Marsh harriers have recovered in the UK through reedbed restoration but remain dependent on large connected wetlands for successful breeding.
Small isolated reedbeds below minimum territory size cause nest failure. Disturbance from kayakers, paddleboarders, and anglers causes nest abandonment. Reed harvesting at the wrong time of year destroys active nests. Storm events that flatten reed structures collapse nests with eggs or chicks. Persecution on game estates, though less common than for terrestrial harriers, still occurs.