Urban forestry for green city | The Daily Star
12:00 AM, September 22, 2012 / LAST MODIFIED: 12:00 AM, September 22, 2012

Urban forestry for green city

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Urban forestry is a must for building a green city.

The global population pressure has increased in urban areas with people thronging the cities in quest of a better life. According to the UN Population Division, about 44% of the total populations in developing countries are living in urban areas. There is no doubt that the urbanization will proceed to have significant impact on the ecology, economy and society at local, regional, and global levels. The great impact has been observed in the urban green spaces including urban forestry, parks, playgrounds, domestic gardens, roadside open spaces and urban vegetation.
According to World Health Organization (WHO) there should be 9 sq. meter green space per city dweller for ensuring better life. In developed countries, normally, they have more trees (more than 20 sq. meter green spaces per city dweller) to meet the ecological balance for human well-being compared to cities in developing countries, which often fall below the minimum standard of open green spaces set by WHO. For example, most of the cities of China have 6.52 sq. meter green coverage per head.
Now let us look at the capital city of Bangladesh, Dhaka, which is one of the fastest growing mega cities in the world. This metropolitan city has an area of 131 sq. kilometer with more than 15 million population. Already unplanned urbanization has caused serious ecological imbalances in the city. FAO (2008) pointed out that Dhaka city has 21.57% open space of which city parks occupy 0.89%, urban forestry 0.02%, gardens 0.90% and 12.12% belongs to agriculture. The green space has been reducing gradually while increasing is the number of buildings without considering environmental protection. According to the Chief Town Planner of Dhaka City Corporation (2003), an ideal city needs 20% area covered by trees but there is only 8% vegetation in the city. Currently, almost 15 million dwellers of Dhaka city enjoy limited ecological services from Ramna Udyan, Sohrawardy Udyan, Dhaka University campus, National Parliament Bhaban complex, Usmani Udyan, Botanical Garden and National Zoo etc.
Hence, green space in Dhaka city is now questionable in the context of global standard. Inadequate tree coverage in Dhaka city is resulting in many environmental debility as well as human health related problems. For 14 years, high temperatures have been experienced in Dhaka city. Bangladesh Meteorological Department (BMD) reported that the gap between maximum and minimum temperatures of Dhaka city has gradually increased, resulting in hotter summers and colder winters. On 27 April 2009, the highest temperature was shown as 42.3 degree Celsius in Dhaka city. The urban heat has sharply increased in the recent decades.
Department of Environment (DoE) pointed out that air pollutant (SOx, NOx and CO2) levels in Dhaka city are about 4 to 5 times higher than the prescribed levels of Air Quality Standard (AQS) in Bangladesh. Such pollutants remain and persist with air due to lack of tree coverage. Several research in US shows that trees can remove pollution by intercepting airborne particles. Another study of BAPA (2002) pointed out that air pollution causes headache, burning of eyes, pain in throat, bronchitis, breathing problems, heart disease, anemia, mental problems, kidney disease and even cancer. According to experts, about 33% of Dhaka dwellers suffer from hearing problems due to noise pollution. In US one research estimate suggests that 7db noise reduction is achieved for every 33 meter of forest. Therefore, vegetation can play an important role in attenuating noise and absorbing sound energy.
Another important hydrological function is growingly distressed as protection of drinking water resources is being lost by reducing woodland and trees. Undoubtedly it is true that increasing the area of green space will increase the volume of pure water for city dwellers. The limited trees in the parks and streets in Dhaka are unable to help infiltrate and recharge required volume of rainwater underground. Considering importance of woodland for water purification, Denmark has demarcated woodland close to the cities.
Forthrightly, we should emphasize urban forestry and incorporate it into the urban planning and development. Generally, we can do this in narrower scale beside the river and canal banks around the city, government office spaces, both private and public universities, schools and colleges, parks and the play grounds, private open spaces, and slums in Dhaka city. The sum total can present a remarkable contribution in the urban forestry towards building a green city, which will play an important role for green job generation, and improving health, environmental quality as well as aesthetic value of urban landscapes.
Apart from that, the master plan of Dhaka city should consider remarkable green space for ensuring urban dwellers a healthy life in future. Rajdhani Unnayan Kartripakkha (RAJUK) should emphasize housing with garden strategy for the planned area under its master plan. A research is crucial for selecting and introducing types of tree in the open areas of Dhaka city. A concrete coordination among Forest Department, Dhaka City Corporation (DCC), RAJUK and other stakeholders is needed to extend the urban forestry. Yet, the forest policy didn't consider urban forestry. Hence, possible sensitization of policy makers is urgent now. Considering all the advantages of urban forestry, a holistic approach is needed for representing green cities of future.

Md. Zahidur Rahman and Saeed Ahmed Siddiquee work in the field of environment and climate change and can be reached at zahidfao@gmail.com and shaikatbangla@gmail.com, respectively.

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