The authorities do not accept dredging will cause the damage the protesters claim.
Dredging allows sea water to flow upriver, increasing the salinity of the wildlife-rich marshes, reedbeds and shallow waters around it that form the internationally renowned Coto Doñana,
which is protected by almost every conservation designation ever invented.
At peak times, half a million waterbirds gather in this aquatic wilderness. About 125 species breed there, including several of global conservation concern. Convert the waters from fresh or
brackish to saline and the breeding rates of many of these species will plummet.
These warm, shallow waters are also breeding grounds for many of the fish caught at sea, and the rice paddies on the river's east bank are in jeopardy too.