& çâÌæÚUæð´ ·¤è ¥ôÚU Îð¹Ùæ ÁæÚUè ÚU¹ð´ ¥ÍæüÌ ¥ÂÙð ÜÿØ ÂÚU ŠØæÙ ÚU¹ð´Ð ãæÚU Ù ×æÙð´, €UØô´ç·¤ ·¤æ× ·¤ÚUÙð âð ¥æÂ·¤ô ©gðàØ ·¤è Âýæç# ãôÌè ãñ ¥õÚU ÁèßÙ ·¤æ ¹æÜèÂÙ ÎêÚU ãôÌæ ãñÐ ÖÜð ãè ÁèßÙ ×ð´ ç·¤ÌÙè Öè ·¤çÆÙæ§ü €UØô´ Ù ¥æ°, çÁ™ææâæ ¥õÚU ©ˆâæã ÕÙæ° ÚU¹ð´Ð ŠØæÙ ÚU¹ð´, ÜÿØ ã×ðàææ ¥æÂ·Ô¤ Âæâ ãôÌð ãñ´ çÁ‹ãð´ ÂæÙð ·Ô¤ çÜ° ÂýØæâ ¥æÂ ·¤Öè Öè àæéM¤ ·¤ÚU â·¤Ìð ãñ´Ð

Climate change threatens plant diversity in Bangladesh

Dr. Mohammed Kamal Hossain
FORESTS cover one third of the earth’s surface and estimation is that more than two thirds of all available terrestrial species arc found in the forests. Bangladesh also suppons a wealth of plant diversity and is located in transition of two mega-biodiversity hot spots of IndoMalayan region. The country has been endowed with rich plant diversity' because of its fertile alluvial land, warm and humid climate. More than 5,700 angiosperm species and several sub-species are available in Bangladesh. The diverse agro-ecological (30 agro-ecological zones) regions or the 12 Bio-ecological zones of the country' have sustained rich genetic resources of crop plants, which are unique to this country. The forest of Bangladesh covers approximately’ 2.60 million ha which is about 17.62 percent of the land area of the country Of these, the hills consist of moist tropical evergreen and semi-evergreen forests, which extend from northeast to southeast of the country'. The forests are generally uneven-aged and multistoricd with the valuable
tropical species of Dipterocarpus turbinatus, D, alatus, D. costatus, Swintonia flonbunda, Aphanamaxis polystachya. Artocarpus chaplasha. Tetrameles nudiflora, Duabanga grandifolia and Ptcrygota alata. The understorey is a tangle of shrubs, creepers, climbers, fems and orchids. The species were adapted to the different ecosystems after a long successional process.
Though the native plant species of the country have been enriched with new species and varieties introduced from abroad, but the invasive plants are becoming a major threat to natural ecosystems and their species. The impacts of alien invasive species are immense, insidious and usually irrecoverable. The scope and cost of alien invasions is global and enormous. in both ecological and economic terms. But. unfortunately in Bangladesh introduction of alien invasive species of flora were deliberate primarily in order to increase productivity to support the needs of a huge population. The deliberate preferences of fast growing high yielding cultivars eroded some of the native species and the genetic resources abruptly. We have scarce
information about the alien species in Bangladesh and their impacts on the ecosystem and the species.
More than 300 exotic species are supposed to either wildly growing or cultivated as an economic crop in Bangladesh. Some of the invasive plants arc so well established that have become noxious weeds of forests and wastelands (Chromolaena odoratum. Mikania cordata, Lantana camara etc.). Some are considered as noxious weeds of cultivated fields also (Alternanthera, Scoparia and Heliotropium spp). Some troublesome weeds are also found in water land, e.g. Eichhomia crassipes, Pistia stratiotes. The British mostly contributed to the introduction of some economically important forest plants form almost all the continents, e.g. Tcctona
grandis, Paraserianthes falcataria, Albizia saman. Xylia dolabrifortnis, and Swietenia macrophylla. In the 20th century this trend continued to be the same, and some Australian species (Eucalyptus camaldulensis, Acacia mangium, and Acacia auriculiformis) arc getting preferences in the plantation programs. Of these, the Acacia auriculiformis is dominating in all the plantation programmes and growing well in all sorts of degraded lands.
Global climate change is now a reality and the change is mainly happening due to global warming. Global warming is an issue of much concern for both the developing and developed countries. The atmospheric concentration of some gases, mainly carbon-di-oxide has increased and it forms a layer that
traps the heat of the terrestrial radiation. Consequently, the earth temperature is gradually increasing and projection is that the global temperature will increase by 1.5 -- 2.8 degree Celsius by the middle of this century. The IPCC calculation projected that if carbon-di-oxide is doubled in the atmosphere, the mean temperature of the earth will increase by 1.5 --4.50C. The IPCC also forecast that global temperature would rise by 0.20 -- 0.500C in each decade during 21st century with a consequent rise of sea level by 3--10 cm. Temperature rise will result in melting ice and consequently the sea level will rise up to 70 cm! The detailed glacial record in Greenland and Antarctica indicates that the global climate has changed remarkably within the last couple of decades.
Global climate change has an adverse effect on sea level rise, increase in force and frequency of floods, tropical cyclones, tornadoes, drouglit, rainfall, intrusion of salinity, soil erosion, and loss of biodiversity and total degradation of the environment. Moreover, the incidence and extent of malaria, dengue and some other vector bome diseases arc expected to increase with global warming. The effects of sea level rise and flooding of the low lying coastal areas threatens the shelters, resources and livelihoods of several million people in the world. Similarly, a huge population (about 30 million) of Bangladesh living along or very close to the coastal area will suffer severely. Reduction of fresh water flow and salinity increase in the Sundarbans has already
resulted in top dying of Sundri trees and gradual changes of the forest composition. If the situation keeps on prevailing or worsens, then Sundri, the climax species of the Sundarbans may be replaced by some other species.
Temperature increase by one degree significantly lowers the production of wheat and potato of the country. Adverse environmental changes will also affect the production of the major crop rice significantly. Evidence exists that climate change is seemingly changing the existing forest covers significantly. Small changes in temperature and precipitation significantly affects forest growth; even ap increase of one degree in temperature can modify the functioning and composition of forests. Forest dwelling large animals and 9 percent of all known tree species are already at some risks of extinction. Climate change also threatens the forests by pests and fires, making them more vulnerable to invasive species. Deforestation and land clearing activities emit about 1.7 billion metric tons of carbon per year into the atmosphere. Hence, conserva -tion of forests offer important opportu -nities to protect biodiversity and slow climate change.
In Bangladesh, due to population pressure, deforestation and changes of land use pattern, many species of both flora and fauna have became extinct and many more species arc categorized as threatened or endangered considering their existence in wild or cultivated form. In addition, Bangladesh will face serious consequences of biodiversity loss from the global climate change. Considering the present situation and future need, Bangladesh must address the problem of extinction of her native plant resources and immediately needs collection, conservation and management programme for future vulnerable catastrophic climates. Scientists, policy makers, administrators, civil society and public representatives including political leaders could play a vital role to save the diverse plant resources from extinction. Regional and international cooperation with countries have much to gain from partnership in research and development programme devoted to the conservation and use of plant resources.
Dr Mohammed Kamal Hossain is Professor, Institute of Forestry and Environmental Sciences, University of Chittagong E-mail: hossanmk2001@yahoo.com