IAPRS & SIS, Vol.34, Part 7, "Resource and Environmental Monitoring", Hyderabad, India,2002 
  
  
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Figure 1. Study area 
The study area has a population of six million, with density of 
564/sq.km. Agriculture is the main occupation. Compared to 
the other areas of Bangladesh, the distribution of land 
ownership is highly skewed in the south. A large segment of the 
population is landless and poor. In addition to working as 
agricultural laborers, they work as fishermen and collect wood, 
honey, shrimp fry, etc., from the Sundarbans mangrove forests. 
1.2 Problem definition 
" »od security .i.e. self sufficiency in paddy production, is an 
important consideration in Bangladesh. On the other hand, 
shrimp farming, which displaces paddy cultivation, has become 
an important source of export earning in recent years. The total 
value of shrimp export is more than US$275 million which is 
now second to garment export in export earning. The study area 
accounts for almost 80% of the total Bagda shrimp area of 
Bangladesh. Although the shrimp business is highly profitable, 
it has considerable social and environmental consequences. The 
negative environmental impacts include land degradation, loss 
of livestock, negative impact on public health and overall 
quality of life and degradation of the mangrove ecosystem 
(CPD, 1999). 
The reduced freshwater flow through the Gorai River into the 
study area, augmenting salinity intrusion, is also changing the 
ecological settings and leading to preference for certain land 
use types. 
2 DESCRIPTION OF THE SHRIMP-CROP DSS 
This DSS analyzes the environmental and socioeconomic 
consequences of landuse policies under different scenarios of 
salinity intrusion as a result of upstream fresh water inflow. It 
focuses on a trade-off between shrimp and rice crop cultivation. 
The starting point is a land use classification based on optical 
and radar satellite images of different cropping seasons. A 
salinity intrusion model divides the study area into five salinity 
classes. The extent of land area in each salinity class is outside 
management control as it depends on the upstream water 
inflow. Image analysis, field information, ancillary data, and 
expert knowledge identified five different production regimes, 
meaning different types of shrimp and agricultural cropping 
cycle and their distribution under each salinity class. The DSS 
evaluates the impacts of re-allocating the areas under the 
different production regimes in terms of economic, social and 
environmental criteria. 
The shrimp and agricultural production activities are analyzed 
considering the complete chain of activities from inputs, 
production and distribution of the outputs. An economic 
assessment model calculates the returns from different 
production regimes, while social and environmental impact 
assessment models quantify the various social and 
environmental indicators. 
2.1 A framework for analysis 
The structure of the DSS follows a generic framework for 
analysis (Rijsberman and Koudstaal, 1989). Following this 
framework, the main steps for analysis are: 
e Definition of problems 
e Specification of objectives and criteria. 
e Determination of exogenous developments or 
scenarios. 
e Development of strategies or selection of measures. 
e Analysis of the impacts of the combinations of 
strategies and scenarios in terms of criteria 
(using a computational framework.) 
e Evaluation of strategies 
The DSS allows the user to follow this framework in the 
decision-making context by presenting a stepwise approach 
through an interface as shown in Figure 2. This approach 
provides a conceptual framework, in combination with a 
computational framework. The conceptual framework provides 
the context of the quantitative approach in terms of the concrete 
decision making objectives and corresponding criteria and 
indicators to be used in the final assessment of the available 
alternatives. Figure 2 gives an overview of how the DSS links 
the conceptual and computational frameworks through a 
stepwise approach. 
2.2 The stepwise approach through a user interface 
The interface of the Shrimp-Crop DSS presents the stepwise 
approach in a sequential manner. The first step allows the user 
to understand the problems and issues. In the second step the 
user has to specify what the objectives and criteria are. These 
choices are ‘commands’ for the computational framework, 
specifying which outputs are required. In the third and fourth 
steps the strategies and scenarios (exogenous developments) 
have to be specified. Strategies and scenarios combine in the 
"cases for the analysis", which specify the input-settings of the 
computational framework. The computational framework 
integrates / links the available databases of the resource system 
under consideration with (simulation) models that do the actual 
computing. This computing is done under the fifth step, after 
which the results are presented to the user. After the fifth step it 
is up to the user to evaluate the results and use them to support 
decision-making. The interface may also include formal 
evaluation procedure (e.g. multi criteria analysis) to reach a 
decision. 
23 Description of problems and issues 
The DSS provides a structured and illustrated knowledge base, 
through which planners and decision makers can familiarise 
themselves better with the problem and its context. To 
understand the conflicts and the factors affecting it, the user is 
presented with information on the “physical” and “socio- 
economic” situation of the study area. Information is also 
available on the “production systems” of paddy and shrimp, 
describing the recent trends and returns from agriculture and 
shrimp farming activities in the form of graphs and tables in 
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