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Vol. 15 No. 1 - January 2009

Botanist in Urban Environment

 By: Sharad B. Chaphekar*

The Urbanization Process

While addressing the World Conference on Environment at San Francisco in 2005, the then Secretary General of the U.N., Kofi Annan, stated that in the middle of the last century about a third of human population lived in cities, the number increased to 50% by the end of that century and that in another 20-odd years, 60% of humans will be urbanites. There were 1,022,400,000 people in big cities (more than a million population)  in the year 2000. Since villages are gulped by towns, towns are rapidly getting converted into cities (population – > 100,000) and cities into big cities or metros (population > 1 million), it is reasonable to consider a habitat of over 100,000 population as an urban area. Considering the fact that the present human population is already six billion, the expanding frontiers of urban habitats invite concern.

A majority of these expanding cities is in developing countries. In Maharashtra for example, big towns with population exceeding one lakh increased from 12 in 1961 to 27 in 1991. Percentage of urban population of big towns also increased from 60.49 % to 77.83 % in the same period. Figures for cities, apart from Mumbai, also show a trend of increasing populations.  The cumulative effect of meeting even the minimum needs of this population – food, shelter, clothing and employment, would cause a degradation of the environment, especially since development of infrastructure in these areas cannot keep pace with the rapidly swelling urban populations.  

Healthy Tree Cover, The key to good environment

The World Conference dwelt extensively on this problem and suggested that some fifty-odd selected big cities in the world should be developed as “ecologically sustainable, economically dynamic and socially equitable” cities for future urban citizens. Twenty-one action points were suggested to put these cities on path to greener, healthier environments for the current residents and to the approximately one million people that migrate globally to cities each week. The goal for development of green cities is to have public parks within half a mile of every city resident by the year 2015, to reduce green house emissions by 25 % by the year 2030, and zero % waste going to landfills and incinerators by 2040. For achieving these goals, one has to study the urban habitats for their environmental problems and look for solutions. Since environment is often assessed on the basis of green cover it has, a botanist cannot afford to remain aloof from urban problems. In this context, many cities in the country should use the expertise of botanists.

Mumbai – The Urbs Prima of India

If anyone wishes to look deeper into the urban environmental problems, one does not have to go far. A metropolitan city like Mumbai provides an example where environ-mental problems are calling for urgent corrective steps. Horizontal and vertical expansion, adverse changes in land use, degradation of land pollution of air and water, including coastal waters, noise pollution, increasing built up area at the cost of virgin and agricultural land, mountains of municipal solid waste – you name the problem and it is there staring at you. Heat island effect is perceived for decades and frequency of atmospheric brown clouds is on an increase affecting health of people, especially children.

The Biotic (Human) Factor

Since humans are always (and most justifiably) blamed for degrading the environment, let us look at an important aspect (the mere existence of numbers) of this biotic factor closely as it exists in Mumbai. With minor variations and modifications, lessons from this city should be applicable to other rapidly growing cities in the country.

The administrative area of the city has increased significantly since 1957, when Bombay became Greater Bombay (now Bruhan-Mumbai). The population of Bombay was estimated to be 13 million in 2005, on a land area of 438 sq. km. This works out to an overall population density of 29,680 per sq. km. More than 60% of inhabitants of the city live without proper houses, they live in slums and on pavements.

For more than a million vehicles, there is hardly any parking space, their movement on roads is also at a snail's pace. Measures are taken and or planned in the form of high-rises for pavement and slum dwellers, sky-walks and subways for pedestrians, construction of flyovers and vestibules to supplement roads for vehicular traffic and subterranean (metro-rail) and aerial (monorail) railways as additional means of mass transport. An organized water transport along coastal areas of the city is also under consideration.

Urban Greenery – Is Anyone Serious?

Trees are recommended for pollution abatement in urban-industrial areas, for aesthetic improvement, beautification of urban settings; improvising pattern in urban land-scape; complement to urban design; softening of microclimate - radiations, temperature, relative humidity; sorption of air pollutants; indication of pollution; habitat for avifauna; shelter for poor humans; barriers, fences to mark boundary. Pollution-sensitive plants are also recommended for indication of pollution as an early warning system for protecting human health.

The tree census carried out in the year 2000 revealed that there were 5,00,024 trees in the city, compared to 11,914,398 humans (as per 2001 census) returning a ratio of one tree per 24 humans. No standard has been suggested for this ratio so far, but the proportion appears to be too low to be acceptable for any environmental norm.

Area-wise, there were 312 trees per sq. km. There are several municipal wards in the city, where the number of trees per sq. km is less than 1000, but in some other wards that are a part of the old city there are more than 15,000 trees per sq. km. Just as human  population density varies greatly in different areas, tree density also varies tremendously, giving tree: humans ratios of 1: 10 at the highest, to 1: 134 at the lowest end. 

Land – A Scarce Resource in Big Cities

In Mumbai, where an acre of land sells for tens of crores of rupees, value of land need not be overemphasized. With multiple demands on space, it is not easy to spare land for plantation. It therefore becomes necessary to ensure that optimal utilization of land is planned in cities and that every tree planted survives to maturity and carries out its ecological functions to the maximum. Just as norms have been developed for green belts around industries at the instance of Central Pollution Control Board, it is necessary to develop norms for development of greenery in urban areas, corresponding to different types of urban land-use.

Urban Stresses Affecting Trees

There are several stresses operating in urban habitats that affect plants adversely. These are: excessive compaction, presence of rubble, cement and construction waste, municipal solid wastes, presence of industrial solid waste, presence of leachates from industrial liquid waste, quantity and quality of water available, chopping, illegal trimming, mutilation of trunk, branches, canopy, change of land use, road excavation, road widening, pollution of air, urban amenities, underground - drains, cables, etc., salt spray along coastal areas, perception of tree as traffic hazard, perception of tree as a source of allergens, perception of tree as a source of litter, perception of tree as a habitat for insects, mosquitoes and rodents.

Recommendation about planting indigenous tree species is easy to make, but difficult to practice. Propagation of several indigenous tree species is not standardized; domestication of trees found only in wilderness is still a far cry. Professional horticulturists design and maintain beautiful gardens even in small patches of land, as is evident from several traffic island gardens. It is felt however, that these are mainly islands of beauty, maintained at great cost, paid by industrial / commercial interests. They hardly answer the demand for urban trees contributing ecologically sustainable environs.

Architect's Vision of Trees

Normally town-planners reserve places for trees in the development designs of areas. Architects also include green spaces in their designs for institutional or residential areas. In both the cases however, the emphasis is on aesthetics; ecological sustenance against urban stresses, if present, is incidental. During a scrutiny of proposal s f or development of residential/commercial estate in the State of Maharashtra, it became evident that most planning was done taking for granted, existence of ideal conditions for tree growth. Selection of tree species was based on ease of growth. It is generally ignored that trees with horizontal buttresses, planted near compound or other building walls create instability to those structures. Trees with deep roots ruin underground water tanks and other services. While planning plantation of trees on footpaths, less than a sq. meter opening is marked per tree, as a result of which hardly any space is left around a mature tree, for entry of water in the ground for roots to absorb, or that the compact-ness of ground prevents roots from breathing freely. Trees producing abundant pollen, carried on air currents, are looked at with hostility by many citizens fearing allergic reactions and they would chop off flowering branches at first available chance.

Transplantation of existing trees is recommended without consideration about possible success of the costly exercise. It is a fact that all tree species can't be transplanted with success; either can not inherent character of the species concerned, or the level of maturity of the individual tree, apart from managerial pitfalls. Plantation on municipal waste dumps is recommended forgetting the need for proper waste treatment. Management of water for irrigation also needs to be meticulously planned.

Roadside Trees

Sustainable roadside trees have to be able to tolerate auto-exhaust; at the same time, their branches should not affect vehicular traffic. Seasonal phenomena like leaf-fall and fruit-fall may create traffic hazard with incalculable harm. Along wide roads with high-speed traffic, trees and bushy perennials have to be planted carefully, taking their canopy shapes and sizes into account, especially on inner arc of bends and medians.

Trees on the Waterfront

Trees along waterfronts, especially along coastline, need to be tolerant to salt-sprays, high soil salinity and capable of blooming effectively in high humidity conditions.

Role of a Botanist

Under the conditions discussed above, a botanist has his / her role already cut out. There are many botanists who are experts in identifying and describing wild, indigenous as well as urban trees, along with their natural distribution regions. What is necessary is to understand the ecological amplitude of the indigenous species for their successful introduction in urban areas. Methods of their propagation also need to be standardized, for their conservation, if they are anywhere near Red-Data books. Biological information in all possible detail, from root shape, size and growth behavior, to branching pattern of stem, size and shape of shoot and canopy, season and abundance of bloom, pollen and fruit production, etc. is necessary for selection of tree species in human activity-dominated habitats.

Much of this information is available in literature, but is rarely accessed by architects and town planners, as they have other priorities. They look at trained botanists for ready information about growth habits of trees, their pollution tolerance and absorption potential, their reaction to subterranean structures and service facilities, their benefits and nuisance values, etc. A conventional trained botanist is hardly equipped at present, to answer several queries posed by development planners. It is time that botanists collect and compile the relevant information, useful in varied urban situations. Like wildlife botanists and naturalists and agricultural botanists, the time now has come for 'urban botanists' to take up the challenge to make urban areas hospitable and ecologically sustainable, as suggested in the 2005 U.N. World Conference on Environment.


*Formerly Professor of Botany, Institute of Science Mumbai & Professor of Environmental Science, Pune University

Laxmi Niketan, 14, Dhus Wadi, Thakurdwar, Mumbai-400 002., <[email protected]>

This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.

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