The effect of global climate change on desertification is complex and not yet sufficiently understood. On the one hand, higher temperatures resulting from increased carbon dioxide (CO2) levels can have a negative impact through increased loss of water from soil and reduced rainfall in dry lands. On the other hand, for certain species, an increase in carbon dioxide in the atmosphere can boost plant growth.
Vulnerable Areas
Bangladesh is the largest delta on the earth created by alluvial deposits of the three large rivers--Ganges, the Brahmaputra and the Meghna. Including the largest ones, Bangladesh has seven hundred small rivers and a rainfall that may be one of the highest in the world. But the country is at the risk of desertification. In-depth and detailed studies are lacking in Bangladesh which could delimit precisely the area affected by or susceptible to land degradation (desertification). In terms of geographical extent, this vulnerable area includes the greater districts of Rajshahi, Kushtia, northwestern Jessore, Pabna, western Bogra and southern Dinajpur.
Causes and Effects of Land degradation
The whole-sale change of the country's environment is happening due to both human and natural causes. The country is situated at downstream of major transboundary rivers between India and Bangladesh. The diversion of Ganges water occurs at Farakka point located just 10 miles from the north-west border of the country. This situation is causing severe water shortage and is affecting the flora and fauna in the north-west region of Bangladesh. Because of Farakka barrage the water-flow was recorded at 9000 cusecs in 1994 March (with some insignificant variation in the recent years) in place of the 75000 cusecs in the same dry season before the barrage was built. Such kind of alteration causes severe climatic changes in an ecological area where it has been functioning since long. This abrupt climatic change creates adverse situation for survival of biological resources (both plants and animals) there.
Moreover, not only Farakka barrage over the Ganges, various types of water control structures have been constructed by India on about 50 shared rivers between Bangladesh and India. These water control structures are the major causes for desertification.
The artificial shortage of water flows in common rivers affects Bangladesh seriously by drying up the river beds, shrinking country's flood plains, pushing down ground water level and providing further upward access of the salinity level in the south-eastern region.
Bangladesh is located between 22" and 26" north latitude, a geographical region within which a number of deserts in Asia and Africa are located. Four hydrological regions are present in Bangladesh: a) the north-western region; b) the south-western region; c) the central; and d) the eastern region. An area of about 29000 squares miles is being occupied by the north-western and south-western part of the country. This area takes more than half of the land area of Bangladesh. In this area the highest fluctuation of rainfall levels contributes to the development of drought and aridity.
A study of SPARRSO reported that the country's south-eastern region experiences four arid months and the north-west region six arid months in a year.
Fifty per cent land area of our country is covered by wetlands. The physical size and ecological diversity of the country's wetlands are shrinking by various important causes, among the major ones are human activities like the flood embankments, water diversion, siltation and ground water extraction.
Because of the additive factors, biodiversity in Bangladesh is depleted by deforestation, improper forest conservation, agro-chemical use and industrial establishments, large-scale development and flood projects, land use changes, and biological resource over-exploitation. Some of the above reasons contributed to the destruction of the natives and secondary forest diversity, including indigenous species.
Encroachment on forest lands for agriculture and settlement, exploitation of resources like bamboo and canes, reduced freshwater flow in the Ganges river system, increased salinity intrusion in the Sundarban mangrove forest, converting forest for urbanization and industrialization are among the main causes for loss of biological diversity in the country.
Biodiversity losses
The biodiversity depletion is caused by degradation of land, erosion of valuable top soil, creeping salinity, over extraction of ground water, indiscriminate land conservation, declining soil fertility, water logging and destruction of forests.
During last 100 years, all species of rhinoceros, wild buffaloes, wolves and swamp deer have disappeared from Bangladesh. At least one reptile, the marsh crocodile, has disappeared from the wild. Among the listed 129 species of wildlife, the threatened and endangered included the list of 37 mammals, 21 reptiles, two amphibians and 69 birds. The tentative list of threatened plants includes 27 species of vascular plants, including nine endemic (Report: 1991).
The terms 'land degradation', and 'desertification' (and sometimes 'drought') have been used so widely and in such diverse contexts that they have often created problems in interpretation among policy makers. The dynamics of land degradation/desertification are best understood within the context of the natural environment and human intervention into that environment. Land degradation/desertification is not an isolated climate induced phenomenon, rather it is an aberrant and unsustainable human response to the broad parameters of the natural environment. With a dedicated agenda, local action and appropriate technology, it is not impossible to offset the effects of land degradation, and strike an equilibrium between the seemingly incompatible process of land degradation and sustainable land management.
