Tatsuya Amano, Brody Sandel, Heidi Eager, et al. have a paper in Proc. R. Soc. B 22 of obvious LH interest; the abstract begins:
Many of the world’s languages face serious risk of extinction. Efforts to prevent this cultural loss are severely constrained by a poor understanding of the geographical patterns and drivers of extinction risk. We quantify the global distribution of language extinction risk—represented by small range and speaker population sizes and rapid declines in the number of speakers—and identify the underlying environmental and socioeconomic drivers.
The whole paper is online (way to go, Royal Society!); there’s also a summary at ScienceDaily that boils it down conveniently: “Thriving economies are the biggest factor in the disappearance of minority languages and conservation should focus on the most developed countries where languages are vanishing the fastest.” Thanks for the links, Paul and Martin!