Peter Ehrlich loved trees and birds and had just returned from two weeks in Costa Rica, one of his favorite places to relax and take in exotic flora and fauna.

For Ehrlich, it was more than a hobby. He also was head forester at the Presidio of San Francisco and was the former urban forester for the city’s parks department.

But on Monday afternoon, the Petaluma resident was riding his mountain bike when he crashed and suffered head injuries that proved fatal. The 69-year-old died the next morning in the hospital.

Petaluma Police said he was apparently going too fast down a B Street hill and lost control at the intersection with El Rose Drive.

“He’s done that route for years,” said his former wife, Marlene Slutsky of Petaluma. “We’re not sure what happened,”

Born in the Bronx, Ehrlich attended Hobart College in upstate New York. He studied English literature before graduating with a degree in forestry from UC Berkeley.

By the early 1980s, he was working for San Francisco city parks, according to his family, and by the early 2000s was working at the Presidio.

The former Army military post had 100,000 trees planted in the late 1800s to serve as a windbreak and add some natural beauty, but more than a century later, many were slowly dying.

Ehrlich’s task was to preserve the 300-acre forest, cut down aging trees and plant new saplings.

He also had to take into account some of the native endangered plants and animals.

Presidio officials said Ehrlich had the right mix of expertise and enthusiasm, as well as negotiating skills to deal with activists lobbying to protect the animals and plants.

He also was a former board member at Audubon Canyon Ranch, a conservation group with wildlife preserves in Marin and Sonoma counties.

“He was a lover of the natural world,” his daughter, Lily Ehrlich of Oakland, said. “Whenever he traveled he was usually looking for a type of tree, plant or bird or all of the above.”

In a 2004 interview with the San Francisco Chronicle, he told the newspaper, “I’m obsessed with trees. I grow trees in my backyard. I give trees away.”

On Wednesday, local tree nursery owners were stunned to hear of Ehrlich’s death but fondly recalled his visits and love of trees.

He was known as “Dendro Pete” a reference to dendrology, the study of wooded plants.

“He is crazy for manzanitas, passionate about native plants and trees,” said Sherrie Alphouse, co-owner of California Flora Nursery in Fulton. She said he would shop at the nursery to buy trees and conifers for the Presidio.

“He was a wealth of information and really generous with his time and sharing cuttings and plants,” said nursery co-owner Philip Van Soelen. “He would come by the nursery and be a delight.”

In addition to his daughter he is survived by two sisters, Toni Ehrlich-Feldman of El Cerrito, and Iris Greenberg of Ithaca, New York.

No services have been scheduled.

You can reach Staff Writer Clark Mason at 707-521-5214 or clark.mason@pressdemocrat.com. On Twitter@clarkmas.

Crisis care: The new mental institutions

Sonoma County has a chronic shortage of psychiatric hospital beds. As as a result, a growing number of mentally ill residents are ending up in local emergency rooms and in the jail system. A four-part series, run on four consecutive Sundays, examines the causes and ramifications of the current state of the county’s mental health system, and the people who are impacted the most.

Aug. 6 — Hospitals: The closure of two psychiatric hospitals in Sonoma County has left a gaping hole.

Today — Jail: The Sonoma County Jail has become the largest psychiatric treatment facility in the county.

Aug. 20 — Solutions: Sonoma County explores ways to improve services to people suffering from severe mental illness.

Aug. 27 — Your response: Readers share their stories about Sonoma County's mental health system.

Ongoing coverage: www.pressdemocrat.com/crisiscare

Share your story

We want to hear about your experience with local psychiatric emergency services. What do you do when you or a loved one faces a mental health crisis? Have you or a loved one sat in a hospital bed waiting to be transferred to an out-of-county psychiatric hospital or other mental health facility? Have you or a loved one received psychiatric services in the Sonoma County Jail’s mental health unit? Please send a brief account of your experience to Martin Espinoza at martin.espinoza@pressdemocrat.com.