As much as these divisive times concern advocates of multiculturalism and human rights, so too do they concern linguists and educators.

With the rise of populist nationalism, the threat of walls between sovereign neighbours, religious profiling, and suspicion of regional integration, we worry what the resulting political milieu means for migrant and Indigenous languages. Language is, after all, a salient index of culture.

Evidence suggests bilingualism delays cognitive impairment later in life. ( Supplied: Julia Colleen Miller )

An assault on cultural diversity is synonymous with an assault on linguistic diversity.

The question is whether minority communities, whose language and culture differ from the mainstream but who are rightfully accepted as new migrants and citizens, should be encouraged to retain their languages.

Of course they should. For linguists, that answer is very clear: Let these languages flourish.

But our reasoning should not simply be branded as a political nod towards the left. Supporting the diversity of mother tongues in our communities is much more than politics. It has legal, economic, and cognitive implications for our children.

Tomorrow is International Mother Language Day — a worldwide annual observance launched by UNESCO in 1999. It is a good opportunity to remind ourselves that children of migrants and Indigenous people have an international right to speak, grow up with, and celebrate their own heritage languages, wherever they reside.

Languages enrich society, economic mobility

The Convention on the Rights of the Child requires that governments ensure "the development of respect for the child's parents, his or her own cultural identity, language and values, for the national values of the country in which the child is living, the country from which he or she may originate, and for civilizations different from his or her own".

This does not mean creating communities that cannot speak to each other and eroding national cohesion, as is often the concern of anti-multiculturalists. In fact, it means the opposite: building linguistically mobile, bilingual, contemporary citizens in touch with their heritage and their citizenship in equal measure.

A total of 196 states are party to the convention. Upholding international law includes upholding this promise to speakers of mother languages different to the mainstream.

What is more, languages enrich not just society but also our socioeconomic mobility.

Bilingualism creates a highly skilled workforce ready to engage the world's economic and political challenges in the very languages of those challenges. What better way to gather intelligence about North Korean threats than through Korean, or to land a Chinese contract than through Mandarin?

That's why bilinguals often earn more.

Bilingualism is good for the brain

And this all adds to the growing evidence that bilingualism is good for the brain. Bilinguals are agile, abstract, and creative thinkers, and evidence suggests that bilingualism even delays cognitive impairment later in life.

Helping communities retain their mother tongues and become mobile bilinguals therefore seems moral, lucrative, and wise.

Unfortunately, not all our leaders agree as they see multilingualism in society as threatening nationhood.

Denmark is calling for mandatory language tests for toddlers with punitive measures against families who don't speak sufficient Danish.

The United States has an ongoing tumultuous relationship with bilingual education and the linguistic rights of its children.

To access any education in their own language, Polish children in the UK often have to forgo their Saturdays, and Indian children in Oman are denied access to local education, and instead attend Indian schools that teach through English, rather than Indian mother languages.

A map showing Australian Indigenous language groups. ( Supplied: AIATSIS )

Look what they're doing in Sweden

Thankfully, not all is doom and gloom for mother tongues.

Many African nations have long recognised and harnessed the power of their linguistic diversity. Singapore sees bilingualism as social policy central to its multiculturalism, and Sweden supports the development of migrant children through education in their own mother tongue.

In Australia, legislation has finally been passed to protect and revive Aboriginal languages, similar to the mounting pressure in Canada, and Bolivia operates a policy of plurilingualism, with literacy programmes in 36 Indigenous languages.

On International Day of the Mother Tongue, we call on all our communities not to just celebrate diversity of languages, but recognise the vital contributions they can make.

Our call is beyond politics. We have a responsibility to our children, their rights, their socioeconomic opportunities, their cognitive development, and their well-being to champion their bilingualism.

Nathan Albury is a critical sociolinguist from Hong Kong Polytechnic University, Dr Susana Eisenchlas is a senior lecturer in linguistics at Griffith University, and Andrea Schalley is an associate professor at Griffith.