This BBC article says:
Conservationists believe they have identified the cause of a decline in numbers of a rare duck.
In the UK, common scoters breed at only a few locations in the Flow Country of Caithness and Sutherland and lochs in the hills and glens near Inverness.
A key cause is now thought to be rising numbers of trout which eat the ducks’ main food source, freshwater insects.
RSPB Scotland and others have raised concerns the bird could become extinct locally because of poor breeding.
The charity suspects declining angling on the lochs has helped boost brown trout populations.
The article explains further but this sequence of events starting with the failure of anglers – yes, its all our human fault – is interesting.
The solution: more anglers. Get back out there,guys and gals.