Language death happens when the last speaker of the language dies. Its process is usually gradual, and most commonly occurs when the native speakers of a language start using a second language (usually imposed by the majority or voluntarily done due to political or economic reasons) until they stop using their first language.
As a country with very diverse ethnicities, Indonesia has more than 700 local languages. With people speaking different languages that mostly are not mutually intelligible, Indonesia chose Malay language, dubbed as Bahasa Indonesia (Indonesian language), as the language of unity. The choice was made not because Malay language was spoken by the majority, nor was it the language of the forefathers; in fact, Javanese was and is the largest ethnic group in Indonesian and most of the forefathers are Javanese. Malay was chosen because it was the lingua franca of the whole archipelago and considered to be practical. It was and still is more practical than Javanese. Now, more and more people speak Indonesian as its first language.
As a national language, Indonesian is used in everyday life, in government offices, in education, and interacting with people, especially from other ethnic groups. Places with economic or educational significance are usually where people from different ethnicities gather. In these places, Indonesian serves as a uniting element.
With Indonesian used widely, the existence of other languages are threatened, to some extent. In 2009, 16 languages died in the course of two years (from 742 languages in 2007 to 726). Because people think that learning and getting used to Bahasa Indonesia will contribute to a better life, better accessibility, they stop using their local languages; they assimilate. Furthermore, some people avoid using their local languages, because they’re afraid that other people might disparage them. This shift in using Indonesian has taken its toll on the largest local language in Indonesian, i.e. Javanese. Many young Javanese people now forget specific vocabulary, e.g. those related to animals’ offspring, flowers, specific actions, certain sounds (onomatopoeia), etc.
Let’s think of a hypothetical condition where Indonesian is not used; it doesn’t exist. It does make sense, since Indonesian language doesn’t really have a long history compared to some other local languages. A local language with the largest groups of speakers would be Javanese. Due to its historical significance, its enormous number of speakers, the distribution of the Javanese people all over Indonesia (not to mention those who live in Suriname), the importance of Java Island in education, economy, and politics, Javanese language will most likely take over the role of Indonesian language as the language of power and unity.
Besides Indonesian language as its national language and Javanese as the language with most speakers in Indonesia, Indonesia also has at least twenty local languages that are spoken by more than one million people. Even without the existence of Indonesian language, these languages can serve as lingua franca on smaller levels, which then contribute to language abandonment of other minority languages.