In Goa, the Chorão mangrove was a rice field until the 1970s

Almost everyone who arrives in Goa thinks of the coast: long beaches, palm trees, the Arabian Sea. But between the beach and the inland hills there is another landscape you cross without looking at it, by car or by ferry: flat green banks, channels, low walls of reddish stone by the water and, in some stretches, a dense mangrove that reaches the edge of the river. It looks like untouched nature. Largely, it is not.

This article explains what khazans are, how a gate that nobody operates works, and why a protected mangrove in Goa is, in fact, the sign of a field that stopped being tended. Understanding it changes what you see as soon as you leave the beach.

The best place to start is a few kilometres from Panaji, the state capital. At Ribandar, on the Mandovi river, a ferry crosses to the island of Chorão. On the other side, next to the landing, begins the Salim Ali Bird Sanctuary: about 178 hectares of mangrove, declared a protected area in 1988 and named after India's best-known ornithologist.

From the water, the sanctuary looks like what you expect from a mangrove: a compact mass of glossy-leaved trees, roots sunk in the mud and the tide moving in and out between them. Inside there is a path of paving slabs between species such as Rhizophora mucronata and Avicennia officinalis, with herons, fiddler crabs and mudskippers in view. Nothing in the scene suggests that anyone ever planted rice there. And yet, according to researcher Aaron Savio Lobo, writing in Down To Earth in 2020, that 'primeval' forest was, until the 1970s, largely a set of privately owned rice fields.

To understand how a rice field turns into a mangrove, you first have to understand how a mangrove turned into a rice field.

Goa is a territory cut by short, wide rivers such as the Mandovi, the Zuari and the Chapora, which flow into estuaries where seawater comes in with every tide. According to a description by the cultural platform Goya, the reach of the salty tide can extend some 40 kilometres upstream. The low banks of those rivers were, naturally, salt marshes and mangroves: land that floods twice a day.

Khazans are those marshes turned into fields. Marine biologist Sangeeta Sonak, who devoted a book to them published by Springer in 2014, defines them as reclaimed wetlands, salt marshes and mangrove areas where tidal influence is regulated by embankments and sluice gates, and which are, above all, rice and fish fields. A study by ICLEI South Asia carried out between 2021 and 2024 identifies them by a set of features: low-lying, saline, reclaimed floodplain, below river or sea level, protected by a bund and surrounded by mangrove.

They are not a recent invention. The oldest known written reference is a copper plate from Bandora, attributed to a king named Anirjita-varman and dated by its script to the fifth or sixth century. It records the tax-free grant of land in Dwadasa-desha, today's Bardez, including one unit of 'khajjana' land. Whoever received it was expected to turn that wetland into a cultivated field by building a bund to keep out the salt water. In other words, some fifteen centuries ago the task was already described in the same terms used today.

The defence has three layers. On the outside, an outer bund built mostly of laterite, the reddish rock you see in walls and houses all over Goa, with a strip of mangrove in front of it to break the waves. Inside, lower bunds of mud, straw and poles that divide the fields. And at the point where a channel crosses the outer bund, the sluice gate. Official figures put khazans at about 18,000 hectares across the state, roughly 5 per cent of its area.

The sluice gate, called a mano in Goa, is the piece most often misread, because at first sight it looks like a simple lock that someone opens and closes by hand. It works differently. Lobo describes it as a one-way valve. On the incoming tide, river water pushes the gate's shutters and fills the perimeter channels around the fields, called poiems, and fish, crabs and shrimp come in with the water. When the level is equal on both sides, the gate closes by itself. When the tide goes out, it opens outwards, again by itself, and lets the water drain from the channels.

The key detail is that salt water enters the channels, but not the paddies. The fields are slightly raised by the inner bunds, and the channel around them takes the water without it reaching the crop. In the monsoon, the same gates do the opposite job: they release surplus rain into the river and keep the fields from waterlogging. At the lowest point of the system, a depression called a poim serves as a reservoir for excess water and protects the fields from high tides.

Nobody opens or closes the gate. The tide pushes it as it comes in, shuts it when the levels match and opens it as it falls. The human work lies in keeping it in repair.

The gate does not only protect the rice. It is also a fishery. When the tide falls and the water drains out of the channels, a bag net is set at the mouth of the gate to catch the fish that came in on the previous tide. The person who works it is called the manshekar, the fisher of the gate.

This trade matters most in the rainy months. Every year the west coast of India enforces a monsoon fishing ban for mechanised boats, which in 2015 was extended from 45 to 61 days in Gujarat, Maharashtra, Goa and Karnataka. During those weeks, as Lobo reported in Scroll in 2016, the gates keep working, and out of them come species with local names such as mudoshi, chonak, shevtali or tambuso, that is, ladyfish, sea bass, mullet and snapper, along with shrimp that anglers seek as bait.

And here is the piece that holds the system together. According to Down To Earth, the right to fish each gate is auctioned every year, and the proceeds go to the association responsible for the bunds. The fish pays for the wall that protects the rice. When that circuit breaks, because the winning bidder does not pay or because nobody invests in repairs, the bund starts to fail.

What grows behind the bund is not just any rice either. The variety most associated with khazans is korgut, salt-tolerant and able to grow in brackish water, a mix of fresh and salt. It is grown only during the monsoon, when rain dilutes the salt in the soil. According to ICAR-CRIDA's crop calendar for Goa, broadcast sowing on khazans takes place between the third week of June and the first week of July, and the harvest comes between mid-October and November.

Korgut is a tall plant, over a metre and a half according to Goya, which lets it withstand flooding, with a plump brown grain that is eaten parboiled. It yields 2 to 2.5 tonnes per hectare, compared with 4 to 4.5 for modern varieties such as Jyoti or Jaya, which now dominate the state's production. That yield gap explains why many farmers dropped it; its salt tolerance explains why agricultural research centres still study it.

A khazan is a balance that has to be maintained every year. Mud bunds erode, crabs burrow into the walls, the wooden gates rot. If nobody repairs them, the tide finds a breach, salt water enters the fields and the rice stops growing. Down To Earth and India Water Portal have documented breached bunds, fallow fields and salt-invaded land for years; the figures vary by source, but all point to a large share of khazans no longer being farmed.

What happens next is what you see on Chorão. According to Lobo, with changes in land tenure in the second half of the twentieth century and the neglect that followed, the island's bunds gave way, water from the Mandovi entered the fields and left them unfarmable. Birds frequenting the island helped spread mangrove seeds, the trees took root in the soft sediment and, within a few decades, the rice field became the forest the sanctuary protects today.

The mangrove did not invade anything foreign: it reclaimed the place it held before the bunds were raised. That is why the same landscape allows two readings that do not cancel each other out. For an ornithologist, Chorão is a regeneration success. For someone who knows the system, it is also a rice-and-fish field that ceased to exist.

First: 'the sanctuary's mangrove is a virgin forest.' It is not. It is a young mangrove, grown largely over rice fields that were farmed until the 1970s. That does not reduce its ecological value, but it changes its story: it is a forest that came back, not one that was always there.

Second: 'the fields along the rivers are natural wetlands.' Many are the opposite: land won from the tide and held below its level by bunds and gates, with a written record dating back some fifteen centuries. What looks flat and spontaneous is a work of hydraulic engineering maintained by hand.

Third: 'the gate is a lock that someone operates.' Nobody is needed for it to work: the tide opens and closes it. What is needed is a community that repairs it, auctions the fishing and uses that money for the bund. As Lobo puts it, it is not technology that keeps the system alive, but the organisation of the people who look after it.

None of this requires a long detour. It is enough to know what to look for the next time you cross a river in Goa.

The shift this article proposes is a concrete one. Before reading it, Goa's riverbanks were background scenery, and the Chorão sanctuary a mangrove that had always been there. Afterwards, they are a system of bunds, gates, rice and fish that runs on the tide and depends on people's care, and the mangrove is what appears when that care stops.

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