Author Mark Abley, who has written about the dynamism of the English language, agrees.
"I don't believe there's a straightforward balancing act in which urban dialects grow as rural ones shrink," he said in an email. "Cities are always melting pots, and isolation for any group is very hard to maintain."
As the worlds' melting pots grow ever bigger — half the Earth's population now lives in cities — lesser-known dialects are evaporating. Worldwide, languages are disappearing regularly, with half of the globe's 6,000-plus languages expected to be extinct by the end of the century, according to UNESCO.
The British Isles saw two languages go extinct within living memory, UNESCO says. The last native speaker of Alderney French, a Norman dialect spoken in the Channel Islands, died around 1960, and the last speaker of traditional Manx, the language once spoken on the Isle of Man, died in 1974.
Donna Heddle, the director of the Center for Nordic Studies at Scotland's University of the Highlands and Islands, said the loss of each language or regional dialect leaves the world poorer than it was before.
"It's one less little sparkle in the firmament," she said. "One little star might go out and you might never notice it, but it's not there anymore."
The Cromarty Fisherfolk Dialect: http://www.ambaile.org.uk/en/download/files/The%20Cromarty%20Fisherfolk%20Dialect.pdf (PDF)
UNESCO Atlas of the World's Languages in Danger: http://www.unesco.org/culture/languages-atlas/index.php