An excellent article on the subject of “language loss” (although as it will explain, that’s not a great term for it) is Towards a New Language of the Global Language Crisis . It’s not really right to talk about endangered languages “being lost” or “in decline”. Languages don’t just lose themselves; their speakers face oppression for using those languages and this incentivises a shift to using majority languages. We have to be honest about this if we want to stand a chance at halting language loss.
Two major driving factors in language loss around the world have been colonisation and nationalism. (In many cases, these are difficult to disentangle from each other.)
The impact of colonisation can be seen in countries like Australia, Canada, the US and Mexico (and many others!) – colonial authorities sought to replace the local languages with the colonial one (e.g. English or Spanish) to the point that indigenous languages are now really marginal in all of the above, only able to be used in restricted settings. This is on top of the actual genocides that have taken place in many colonial states, dramatically reducing indigenous populations and severely disrupting their communities. In Australia and Canada, for example, the forced removal of indigenous children from their families and sending them to boarding schools, where they were required to speak English, severely curtailed the normal intergenerational transmission of language that would otherwise probably have taken place.
Nationalism has been another huge factor, including in countries that don’t have histories of settler-colonialism. Starting from about the 18th century, “states” (governments controlling defined territories) in the modern sense of the word began to arise, but in order to convince entire populations to accept their legitimacy they had to devise some kind of explanation, and in many cases that explanation was nationalism – that they were a nation-state. What this also meant is that they wanted to play down any kind of ethnic or linguistic differences that existed within the country, and convince everybody that they were “just French” or “just Spanish” or whatever. Obviously, this process did not take place overnight, but over many decades, even over a century. It’s also not like these governments have actually succeeded in convincing every single citizen that they are “just French/Spanish/etc.”. However, the linguistic impact – that effectively every single citizen is fluent in the “national language”, while minority languages and dialects have been lost or become extremely endangered – is evident.
It’s not like this process of nationalism causing language loss is restricted to Europe, either. In both China1 and Taiwan,2 regional languages have declined in prestige and use as citizens have been heavily encouraged to switch to Mandarin. In Israel (which is a settler-colonial state anyway, but) diaspora Jewish languages with long and illustrious histories like Yiddish and Ladino have declined precipitously as the state for a long time enforced a Hebrew-only policy. Many Arabic-speaking countries have minority language communities which have been marginalised in favour of Arabic, many former Soviet states have complicated dynamics with a dominant “national” language and significant linguistic minorities, and honestly similar kinds of situations exist in many, many countries with a clear “dominant” language. These kinds of situations don’t necessarily lead to language loss, but slow and incremental attrition does come to pose a danger to minority languages over time.
The term language revival refers to efforts to halt or reverse this process, or even resurrect a language that has already “died” (as in, it is no longer spoken as anyone’s first language).