Multi-millionaire Philip Day, who owns the Edinburgh Woollen Mill chain of shops, had tried to use the "power of his wealth to avoid responsibility", a court heard.
He was fined £450,000 and ordered to pay prosecution costs of £475,000. His own defence legal costs are not known.
Mr Day, 47, whose firm has a turnover of £240 million, admitted two counts of damaging Gelt Woods, designated a Site of Special Scientific Interest (SSSI).
Natural England, a quango with responsibility to protect the environment, brought the prosecution after it said he caused unauthorised damaging work to be carried out on the site, which is protected due to its age because it is a pristine example of gorge woodland, of a type peculiar to northern Cumbria and parts of Scotland.
The woodland has become an important habitat for flora, fauna, insects and birds on the slopes around the banks of the River Gelt near Brampton, Cumbria, where the water has cut a rocky gorge through the New Red Sandstone.
The prosecution told the court the trees were felled to provide a track for access for shooting.
Mr Day claimed the work was being carried out to make the river bank safe after a landslip.
Presiding Judge Peter Hughes QC, who gave his judgment at Carlisle Crown Court on Wednesday, said that Mr Day had been "grossly negligent" in relation to the works done and that the conduct of his defence "seeking to use the power of his wealth to avoid responsibility" rebounded to his lasting disgrace.
Judge Hughes said that public concern for the preservation of the countryside and much greater awareness of the harm that can be done to the environment and ecology by ill-considered and uncontrolled activities has grown over recent years.
Passing sentence he said the financial penalties for harming the environment in such a way must be set at a level to remind landowners of the importance attached to areas of special importance and act as a deterrent to anyone intending to break the law.
Janette Ward, Natural England's regulation director, said: "Legal action is always regrettable, and we were disappointed that a woodland of such ecological importance, and one that was very special to the local community, was so severely damaged. We work with landowners across the country to ensure that such special areas of our natural heritage can be protected. We welcome the fact that Mr Day has undertaken a programme of voluntary restoration and hope that he will now work with us to manage this special area more appropriately in the future."
Mr Day was not available for comment.