Wars, earthquakes, tsunamis and such kinds of natural catastrophes can shift the balance between languages. According to Barbara F. Grimes, the Paulohi language speakers in Maluku, Indonesia, experienced a severe earthquake and tsunami several years ago which killed all but about 50 of them.
Related to this point we can also say that migrations to a place other than the traditional territory can be a reason why the speakers of a language are forced to acquire another language and then, substitute the former one for the new one. The Naka'ela in Maluku, Indonesia, reportedly decreased in number after moving down from the mountains to a coastal town on Seram Island. 3 Colonization and the introduction of a new language into the territory of a existent cultural group can also put at risk the traditional language, as with the Hawaiian people, who now form only about 20% of the total population in their traditional territory.4 The most widely known example is that of North America, where the colonizers forced the native population to speak the language that they were bringing with them and created institutions that cut them off from all the connections that they could have with their ethnic language and culture.
Furthermore, even if it can't be considered to be one of the main reasons for this discrimination, we can observe that parents have preferences when they have to choose the language their children are going to learn at school. Sometimes they decide to use a different language from their mother tongue because it is more prestigious and it can be better accepted in industry, business and education.
People should prefer to use their mother tongue to communicate with the people they are closest to and because they feel more comfortable using it. Otherwise, the changing world, urbanization, industrialization and the dynamism of the population make it possible that language shifts will appear and put at risk entire ethnic groups.