As exotic plants and trees multiply, vital indigenous species are being pushed out of city spaces

The kanaka champa (bayur) tree at the corner of the busy IT corridor in Chennai gave way to flowing traffic some years ago. Mahadeshwara Swamy, scientist, and tree lover, remembers the luxuriant flowers and swaying branches of this tree, indigenous to Southeast Asia. Sadly, not one nursery source across the city could help replace that glorious tree.

Meanwhile, garden enthusiast Sarala Raman laments how difficult it is to source the kodi sampangi (jasmine telosma) and molaga chembarathi (a variety of hibiscus) plants from her childhood. A new kind of extinction drive is happening in cities, insidiously and relentlessly.

Intensive research carried out in Bengaluru has focused on understanding the spaces within the city: its streets, parks, lakes and home gardens. And its results have proved that biodiversity patterns are shaped by the preferences of people for a specific type of vegetation. For instance, close to 80% of the trees found in parks are not local (Nagendra and Gopal 2011). Shared apartment gardens tended to harbour relatively distinct sets of species, especially trees, palms and plants with ornamental significance, while single domestic gardens contain more flowering and medicinal plants used in daily worship, as well as fruit bearing plants and trees. Residents also indicated a decrease in wildlife biodiversity over time.( Jaganmohan M, Vailshery L S, Gopal D. et al. Urban Ecosyst (2012)).

P Hariesh, a Chennai-based landscape horticulturist, says, “When I started my career three decades ago, it was either hibiscus or ixora in home gardens. Since indigenous varieties are not so showy and as colourful, exotics like adenium, dahlias or orchids began to enter. Currently, more exotic varieties are chosen as they are cheaper, since ‘mass produced’ to cater to the demand.

Also, people want species that are easy to maintain. Local varieties like chembarathi or nandiavattai (crepe jasmine) that were tolerant to local pests are found unable to resist those like the mealy bug that come in with the exotics.

Native bird species are codependent on native vegetation for feeding as shown in Delhi ( Khera, Mehta and Sabata 2009). And invasive species like the thorny lantana originally introduced as an ornamental plant for gardens are recorded to have spread from cities to engulf dry forests in the surrounding countryside. As exotic entrants that have naturalised replace the old for intensively landscaped gardens, hybrids of different species that are simply more dependant on chemical fertilisers are foisted onto unsuspecting customers. Grassy lawns ‘fit’ into aesthetics while biodiverse gardens don’t. And inexorably the bewildering imposition of choice impacts the rapidity of change.

Where are the birds?

Urban residents are not always conscious of the links between the surrounding environment and our well-being. ‘Trouble free and low maintenance’ might be a convenient mantra, but one that can be ominous for our futures. Young mom Priya Mahesh worries, “Not many trees on our street, and mostly only exotics like the gulmohur. I have seen woodpeckers or kingfishers winging by only in the suburbs!”

Ecologist and renowned academician P Dayanandan rues, “The population in cities is increasing and that impacts biodiversity. For instance, as lakes give way to high rises, the plants associated with it have gone, and the animals with them.”

D Narasimhan, an academician who works closely with both local communities and the Government, says, “It is imperative that NGOs and individual groups are regulated by authorities and experts to encourage sensitive planting choices. Otherwise large-scale calamities like floods and cyclones will affect existing the green cover, keep returning, and cause even more damage.”

The ominous truth is that we know very little about the snowballing patterns and impacts of change. Convenience might well decide the composition of a city’s green cover and urban commons. In spite of thousands of research papers and theories, the sensitive greening of a city, might just depend on citizen action. Starting from each beautiful sensitive mind.

(Shobha is the Founder-Trustee of Nizhal, an NGO that works towards tree conservation)