Where Rivers Spread Out: Deltas and Great Wetlands

The Camargue sits in the delta of the Rhone River in southern France and covers a little over 930 square kilometres, which the source calls one of western Europe largest river deltas. Its salt marshes, rice paddies, pink flamingos and semi-wild white horses show a delta shared between wildlife and farming.

Here the Rhine, Meuse and Scheldt meet the North Sea in the Netherlands, on a delta of about 25,347 square kilometres that the source calls the largest in Europe. Dikes, dams and storm-surge barriers, including the Delta Works built after the 1953 flood, protect a densely populated lowland.

The Danube enters the Black Sea through a delta of about 4,152 square kilometres, most of it in Romania with the rest mainly in Ukraine. It is among the best-preserved river deltas in Europe, and its reed beds support one of the continent richest concentrations of birdlife.

The Niger reaches the Gulf of Guinea in southern Nigeria through one of the largest river deltas in the world, about 69,930 square kilometres by the recorded figure. It is also the centre of Nigeria oil industry, which has brought national revenue and serious damage to its wetlands.

The Indus meets the Arabian Sea in Sindh, Pakistan, on a delta of about 41,440 square kilometres and roughly 210 kilometres across where it meets the sea. Mangrove wetlands once covered much more of it, and upstream diversion of water has reduced the freshwater flow and let seawater creep into the soils.

The Sundarbans spread across 10,277 square kilometres of the combined delta of the Ganges, Brahmaputra and Meghna in Bangladesh and India. It is the largest mangrove forest in the world and the last major stronghold of the Bengal tiger living in mangrove habitat.

The Mekong ends in southern Vietnam as a delta of about 43,000 square kilometres opening onto the South China Sea. Its dense network of distributary channels supports one of the most productive rice-growing regions in the world and a large fishing population.

The Pearl River Delta in southern China covers about 55,800 square kilometres and holds Guangzhou, Shenzhen and Hong Kong among a dense cluster of major cities. A delta built by sediment has become one of the most heavily urbanized and industrialized regions anywhere.

The Yangtze reaches the East China Sea near Shanghai across a delta recorded at about 110,755 square kilometres, the largest on this path. Its fertile plains have long been central to Chinese agriculture and, more recently, industry, in one of the most densely populated regions of the country.

The Pantanal is the world largest tropical wetland, about 195,000 square kilometres in the upper basin of the Paraguay River across Brazil, Bolivia and Paraguay. Seasonal flooding gathers one of the richest concentrations of wildlife in South America, including large populations of caiman and jaguar.

The Everglades in southern Florida form when a slow sheet of water drains from Lake Okeechobee toward Florida Bay, across about 7,800 square miles, or roughly 20,200 square kilometres. Sawgrass marshes and mangrove forests shelter alligators and many wading birds.

The Sacramento and San Joaquin meet in central California on an inland delta of about 2,800 square kilometres before draining into San Francisco Bay. Its leveed islands and channels supply drinking and irrigation water to a large share of the state population and farmland, which closes the path on a delta that people have remade.