Marsha Lynne Karle was born in Fresno, California on July 25, 1954, the daughter of Albert Karle (1924-1973) and Dorothy Rosenthal Karle (1928-2013). She attended schools in Sanger, CA, graduating from Sanger High School in 1972. She attended the 2-year community college in Reedley, CA, graduating in 1974 with an Associate Degree in Business Administration. She grew up working on her family's ranch where she developed a deep affection for the agricultural landscapes of the Central Valley and the spectacular wilderness settings of the nearby High Sierra. In 1981, she began a career with the National Park Service in Denali National Park, Alaska, where she served as the superintendent's secretary until 1983. Her first posting to Yellowstone National Park began that year when she became the secretary of Superintendent Robert Barbee and stayed until 1985. Superintendent Barbee became her NPS mentor, encouraging her to pursue a public affairs career, starting in 1987 in the National Park Service's Regional Office in Denver. In 1989 Karle returned to Yellowstone as assistant chief of public affairs and became chief in 1993, a position she held for 11 years, during which she oversaw countless large public events, VIP visits, and performed many other duties integral to the operation of the world's first national park. This work involved daily contact with regional, national, and international media, as she and her staff facilitated all journalist and film-crew activities in the park, whose often-controversial management issues are constantly in the public eye. Among other work, Karle oversaw all Freedom-of-Information-Act requests from the general public and interest groups, and served a term as chair of the Information and Education Subcommittee of the Interagency Grizzly Bear Committee.

Because of Karle's stature as a public-affairs professional, during her Yellowstone tenure she also accepted extended details in other National Park Service units. She was thus public-affairs lead for five presidential events, including the 50th anniversaries of Mount Rushmore National Monument and the attack on Pearl Harbor, as well as three presidential visits to Yellowstone, all of these events involving close and extended work with the White House and the Secret Service. Karle also spent two years (1992-1993) on a National Park Service all-risk management team, a small group of top specialists from various parks who were called upon on short notice to converge on any unit with an emergency or other unusual situation. Karle's work on this team included stints in the Washington NPS Office (WASO) for the re-organization of the agency, and in Everglades National Park during the immediate aftermath and recovery from Hurricane Andrew.

During her time in Yellowstone Karle began carrying a watercolor sketchbook while hiking, skiing, and wildlife-watching. Susan Blackwood of Bozeman, Montana, became her artistic mentor and has remained so for more than 25 years. Karle has also participated in workshops with several other prominent artists, including Charles Reid at the Southern Vermont Art Center and Jean Haines in England. In the 1990s, Karle's growing artistic enthusiasm and expertise led to her serving as Yellowstone's representative at the annual international competition in Jackson Hole, Wyoming, where she oversaw several purchase prizes of art for the Yellowstone museum collection.

Since her retirement from the National Park Service in 2004, Karle has worked full time as an artist, participating in many regional and local shows and exhibits. Though her work has included hundreds of portrayals of regional wildlife and settings, Karle has also devoted much of her output to national and international subjects, the latter including the wildlife, landscapes, and cultural settings of England and Italy. Karle's paintings have been juried into prestigious national and international competitions and exhibitions, including , and she frequently donates originals to the fund-raising efforts of various good causes. In 2018, again under the mentorship of Susan Blackwood, she began oil painting in addition to continuing her watercolor work.

During Yellowstone's 1988 fires, when Karle was in the park on a temporary detail from the Denver office, she met nature writer and historian Paul Schullery, and they were married in 1996. Adding another dimension to her art, they have collaborated as artist and author on seven books, including (2006), (2007) and . The illustrations from these three books are part of the MSU Library Special Collections.