Chibayish Mohammed Hamid Nour is only 23, but he is already nostalgic for how Iraqs Mesopotamian marshes once were before drought dried them up, decimating his herd of water buffaloes.

Even at their centre in Chibayish, only a few expanses of the ancient waterways home to a Marsh Arab culture that goes back millennia survive, linked by channels that snake through the reeds.

Pull back further and the water gives way to a parched landscape of bald and cracked earth.

Mohammed has lost three-quarters of his herd to the drought that is now ravaging the marshes for a fourth-consecutive year. It is the worst in 40 years, the United Nations said this week, describing the situation as alarming, with 70 percent of the marshes devoid of water.

I beg you Allah, have mercy! Mohammed implored, keffiyah on his head as he contemplated the disaster under the unforgiving blue of a cloudless sky.

The buffaloes of the marshes produce the milk for the thick clotted geymar cream Iraqis love to have with honey for breakfast.

As the marshes dry out, the water gets salty until it starts killing the buffaloes. Many of Mohammeds herd died like this, others he was forced to sell before they too perished.

If the drought continues and the government doesnt help us, the others will also die, said the young herder, who has no other income.

Both the Mesopotamian marshes, and the culture of the Marsh Arabs or Maadan like Mohammed who live in them, have UNESCO world heritage status. The Maadan have hunted and fished there for 5,000 years, building houses from woven reeds on floating reed islands where the Tigris and Euphrates rivers come together before pouring into the Gulf.

Even their beautifully intricate mosques were made of reeds.

But the marshlands have shrunk from 20,000 square kilometres (7,700 square miles) in the early 1990s to 4,000 (1,500 square miles) by latest estimates choked by dams on the great rivers upstream in Turkey and Syria and the soaring temperatures of climate change. Only a few thousand of the quarter million Maadan who lived in the marshes in the early 1990s remain.

Experts say that Iraqs management of the waters has not helped.