INVASIVE PLANTS: A THREAT TO FOREST ECOSYSTEM

Invasive species

For long times, economic valuable plants have been introducing in Bangladesh. Plant's migration or introduction from one place to another sometimes may be natural or planned. Many other countries, including Bangladesh have been introducing plants from different countries or geographic areas of the world. Settlers, invaders, seamen and traders have been brought most of the plants, having no detailed records of these exotic plants. Many of them are of economic benefit. However, a good number of exotic plants is weedy in nature. Most of them were introduced as ornamental plants before becoming established elsewhere. Some of them are so well established that they are now the dominant plant and became noxious weeds of forests and wastelands (Eupatorium odoratum, Mikenia cordata, Croton spp. etc.). Some are also considered noxious weeds of cultivated fields (Alternanthera, Scoparia and Heliotropium spp.). Others are found in water land (Eichhornia, Eleocharis and Monocharia spp.).

In the 19th century, the British was mostly contributed to the introduction of some economically important forest plants from almost all the continents. The introduced species are Tectona grandis, Albizia spp., Samanea saman, Xylia kerrii, and Swietenia macrophylla. In the 20th century, this trend continued to be the same and some Australian species (Eucalyptus camaldulensis, Acacia mangium, Acacia auriculiformis) are getting preferences in the plantation programmes in Bangladesh. Leucaena leucocephala (Tropical America) are also found all over the country and pines (Pinus oocarpa and P. caribaea) are also planting in the hilly areas. Of these, the Acacia auriculiformis is dominating in all the plantation programmes and growing well in all sorts of degraded land. Recently, the controversy arose out of that pollen of the species is allergic to many people. Very recently, the cultivars and hybrids of different crops and ornamental plants have been also introduced haphazardly. Some weedy species dominate crop fields, forests, wasteland and marginal lands. Some of the species have luxuriant growth and suppressed the growth of other native species. This results in a loss of native floral diversity across the country.

The danger posed to natural habitats by these alien invasive plants is becoming a major concern among conservationists, ecologists, foresters, policy makers and scientists. To overcome such problems caused by the invasive plant species to the natural ecosystem, the possible suggestions such as to raise awareness among the planters, growers and public; to develop a database on invasive species; to quantify the abundance of the invasive species; to develop environmentally sound eradication methods; and to introduce the necessary quarantine, legislation and regulations on the spread of the invasive plants.