The Floating Farms of Bangladesh

In the low-lying wetlands of southern Bangladesh, where land can stay underwater for months each year, farmers have developed an ingenious way to keep growing food: they build their gardens on the water itself. Known locally as dhap or baira, these floating gardens have been used for at least two hundred years in districts such as Pirojpur and Gopalganj, and the technique has been recognised by the United Nations Food and Agriculture Organization as an important agricultural heritage system.

Building a floating garden begins with water hyacinth, a fast-growing plant that covers many rivers and ponds in the region. Although it is often considered a weed because it blocks waterways, it is ideal for this purpose. Farmers gather large quantities of hyacinth and pile it into a raft, typically around one metre deep and up to fifty metres long. Layers of rice straw, coconut husks and other plant material are added on top. After a week or two, the base begins to rot, creating a rich compost in which seeds can be planted.

Seedlings are usually raised first in small balls of mud and decomposed weeds, called doulas, which are placed on the raft once they have started to grow. A wide range of vegetables can be produced in this way, including okra, gourds, aubergines, spinach and turmeric. Because the gardens rise and fall with the water level, crops are protected from flooding: a major advantage in a region where floods destroy fields on dry land almost every year.

The gardens offer other benefits too. Farmers do not need to buy chemical fertiliser, as the decaying plants provide all the nutrients the crops need. At the end of the season, the rafts break down and the remains can be spread on fields as compost when the water recedes. Many families also earn extra income by selling seedlings to their neighbours.

Nevertheless, floating agriculture is hard work. Building a single raft can take a team of people several days, and much of the labour involves standing waist-deep in water. Access to water hyacinth is becoming a problem in some places, as wetlands are drained for fish farming. Development organisations have responded by training farmers in other parts of the country and by experimenting with lighter rafts built on bamboo frames, which last longer than traditional ones.

As climate change brings heavier rains and rising sea levels, interest in floating gardens is spreading beyond Bangladesh. Similar projects are now being tested in parts of India and Cambodia, and researchers believe the method could help millions of people living in flood-prone areas to grow food all year round.