By Stuart Bunting, University of Essex and Nesar Ahmed, Bangladesh Agricultural University
Prawn-fish-rice agroecosystems consist of farming freshwater prawns (Macrobrachium rosenbergii) and selected fish species in rice fields. Wider spacing of rice plants in such integrated systems promotes primary production throughout the water column. Ecological functions performed by rice plants contribute to favourable water quality and temperatures for optimum prawn and fish production. The plants provide shelter for the cultured fish, helping reduce predation and stress. Foraging of sediments and consumption of phytoplankton by the fish promotes nutrient exchange between the water and soil; the fish also consume rice pests and weeds. Overall, the presence of cultivated fish and prawns results in a reduced need for pesticides and fertilizers. Dike-cropping in these systems can also optimise the productive use of nutrient and water resources.
This practice has been widely adopted by smallholder producers across 30,000 hectares (115 square miles) in the coastal districts of Bagerhat, Khulna and Satkhira in southwest Bangladesh. As a consequence of traditional land-holding patterns and contemporary land-use policy, individual farms are relatively small in size (0.15 to 0.4 hectares or under one acre). Thus, benefits accrued from the substantial area under prawn-fish-rice cultivation are being shared amongst a large number of farming households.
Prawn-fish-rice culture has generated notable benefits for farmers, local communities and the country. Prawns cultivated in the rice fields are destined for export markets and generate vital foreign exchange. The staple rice crop and nutritionally important fish find their way to local markets and play a significant role in subsistence consumption and local food security. Catches of small indigenous fish from the integrated rice fields are consumed preferentially by farming households and constitute an invaluable source of micronutrients, minerals and vitamins. A formal sustainable livelihoods assessment of these communities demonstrates that they benefit from enhanced income, food and fish consumption and fulfillment of basic needs.
These integrated aquaculture-agriculture agroecosystems are well-suited to the prevailing environmental and hydrological conditions in the area and significantly increase agrobiodiversity and lessen production risks faced by producers. However, the low-lying coastal areas where prawn-fish-rice culture has been established are particularly vulnerable to climate change impacts including drought, flood, cyclone, sea-level rise, greater salinity and sea surface temperature variability.
Consequently, appropriate adaptation measures are needed to cope with climate change impacts and maintain these important ecosystems and livelihoods. After reviewing the complex socio-economic setting, we advocated for “Community-based climate change adaptation strategies for integrated prawn-fish-rice farming in Bangladesh to promote social-ecological resilience.” Adaptation must facilitate the participation of all concerned stakeholders, while increasing the capacity of communities to plan for anticipated worsening climate change impacts. Establishment of resilient livelihood strategies, disaster risk preparedness and reduction strategies, empowerment and social mobilization and capacity development within institutions also constitute critical elements of such adaptation strategies.
Barriers to establishing prawn-fish-rice plots in less vulnerable areas may or may not exist. Systematic evaluation of key criteria are needed and could be achieved, for example, through Bayesian Belief Network analysis, facilitation of a stakeholder Delphi assessment or the formulation of a suitable Geographical Information Systems planning tool to demarcate potential development zones. Policies could be conceived to encourage uptake and relocation, coordinate supporting infrastructure development and enable equitable credit and services provision in partnership with NGOs and the private sector. Composition and dissemination of better management practice guideline—including measures to promote social capital, ensure environmental protection and enhance aquatic and terrestrial biodiversity—are crucial.
Estimates indicate that converting 25% of the existing seasonal rice fields in Bangladesh to prawn-fish-rice culture could generate an additional US $2.35 billion in export earnings, while contributing to increased local food security and environmental benefits. Therefore, assuming it is possible to identify geographical areas where these agroecosystems could flourish, this poses the question: how can we best garner support from policy-makers and promote uptake amongst farmers, while ensuring that a transition to landscapes dominated by prawn-fish-rice cultivation does not adversely affect biodiversity, compromise ecosystem services or disadvantage poor and marginal groups?Photo: Nesar Ahmed, Bangladesh Agricultural University