Here's why:
* Migration: When people move, they take their language with them. If they settle in a new area where their language is not spoken, they can spread it to others, potentially leading to its growth. Conversely, if they are absorbed into a larger population speaking a different language, their native language can shrink and eventually become extinct.
* Contact: When speakers of different languages come into contact, it can lead to:
* Language shift: People may switch to the more dominant language, especially if they need it for economic or social reasons. This can contribute to the decline of less dominant languages.
* Language convergence: Languages can borrow features from each other, eventually merging into a single language. This can lead to the growth of a new language and the decline of the original ones.
* Language death: If one language has significantly more power or prestige, it can displace others, causing them to die out.
Other geographic factors also contribute to language dynamics:
* Isolation: Isolated communities often maintain their unique languages for longer, as they have less contact with other languages.
* Political boundaries: National borders can influence language spread and maintenance, especially if official policies favor one language over others.
* Natural disasters: Events like earthquakes or floods can disrupt communities and lead to language shift if survivors are forced to relocate.
It's important to note: While geographic factors play a significant role, language dynamics are complex and influenced by a variety of social, economic, and cultural factors as well.