The World contains about 6,000 forms of speech, though so many are endangered that only 300 languages may be spoken in a hundred years or so. This is because the gradual move to fewer and fewer common languages continue at the expense of other languages, and dialects around the world. This is an overwhelming and unacceptable loss of humanity's heritage, in terms of culture and the invaluable knowledge and insights these languages and dialects carry. Whilst it is unavoidable that more and more people will learn common world languages, all effort should be made to ensure that this process does not occur at any significant expense of lesser used and endangered languages.
It has been calculated that half the world's languages are no longer being learnt by the children of native speakers. California (USA) is home to 50 Native American languages, yet most are only spoken by people more than 70 years old. In 1995, the world's last speaker of Northern Pomo Indian died in the same State. In learning a common language, minority language speakers should consider (and be helped to maintain) the common language as their second language, their own language as their first.
Language vitality and economic viability are two sides of the same coin; cultural and linguistic diversity can be an important source of innovation and dynamism.