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Bangladesh's floating gardens, built to grow food during flood seasons, could offer a sustainable solution for parts of the world prone to flooding because of climate change, a new study has found.

The study, published recently in the Journal of Agriculture, Food and Environment, suggests that floating gardens might not only help reduce food insecurity, but could also provide income for rural households in flood-prone parts of Bangladesh.

"We are focused here on adaptive change for people who are victims of climate change, but who did not cause climate change," said Craig Jenkins, a co-author of the study and academy professor emeritus of sociology at The Ohio State University. "There's no ambiguity about it: Bangladesh didn't cause the carbon problem, and yet it is already experiencing the effects of climate change."

Bangladesh's floating gardens began hundreds of years ago. The gardens are made from native plants that float in the rivers—traditionally, water hyacinths—and operate almost like rafts, rising and falling with the waters. Historically, they were used to continue growing food during rainy seasons when rivers filled with water.

The farmers—or their families—layer the plants about three feet deep, creating a version of raised-bed gardens that float in the water. Then, they plant vegetables inside those rafts. As the raft-plants decompose, they release nutrients, which help feed the vegetable plants. Those vegetable plants typically include okra, some gourds, spinach and eggplant. Sometimes, they also include spices like turmeric and ginger.

Floating gardens are also in use in parts of Myanmar, Cambodia and India. The United Nations Food and Agricultural Organization has named Bangladesh's floating gardens a Globally Important Agricultural Heritage System.

But as climate change has affected the volume of water in those rivers—creating extreme highs and floods, along with extreme lows and droughts—floating gardens have become a way for rural farmers to keep producing food during unpredictable weather. Climate change increases weather extremes and the severity of flooding, and droughts as well.

The researchers wanted to understand whether Bangladesh's floating gardens could be a sustainable farming practice as climate change continues to cause floods and droughts, and to see whether the gardens bring better food security to individual households.

"They've got to be able to grow specific crops that can survive with minimal soil," said Jenkins, who is also a research scientist and former director of the Ohio State Mershon Center for International Security Studies. "And in Bangladesh, a lot of small farmers that had typically relied on rice crops are moving away from those because of the effects of climate change and better returns from alternative crops."

For this study, the researchers interviewed farming families who use floating gardens, and found strong evidence that floating gardens provide stability, both in the amount of food available to feed rural populations and in a farming family's income, despite the instability created by a changing climate.

They found that farmers typically use hybrid seeds, which must be repurchased each year, to grow a diverse range of vegetables in the floating gardens. The gardens are also susceptible to pests, so farmers end up spending some money on both pesticides and fertilizers. But even with those expenses, they found, benefits outweighed costs.

Generally, entire families work on the gardens, the researchers found: Women, children and the elderly prepare seedlings and collect aquatic plants to build gardens. Men cultivate the gardens and protect them from raiders. Some families also farm fish in the waters around their floating gardens.

One farmer told the research team that he earns up to four times as much money from the gardens as from traditional rice paddies.

Still, the system could use improvements, the researchers found. Farmers often take out high-interest loans to cover the investment costs of building the beds and stocking them with plants. Lower-interest loans from responsible government or non-governmental organizations could alleviate that burden, they found.