Nagendra, H. | Search bioRxiv

bioRxiv2022

Beyond the metropolis: Street tree densities and resident perceptions on ecosystem services in small urban centers in India

The role of urban street trees has been extensively studied in large metropolises, where they contribute significantly to faunal habitat, provide critical ecosystem services to residents and contribute to human well-being. On the other hand, rapidly urbanizing cities in India have been poorly studied, despite multiple types of irreplaceable losses related to tree cover. However, being early in their urbanization history, these centers also represent opportunity for urban sustainability with potentially high remnant vegetation and human-nature connections. While megacities in developed countries move towards biophilic urban planning and participatory decision making, basic information on tree communities and their perceived services is a bottleneck in achieving these goals in such small urban centers. We assessed the street tree community and resident perceptions of ecosystem service values in Kochi and Panjim, two coastal cities in India under rapid development, through a combination of field measurements (258 transects, 931 trees) and semi-structured interviews (497 individuals). We found that mean street tree density is low in both cities, especially so in Kochi, and corresponds to perceptions of recent change in tree cover (-28% in Kochi, -11% in Panjim). The street tree community in both cities were dominated by ornamental avenue trees such as Albizia saman and Peltophorum pterocarpum, but native coastal species like Cocos nucifera, Terminalia catappa and Thespesia populnea were also common. Despite recent urban growth, residents in both cities reported low value of trees for food, fodder and medicine, but high value for regulating services like shade and water. Moreover, we found strong evidence for aesthetic and cultural values of trees in both cities, including through qualitative interviews. Our study establishes critical baselines for biophilic planning in these small urban centers towards urban sustainability.

ecology↗

bioRxiv2020

From local spectral species to global spectral communities: a benchmark for ecosystem diversity estimate by remote sensing

In the light of unprecedented change in global biodiversity, real-time and accurate ecosystem and biodiversity assessments are becoming increasingly essential. Nevertheless, estimation of biodiversity using ecological field data can be difficult for several reasons. For instance, for very large areas, it is challenging to collect data that provide reliable information. Some of these restrictions in Earth observation can be avoided through the use of remote sensing approaches. Various studies have estimated biodiversity on the basis of the Spectral Variation Hypothesis (SVH). According to this hypothesis, spectral heterogeneity over the different pixel units of a spatial grid reflects a higher niche heterogeneity, allowing more organisms to coexist. Recently, the spectral species concept has been derived, following the consideration that spectral heterogeneity at a landscape scale corresponds to a combination of subspaces sharing a similar spectral signature. With the use of high resolution remote sensing data, on a local scale, these subspaces can be identified as separate spectral entities, the so called "spectral species". Our approach extends this concept over wide spatial extents and to a higher level of biological organization. We applied this method to MODIS imagery data across Europe. Obviously, in this case, a spectral species identified by MODIS is not associated to a single plant species in the field but rather to a species assemblage, habitat, or ecosystem. Based on such spectral information, we propose a straightforward method to derive - (local relative abundance and richness of spectral species) and {beta}-diversity (turnover of spectral species) maps over wide geographical areas.

ecology↗