Since 1980, one-fifth (3.6 square kms) of the mangroves are lost.
Search crews are expected to finish their sweep of the 120,000 square kms (46,000 square mile) search zone in the Indian Ocean by December.
But it is surrounded not just by a maginficent cathedral but by nine square kms (3.5 square miles) of Spanish-colonial houses, churches and public buildings, some dating back to the 16th century.
The environment ministry began to get alarmed in January: in the previous two, usually wet, months nearly 2,000 square kms (770 square miles) of forest were cut down.
Most of the power would be exported to Brazil to start with, but the proportions would slowly reverse and after 30 years Peru would own the $4 billion project.The dam would create a lake of up to 450 square kms (175 square miles), flooding some 60 villages, as well as roads and forest.
The lagoon, which would take about two years to build, would comprise an impounding "breakwater or seawall" capable of holding 11 square kms (4 sq miles) of water.
