Decimating wetlands: a courtship with calamity

A rapid decline in wetlands would have tremendous impact on the recurrent flooding in the city, and probable climate change may exacerbate the situation. Flooding and water-logging may assume catastrophic proportions in the absence of these expensive natural resources, 

writes Dr Ashraf Dewan
WETLANDS are among the most important natural habitats that support biodiversity and provide subsistence for humans. Although wetlands occupy only 6 per cent of the earth’s surface, they support roughly 20 per cent of all living organisms on this planet. Bangladesh is endowed with water resources. Numerous rivers, haors, beels, estuaries, ponds, baors, mangrove swamps and low-lying floodplains cover 72,499 square kilometres or 50 per cent of the total land surface. These water bodies have wider ecological, economic and commercial values for Bangladesh. For instance, 80 per cent of the nation’s daily animal protein intake comes from fish, and the fisheries sector contributes more than 5 per cent to the country’s gross domestic product. Moreover, the fisheries sector employs approximately 10 per cent of the country’s labour force. Sadly, as the demand for lands for housing and agriculture increases, these water bodies are under tremendous pressure. Many of them are either encroached upon or about to die because of acute water shortage resulting from development activities. Upstream water diversion is another significant factor that has contributed to water shortage in lean season. For example, many rivers in the Ganges basin in Bangladesh have been dried up due to water withdrawal by the Farakka Barrage in India.
   Dhaka, one of the fastest growing cities in the world, is facing a number of environmental crises. Rapid population growth along with unplanned and breakneck urbanisation is compounding the situation day by day. Historically, the city was endowed with natural water bodies. With the span of time, most of them have been either filled up to meet the growing demand for housing or are in the process of being filled up by land grabbers. An increasing demand for housing is now being met by filling up natural water bodies by real estate agencies without considering the environmental impact. In order to quantify wetlands of Dhaka and their role in alleviating flood damage, various data have been used in this write-up. They include multi-temporal remote sensing images (e.g. Landsat, IRS, ALOS), historical paper maps and flood data. In addition, a number of field visits were made to estimate and delineate existing wetlands in the city.
   Though there are a number of definitions of wetlands, only permanent and temporary water reservoirs, swamps and low-lying lands have been considered to be defined as wetlands in this article. Note that river networks have not been considered as wetlands. A geographic information system has been used to estimate wetlands in the Dhaka metropolitan area. It may be noted that a rectangle of 42,000 hectares of the entire metropolitan area has been extracted from satellite images and considered to study the wetlands scenario. The rectangle covers the entire city corporation area and adjacent fringe zones in all directions. The timeframe of the study includes 1960-2008. The estimation of wetlands in the metropolitan area by using latest technology provides a frustrating as well as distressing picture. In 1960 wetlands in the metropolitan area covered 14,000 hectares but were and reduced to about 13,155ha in 1975. In 1988 the area covered by wetlands was 11,715ha but shrank in 1999 to 10,797ha. The situation is getting worse.
   As the population continues to grow, demands for housing and infrastructural development have also increased to a greater extent. Consequently, vast tracts of low-lying floodplains and wetlands have been earth-filled by real estate agencies since 1980s. In 2003 and 2005, further depletion of wetlands was observed, amounting 9,124ha and 7,129ha respectively. In 2008 the situation became alarming, and only 7,128 ha of lands remained as wetlands. In contrast, urban areas have shot up to 10,858ha and 23,549ha in 1988 and 2008 respectively. Note that only 4,625ha of lands were urbanised in 1960. Since wetlands are considerably low lying lands in the periphery of the metropolitan area, massive earth filling was observed after 1975. It was found during public interview that the scarcity of flood-free lands, and relatively cheaper low-lying water bodies/wetlands were the major factors for carrying out earth filling activities in order to meet consistent housing demand. In addition, absence of land uses policies in the country as well as loopholes in the Water Bodies Conservation Act 2000 assisted developers greatly to go for rapid encroachment.
   As of today, a good amount of wetlands has been earth-filled. In 2005 1774ha of wetlands were filled up and 2,345ha in 2008. This clearly demonstrates that the Water Bodies Conservation Act 2000 is not enforced by the relevant agency. Private developers cannot be blamed alone for land development in the metropolitan area, Rajdhani Unnayan Kartripakkha, a state-run organisation, is equally responsible. The recent plot allotment in Uttara 3rd Extension Project is a glaring example of wetlands encroachment. Another reason for wetlands depletion in the metropolitan area is the construction of a 32-kilometre flood embankment on the western fringe of the city. Since the embankment provides flood security, land grabbers have already encroached vast tracts of wetlands in the western zone for housing purpose. A similar situation is feared in the eastern part of the city when the eastern embankment-cum-bypass will be in place.
   Wetlands in the metropolitan area are of significant value in terms of alleviating flood loss, providing means of livelihoods to people, etc. A rapid decline in wetlands would have tremendous impact on the recurrent flooding in the city, and probable climate change may exacerbate the situation. Flooding and water-logging may assume catastrophic proportions in the absence of these expensive natural resources. A recent study using historical records revealed that flood damage in the city is rising as development activities continue on lowlands and wetlands. About 47 per cent of land area was flooded in the 1988 flood while 53 per cent area was flooded in 1998 as depicted from remotely sensed data. The flood damage was double during the latter event. Estimation shows that a total of $4.4 million was lost during 1998 flood whereas in 1988 the amount was just half. Again, during the 2004 flood, only 43 per cent area out of 42,000ha was flooded but the damage was massive, amounting to $5.6 million. These results can be used to visualise the importance of wetlands in the city not only to lessen the flood damage but also for other purposes such as preservation of environmentally sensitive areas, groundwater recharge, conservation of biodiversity, etc.
   In order to save the remaining wetlands of the metropolitan area, the government needs to revise the existing Water Bodies Conservation Act 2000 since a number of drawbacks in the act are observed. For example, the act supports the preservation of cities, towns and divisional water bodies. There is no clear-cut rule on saving rural water bodies. Since most of the wetlands are located on the outskirts of the in the metropolitan area and necessarily pertaining to rural area, the developers are just taking the advantage of this loophole. Moreover, water bodies are also loosely defined in the act. In order to revitalise wetlands in the metropolitan area, actual demarcation is needed on the basis of historical documents. A tough and comprehensive law for preserving different types of water bodies can hardly be over emphasised. Stakeholders’ participation should be ensured and awareness should be raised among wetlands users.
   We are talking about climate change, sea level rise and adaptations. The government is about to invest huge resources for the development of adaptation measures. Is not it a natural adaptation to save wetlands of the metropolitan area which provide many benefits to us? Are not these wetlands and floodplains conserving biodiversity? Are not they useful as flood retention basin? We do talk a lot during wet season to save the city from flood and water-logging but right after the flood, we forget everything. Every year, we witness hue and cry during flood time, however as days pass away, nobody thinks to make the city flood free.
   A one metre rise in sea level by the year 2100 is far away and we can easily take necessary steps to save lands of Bangladesh from inundation. Hence, saving Dhaka from a number of environmental impairments is also as important as saving lands from sea level change because Dhaka contributes greatly to the national economy. Also, it is home to more than 12 million people. At present, Dhaka is facing massive wetlands encroachment by the private developers. We are not bothered about these but we are much worried about global warming and associated impacts. Initiatives to save wetlands are badly needed to make the city liveable otherwise the future of the city looks uncertain.
   Dr Ashraf Dewan is associate professor of the Department of Geography and Environment at Dhaka University. dewan1971@gmail.com
source: New Age