The world's native languages are dying out at an unprecedented  rate, taking with them irreplaceable  knowledge about the natural world, according to a new study. The study identified five global "hot spots" where languages are _ faster than anywhere else ---- eastern Siberia, northern Australia, central South America, the US state of Oklahoma and the US Pacific Northwest. "Languages are suffering a global extinction crisis that greatly goes beyond the pace of species extinction," linguistics  professor David Harrison noted, who said half of the world's 7,000 languages were expected to disappear before the end of the century. Native people had an intimate  knowledge of their environment that was lost when their language disappeared, along with other certain things often unfamiliar to us, Harrison stressed. "Most of what we know about species and ecosystems is not written down anywhere, it's only in people's heads," he said. "We are seeing in front of our eyes the loss of the human knowledge base." Harrison was one of a team of linguists who carried out the study. The researchers traveled to Australia this year to study native languages, some of the most endangered. According to Harrison, in Australia, they were heartened to see a woman in her 80s who was one of the only three remaining speakers of the Yawuru language passing on her knowledge to schoolchildren. He said such inter-generational exchanges were the only way native languages could survive. "The children had elected to take this course, no one forced them," he said. "When we asked them why they were learning it, they said,'This is a dying language, we need to learn it'." Also, while there they found a man with knowledge of the  Amurdag  language, which had previously been thought extinct. The researchers said all five of the hot spots identified were areas that had been successfully colonized and where a dominant language such as Spanish or English was threatening native tongues. According to Harrison, language extinction  _  .
causes the researchers lots of worries speeds up the pace of species extinction threatens the existing of Spanish and English brings about a loss of knowledge about the environment