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Robbing land from the sea March 25th, 2018 by

The low-lying Netherlands is famous for its polders, the land behind the dikes, reclaimed from the sea. Beginning about 1000 AD, people made dikes, or earthen dams, to protect communities from flooding. At first the water was simply drained through canals, but with time the land in the polders subsided, and by the 1400s water was being pumped out with windmills. Thanks to hard work, investment and some clever engineering, people still live in and farm the polders.

Much of Bangladesh is also right at sea level and densely populated. So why doesn’t Bangladesh have polders too? I wondered out-loud during a recent visit last October.

“But we do! Bangladesh has many polders,” my colleague Salahuddin retorted. He explained that there was a string of some 123 polders over much of southern Bangladesh, an area where several large rivers cut the delta into finger-like strips of lowland.

The polders were built between the 1960s and the 1980s, first by the provincial government of East Pakistan, and later by the Government of Bangladesh, after independence from Pakistan in 1971.

Each polder is ringed by a low earthen embankment (basically a dike), sometimes just two meters high and made by hand. The roughly oval-shaped polders are dozens of kilometers in circumference.

The Bangladeshi polders are drained by an ingenious network of canals, radiating like veins from the center of the polder to the edge, where the flow of water is controlled by a sluice gate in the embankment.The sluice gate is a concrete structure with metal doors that can be raised by a hand-crank to let the water out during the rainy season, and lowered during the dry season to keep out the saltwater.

Originally the wetlands of the delta region had been sparsely populated by fisher-farmers who grew low yielding rice varieties that tolerated brackish water. The polders soon became attractive places to live and settlers trickled in. The people who were born in the polders tended to stay there and so populations increased.

Some of the polders have benefited from some sort of project, and have been reasonably well managed. By 2018 the better polders are like gardens, with comfortable farm houses surrounded by shimmering green rice fields.

The polders have had their share of troubles. Sometimes one of the rivers changes course, depositing a bank of silt next to the sluice gate, so the water inside the polder cannot drain out.  Other problems are man-made. Loggers float timber down the canals, and when the logs reach the sluice gates, the workers take the easy route to the river. Instead of hoisting the logs around the sluice gate, the loggers force the timber through the delicate metal gates, twisting and denting them so they no longer open and close. Wealthy, powerful people sometimes block the drainage canals to raise fish in them. Or they string nets over the canal to catch fish. But this slows down the flow of water, allowing silt to settle and eventually block the canal. The canals are as wide as a highway, and can be just as difficult to maintain. So once the drainage canal stops working, villagers are unable to open them up again without help from outsiders.

The polders are essentially a government mega-project, which sounds at first like a recipe for disaster. But as one drives along the top of a polder embankment, the muddy river on one side and the tidy green fields and villages on the other, it is hard to ignore the fact that the government got something right.

Ironically, country that is flooded during the rainy season may be completely dry a few months later. Various initiatives are now promoting dry-season irrigation for high value crops besides rice, and the farmers in the polders are avidly buying motorized pumps. In many places the rich, black earth inside the polders is now producing two or three crops a year of rice, mung beans, mustard, watermelon and vegetables.

Such changes in the farming system are creating more wealth for the farmers in those polders that are well run. But it will take collaboration, for local government to protect the canals and embankments, for the private sector to provide farm supplies and buy the produce and especially for innovative farmers, to continue re-inventing the agriculture of this marvelous, human-made environment.

Further reading

In characteristic modesty it was some time before my friend Salahuddin told me that he had written his masters’ thesis on the polders of Bangladesh.

Salahuddin, Ahmad 1995 Operation and Maintenance of Small Scale Flood Control Projects: Case of Bangladesh Water Development Board. Master’s Thesis: Institute ofSocial Studies, The Hague.

See also Paul’s blog from last week on coastal Bangladesh: Floating vegetable gardens.


I am indebted to Md. Harun-ar-Rashid, Guy Jones and many others for enlightening me about polders on a recent trip to Bangladesh, supported by the Blue Gold Program, with funding from the Embassy of the Netherlands. Thanks to Harun-ar-Rashid, Ahmad Salauddin, Paul Van Mele and Eric Boa for reading and remarking on previous versions.

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Fishing changes November 12th, 2017 by

Two million years ago in East Africa, long before humans lived on any other continent, our ancestors followed the receding shorelines of shallow ponds and lakes, during each annual dry season, scooping up the stranded catfish and eels. People have eaten fish ever since, and fishing may have shaped humans more than big game hunting.

From Rome to China, early civilizations would have been impossible without fish, as renowned archaeologist Brian Fagan tells us in a new book, Fishing. Mesopotamians could always rely on fish, even when the flooding Tigris and Euphrates failed to water the crops. When the Nile flooded, it covered the land in fish, as well as water. The pyramids of Egypt were built by laborers fed on rations of beer, bread and dried catfish, caught every year in the shallow, receding flood waters of the Nile.

Ancient sailors in small boats could not carry enough provisions for long voyages. The mariners would never have been able to explore the Indian Ocean and create the trade routes that linked Europe and Asia, without settled communities of fisherfolk, who caught and dried fish to sell or trade.

Fishing would have been impossible without local knowledge. The Tahitians sailed sophisticated, deep-sea canoes to catch large, predatory fish. The big fish and the sea birds both followed dense schools of smaller fish. The Tahitians recognized that the big fish followed the birds to find the small fish. Fishers scanned the horizon for birds, and could tell by the species flying over the water what type of fish to expect there.

Commercial fishing began with herring in the North Sea in the 1300s. Dutch and Flemish crews caught the fish from deep-water wooden ships called busses, which required a large crew and started the season every year on the night of St. John, 24 June. The fish were salted, packed into standard-sized barrels, branded with the seals of the merchants who sold them, and traded all over Europe until 1810. By then the herring were becoming scarce, and salted cod from the Atlantic had captured the market. While there is still fishing in the North Sea, before the 1800s the herring were so abundant they were compared to ants.

As waters were fished out, fishers sailed farther and farther from home. The English were fishing off the shores of Iceland in 1420 and off the banks of Newfoundland in 1600. By about 1880, new technologies such as steam trawlers extended the reach of commercial fishing to deep ocean water. But some modern techniques are devastating, such as the large nets that drag the bottom, destroying the places where the fish spawn.

Many countries have reacted to over-fishing by creating 200-mile exclusion zones and limiting catches. The Canadian government closed the cod fishery in 1992 when stocks hit 1% of their peak. Thanks to the ban, the cod have since partially recovered.

Although subsistence fishing is ancient, it has never destroyed the fishery it depended upon. Salmon and sturgeon once swam up the Danube River to spawn. Communities of fishers had survived for thousands of years at the Iron Gates (on the Danube between Serbia and Romania), until nineteenth century pollution, dam-building and over-fishing destroyed the stocks.

But waters far from home, as in the Antarctic, are uncontrolled and fished recklessly, as though there were no tomorrow. Commercial fishing is now in a slow decline, while artisanal and subsistence fishing are both on the rise. Fish farming is increasing rapidly. By 2012, for the first time in history, more fish were farmed than caught wild.

I saw a glimpse of artisanal, peasant fishing recently in Bangladesh, where many villages have fields interspersed with fish ponds. Farmers throw nets and use various other techniques, bringing home one small bag of fish at a time for the supper pot.

On one especially rainy day, the ponds were over-flowing, and some people were setting up long, gently tapering nets over the drainage ditches, to catch any fish that may have escaped from the ponds. No fish was going to be wasted.

Subsistence fishers are often smallholder farmers. Fishing and farming combine easily. If fishing fed civilization, as Fagan explains, it is the smallholders who will keep fishing alive into the future. The fish ponds in Bangladesh are highly commercial, run by knowledgeable farmers. With the increasing demand for proteins, fish species will continue to feed humanity only with a good balance between open sea fishing that respects quotas (based on science and policy) and fish farming that will require stringent food safety measures, such as guarding against the abuse of antibiotics.

Further reading

Fagan, Brian 2017 Fishing: How the Sea Fed Civilization. New Have: Yale University Press. 346 pp.

Related blog stories

Cake for fish? hold the coconut, please

Fishing on a hill

Further viewing

Food for fish

Stocking fingerlings in a nursery pond

Preparing low-cost concentrate feed

Growing azolla for feed

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Cake for fish? Hold the coconut, please November 6th, 2016 by

cake-for-fish-1A good farmer training video inspires farmers to modify practices, for example, replacing an ingredient of a locally-made animal feed. But when changing ingredients, one has to know a lot about them, as we learned recently while teaching a video production workshop in Tamil Nadu, southern India.

Explaining the principles behind a certain technology or why something is done in a particular way helps farmers to better understand the innovation and to try it out with whatever resources they have at hand. The different examples shown in a video help to give farmers more ideas to work with.

In Tamil Nadu, one group of trainees was making a video on home-made animal feed, which only costs half as much as concentrated feed that one can buy in a shop.

cake-for-fish-2By interacting with various farmers, the trainees learned quite a few things. While shops sell specific feed for different animals, farmers make a base mix of grains, pulses and oil-cakes that they use to feed all their animals and fish. This saves the farmers time, while allowing them to still tailor the feed for each species of livestock. Depending on whether it is for cattle, goats, poultry or fish they will then add some extra ingredients, like dried fish (if the feed is for fish or poultry).

The trainees also learned that when you want to use a base mix for fish, you need to consider a few things. Farmers rear up to 6 different species of fish. Two species are surface feeders, two feed in the middle layer, and two species are bottom feeders. As you want the feed to be eaten by all fish, the mix should be milled to a course flour. When ground too fine, the feed will float and be available to the surface feeders only.

One other thing the team of trainees learned was that for fish you can use groundnut oil cake or cotton seed oil cake, but you should never use coconut oil cake (which is readily available and cheap in coastal India). Why? Well, if coconut oil cake is used in the base mix, two days after feeding the fish, an oily film will develop, blocking the pond from sunlight and oxygen and slowly killing the fish. The household can still use coconout oil cake in base feeds intended for livestock.

Clearly, oil cakes are not all the same and not all are interchangeable.

Good farmer training videos should present a range of different options and locally available resources, but they should also warn farmers of any possible risks. Videos for farmers should always say why an option will (or won’t work), as in this case: don’t feed coconut to your fish or the oil will block their sunlight and kill them!

Related video

Preparing low-cost concentrate feed

To watch the video in French, click here.

To watch the video in Tamil, click here.

To watch the video in Bangla, click here.

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Fishing on a hill September 19th, 2014 by

School teachers across the world hold a special position in society. They are respected for the knowledge they share with new generations. But teachers in developing countries also have something else in common: they often find it hard to make ends meet. On a recent visit to Iran I was fortunate to meet Sadegh Mohammadi in Sohrevard city in Zanjan province. Like most Iranian school teachers, Sadegh has a second job, but his is innovative: he rears fish on a steep slope in the back of his garden.

Creating rural employment is as important as ever before, in Iran and elsewhere. Over 15 years the people employed in fisheries in Iran doubled to 181,000 (FAO, 2014). The fish tanks that Sadegh installed in his backyard give direct work to three families and indirectly (supply of fish feed, rearing and selling of fingerlings, marketing) to another 7 families. “Even in the worst situation, the fish gives much more income than a teacher’s salary of 500 US dollars a month,” Sadegh says.

Sadegh learned about aquaculture from the extension service, which also loaned him money to set up his concrete fish tanks. Trout likes cool climates and fresh, fast-moving water. Hence Sadegh pumps up water from the lake in the valley bottom to the upper tank and then lets the water flow by gravity through the various fish tanks. From experience Sadegh learned that if the fish all gather at the entrance of the tank, they lack oxygen, after which he switches on a small fountain to pump extra air in the water. The many mature walnut trees in his garden provide a pleasant shade from the summer sun, which keeps the fish happy, and provides picnic spots for the many local tourists who come to the village on weekends.

In southern Vietnam, in the late 1990s I saw how creative entrepreneurs built fish ponds in the middle of fruit orchards to attract local tourists. People could fish for a fee, and food was served. Agro-tourism comes in many ways, building on local dynamics and cultures. Bringing the culture back into agriculture is a great way to create rural employment and for urban folks to learn about farming (and sometimes about fishing too).

Reference: FAO. 2014. Iran National Aquaculture Sector Overview. http://www.fao.org/fishery/countrysector/naso_iran/en

To watch or download a training video, see: Food for fish

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