One of Utah's first and longest-serving female leaders in state government, retired Department of Environmental Quality Director Dianne Nielson, has died.

She died Nov. 7 at age 71 of natural causes.

Nielson may have been soft-spoken, but colleagues remembered her as a firm, effective leader who was taken seriously by the industries she regulated, first as director of the Division of Oil, Gas and Mining (DOGM), then as DEQ director from 1994 to 2007 under three governors.

“Dianne Nielson literally left the earth a better place,” said former Gov. Mike Leavitt, who first appointed Nielson to DEQ, an agency created in 1991, to protect and improve the quality of Utah’s air, land and water. He said he was grateful for having shared “the great adventure of public service” with her.

“She will be a historically significant person in the history of Utah’s quest to guard environmental quality. Her competency, even-temperedness and good judgment were delivered in the kindest of ways,” said Leavitt, who also served as administrator of the U.S. Environmental Protection Agency. “She affected and inspired sound environmental policies throughout the American West, mentoring young leaders in other states who admired her. They constantly turned to Dianne for leadership on regional issues.”

DEQ spokeswoman Donna Spangler also considered Nielson a mentor who will be deeply missed.

“She was incredible,” said Spangler, a one-time newspaper reporter Nielson hired 15 years ago. “One time I came into her office and she was working without the lights on. It was to conserve energy. She was someone who practiced what she preached.”

Nielson played a central role in Utah’s efforts in the early 2000s to block spent nuclear fuel from being stored on tribal lands of the Skull Valley Band of Goshute.

Her tenure spanned much of DEQ’s existence as an agency, beginning in 1994, when Leavitt asked her to move from the Department of Natural Resources, where she had been running DOGM since 1983. A native of Elgin, Ill., Nielson held a doctorate in geology from Dartmouth College and started her career doing mineral exploration for private industry.

She joined Utah government as an economic geologist with the Utah Geological Survey. In 2007, she left DEQ to serve as Gov. Jon Huntsman Jr.'s energy adviser. She retired from public service in 2011.

After retirement, Nielson spent lots of time with her grandchildren and advised Utah Clean Energy, promoting dialogue on climate change through an initiative called Path to Positive Utah, according to the nonprofit advocacy group’s executive director, Sarah Wright.

“This is a loss. She was force for good in the world,” Wright said. “She has stayed engaged even after she retired and supported smart policies for the state.”

On a personal level, Wright saw Nielson as a bridge builder in a state split by divisions over energy policy.

“She inspired me to think bigger and bolder and also to expect more from others,” Wright said. “She was able to work with a wide diversity of interests to find common ground and solutions that you might not have been able to see when you started working on the problems.”

Arrangements for a memorial service are pending.