Marin County is quietly playing host to the state’s fastest growing aging adult population, and nonprofit organizations like West Marin Senior Services are calling for more volunteers to help fill the gaps in elder care. 

According to the 2010 census, 27 percent of Marin’s population is over the age of 60, and several studies estimate this number will rise to over 33 percent by 2030. West Marin Senior Services faces the challenge of caring for…