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The Norber Erratics are a remarkable scattering of Yorkshire boulders and one of the geological wonders of the UK. John Craven meets geologist Chris Darmon to find out how these huge hunks of sandstone came to rest on the relatively tiny chunks of limestone beneath them. Then John speaks to the various artists who have been inspired by the boulders, including local painter John Osborne, who sees life in the rocks, and Louise Ann Wilson, who created a unique dance on, over and around the erratics.

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Despite its dilapidated appearance, the abandoned oil refinery site of Canvey Wick in Essex is teaming with life. Dumped sediment from the dredging of the River Thames has created a patchwork of habitats that house an abundance of plants and creatures. Ellie Harrison meets the conservationists trying to preserve this hidden treasure. Then Ellie travels to nearby ex-rubbish tip Thurrock Thameside to discover how the local Wildlife Trust has transformed the dump into a wildlife haven.

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White-clawed crayfish, which are native to the UK, are now seriously endangered due to the spread of invasive American signal crayfish. These crayfish not only compete for food and habitat, they also carry a plague which is fatal to the white-clawed crayfish. Native crayfish could become extinct in the wild within decades if efforts are not made to protect them. John meets Paul Bradley and Neil Handy, who are running the first ever captive breeding programme for native crayfish. He also helps them release the new crayfish into ‘ark sites’ in the wild where they can live in safety.

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Foraging, the gathering of food from the natural environment, has been practiced by humans for thousands of years. These days, whether picking blackberries or wild mushrooms, we do it more for enjoyment than necessity. But for some it’s become a business. Tom Heap finds out how a fashion for wild produce has led to large scale foraging, with some areas of woodland being stripped clean. He discovers the lengths that some landowners have gone to stop it and learns how to forage responsibly.

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There is a double dose of One Man and His Dog this week as we meet the English and Irish teams taking part in the sheepdog trials.Ìý Helen Skelton heads to Cornwall to visit our youngest competitor and to Northumberland to speak to a man determined to take home the prize.Ìý Meanwhile, Adam Henson is in Ireland visiting a part-time farmer who is also a full-time telephone engineer and a young lad who believes he’s capable of winning – if luck is with him on competition day.Ìý Find out how they get on in next week’s Countryfile.