Exotic species outnumber native trees along city's streets.

Byline: Faiza Ilyas

KARACHI -- The exotic Conocarpus heavily dominates streets of Karachi, which exhibits extremely low flora diversity with exotic species outnumbering native ones. Several major streets do not have any trees at all while countless trees have been uprooted for redevelopment of urban infrastructure over the years, says a Karachi University (KU) study recently published in an international journal.

Titled Town socio-economic status and road width determine street tree density, the study is published in the Urban Forestry and Urban Greening.

Led by their research supervisor, Dr Zafar Iqbal Shams, six students of the Institute of Environmental Studies collected the data during 2016-17. They were: Mubah Shahid, Zara Nadeem, Shafaq Naz, Dania Raheel, Darakshan Aftab, Tayyab Raza Fraz and Muhammad Sohaib Roomi.

An important initiative in recent years, the research based on the data collected from 18 (defunct) towns of Karachi provides detailed information about the species planted along streets, its relation with the socio-economic status of residents, as well as gaps in the government approach towards city's plantation.

According to the study, there is a lack of appreciation and dearth of knowledge regarding street trees in Karachi despite growing importance and understanding about urban forestry.

Of the total 62 species found here, 54 have less than one per cent presence

'Karachi exhibits low species diversity mainly due to repeated planting of one or few species on its streets over the years. Overreliance on a few species could be a potential threat of their complete elimination from the streets due to diseases, pests or environmental changes.'

Overall, the study recorded 62 species (30 native and 32 exotic) along city's streets. Of them, the proportion of 54 species, many of which were native, was less than one per cent.

The street tree community, according to the study, had 62 per cent plants of Conocarpus, demonstrating its dominance on the streets.

Top five species recorded were; Conocarpus, lignum, neem, white fig and eucalyptus.

The study also found that the towns of high-income residents demonstrated high tree density compared to those of low-income residents.

The study attributed this pattern to high land value, better infrastructure of roads and sidewalks in high-income areas and lack of interest by relevant civic agency in plantation in low-income areas.

Some towns of low-income residents, Orangi, Baldia and Korangi...

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