Floating agriculture is a way of utilising areas which are waterlogged for long periods of time in the production of food. The technology is mainly aimed at adapting to more regular or prolonged flooding.
The approach employs beds of rotting vegetation, which act as compost for crop growth. These beds are able to float on the surface of the water, thus creating areas of land suitable for agriculture within waterlogged regions. Scientifically, floating agriculture may be referred to as hydroponics. In Bangladesh, it has regional names such as baira, geto, dhap and bed.
The description of this technology originates from Linham and Nicholls (2010).
Floating agriculture can be used in areas where agricultural land is submerged for long periods; the approach is reasonably widespread in Bangladesh where agricultural land is inundated for extended periods during the monsoon season (APEIS & RIPSO, 2004). The practice is similar to hydroponic agriculture whereby plants can be grown on the water on a floating bed of water hyacinth, algae or other plant residues (Saha, 2010).
A typical example of floating agriculture in Bangladesh involves a floating layer of water hyacinth, straw or rice stubble to which is added upper layers of small and quick-rotting waterworts which make for good manure (APEIS & RIPSO, 2004). The structure of the floating raft is strengthened with bamboo, while bamboo poles are used to fix it in position to avoid damage caused by wave action or drifting (Saha, 2010). This floating raft can then be transferred to any submerged location for agricultural purposes (APEIS & RIPSO, 2004). An example of a floating agricultural system is shown in Figure 1.
The practice helps mitigate land loss through flooding, by allowing cultivation of these areas to continue. In this way, the total cultivatable area can be increased and communities can become more self sufficient. In addition to this, the area under floating cultivation is up to 10 times more productive than traditionally farmed land (Haq et al., 2004) and no additional chemical fertilisers or manure is required. When the crops have been harvested and floating rafts are no longer required, they can be used as organic fertilisers in the fields or incorporated into the following years floating beds as a fertiliser (AEPIS & RIPSO, 2004; Saha, 2010).
The approach uses water hyacinth, a highly invasive weed with prolific growth rates, in a highly beneficial way. By harvesting water hyacinth, areas covered by the weed are cleared, with the beneficial side-effect of reducing breeding grounds for mosquitoes and improving conditions for open-water fishing (Saha, 2010). By cultivating crops in water, it is also possible to simultaneously harvest fish populations which reside in the beds (APEIS & RIPSO, 2004).
The practice of floating agriculture also helps supplement the income of local communities and contributes to alleviation of poverty (Saha, 2010). It also provides greater food security by increasing the land output and supporting capacity for poor and landless people (Irfanullah et al. 2007). People practicing floating-bed cultivation are enjoying a better life economically, than those in other flood-affected areas who have not yet adopted this practice (Saha, 2010).
Because the system is fairly labour intensive, it also has the capacity to provide employment opportunities within communities (Haq et al., 2004). As both men and women can carry out the floating agriculture practices, it can also lead to improvements in gender equity.
While this technology works well in some areas today, it is unclear how it may be affected by SLR and increases in salinity, which are likely to occur under scenarios of climate change. Additionally, while the technique is applicable in several mega-deltas such as the Ganges-Brahmaputra, the success of a more general application of this approach seems unlikely and we recommend caution in applying this approach more widely.
The methods used in floating agriculture have the drawback of encouraging insect and rodent infestation. This may cause health problems and damage to crops (Saha, 2010).
The technology can also cause conflict within the community if common property areas are dedicated to the practice. Such an approach may lead to politically more powerful individuals attempting to acquire these areas for their own gains (Islam & Atkins, 2007). Although this technology provides the advantage of maintaining food production, it may be difficult to transport produce to market because the area remains waterlogged most of the time (APEIS & RIPSO, 2004).
Floating agriculture practices have minimal infrastructure and very little capital requirement (Saha, 2010). Costs can also be kept low because raw materials for the construction of floating beds are readily available from local waterways.
Haq et al. (2004) conducted an analysis of the costs of implementing floating agriculture in Bangladesh. Their findings are shown in Table 1.
Table 1: Costs of implementing a floating agricultural system in Bangladesh
|Activity||Duration||Total Cost (Tk)||Total cost converted to US$ (in 2009 US$)|
|Construction of floating beds||60 man days||3000||63|
|Collection of raw materials (weeds)||20 man days||1000||21|
|Seed and/or seedling purchase||600||13|
|Bamboo, rope, crop harvesting and maintenance||1000||21|
|Total||Tk 5600||US$ 118|
The use of floating agriculture as an adaptive measure also provides direct economic benefits. Vegetables and spices produced on the floating beds can be sold at markets and since the approach is fully organic, the produce receives special attention from local buyers and consumers (Haq et al., 2004).
Due to a lack of awareness of floating agriculture and its methods, it will be necessary to raise awareness and educate local communities. A recent scheme in Bangladesh was promoted by the Wetland Resource Development Society (an international research and development organisation), which provides training and technical support to local communities.
Provided communities are furnished with the appropriate knowledge, implementation of floating agricultural systems should be achievable at the community scale. This is because raw materials are widely available and costs are low and offset by the production and sale of food stuffs.
In order to implement these schemes at the local level, communities are required to work together. It has been observed that in doing so, the local community and communal harmony can be strengthened (APEIS & RIPSO, 2004).
Through a programme to encourage floating agriculture in Bangladesh, it was found that one of the most important aspects of implementation is to organise small-scale and poor farmers at grass-roots level and build up their entrepreneurial capacity for running small businesses (LEISA, 2009). This builds the benefits to less well-off farmers and can be accomplished on a local level.
The availability of high volumes of fast growing organic material may be limited in some areas and may be problematic if the uptake of this technology becomes widespread. As this is an essential material for floating agriculture, a limited supply will limit the uptake of this technology.
It is essential that knowledge of this technology be passed on to local communities in areas where floating agriculture is not carried out. To an extent, this has naturally occurred in Bangladesh where the practice has spread throughout the country (APEIS & RIPSO, 2004), but on a global scale, the approach will require local awareness raising.
Poorer farmers can be prevented from participating in floating agriculture schemes if their rights to common property and ownership of technology are not protected. While many wetland areas with plentiful water hyacinth may exist, they are likely to be grabbed by the upper levels of the rural and urban society if extensive and persistent advocacy is not considered by the implementing bodies (LEISA, 2009).
Floating agriculture is an environmentally-friendly option for increasing the land available for agriculture. As such, the practice could be sustainable and profitable in developing countries, helping to supplement incomes and to increase food security (APEIS & RIPSO, 2004).
Regular, land-based agriculture requires farmland to be protected behind embankments or reclaimed from estuarine systems. Both of these activities can have detrimental side effects upon the local environment and economy. In contrast, floating agriculture can be conducted without land claim and hard defences. The procedure can even contribute toward maintaining healthy wetlands (Haq et al., 2004), which have coastal defence functions and also support a wide range of biodiversity.
Aquatic invasive species used in floating agriculture are considered to be the second largest reason for biodiversity loss worldwide (Haq et al., 2005). Clearing waterways to collect these plants is therefore beneficial to the health of wetland ecosystems and may contribute toward maintaining high biodiversity and associated benefits.
The practice is already widely applied in some developing countries such as Bangladesh, and the uptake of the technology is already increasing due to its sustainable, positive features (APEIS & RIPSO, 2004).
APEIS and RIPSO (2004) Floating Agriculture in the flood-pr one or submerged areas in Bangladesh (Southern regions of Bangladesh). Bangladesh: APEIS and RIPSO. Available from: http://enviroscope.iges.or.jp/contents/APEIS/RISPO/inventory/db/pdf/0146.pdf  [Accessed: 22/07/10].
Haq, A.H.M.R., Ghosal, T.K. and Ghosh, P. (2004) Cultivating wetlands in Bangladesh. India: LEISA. Available from: http://bit.ly/c3Ah0o  [Accessed: 05/08/10].
Haq, A.H.M.R., Ghosh, P. and Islam, M.A. (2005) Wise use of wetland for sustainable livelihood through participatory approach: A case study of adapting to climate change. Bhubaneswar: Asian Wetland Symposium. Available from: http://bit.ly/95hEqV  [Accessed: 05/08/10].
Islam, T. and Atkins, P. (2007) Indigenous Floating Cultivation: A Sustainable Agricultural Practice in the Wetlands of Bangladesh. Development in Practice, 4(1), 130–136. (LEISA, 2009)
Linham, M. and Nicholls, R.J. (2010) Technologies for Climate Change Adaptation: Coastal erosion and flooding. TNA Guidebook Series. UNEP/GEF. Available from: http://tech-action.org/Guidebooks/TNAhandbook_CoastalErosionFlooding.pdf 
Saha, S.K. (2010) Soilless Cultivation for Landless People: An Alternative Livelihood Practice through Indigenous Hydroponic Agriculture in Flood-prone Bangladesh. Beppu: Ritsumeikan Asia Pacific University. Available from: http://tiny.cc/8ncx1  [Accessed: 22/07/10].
Matthew M. Linham, School of Civil Engineering and the Environment, University of Southampton, UK
Robert J. Nicholls, School of Civil Engineering and the Environment and Tyndall Centre for Climate Change Research, University of Southampton, UK