The lake is called Buada and it is the island's exception. Everything else in Nauru is coastal strip or stone plateau; here there is a bowl with permanent water, fertile soil and shade, in the place you would least expect it.
01 A karstic bowl in the middle of the plateau
Buada sits in a twelve-hectare swampy depression in the south-west of the central plateau. The water measures some 280 metres north to south and about 140 east to west, one or two metres deep on average and five at its deepest.
The hollow came from the dissolution of the coral limestone that forms the plateau: the ground sagged into itself and left a karstic bowl. The water surface sits close to sea level, although it lies more than a kilometre from the coast.
The lake is endorheic: it has no outlet and only rain feeds it, because Nauru has no rivers or streams. Its level swings hard between the November-to-February monsoon and droughts, which in La Niña years can leave it five metres below sea level. The water is greenish, slightly brackish — around two per cent salt — and basic, with a pH of eight.
02 A sea fish raised inland
The milkfish, Chanos chanos, spawns at sea and its fry come close to shore. Nauruans collected them in the surf along the shoreline — the fry are called ibija — acclimatised them step by step to less salty water and released them into the lake and into brackish ponds near the coast.
There they grew for eight or nine months, to around a kilo, and were fished out to eat. Many of the fry did not survive the transfer, but those that did were enough to give the island a steady source of protein that did not depend on going out to sea.
The system had owners. The lake and the ponds were divided by holding, with the boundaries marked out with coconut fronds and, later, low concrete walls. Nauru's aquaculture predates European contact and is the oldest documented anywhere in the island Pacific.
03 The only piece of plateau never mined
Phosphate of very high purity accumulated among the plateau's pinnacles, and extracting it took up almost the whole twentieth century, until it had affected around 80 per cent of the country's surface. The Buada bowl is the only part of the plateau where that ore was never worked.
The consequence is visible from the edge. Around the lake stand some forty hectares of vegetation on waterlogged, fertile soil, dominated by tamanu, a remnant of the tropical forest that covered ninety per cent of the island before mining.
In that band people grow banana, papaya, mango, guava, pandanus and vegetables on small plots. It is, in practice, the country's vegetable larder, and it explains why the bowl always mattered more than its size suggests.
04 Why it ended
Milkfish rearing faded out in the late 1970s, shortly after Mozambique tilapia was introduced as a new food source. The tilapia behaved like a pest in the island's brackish waters and pushed the milkfish out of the ponds and the lake.
An FAO trial in 1992 showed that the two species can coexist, but at a cost: to reach about twenty centimetres, milkfish needed four more months than they need when no tilapia is present. The milkfish eaten in Nauru today arrives imported from the Philippines and Kiribati.
The lake still holds fish — milkfish, tilapia and gambusia, the last brought in to eat mosquito larvae — and the FAO considers it the only spot on the island capable of supporting aquaculture. An association of lake owners is working to bring the practice back.
05 What it reveals
A country of twenty-one square kilometres with no rivers, a reef that prevented a harbour and a stone plateau in the middle solved its food security by doing the least obvious thing: bringing the sea inland, a bucket of fry at a time.
When you look at Buada Lagoon from the edge of the road, what you are seeing is not a pretty landscape inside a stripped island. It is the part of the island that was never touched, and the reason it was left standing.
