within the city. Interestingly, results suggests that density of NPs is more important rather than the size of NPs. Also, the presence of high density of NPs within a neighbourhood could support similar biodiversity that large green spaces support. Finally, this study provides insights on the landscape matrix that could help enhance biodiversity support service within NPs and the surrounding neighbourhood.
Fragmented and isolated habitat patches are the signature landscape of most cities . These habitats are heterogeneous and can vary from small home gardens to large sprawling campuses and heritage parks. Regardless of the size, they support biodiversity and provision a range of ecosystem services to the community [2–4]. Although large green spaces (henceforth LGS) support more biodiversity, the smaller patches surrounding them help connect the LGS which are otherwise isolated due to the built-up environment, additionally providing resources and habitats for various taxa. The role that these small green patches play often goes unnoticed and neglected as LGS provide more services, support more biodiversity and comprise more of natural vegetation . Neighbourhood parks (henceforth NPs) are pockets of green spaces within cities. Although NPs, are small and may not support biodiversity on their own, they could be acting as stepping stones, there by facilitating movement for vagile taxa such as birds, butterflies and insects, resulting in an increase in biodiversity at the regional scale [6–8]. NPs can serve as vital spaces for biodiversity that could strengthen the health of the ecosystem and the services provisioned to the society [9,10] especially at the neighbourhood scale. Therefore, it is essential to understand the landscape features and habitat complexities that may affect biodiversity within and around these small habitat patches.
Habitat determinants within the park could be the key factor for local species richness than size .The study showed that habitat characteristics that influenced each of the taxa varied and almost all showed only moderately linear relationships. Large NPs have a higher representation of birds, butterflies and insects in comparison to medium and small NPs. Results also showed that among the habitat variables—the canopy cover for birds, proportion of shrubs for butterflies and proportion of lawns for insects showed some influence on their presence. Other studies have also shown plant diversity at a local scale for butterflies; canopy cover, presence of trees, shrubs for birds and leaf litter for insects could influence their local species richness [22,29,30,31,17]. Even overall habitat complexity showed moderately linear relationship with all the 3 taxa. In general, there was a lack of very strong relationship with habitat variables that were examined at the park scale. This probably suggests that the immediate landscape matrix surrounding the NPs could have a major influence on the biodiversity. High density of small NPs determined the butterfly diversity in the absence of LGS. Implying that in a highly fragmented landscape, butterflies are more dependent on the density of green spaces at the neighbourhood scale. Suggesting that along with microhabitat composition and heterogeneity within NPs, the neighbourhood matrix within which NPs are embedded plays a crucial role in determining the local biodiversity. Birds are dependent on LGS, however, we recorded the Greenish Leaf Warbler (Phylloscopus trochiloides) and Blyth’s ReedWarbler (Acrocephalus dumetorum) which are migrant bird species, within neighborhoods which comprised several unmaintained vacant sites comprising wild vegetation surrounding the NPs. Neighbourhood green spaces with unmanaged vegetation such as tall grass, shrubs and thick bushes could be essential to support local biodiversity . The migrant bird species were recorded within the second belt, which comprised of LGS, several tree lined avenues and large number of NPs. Presence of street-lined trees within neighbourhoods could act as critical corridors for birds to move from one habitat to another . In reality, specialized species cannot use all habitats present in a landscape [33,34,35]. Hence, there is a need for heterogeneity and presence of closely knit NPs could be an important landscape feature that vagile taxa rely on to extend their habitat requirement beyond just the local habitats. The number of habitat types is positively related to biodiversity across landscape . Dramstad et al. (1996) argue that land cover diversity can contribute to biodiversity across different scales. Nielsen et al. (2013) reviewed 62 empirical research studies from 25 countries and pointed out that land cover heterogeneity may be the most important factor supporting urban biodiversity.