The Highland Clearances was the forced displacement during the 18th and 19th centuries of a significant number of people from traditional land tenancies in the Scottish Highlands, where they had practised small-scale agriculture. It resulted from enclosures of common lands and a change from farming to sheep raising, an agricultural revolution largely carried out by hereditary aristocratic landowners. The Clearances were a complex series of events occurring over more than a hundred years. A Highland Clearance has been defined as "an enforced simultaneous eviction of all families living in a given area such as an entire glen".
The Clearances are particularly notorious as a result of the brutality of many evictions at short notice (year-by-year tenants had almost no protection under Scots law), and the abruptness of the change from the traditional clan system, in which reciprocal obligations between the population and their leaders were well recognised. The cumulative effect of the Clearances, and the large-scale "voluntary" emigrations over the same period, devastated the cultural landscape of Scotland in a way that did not happen in other areas of Britain; the effect of the Clearances was to destroy much of the Gaelic culture.
The Clearances resulted in significant emigration of Highlanders to the coast, the Scottish Lowlands, and further afield to North America and Australasia. In the early 21st century, many times more descendants of Highlanders are found in these diaspora destinations than in Scotland https://en.wikipedia.org/wiki/Highland_Clearances