Here is an excerpt from an article in the NY Times. It is on rare and endangered languages.
"...
The Endangered Language Alliance will apply field techniques usually employed in exotic and remote foreign locales as it starts its research in the city’s vibrant ethnic enclaves.
“Nobody had gone from area to area looking for endangered languages in New York City spoken by immigrant populations,” Professor Kaufman said.
The United Nations keeps an atlas of languages facing extinction, and experts there as well as linguists generally agree that a language will probably disappear in a generation or two when the population of native speakers is both too small and in decline. Language attrition has also been hastened by war, ethnic cleansing and compulsory schooling in a national tongue.
..."
(
http://www.nytimes.com/2010/04/29/nyregion/29lost.html?src=me&ref=general)