Afforestation of Roadsides
An Avenue is defined as a way of access, an approach to a country house bordered by trees. It has come to mean the row of trees planted along roads and paths.
The concept of planting trees along the roadsides is as old as the Vedas. In the Padma Purana it is stated that "Man planting tree by the wayside will enjoy bliss in Heaven for as many years as there are fruits, flowers and leaves in what he planted."
Planting of trees along roads was ordered in the form of an edict by Emperior Ashoka. Feroz Shah and Tughlak in the 14th Century ordered planting of trees along the roads. When the capital was thought to be shifted from Agra to Daulatabad the entire population was ordered to move and for their protection from the elements, trees were raised along the roads, many of the old trees found along roads and canals are 100 to 200 years old and some are even older.
The following are the objects in raising trees along the roads:
1) Assistance in increasing agricultural production by way of shelter belts, provide fuel wood to divert cow dung to fields, reduces damage of sugarcane and cotton from desiccating winds, reduction of evaporation.
2) Maintenance of ecological balance. Increase of area under tree cover provides shelter for insectivorous birds, in addition to providing various wood produces.
3) Trees provide comfort to travelers on hot sunny days. Tree shade is most invigorating. For this purpose trees with thick foliage are most desirable.
4) Tree on the roads act as noise ablators. Excessive noise is one form of environmental pollution. This factor has gained much importance due to high increase in traffic and due to industrialization. Vehicular traffic on a busy national highway generates a sound intensity of about 72 to 78 decibels, a beeping horn up to 110 decibels, and a screaming jet more than 140 decibels. Sound levels of above 50 decibels are irritable and above 130 decibels are harmful. Trees and shrubs along the roads will reduce the effect of sound. A 30 meters wide tree cover can absorb 6 to 8 decibels of sound intensity. However, this depends on the width, height and density of the belts. To reduce truck noise a belt of 20 to 30 meters wide and for car noise 7 to 8 meters wide belts can be raised. In case of roads on hills, a belt on the uphill will be more beneficial.
5) Aesthetic Value of the Roads: If the species selected produce colored flowers and are of good foliage, they add to the beauty of the road. This sort of planning is called bio-aesthetic planning.
6) Lastly a belt of trees along the roads helps in camouflaging the traffic, which in war times is of great importance.
The following are the main criteria for selection of trees for planting along roads of all types:
a) Quick growing and shade giving trees to be selected
b) Timber / fruit trees to be selected
c) Hardy, so as to have good endurance and easy recuperative power, since much damage is likely to trees by travelers and other agencies
d) Collectively the species should add to the aesthetic value of the road
e) The trees must be deep-rooted, otherwise in periods of heavy wind, they are likely to be uprooted and block the traffic.
f) Dust absorbers such as tamarind and other species with small compound leaf should be performed.
The species selected should be preferably evergreen with clean and straight trunk up to 4 to 5 m in height; otherwise they will obstruct the traffic.
A mixture of species will be unsightly, therefore, pure avenues of one species in same length which provide a better skyline, should be aimed. The species recommended are (Particularly for highways) Ailanthus excalsa, Albizzia procera, Alstania scholaris, Azadirechta indica, Tamarindus indica, Eugenia Jambalana, Cassia latifolia, Sissoo, Fiscus infectoria, Fiscus retusa, Mangifera indica etc.