Changes in diversity and composition of flora along a corridor of different land uses in Karachi over 20 years: Causes and implications

Karachi Metropolitan Corporation has been extensively planting few species along the streets over the last few decades. However, the suitability of the species was not properly studied before planting them in Karachi. This is evident from the fact that many species were profusely planted in Karachi during different decades, which were later removed for various reasons. For instance, Eucalyptus was extensively planted during 1980s and 1990s along the streets in Karachi, which was later removed due to their fast growing roots and shoots that damaged many civic services. Therefore, the current study investigates (i) the changes in taxonomic diversity and the composition of the species growing along a major roadway of different land uses in Karachi, (ii) causes and implications due to the changes in their diversity and composition. This study reveals that monoculture plantings were commonly practiced in Karachi. Currently, Conocarpus erectus is the most frequent species, which alone has 83.55% individuals on the street under study. Earlier, the same street was extensively planted with Eucalyptus and Guaiacum officinale. In 1993, the street under study was represented by 32.04% native plants and 67.96% exotic plants from 67 different species. Currently, the same street is represented by 53 species. The target-based 10:20:30 heuristic guidelines and non-target based Shannon and Inverse Simpson Diversity indices have been applied to analyze the flora of the street. Inverse Species Diversity index of the plants along the corridor has declined substantially from 8.75 to 1.41 over the last two decades that shows an increase in monotonous landscaping along the street under study, which make them vulnerable to diseases and pests. The changes in species richness along different land uses have also been analyzed.