Contributions of green spaces and isolated trees to landscape connectivity in an urban landscape

Abstract

Vegetation plays a fundamental role in conserving the biological diversity of urban areas. From isolated trees to multi-hectare patches, green spaces are critical to species conservation in urban landscapes. The abundance of green spaces can regulate the availability of habitat and resources for species’ survival. In many urban areas, the lack of vegetation inventories and ecological information at fine spatial resolutions limits conservation efforts. To evaluate the potential of very high-resolution imagery (WorldView-2, 30-cm resolution) to fill this gap, we sought to a) map contrasting urban vegetation cover types (grass, shrubs and woody vegetation) at the meter scale and with high accuracy, b) quantify the structural and functional connectivity of urban vegetation, and c) estimate the status of productive vegetation. We focused our analysis on land use and cover in the city of Xalapa in Veracruz, Mexico, and employed multiscale satellite imagery to estimate vegetation cover, connectivity, and health. We identified 38,579 patches of woody vegetation, of which 93 % corresponded to isolated trees contributing to 27 % of vegetation connectivity. Without woody vegetation, the connectivity index decrease up to 97 %; removing grass or shrubs would reduce connectivity by 38 % or 32 %, respectively. We identified 10 patches disproportionately important to connectivity, of which seven had some type of legal protection. Across vegetation types, 38 % of the vegetated area was unhealthy. Wooded element connectivity assessment at a fine spatial resolution is crucial to conserve and restore these key resources for biodiversity and human well-being in urban environments.