Novel ecosystems: How our cities are changing nature

URBAN AFFORESTATION AND BIODIVERSITY

Prosopis juliflora, or the Kikar. Pic: Dinesh Valke (via Flickr.com)

They are always a familiar sight – MCD workers patiently sweeping the tiny green leaves that rain down in a never-ending shower from the evergreen trees that line Delhi’s neighbourhoods; children playing with the long brown seed pods scattered on pavements; lovers resting against its muscular trunk. If ever a tree has ‘gone native’, it is the vilayati kikar (Prosopis juliflora).

The Mexican tree species was first brought into the city by the British who wanted a hardy tree that grew fast in Delhi’s arid soil to best implement their idea of an ‘ideal’ colonial capital with avenues lined by luscious evergreens. The victims were native deciduous trees, popular with the Mughals, which had no place in ‘Lutyens’ Delhi’.

The experiment worked all too well. Now, nearly 80 percent of Delhi’s Ridge area has been taken over by this invasive plant species, eliminating over 450 species of native vegetation in the area, according to ecologist C R Babu. Most experts quoted on the subject have termed it an “ecological disaster” since the tree is notorious for depleting water table reserves.

The case of Delhi’s kikars is however not an isolated one.  Other invasive tree species, like the eucalyptus (another water guzzler) and acacia, has been favoured by successive governments in India because they grew fast with very little maintenance and because of their contributions to revenue earned through agro forestry activities.

Besides beautification and commercial concerns, another reason why fast-growing, non-native trees or ‘exotics’ are still encouraged in ‘compensatory afforestation’ drives is that many city and state forest departments are under pressure to quickly ameliorate the situation, for example, after state-sponsored deforestation for development projects like the Mumbai Metro III in Mumbai that will affect over 5,000 trees in the city.

Invasive exotics like the kikar, eucalyptus and acacia species have resulted in monoculture ‘forests’, with the rapid loss of native trees which in turn has affected biodiversity in terms of animal, bird and insect species. Even though on paper, India’s forest cover increased by 21.34 per cent  between 2013 and 2015, a critical research paper published in 2011 revealed that India had actually lost 80% of its native forest cover, replaced by invasive exotics.

In such circumstances, most would regard the news that the Delhi Government has allocated Rs 50 lakhs for the removal of kikars from the Ridge area, as promising.  But here is the twist in the tale.  Given that the forest department officials regularly fight a losing battle with real estate encroachers and dumping of waste in the Ridge area, some environmentalists are raising concerns about whether the whole scale felling of the kikar trees is the right move, given the Ridge area’s importance in combating soil erosion and air pollution.

This clash of opinions and effects of city-level policies geared towards conservation and sustainability is emblematic of what is referred to as ‘novel ecosystems’. Human activity and urbanisation are creating ecologies that have no historical predecessors. In contrast to slowly evolving ‘natural’ ecosystems with a stable assemblage of species that are well-documented, cities represent ecosystems that have changed rapidly, significantly impacted by intensive and widespread human activities.

Metros like Delhi, Mumbai, Bangalore, Kolkata and Chennai and even smaller ‘industrial’ townships are all centred around what were once biodiversity hotspots. Urban land uses have resulted in the planting of invasive species, extensive landscaping (especially in rich neighbourhoods or residential enclaves), habitat fragmentation along ‘corridors’ of urban development and the creation of ‘heat islands.’

All this is of course accompanied by rapid changes in existing natural geographic features like rivers, lakes, wetlands, coastlines, variations in soil, water and air composition and the consequent changes in ecological cycles. In addition, socioeconomic activities also affect biodiversity by promoting or discouraging certain species and their propagation.

Urban ecology studies have long suggested that cities should be looked as ‘socio-ecosystems.’ More recent approaches suggest that understanding, assessing and enhancing urban biodiversity, after studying the interaction and functioning of environmental and social drivers, is the key to conservation initiatives, combating climate change, enhancing the sustainability of cities as habitats through ecosystem services like reducing the toxicity of air and soil, building groundwater reserves or mitigating floods as well as other ecosystem services that improve public health, and fulfil social or spiritual needs.

A reality of the anthropocene era is that most of us will experience ‘nature’ in urban settings. ‘Novel ecosystems’ are here to stay as urbanisation affects regional, local and the overall global environment and its ecological cycles. It is impossible to revert to the original or close-to-original states of nature. However, cities have the potential of hosting a far more varied assemblage of species than ‘untouched’ virgin spaces as noted in ‘wild’ lands like former industrial towns in decline that have been overtaken by natural elements or the city’s outskirts where the urban and rural sprawls mingle.

Experts attribute this ability of ‘novel ecosystems’ to two factors. One, the high heterogeneity of environmental and social components that create a variety of habitats that support different kinds of species – from semi-natural spaces in peri-urban areas to entirely novel environments like sewer and drainage areas, corporate office complexes, extensively landscaped spaces or squatter bastis. Two, the high number of introduced species through gardening, landscaping and afforestation activities.

Given sustainability and climate change concerns, there is a critical need to assess whether, to what extent and how flora and fauna species can survive in urban settings and to what extent urban biodiversity can be engineered or managed to provide the maximum number of ecosystem services. This would mean breaking the false dichotomy between ‘native’ and ‘exotic’ vegetation by focusing on the combination of trees and shrubs that would provide and maintain the most number of ecosystem services with the least number of trade-offs, for example in terms of ground water consumption.

In the case of Chennai, for example, a number ‘exotics’ like the tamarind, the Indian almond and the white silk-cotton tree (Ilavanpanju) have worked well in terms of the local ecology and its specific needs. The idea around planning urban biodiversity around a ‘greening design’ means unplanned or rushed tree planting is no longer an option. It also means involving various stakeholders like citizens, ecological experts, environmental scientists, urban planners, policy makers, government departments, and ‘green’ start-ups or companies to plan interventions.

Smita Mitra
About Smita Mitra 3 Articles
Smita Mitra has worked as an editor and writer for publications like Hindustan Times, Outlook and Himal Southasian. She is currently based in Bangalore.

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