Wednesday, 31 August 2016

Urban tree cover and air-pollution - India

Felling of tree. www.atlasobscura.com
bats of Bangalore jlrexplore.com

 In the last two and a half months I have traveled quite a bit in and around the Delta districts of Tamil Nadu, namely Thanjavur, Tiruvarur and Nagapatnam districts and observed that at many places highways are being widened to accommodate ever-increasing motor vehicle traffic. In  the process, lots of trees are removed to make additional space available. That the government will plant saplings two times more than what ts removed is a good thing. Care must be taken to implement it to make up for the lost tree cover so that in the future many living spaces will have better tree canopy over them. Trees are an integral part of our ecosystem, giving us shadow, food and vegetables, besides providing shelter for birds and animals. Little do we know that they not only protect our environments against soil degradation and erosion in the hilly areas but also cut down air pollution in many places, including towns and cities. Tree canopy gives us protection against fine "particulate air pollution" that has serious health effects on population.

Forest cover, India. en.wikipedia.org

  In the last decade or so in many parts of Asia, particularly in India, in the name of urbanization,  thousands  of trees are felled down to make ways for housing developments, building of new highways, industries, etc and in the aftermath,  the tree covers in many Indian cities have shrunk considerably, leading to increasing heat- radiation and air pollution. Consequently people are living among fewer trees and are more exposed to fine particulate air pollution - less than 2.5 microns. In Tamil Nadu, many cities are losing their urban tree cover for many reasons: poor urban town planning, lack of  awareness, neglect of environmental impact and poor coordination between environmentalists and the government agencies. The detailed study undertaken by the Center for Ecological Science, IISc, Bangalore brings out the following facts:

01. Kolkata’s tree cover fell from 23.4% to 7.3% over 20 years; built-up area up 190%. By 2030, vegetation will be 3.37% of Kolkata’s area.

urbantreekey.calpoly.edu

02. Ahmedabad’s tree cover fell from 46% to 24% over 20 years; built-up area up 132%. By 2030, vegetation will be 3% of Ahmedabad’s area.  

 03.Bhopal’s tree cover fell from 66% to 22% over 22 years. By 2018, it will be 11% of city’s area.  

04. Hyderabad’s tree cover fell from 2.71% to 1.66% over 20 years. By 2024, it will be 1.84% of city’s area  

The above results are not encouraging and if unchecked, fine particulate air pollution will cause a host of serious heath problems to the urban dwellers such as pulmonary inflammation, sinusitis, premature mortality, accelerated atherosclerosis, altered cardiac function, etc. A study conducted in ten US cities by the US Forest Service - Davey Institute in Syracuse, New York has found that there is a direct correlation  between total tree cover in urban or semi urban areas and its impact on PM2.5 concentration and that urban trees and forests are saving an average of one life every year per city. The more tree cover in a city, the lower the PM2.5 concentration. So, in the urban and semi urban areas, trees form an effective filter against fine particle air pollution (particulate matter less than 2.5 microns, or PM2.5) and play a vital role by providing cleaner environment. The American researchers have found out that "urban forests are critical capital investments helping produce clear air and water; reduce energy costs; and, making cities more livable. Simply, it implies that "our urban forests improve people's lives."

 "Trees can make cities healthier, and  are an effective tool in reducing air pollution and creating healthier urban environments. It is imperative that the urban city development authority before venturing into a new project should seriously ponder and actively engage in increasing the tree cover in cities and its suburbs. Much  emphasis should be given to the  total amount of PM2.5 removed annually by trees in  Indian cities that may run into several metric tons and better tree cover will help the future generation lead a healthier life free from air pollution. It will be conducive to oxygen rich living environment.

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