In recent years we have seen a growing understanding and appreciation of the role that town and cities can play in preserving biodiversity if the green areas are managed appropriately. Recent studies show that this is true even in the densely population megacities in the developing world. I have been lucky to be involved in a three year-long study looking at the factors that determine species richness of butterflies in green areas (university campus, botanical garden and urban park) in Dhaka, Bangladesh. The study, conducted by the very talented early career researcher, Shawan Chowdbury, found that almost half of Bangladesh’s butterfly species could be found in these three urban parks, where species richness was positively influenced by temperature, and negatively by humidity. Worryingly, though all three parks show a negative trend of monthly species richness over the three years. The resulting paper has now been published in Journal of Urban Ecology.
Chowdhury, S.m Shahriar, S. A., Böhm, M., Jain, A., Aich, U., Zalucki, M. P., Hesselberg, T., Morelli, F., Benedetti, Y., Persson, A. S., Roy, D. K., Rahman, S., Ahmed, S. and Fuller, R. A. (2021). Urban green spaces in Dhaka, Bangladesh, harbour nearly half the country’s butterfly diversity. Journal of Urban Ecology 7, Issue 1,
https://doi.org/10.1093/jue/juab008
Abstract
Cities currently harbour more than half of the world’s human population and continued urban expansion replaces natural landscapes and increases habitat fragmentation. The impacts of urbanisation on biodiversity have been extensively studied in some parts of the world, but there is limited information from South Asia, despite the rapid expansion of cities in the region. Here, we present the results of monthly surveys of butterflies in three urban parks in Dhaka city, Bangladesh, over a 3-year period (January 2014 to December 2016). We recorded 45% (137 of the 305 species) of the country’s butterfly richness, and 40% of the species detected are listed as nationally threatened. However, butterfly species richness declined rapidly in the three study areas over the 3-year period, and the decline appeared to be more severe among threatened species. We developed linear mixed effect models to assess the relationship between climatic variables and butterfly species richness. Overall, species richness was positively associated with maximum temperature and negatively with mean relative humidity and saturation deficit. Our results demonstrate the importance of urban green spaces for nationally threatened butterflies. With rapidly declining urban green spaces in Dhaka and other South Asian cities, we are likely to lose refuges for threatened fauna. There is an urgent need to understand urban biodiversity dynamics in the region, and for proactive management of urban green spaces to protect butterflies in South Asia.
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