Phyllis Faber, an environmentalist who played a key role in protecting West Marin’s pastoral landscape from development, died at her home in Mill Valley on Jan. 15. She was 95.

Ms. Faber co-founded the Marin Agricultural Land Trust in 1980 with the late Ellen Straus, a West Marin dairy rancher and environmentalist from Marshall. Together, they worked to forge bonds between environmentalists and ranchers who often found themselves at odds about how to protect the county’s traditions, landscape and ecology. The land trust developed an innovative approach to maintaining farmland at a time when West Marin seemed at risk of being consumed by suburban sprawl.

“Phyllis understood that there was a more effective way to achieve environmental goals than confrontation,” said Ralph Grossi, the president of MALT’s first board of directors. “She understood that working with people and understanding their needs would get to a better conclusion.”

In addition to her work with MALT, Ms. Faber campaigned for the passage of legislation that led to the California Coastal Act and later served on one of the first regional boards it established. A botanist, she edited Fremontia, the journal of the California Native Plant Society, from 1984 to 1999. More recently, she was co-editor of the natural history series for the University of California Press.

Ms. Faber was a founding instructor at the Environmental Forum of Marin, which led classes and tours around the county, one of which took students to Ellen Straus’s ranch. 

“It was that partnership that led to MALT and became such a strong force for the conservation of farmland in Marin,” said Bob Berner, who served as MALT’s executive director from 1984 until 2012.

Ms. Faber was born in Pittsburgh. She earned her bachelor’s degree in zoology from Mount Holyoke College and her master’s in microbiology from Yale University. Before moving west, she began her career teaching at a private Connecticut high school.

“Phyllis told me once that having young children at home had prevented her from taking a lab job doing what she’d been trained to do, which was unraveling the structure of DNA,” said David Kupfer, a friend of Ms. Faber and a former executive director of the Environmental Action Committee of West Marin.

The teacher she replaced in Connecticut spoke with her about the loss of wetlands and the need to protect them, Mr. Kupfer said. She also encouraged Ms. Faber to think about the connection between science and politics.

After moving to Mill Valley with her husband and three children in 1970, Ms. Faber quickly became engaged in Marin County’s environmental movement, focusing her attention on wetlands. She taught with a group of biologists at Audubon Canyon Ranch on the Bolinas Lagoon.

She also dedicated her time and passion to the campaign for the California Coastal Zone Conservation Act, and, after it was approved in 1972, she was appointed to a regional coastal commission.

“She was curious, she was passionate, she was funny, and she did not let obstacles get in her way,” said Nona Dennis, an environmentalist and neighbor of Ms. Faber. “Sometimes that meant disagreeing with people.”

In a conflict that stirred passions across West Marin, Ms. Faber stood up for Drake’s Bay Oyster Company when it sought to renew its lease with the National Park Service. Some environmentalists argued that the operation posed an environmental threat, especially to seals, and they wanted the area restored as “true wilderness.”

Ms. Faber defended Drake’s Bay Oyster Company, arguing that the decades-old operation was part of the region’s agricultural heritage and brought environmental benefits because the oysters filtered water. The park service terminated the lease and the farm was closed in 2014.

“Why deprive the Bay Area of this popular and sustainable source of protein?”  Ms. Faber asked in a 2010 letter published in the Light.

Her stand in the oyster debate alienated some of her environmentalist colleagues and illustrated Ms. Faber’s fierce independence, said Kevin Lunny, a rancher and businessman whose family ran the oyster company.

“She recognized that agricultural food production and resource conservation are not mutually exclusive,” Mr. Lunny said. “The one word I would use for Phyllis is fearless. She would walk into a room knowing the opposition was there and she would be undaunted. She was willing to talk, willing to take criticism and help people understand.”

Mr. Lunny lauded Ms. Faber for her work establishing MALT. “We didn’t want the kind of development that was being planned for West Marin, which would have made it a bedroom community of San Francisco,” he said. “Our land would have had a golf course and condos on it.”

Shortly before MALT was formed, the county implemented A-60 zoning, which prohibited the construction of more than one house per 60 acres of farmland. But farmers, environmentalists and county officials feared that measure alone would not be enough to stop Marin from being overtaken by development.

Ms. Faber and Ms. Straus devised the idea of using property easements to protect agricultural lands from being carved up for housing. Instead of selling their property to developers, farmers could sell an easement to MALT, allowing them to continue ownership of their land if they agreed to maintain their farms and ranches as agricultural land in perpetuity. They would also be required to follow environmentally sound land-management practices.

At first, some farmers were skeptical of the idea. But Ms. Faber and Ms. Straus worked hard to persuade them that the entire community would benefit from a collaboration among environmentalists, farmers and government, said Albert Straus, Ellen Straus’s son.

“Phyllis was instrumental in working to achieve that vision,” he said. “She was a force to be reckoned with.”

Winning ranchers over to the land trust concept required intensive educational outreach, Mr. Grossi said. And Ms. Faber had the right temperament for the task. “She was a woman of great energy—energy, persistence and knowledge.”

MALT now protects more than 55,000 acres in Marin and supports efforts to protect water quality and improve soil health and grasslands. Its model has since been adopted thousands of times across the country.

“More than 50 percent of Marin’s agricultural land has been protected by conservation easements that extinguish development rights,” Mr. Kupfer said. “In 1980, it was a brand-new concept. No one had ever done anything like it.”

On MALT’S 25th anniversary, Ms. Faber published a column suggesting that voters approve funding for the continued purchase of easements, which were becoming more costly as land values increased.

“Everyone benefits from the extensive amount of farmland that the owner takes care of, as well as providing healthy crops for us to eat,” she wrote. “So, wouldn’t it be fair for everyone to contribute a small amount to protect that land?”