Plants, animals and microbes together constitute the essential natural biotic community of any sustainable ecosystem. Decomposer microbes are usually in plenty where the producer plants and consumer animals live together in harmony. But we the humans, known as the most destructive animal species, did not let most of the plants thrive well and thereby caused extinction of many animal species as well.
After identifying the harms we have done to nature by unwise deforestation, we are now crying for reforestation. It has been calculated that about 25 percent of the total land area of the earth and any part thereof need to be covered by forest. Only counting the total percentage of forest will not contribute to replenish natural ecosystem, rather the forests should contain many types of plant species so that animal species specifically dependent on certain plants can sustain. Due to unwisely growing human population, Bangladesh does not have enough scope to reforest about 25 percent land area. Yet we are not sitting idle, rather planting many trees every year.
It is over a decade that Bangladesh Government inaugurates the tree plantation season in June every year, though the main plantation season can spread over June through September. The tree fairs are arranged all over the country. So tree plantation is receiving the due importance. But question arises if our reforestation comply with the needful polyculture.
I have seen patches of land in both Madhupur and Bhawal forests where after cutting or somehow clearing the natural diverse plant community, only lines of eucalyptus or acacia trees were planted. Such monoculture might have been the trend in other areas as well. Not only in reforestation attempts, we have committed the similar mistakes in selecting the kind of trees while planting saplings by the sides of highways, city roads and road islands. We make monoculture acacia (that rarely has a straight trunk) jungles by the sides of national highways. Still many eucalyptus (the known contributor to dryness through transpiring much water) saplings are planted on both sides of roads and some also in homestead gardens!
For obvious reasons, we don't have enough space for plantation. The scanty space we find must be used optimally through planting the best species suited to the site of plantation. We need to mind the various kinds of needful trees before planting. These can be as follow: 1) trees having fruit-bearing and timber quality together (e.g., jackfruit); 2) trees having straight long trunk and appreciable timber value (e.g., Gorjan); 3) rapidly growing varieties (e.g., rain tree); 4) trees that spread over large areas and provide shelter to birds (e.g., banyan); 5) trees that produce fibre and/or cotton (e.g., Shimul); and 6) trees having medicinal value (e.g., Neem). Besides, minding only fruits, flowers and otherwise ornamental can also be appreciated.
We know of many trees famous for both timber and fruits. Black berry (Syzygium cumini: Jam), jackfruit (Artocarpus heterophyllus), mango (Mangifera indica) and palmyra palm (Borassus flabellifer) are some of them. Black berry is famous for its tall straight trunk. The fruit it produces is smaller in size and some fruits are usually left out for birds. So this plant can act as a good source of food and shelter for our dwindling bird species. Jackfruit is our national fruit. The tree, though does not grow very tall, its quality of timber is very high. Mango is called the king of fruits and this fruit is no more in plenty; planting some mango trees by the road-sides can provide more fruits as well as shades to the pedestrians. Once palmyra palms were in plenty and these plants were a source of fruits, sugar and lastly hard wood for frameworks of houses. There can be nothing wrong in sowing palm seeds along the sides of roads that can provide the goods mentioned above as well as act as natural strong barriers against falling vehicles.
Trees grown mainly for timber are wood-oil tree (Dipterocarpus turbinatus: Gorjan in Bangla), teak (Tektona grandis: Segun), redwood (Dalbergia sisso: Shishu), Indian lilac (Lagerstroemia speciosa: Jarul), mast tree (Polyalthia longifolia: Debdaru) etc. Some of them usually grow 10-15 (Debdaru and Jarul) meters straight trunk, while some may reach even 40 (Gorjan and few teak) meters. The timber of these trees is well-known. Our indigenous shilkoroi (Albizzia lucida) yields a good timber as well.
Fast growing trees like rain tree (Samanea saman: Rendi koroi) and mahogany (Swietenia mahagoni) are common all over the country and rain tree alone provides bulk of timber for preparing low-cost furniture. But another fast growing tree, almond (Terminalia catappa) is planted still only for ornamental purpose, especially in the city, around some special offices or houses. I propose planting this in plenty that grows tall trunks and is very similar to our indigenous Bahera (being of the same genus Terminalia), famous for medicinal value.
Banyan (Ficus bengalensis) is, perhaps, the largest and most spread tree in the world. We have our own variety of this. Banyan saplings are conventionally planted in bazaars to provide shades to the people. If grown to its proper size a banyan tree can serve not only as a source of shades, to humans, but with its fruits bushy top also a source of food nest to many birds. The sides of the national highways would not be very suitable for planting many banyan trees, but some planted at some distance can serve the purposes described above.
Red silk cotton tree (Bombax ceiba: Shimul) is now becoming rare in Bangladesh. Its timber is of low quality. But its fruit produces silk cotton that is now scanty and much more valuable than other cotton varieties. Therefore planting some saplings of this species is of utmost importance both for the sustenance of this plant species and for the pillow filling cotton.
Growing some medicinal plants is essential. We were rich in those just few decades back. Tree varieties (many are shrubs or herbs) of the medicinal plants are Arjun (Terminalia arjuna), Bahera (Terminalia belerica) and the well-known Neem (Azadirachta indica). Some such plants can be grown by the sides of all the national highways of the country. The forests can also have a mixture of these trees; even some special areas can be sorted out almost in every village to establish a medicinal plant garden.
I wonder why the people planting saplings during reforestation or planting season on either side of national highways have no choice at all. Every attempt of reforestation should aim at establishing poly-culture forests. The national highways can logically have 3-4 rows of trees along either side. But often only 1-2 rows are planted. That is, not only our selection of types is wrong, the distribution of those is also mistaken and seems unplanned. To sustain more trees of the right kind, saplings should be planted following a good plan. The lowest ebb of the roadside may have Jarul saplings along with some Babla (Acacia arabica) or even Hijal (Barringtonia acutangula). These plants can thrive in water. Mango, mahogany, Gorjan, Debdaru, rain tree, black berry etc. may be planted in the middle. Jackfruit, Shimul, teak, redwood etc. cannot withstand water. So these should be planted along the highest ebb. As mentioned before few banyan saplings and medicinal plants should be planted at some distance along the road-sides.
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