Languages around the world are dying, and dying fast. Today is International Mother Language Day, started by UNESCO to promote the world's linguistic diversity.

The grimmest predictions have 90 percent of the world's languages dying out by the end of this century. Although this might not seem important in the day-to-day life of an English speaker with no personal ties to the culture in which they’re spoken, language loss matters. Here’s what we all lose:

1. We lose “The expression of a unique vision of what it means to be human”

That’s what academic David Crystal told Paroma Basu for National Geographic in 2009. Basu was writing about India, a country with hundreds of languages, at least seven major language families and rapid language loss.

The effects of that language loss could be “culturally devastating,” Basu wrote. “Each language is a key that can unlock local knowledge about medicinal secrets, ecological wisdom, weather and climate patterns, spiritual attitudes and artistic and mythological histories.”

Languages have naturally risen and fallen in prominence throughout history, she wrote. What makes this different in India as well as throughout the world is the rate at which it’s happening and the number of languages disappearing.

2. We lose memory of the planet’s many histories and cultures.

The official language of Greenland, wrote Kate Yoder for Grist, is fascinating and unique. It’s “made up of extremely long words that can be customized to any occasion,” she writes. And there are as many of those words as there are sentences in English, one linguist who specializes in Greenlandic told her. Some of those, like words for different kinds of wind, are disappearing before linguists get the chance to explore them. And that disappearance has broader implications for the understanding of how humans process language, linguist Lenore Grenoble told Yoder. “There’s a lot we don’t know about how it works, or how the mind works when it does this,” she said.

Yoder’s article dealt with the effect of climate change on language loss. In sum: it hastens language loss as people migrate to more central, “safe” ground when their own land is threatened by intense storms, sea level rise, drought and other things caused by climate change. “When people settle in a new place, they begin a new life, complete with new surroundings, new traditions, and, yes, a new language,” she wrote.

3. We lose some of the best local resources for combatting environmental threats

As Nancy Rivenburgh wrote for the International Association of Conference Interpreters, what’s happening with today’s language loss is actually quite different from anything that happened before. Languages in the past disappeared and were born anew, she writes, but “they did so in a state of what linguists call ‘linguistic equilibrium.’ In the last 500 years, however, the equilibrium that characterized much of human history is now gone. And the world’s dominant languages—or what are often called ‘metropolitan’ languages—are all now rapidly expanding at the expense of ‘peripheral’ indigenous languages. Those peripheral languages are not being replaced.”

That means that out of the around 7000 languages that most reputable sources estimate are spoken globally, only the top 100 are widely spoken. And it isn’t just our understanding of the human mind that’s impaired, she writes. In many places, indigenous languages and their speakers are rich sources of information about the world around them and the plants and animals in the area where they live. In a time of mass extinction, that knowledge is especially precious.

“Medical science loses potential cures,” she writes. “Resource planners and national governments lose accumulated wisdom regarding the management of marine and land resources in fragile ecosystems.”

4. Some people lose their mother tongue.

The real tragedy of all this might just be all of the people who find themselves unable to speak their first language, the language they learned how to describe the world in. Some find themselves in the unenviable position of being one of the few (or the only) speakers of their mother tongue. And some, like many of Canada’s indigenous peoples, find their language in grave danger as the result of a campaign by government to stamp out their cultures.

This loss is something beyond all the other losses, linguist John Lipski told Lisa Duchene for Penn State News: “Imagine being told you can’t use your language and you’ll see what that undefinable ‘more’ is,” he said.

What can you do about all this? Educate yourself, to start with. The Smithsonian's annual Mother Tongue Film Festival takes place every February in Washington, D.C. And projects like National Geographic's "Enduring Voices" are a great place to learn about endangered languages and their many speakers, and UNESCO's own website is another resource. There's still hope for some of these languages if we pay attention.