The Aral Sea, once the world’s fourth-largest lake, is one of the planet’s most shocking environmental disasters, according to the UN Secretary General.

The sea which has shrunk by 90 per cent has ruined the once-robust fishing economy and left fishing trawlers stranded in sandy wasterlands. The sea shrank largely due to a Soviet project to boost cottong production in the arid region.

Its evaporation has left layers of highly salted sand, which winds can carry as far away as Scandinavia and Japan, and which plague local people with health troubles.

Ban Ki-Moon toured the sea by helicopter as part of a visit to the five countries of former Soviet Central Asia. His trip included a touchdown in Muynak, Uzbekistan, a town once on the shore where a pier stretches eerily over gray desert and camels stand near the hulks of stranded ships.

“On the pier, I wasn’t seeing anything, I could see only a graveyard of ships,” he said after arriving in the city of Nukus, the capital of the autonomous Karakalpak region.

“It is clearly one of the worst disasters, environmental disasters of the world. I was so shocked,” he said.

The Aral Sea catastrophe is one of Ban’s top concerns on his six-day trip through the region and he is calling on the countries’ leaders to set aside rivalries to cooperate on repairing some of the damage.

“I urge all the leaders … to sit down together and try to find the solutions,” he said, promising United Nations support.

However, cooperation is hampered by disagreements over who has rights to scarce water and how it should be used.

In a presentation to Ban before his flyover, Uzbek officials complained that dam projects in Tajikistan will severely reduce the amount of water flowing into Uzbekistan. Impoverished Tajikistan sees the hydroelectric projects as potential key revenue earners.

Competition for water could become increasingly heated as global warming and rising populations further reduce the amount of water available per capita.