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The reserve has an area of 646.5 ha and protects a sand dune system which supports a large number of Natterjack Toad s. North Walney was formerly a separate Site of Special Scientific Interest , but it has been amalgamated with other SSSIs in the Duddon Estuary .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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