PhD Defense Seminar cum Oral Examination
“The Effects of Urban Greenery on Biodiversity”
All are welcome
Abstract – “The world’s growing urban population and urbanized areas have occurred in areas with high biodiversity value. Frontiers of urbanization are also approaching protected areas and encroaching upon habitats of threatened or endemic species. Urbanization usually involves the destruction of habitat when natural vegetation is cleared to make way for buildings and roads, but cultivated greenery and open green spaces such as parks are also created. Such greenery and green spaces have been used as urban planning tools to improve the quality of life for human residents in cities, but have also been thought to be able to improve habitat quality for urban wildlife.
Using data from surveys of birds and butterflies, and satellite imagery in Singapore, my analyses show that cultivated tree cover and natural vegetation both promoted alpha diversity, while traffic density reduced alpha diversity. However, after controlling for the confounding effects of alpha diversity on community dissimilarity, cultivated vegetation was found to produce homogeneous bird and butterfly communities compared to natural vegetation. In addition, there was evidence of interactions between traffic density and tree cover.
In addition, I explored how abundances of 20 most common bird species in a subset of transects that were surveyed a decade ago (from 2000 to 2001) have changed, and if changes in abundance were related to changes in the urban landscape, or attributable to species interactions. The brood parasitic Asian koel (Eudynamys scolopaceus), which is known to prefer house crow (Corvus splendens) as hosts, has increased in abundance even though the house crow has declined from culling. There was also no evidence that the decline in house crow abundances through culling had resulted in release from competition for its co-invading alien, the Javan myna (Acridotheres javanicus). Instead, increased urbanization was correlated with the increase in abundance of the Javan myna.
In conclusion, cultivated greenery has not been a good substitute for natural greenery in terms of providing for biodiversity. This poses problems for maintaining truly urban biodiversity in compact cities such as Singapore, where future urbanization will necessarily involve the loss of remnant or regenerating natural vegetation within the built-up areas.”