Climate change impacts and adaptation in Bangladesh : an agent-based approach

Bangladesh exemplifies the complex challenges facing densely populated coastal regions. The<br />pressures on the country are immense: around 145 million people live within an area of just 145,000 sq-km at<br />the confluence of three major river systems: the Ganges, the Brahmaputra and the Meghna. While progress<br />has been made, poverty remains widespread, with around 39% of children under five malnourished. Most of<br />its land-mass lies below 10m above sea level with considerable areas at sea level, leading to frequent and<br />prolonged flooding during the monsoons. Sea level rise is leading to more flooding as storm surges rise off<br />higher sea levels, pushing further inland. Higher sea levels also result in salt-water intrusion into freshwater<br />coastal aquifers and estuaries, contaminating drinking water and farmland. Warmer ocean waters are also<br />expected to lead to an increase in the intensity of tropical storms.<br />Bangladesh depends on the South Asian summer monsoon for most of its rainfall which is expected to<br />increase, leading to more flooding. Climate scientists are also concerned about the stability of monsoon and<br />the potential for it to undergo a nonlinear phase shift to a drier regime. Bangladesh faces an additional<br />hydrological challenge in that the Ganges and Brahmaputra rivers both rise in the Himalaya-Tibetan Plateau<br />region, where glaciers are melting rapidly. The Intergovernmental Panel on Climate Change (IPCC)<br />concluded that rapid melting is expected to increase river flows until around the late-2030s, by which time<br />the glaciers are expected to have shrunk from their 1995 extent of 500,000 sq-km to an expected 100,000 sqkm.<br />After the 2030s, river flows could drop dramatically, turning the great glacier-fed rivers of Asia into<br />seasonal monsoon-fed rivers. The IPCC concluded that as a result, water shortages in Asia could affect more<br />than a billion people by the 2050s. Over the same period, crop yields are expected to decline by up to 30% in<br />South Asia due to a combination of drought and crop heat stress. Bangladesh is therefore likely to face<br />substantial challenges in the coming decades.<br />In order to adequately understand the complex, dynamic, spatial and nonlinear challenges facing Bangladesh,<br />an integrated model of the system is required. An agent-based model (ABM) permits the dynamic<br />interactions of the economic, social, political, geographic, environmental and epidemiological dimensions of<br />climate change impacts and adaptation policies to be integrated via a modular approach. Integrating these<br />dimensions, including nonlinear threshold events such as mass migrations, or the outbreak of conflicts or<br />epidemics, is possible to a far greater degree with an ABM than with most other approaches.<br />We are developing a prototype ABM, implemented in Netlogo, to examine the dynamic impacts on poverty,<br />migration, mortality and conflict from climate change in Bangladesh from 2001 to 2100. The model employs<br />GIS and sub-district level census and economic data and a coarse-graining methodology to allow model<br />statistics to be generated on a national scale from local dynamic interactions. This approach allows a more<br />realistic treatment of distributed spatial events and heterogeneity across the country. The aim is not to<br />generate precise predictions of Bangladesh’s evolution, but to develop a framework that can be used for<br />integrated scenario exploration. This paper represents an initial report on progress on this project. So far the<br />prototype model has demonstrated the desirability and feasibility of integrating the different dimensions of<br />the complex adaptive system and, once completed, is intended to be used as the basis for a more detailed<br />policy-oriented model.<br />