Geospatial Technology in Urban Forest suitability

Introduction :- 

At present, the governments of various countries worldwide are attempting to address the issue of climate change. However, there are some major knowledge gaps which need to be looked at. The role played by urban forestry is one of the major factors. It is observed that urban green spaces help in mitigating the impacts of climate change by absorbing the various pollutants including greenhouse emissions and thus playing a vital role as a carbon sink to achieve a low carbon society. 

Urban forest and greenery around cities have seen to have many tangible and intangible benefits. Its development is one of the ways to lessen the gap between people and nature. The carbon cycle is altered because of the process of urbanization, as large parts of land are covered by urban built up. Though it is evident that trees play a vital role is such dry environments, urban planners and architects have neglected their role and least paid attention to it . The trees are the main constituent in an urban forest ecosystem. They provide us with a variety of ecosystem services.

Many people have described or defined urban forestry, It is defined as the art, science, and technology of trees and forest resource management in and around urban community ecosystems for the physiological, sociological, economic, and aesthetic importance that the trees provide to the society. Another definition which describes urban forestry more appropriately is that “Urban forestry is a practice of developing and managing scientifically suitable types of woody plants which thrive in the populated environment of the cities and are influenced by urban population and urban development, which provide a sustainable environment along with other physical, ecological, recreational and economic benefit”.

India is a country having a large population in 29 states and 7 union territories. There has been considerable change in the process of its urbanization. The number of urban centers has increased by 2,774 since last census (2001) to 7,935 in 2011 as reported by Census of India, 2011. The urbanization status has been reported to have shown an increase from 27.81% in 2001 Census to 31.16% in 2011. The spatial growth of cities has been approximately three times faster than the growth of population as observed in
the past 25 years . The protection of trees is a priority. Time immemorial, India has followed the tradition of tree planting during the rule of various Kings and Emperors, who emphasized the need for greenery around their cities .

In recent years urbanization has dominated the scenario and loss of green cover can be seen everywhere. In 2015, the government of India came up with an initiative of developing and renewing the urban cities, under the scheme of Smart cities. Some 100 cities have been chosen initially to develop and set an example for the others. In this context it is necessary that urban forests too find a place simultaneous with the urban built up. Studies have shown that in the developed countries, green space/urban forest/woodland per inhabitant in Europe was 104 m2 /inhabitant . In France, it was 80 m2 /inhabitant , in Netherlands it was 228 m2 /inhabitant  and in Australia it was 80 m2 /inhabitant.

Urban forestry analysis :-

• The overall accuracy of the land use/ land cover classification data was 92% and kappa accuracy was 0.87. The final land use/land cover classes derived are the following dense vegetation, medium vegetation, low vegetation, water, open and urban (settlement).
• The city of Ranchi which lies amidst forests all around has parks and greenery inside the city too. Some of the known parks are Sidhu Kano Park, Machali Ghar, Nakshatra Van, Rock Garden, Gardens of the Governor house, BIT Mesra campus, MECON campus etc. The study conducted  reveals that though the city has good green cover, still places in central, northern, western and south eastern parts of the city are devoid of greenery. Infrastructure and communication development within the city center has hindered development of urban green cover.
• There are open spaces inside the city which can be developed for urban forestry such that its benefits can be tapped more. We identified highly suitable areas for urban forestry within the 30 km radius from city center because these open areas are close to the settlement and have mostly gentle slope, high wetness, high organic carbon and are in the vicinity of drainage system of the city.

Urban heating effect :- 

Land surface temperature in each buffer zone.The process of urbanization has led to an increase in the urban heat. The summer temperatures have been noticed to soar high in the recent years. .Land surface temperature has been used to observe the temperature variations between the urban and rural landscapes in Indian scenario  The average minimum and maximum temperature for each buffer zone was computed.  Land surface temperature or urban heat forms one of the vital parameters influencing the global climate change and is a major factor which determines the energy balance at the surface and physical dynamics of land surface processes

Role of trees in urban forestry :- 

Trees are the basic unit of urban forestry. It brings about changes in the vicinity of urban environment in the following ways.

First is evapotranspiration where the loss of water from the plant as vapor into the atmosphere occurs by absorbing the energy from solar radiation. This cools the leaf surface as well as air surrounding it.

Secondly, trees provide shade and intercept the solar heat from reaching the ground and heating up. This local cooling effect is important in open spaces within the urban built up areas. The movement of air current and heat exchange is affected by the presence of vegetation.

Thirdly, in winters, they alter the wind speeds and reduce the heat loss from the urban structures. The significant benefits offered by urban shade trees are in reducing air conditioning demand and improving urban air quality by reducing smog. Such open green spaces help in creating a stress free environment which is a boon to people who wish to spend more time outdoors . Thus to make urban forestry more effective, trees can be planted along the streets and crossroads and creation of parks should be encouraged.

Maintaining the carbon cycle :-

Trees contribute in balancing the carbon cycle by acting as carbon sink. They absorb the carbon dioxide from the atmosphere. The process of urbanization leads to concrete jungles which fail to absorb the greenhouse gases and thus alter the carbon cycle and warm up the atmosphere too. In this aspect the trees in urban area provide act as an island to absorb the heat as well as carbon dioxide from the surrounding atmosphere. The trees will also provide a habitat to few floral and faunal species as well. Large areas can also act as areas for biodiversity conservation. Larger the area more is the biodiversity . Heterogeneity should be maintained while planting trees, big trees, herbs and shrubs would form a three tier system. Monoculture plantation has less benefits hence should be discouraged.

Conclusion :- 

• The study has shown the strength of geospatial technology in delineating areas suitable for urban forest development in open spaces in and around the city.
• Remotely sensed satellite data is a cost effective, affordable (as Landsat data has a huge archive) and temporal coverage of data is one of the viable methods to analyse city’s vegetation resources .
• Integration of satellite remote sensing data in GIS domain is a prerequisite in generating a base map.
• Coarse resolution satellite data like Landsat can be utilized to achieve this target, which provides good delineation of land use/land cover with considerable accuracy.
• Further, Geospatial technology would also help in monitoring urban forest environment at regular intervals and help in filling the critical knowledge gap due to unavailability of suitable data.
• Such data will help and enable the urban planners and decision makers to incorporate it in urban planning and development programmes which will translate the research into ground action.

By: Shashank Shekhar