A recent study noted that most of the 6,900 languages spoken on Earth occur in regions of high biodiversity. These findings point to a strong correlation between biological and linguistic diversity, with languages closely connected to the habitats where they are found.

Like many people, I’ve spent a lot of time thinking about — and mourning — the cascading extinction of species caused by human activity. But only recently has it occurred to me to frame it this way: Humans have lived past the peak of biological diversity on this planet. There may well be other, higher peaks of biodiversity after we’re gone, but the best I can imagine as long as we’re around is a slight decline in the calamitous rate of extinction.

As it happens, we’ve also lived past the peak of linguistic diversity — the number of different human languages spoken on this planet. The loss would be more evident if each of this planet’s nearly 7,000 human languages was spoken by a separate species — one species per language. But losing language is as human as using language. After all, we live in a country where, for the past two and a half centuries, people have come to abandon their ancestral tongues in the second generation after arrival — a country where most of the aboriginal languages had long since been destroyed.

According to a recent study, there is a close correlation between biological diversity and linguistic diversity. A biological hotspot is likely to be a linguistic hotspot. Put simply, there are more human languages where there are more species. “Of the 6,900 languages currently spoken on Earth,” the authors write in the Proceedings of the National Academy of Sciences, “more than 4,800 occur in regions containing high biodiversity.” The corollary? Most of those languages are threatened. Nearly 60 percent of the languages in high biodiversity regions, like Amazonia and the lowland forests of West Africa, are spoken by fewer than 10,000 people; more than 1,200 of those languages are spoken by fewer than 1,000 people. Every language is a species, but most languages are also habitats, linked closely to the physical habitats in which they occur.

Human languages evolve far more quickly than the single species — Homo sapiens — that speaks them. And languages speciate for some of the same reasons that organisms do — topographic separation, for instance. A good example is New Guinea, which is as rich in linguistic species (972 endemic languages) as it is in biological species. Topographically speaking, New Guinea is famously difficult, a torturous landscape that isolates humans as well as other species.

It’s tempting to assume that the correlation between biological and linguistic diversity is functionally negative. In other words, high linguistic diversity occurs where the conditions of biological diversity — dense forests, harsh terrain, and other barriers, like disease — force small human societies to remain separate. But there’s another way to think of it. What if the correlation is functionally positive? Instead of merely forcing linguistic diversity, high biological diversity also affords linguistic diversity. The richness of one sustains the richness of the other.

There’s something curious and unsettling in all of this. It seems odd to think that such a pure and somehow abstract extension of humanness as language itself (apart from mere vocabulary) is so niched, so profusely and divergently rooted in the natural world. A universally shared language seems like a universal good. But most languages spoken by small numbers of humans in regions of high biodiversity do not and will not survive extended contact with widely-spoken languages like English, Spanish, Portuguese, and French. No matter how desirable it may seem, a universal language is a bulldozer with measles.

I think we inevitably underestimate the bond between biological complexity and cultural complexity. Let me turn to a landscape I know far better than the jungles and mountain ridges of New Guinea: northwestern Iowa.

Within my lifetime, the cultural and biological complexity of rural Iowa has declined precipitously. What underlies both kinds of loss is the decline in the number of farms. Modern farming is a way of spreading vacancy. The farms grow bigger and bigger — declining in number — and fewer and fewer people live on them. This has been accompanied, in Iowa, by a decline in the biological diversity of the farm itself. In most of the state, there are now only soybeans, corn, chickens and hogs, a huge change from even 50 years ago.

This much is easy to see. But so is the loss of cultural complexity. The way to measure that is to ask as many good questions about the components of social and cultural texture as you can. What kinds of questions would you ask to get at the diversity, the complexity of a small town? Some are fairly obvious. How many independent banks are there? How many independent grain elevators? How many independent slaughterhouses? Creameries? Grocery stores? How many farm implement and auto dealerships? How many butchers and livestock breeders? How many farmers sold milk and eggs in town? How many entries were there in the county fairs?

But these are really technical and economic questions. So let’s consider some others. What percentage of the children learned how to play a musical instrument? How many amateur theatrical societies and singing clubs — even small-town opera houses — were there? How many softball teams? What about sewing circles and baling rings and card clubs?

All these questions point in one direction. With the decrease in biological complexity — the regression to corn and soybeans — came a decrease in social and cultural complexity. The farmscape emptied and the towns became ghosts of themselves. You might argue that the one didn’t directly and necessarily cause the other: in other words, if most of the 203,000 farms that existed in Iowa when I was born (1952) suddenly switched to growing only corn and soybeans, that wouldn’t necessarily have reduced the population and complexity of the countryside. But the fact is that Iowa did switch to corn and soybeans and when it was done, fewer than 90,000 farms remained. Not many people live on 90,000 farms.

It may seem far-fetched to compare social and agricultural change in Iowa with linguistic and biological correlation in some of Earth’s biodiversity hotspots. But the underlying premise is the same. Biological diversity and cultural diversity go hand in hand.

This is a hard idea to absorb for the simple reason that humans, in our pride, have always assumed that cultural diversity (and complexity) is the result of who we are, not what nature has made of us and we have made of nature. We still believe fiercely, against all the evidence, that we are independent of most other species. And we still believe fiercely that the habitat that matters most is the one we create. We could not be more mistaken.