Despite large poultry units being a key driver of river pollution, their number has soared near the Wye and Severn

• ‘The sores on the fish are nasty’: what’s behind the changes in the Severn river?

More than 51 million chickens are being industrially farmed in the river valleys of the Severn and Wye – the equivalent of 79 chickens for every person in the region, according to new figures.

The exponential rise in large intensive poultry units (IPUs) in the valleys is a key driver of river pollution. Chicken dropping contains more phosphates – which starve fish and river plants of oxygen – than any other animal manure.