quality:correction, structural:summarization
The Northern Isles are a chain of islands off the north coast of mainland Scotland. The climate is cool and temperate and highly influenced by the surrounding seas. There are two main island groups: Shetland and Orkney. There are a total of 36 inhabited islands, with the fertile agricultural islands of Orkney contrasting with the more rugged Shetland islands to the north, where the economy is more dependent on fishing and the oil wealth of the surrounding seas. Both archipelagos have a developing renewable energy industry. They share a common Pictish and Norse history, and were part of the Kingdom of Norway before being absorbed into the Kingdom of Scotland in the 15th century. The islands played a significant naval role during the world wars of the 20th century. Tourism is important to both archipelagos, with their distinctive prehistoric ruins playing a key part in their attraction, and there are regular ferry and air connections with mainland Scotland. The Scandinavian influence remains strong, especially in local folklore and both island chains have strong, though distinct local cultures. The names of the islands are dominated by the Norse heritage, although some may retain pre-Celtic elements.