The wetland that keeps shrinking

The lake here is a changing estate. South Dongting is the great wetland of the lake's southern arm — about 168,000 hectares across the territory of Yuanjiang city, Miluo and the surrounding lake country — and it is built from named pieces: Hengling Lake, Wanzi Lake and 118 lake flats and islands, each a different depth of water. Its defining behaviour is seasonal drowning. The Chinese phrase for it says that when the water rises the land is lake, and when the water falls it is oasis; in the wet summer the flats drown and merge, in the dry winter they surface as grassland. That rhythm made the shore unusually farmable and unusually uncertain. Neighbouring Xiangyin County, at the lake's southern edge where the Xiang and Zi end their courses, is almost two-fifths open water, a scatter of lakes — Hengling, Helong, Huangni and more — threaded by channels, with villages sitting on the higher flats between them. Fishing, grazing the seasonal grass and cutting reed have been the shore's economy since the lake country was settled. The whole arm is the settling basin of rivers, silting and shifting, which is why its outline on a map is a rumour rather than a line.

In winter the marsh becomes a bird census. The reserve's own counts list 164 bird species, alongside 863 plants, 144 fish, 48 molluscs and 9 shrimp — and, among first-class state-protected animals, ten species including the Chinese sturgeon, the white crane and the Chinese merganser. The headline number is half a million: more than 500,000 waterbirds overwinter on these flats, feeding on the grasslands that falling water exposes through the cold months. For birds moving down the continent's flyways, the shallow lakes of the Dongting system are one of the great wintering grounds, and the south arm — with its maze of islands and seasonally exposed mud — is the quietest and richest part. The richness was known before it was counted; the lake country's older accounts describe Dongting's birds as abundant, with more than 130 kinds recorded around Yueyang. Protection has followed the numbers. A South Dongting provincial nature reserve was established in 1997, and in February 2002 the wetland was listed internationally under the Ramsar convention, giving the birds' winter larder a legal standing that patrol routes and boundaries now mark on the water.

The lake's richness was partly earned by eating itself. Han settlement of Hunan's lowlands meant forest clearance, rice planting and — the decisive technology — river dikes to protect fields from the floods that had made the marsh. Each dike turned a seasonal flat into a polder; each polder pushed the open lake outward, and the cycle of reclaiming and silting has been shrinking Dongting for centuries. On this southern shore the twentieth century organised the process: five great state farms — Datong Lake, Beizhouzi, Jinpen, Qianshanhong and Chapanzhou — worked the reclaimed plain for grain under the prefecture at Yiyang. In December 2000 the farms were dissolved as units, four of them merged into the Datonghu management district and the fifth returned to Yuanjiang, a quiet admission that the lake edge had been fully occupied. Protection is now the counter-movement: the provincial reserve of 1997, the Ramsar listing of 2002, the patrols that guard the wintering birds. The wetland's paperwork is therefore a ledger of two opposite claims — farmland wanting dry ground and waterbirds wanting the flood — filed against the same hectares, with the water deciding, year by year, who wins.