Streams in decline

Sir, I have lived within 50 yards of the chalk-bedded River Wylye for some seven years and it has slowly declined from being a vibrant and living entity to, in parts, a barren and desolate stretch of river bed (letter, July 31).

Even allowing for abstraction, pollution and other factors, the main offender in the decline in my area is the ever-growing swan population. I watched a flock of some 40 swans devastate the stretch nearest my house over a few days in 2000. They completely destroyed the weed beds which have still to recover. All the insect larvae, shrimp and snails that form the diet of a large variety of birds and animals are gone and a bare river bed is all that remains.