The Yorkshire Dales National Park Authority has hit out at work removing former industrial contamination as it is destroying archaeology and threatening to contaminate water courses.
Much of the area around Swaledale, Wensleydale and Arkengarthdale is covered with spoil heaps from 18th and 19th century lead mining and large areas have been removed in recent years to extract the lead and to improve shooting estates.
But the Authority says it raises conservation and environmental issues.
"Uncontrolled removal is severely damaging the historic integrity of largely unrecorded lead mining landscapes," said senior historic environment officer Robert White.
"The various types, colours and sizes of waste material are the physical evidence that allows archaeologists and other scientists to interpret and analyse the minerals, periods of activity and dressing processes involved after the underground rock was brought to the surface. Many spoil heaps contain tools and other artefacts, while others cover the evidence of earlier phases of mining activity. Often it is only the appearance and content of the spoil mounds that allows the story of the underground mining - now often physically inaccessible - to be understood."
He pointed out that many of the heaps are close to water courses and extraction can contaminate them with heavy metals.
He said land owners are being warned to notify the Authority before disturbing spoil heaps.
Large areas are designated SSSIs and some are potential regionally important geological or geomorphological sites.
The lead spoil heaps also support unique plant communities like Calaminarian grassland, rated a habitat of principal importance by the UK Biodiversity Partnership.
