Imma Perfetto
Cosmos science journalist
New research reveals a dire need to protect and preserve not only islands’ biodiversity, but their cultural and linguistic diversity too.
Lindell Bromham, an evolutionary biologist from the Australian National University, has been working with linguists for a decade to understand why, when you plot both language diversity and biodiversity on a map, they tend to follow the same global patterns.
“We’re not trying to say that languages are like species,” Bromham emphasised in an interview with Cosmos, “but that there’s sometimes similar patterns that may or may not reveal similar mechanisms.”
Their latest study, published in Nature Ecology & Evolution, found that islands are drivers of language diversity and change –through size, distance from the mainland, climate, and even elevation – like they are for biodiversity.
Analysis of their database of global language diversity, which contains about 90% of the world’s spoken languages, revealed that nearly a fifth of languages are spoken on islands.
“That’s actually pretty surprising, given that islands are less than 1% of the inhabited land area,” says Bromham.
“So, islands are capturing a much greater proportion of language diversity than you would expect based on their land area.”
To understand why, Bromham and colleagues set out to see whether predictions of island biodiversity also apply to language diversity.
“For ecological theory, there’s this fairly elegant mathematical framework that predicts that the number of species on an island should be this balancing act between the island size – how many populations it can support – and the distance from the mainland, which for species diversity reflects how likely it is that a species will colonise the island,” Bromham says.
Species, she adds, effectively colonise islands by chance. So, the more isolated an island is, the less likely it is to be colonised by any given species.
But their analysis found that, while bigger islands do tend to support more languages, the relationship between the distance from the mainland and language diversity is more complicated.
Unlike other species, humans don’t tend to turn up on a new island accidentally, we seek them out.
“They’ve got ocean-going boats; they’ve got navigation star maps. They set out to seek the horizon and find those islands,” says Bromham.
Languages spoken mostly on islands also often have relatively lower numbers of “phonemes” compared to their mainland counterparts.
Phonemes, Bromham explains, are the sound building blocks from which a language is made. This may include consonants or vowels and, for some languages, clicks or tones.
“English has around 44, depending on which variety of English,” she says.
“Some African languages have huge numbers, they can have more than 80 phonemes, including things like clicks. But in the Pacific, the Polynesian languages and Austronesian languages tend to have lower numbers, so more like 20.
“We can’t explain exactly what the mechanism is driving that pattern. What it’s pointing to is that there is something about being on an island, being isolated from the mainland, that influences the way languages change over time.”
Islands with more tropical climates also tend to support more languages, which aligns with their previous research that identified the growing season as one of the main predictive factors in global language diversity.
To Bromham, their finding that high elevation islands also tend to support more languages is even more interesting, because these islands also tend to support greater biodiversity.
“We can’t exactly explain it … maybe it’s reflecting soil fertility, because high islands tend to be volcanic which have higher soil fertility,” she says.
“Maybe it’s reflecting the fact that an island with a higher elevational extent tends to have more ways of living on it – you can have coastal people and inland people.”
These findings raise intriguing questions around what it is about living on islands that increases the rate at which languages change and new languages are formed.
These questions are essential to understanding linguistic diversity across the globe. Bromham warns we are in danger of losing that diversity.
“We are facing the loss of language diversity that is as catastrophic as the possible loss of biodiversity,” she says.
“More than a third of all languages are considered endangered.”
In a previous study they predicted, based on modelling of diversity and endangerment, that we could lose 1,500 languages by the end of this century. Many of these will be small island languages.
“Understanding language diversity, to me, is part of saying ‘This is what we currently have, this is part of the richness of human culture.’ But now is also the time to act to protect that diversity.”
