The Ganges Delta - Sink or Swim?

The Ganges Delta, located in Southern Asia, covers parts of Bangladesh and the Indian state of West Bengal. Due to the densely populated nature of the region the delta, which covers around 87,300 km², is home to almost 111 million people (Ericson et al. 2005). It is no surprise then that it is the world’s most populated delta. The problem is that sea level rise, accelerated by the effects of global warming, is placing enormous stresses on the region’s already pressured land, water, and food resources.

Figure 1. Location of the Ganges Delta

As I have previously discussed, global sea level rise is increasing and it is placing certain areas at greater risk due to the non-uniform pattern of change around the world. Bangladesh is extremely vulnerable to change as much of the country is covered by river plains and the coastal zone lies mostly below 5 metres elevation (Mohal et al. 2006). Parts of the delta have observed a local sea level rise of 25 mm/year which is in part due to their subsiding nature that results in relative changes (Ericson et al. 2005).

Figure 2. Satellite image of the delta

Humans have a direct role to play on this local scale as groundwater extraction can increase rates of subsidence (Ericson et al. 2005). Additionally, negative impacts on the environment come as a result of activities such as shrimp farming and river damming. Dams retain sediment which could help reduce subsidence downstream and also decrease the amount of freshwater that this land receives (IPCC 2007).

One of the key worries is that sea level rise will lead to ground and surface waters becoming increasingly saline. Saltwater intrusion could result in the displacement of plant and animal species in the coastal zone that rely on fresh or brackish water (IPCC 2007). Additionally, the salt water could increase the salinity of the presently fertile soil so that crops are endangered, as well as running the risk of food insecurity. With increased soil salinity, the growth of rice is inhibited and thus the yield is reduced (Castillo et al. 2003). Currently, the country’s rice crop is the world’s 4th largest so any changes could have a major implications for the nation which rely upon it (FAOSTAT 2012).

Another issue is the loss of land which has been predicted as a result of rising sea levels and subsidence. It has been predicted that 3 million people would be affected by changes by 2050 and a worse-case scenario is that by 2100, almost ¼ of Bangladesh’s land area (in 1989) could be lost (Castillo et al. 2003). This is a massive amount of land which is presently home to millions of people. The implications for this densely populated region would be enormous.

It should be noted that global warming is not just affecting sea levels in the region. Changes in the climate such as more variable precipitation could lead to more frequent flooding and droughts, as well as increased saltwater intrusion during the dry season (Mohal et al. 2006). Rising temperatures could also see rice production fall 8% by 2050 and wheat by 32% (Faisal and Parveen 2004). What can local people do to change these outcomes? At the moment the future looks uncertain and solutions are needed fast.

References

Castillo, E., T.P. Tuong, H.T.T. Trang, T.N.Q. Phuong (2003) ‘Phenological and physiological responses of a rice cultivar to level and timing of salinity stress’, in N. Preston and H. Clayton (eds) Rice-shrimp farming in the

Mekong Delta: Biophysical and Socioeconomic issues, Canberra: Australian Centre for International Agricultural Research.

Ericson, J.P., C.J. Vorosmarty, S.L. Dingman, L.G. Ward and M. Meybeck (2005) ‘Effective sea-level rise and deltas: causes of change and human dimension implications’, Global Planetary Change, 50, 63-82.

Faisal, I.M. and S. Parveen (2004) ‘Food security in the face of climate change, population growth and resource constraints: implications for Bangladesh’, Environmental Management, 34, 487-498.

FAOSTAT (2012) ‘Production, crops, Bangladesh’ (WWW), Food and Agriculture Organisation of the United Nations (http://faostat3.fao.org/home/index.html#VISUALIZE; 8 December 2012).

IPCC (2007) Climate Change 2007: Impacts, Adaptation and Vulnerability, Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge: Cambridge University Press.

Mohal,N., Z.H. Khan and N. Rahman (2006) ‘Impact of sea level rise on coastal rivers of Bangladesh’, Coast, Port and Estuary Division, Institute of Water Modelling, Bangladesh.