About Fairfield Osborn Preserve

OriginsClimateLandsCultural HistoryFacilitiesResearch Management


"Nature may be a thing of beauty and is indeed a symphony, but above and below and within its own immutable essences, its distances, its apparent quietness and changelessness, it is an active purposeful, coordinated machine. Each part is dependent upon another, all are related to the movement of the whole. Parts of the earth, once living and productive, have died at the hand of man. Others are now dying. If we cause more to die, Nature will compensate for this in her own way, inexorably, as already she has begun to do."

- Fairfield Osborn, Jr., Our Plundered Planet, 1948

Marjorie and Fairfield Osborn

Marjorie and Fairfield Osborn

Fairfield Osborn, Jr. (1887- 1969) was known for his 1948 publication, "Our Plundered Planet," a prescient and devastating critique of human stewardship of earth's natural resources that was translated in 13 languages and read by millions worldwide. Despite his grave words, Fairfield Osborn was a man with an irreverent sense of humor. He won many supporters and was a natural leader, serving as President of the New York Zoological Society and working to establish The Conservation Foundation in 1948.

In the 1950s, Fairfield Osborn's daughter and son-in-law, Joan and William Roth, purchased lands on Sonoma Mountain as a summer retreat for their family. Shortly after Fairfield Osborn's death in 1969, they donated 200 acres to The Nature Conservancy (TNC) to honor his life-long love of wild places and legacy in conservation. In accepting the donation in 1972, TNC recognized several natural resources of conservation value on Preserve lands, including the protection of Copeland creek, one of the few fishless perennial creeks in California.

In 1997, TNC donated the Preserve to Sonoma State University, maintaining a conservation easement over the property for educational, research, and conservation. In 2004, the Preserve doubled in size with an additional 190-acre donation from Joan and William Roth managed under a conservation easement with the Sonoma County Agricultural Preservation and Open Space District.


cattails in fog

Preserve climate is typical of Mediterranean regions, with cool wet winters and hot dry summers. The Preserve's proximity to the Pacific Ocean has significant influences on local weather. The thermal mass of the ocean moderates the seasonal extremes: snow is rare and summer temperatures rarely exceed 100F. In addition, Sonoma Mountain is regularly covered in summer fog, allowing some organisms to harvest moisture during the hot summer months. Due to narrow boundary layers in the region, fog is frequently squeezed inland along valley bottoms, leaving the upper slopes of the mountain exposed. The Preserve's most extreme precipitation events are caused by atmospheric rivers ("pineapple connection") that transport moist air to the Sonoma Coast from the tropics, and are responsible for West Coast extreme precipitation and flooding events.


Oaks in Grassland

The 450-acre Osborn Preserve (1,350 to 2,300 feet) (411 to 701 meters) lies on the northwest flank of Sonoma Mountain, predominantly in the Russian River watershed at the dry southern end of the North Coast Range of northern California. Preserve lands span the Copeland Creek and Mark West watersheds, the two southernmost drainages in the Russian River basin. Both drainages discharge into the Laguna de Santa Rosa, a 14-mile long (23-km) wetland complex along Santa Rosa Creek. The Preserve protects roughly one mile of a rugged section of upper Copeland Creek that includes a confluence with a seasonal creek. A small portion of the Preserve drains into Lichau Creek, part of the Petaluma River watershed.

The Osborn Preserve is riddled with basalt exposures that betray the volcanic prehistory of Sonoma County. The most biologically significant geologic feature is a widespread, thick layer of rhyolite. The Preserve and adjacent areas are covered with landslides and slumps which result when rhyolite becomes saturated during winter rains.

Preserve soils are generally shallow clay loam. Due to presence of less permeable clay soils, Preserve aquatic environments are highly diverse, including a complex of perennial and seasonal creeks, ponds and marshes that support red-legged frog, California giant salamander, yellow-legged frog, and a diverse insect community. Osborn Preserve is well-known for early studies of aquatic insects conducted by Larry Serpa in the fishless Copeland Creek during the 1970s.

Terrestrial communities include extensive oak and riparian woodlands and native and exotic grasslands. Chaparral is limited to the Lichau Creek watershed. For more on hydrology, soils, ecology, and history, visit Osborn Preserve entry at Wikipedia. Also see Lozier and Serpa 1981. Guide to the Natural History of the Fairfield Osborn Preserve for a detailed description of communities and species. The guide is used as part of the Osborn Naturalist Training Program Manual.

Cultural History

Preserve lands were used for seasonal hunting and gathering of the Pomo, Miwok, and Wappo people. In the 1860s, the property was part of a Spanish Land Grant, and by the 1890s the land was a working sheep and cattle ranch held by the Duerson family. The woodlands were harvested for firewood, which was taken by wagonload down the mountain to Petaluma. In the 1950s, the land was purchased by the Roth family for use as a summer family retreat.


The Marjorie Osborn Education & Research Center (2,100 sq ft) has 2 meeting rooms that are available for educational and research use, conferences and meetings:

  • The larger room seats up to 24 people and includes full audio-visual equipment (laptop, projector, screen, DVD player, white board).
  • The smaller room seats up to 15 people and has a small kitchenette that includes counter-top refrigerator and sink.

Outdoor seating (weather permitting) can accommodate up to 40 people. The Old Barn includes a small workspace and storage for researchers and is powered on the grid. A trail system provides good, though sometimes rugged, access to most areas of the Preserve.

Solar PanelsThe Osborn Center is solar powered and visitors are asked to conserve energy during cloudy days. Internet access is not available on the Preserve. Cell phone reception is spotty throughout the Preserve but is generally good in parking lot. Overnight facilities for visitors are not available. The Preserve is a 20-minute drive from services in downtown Cotati. Additional information about facilities and reservations is available at Visit a Preserve.


Research at the Osborn Preserve includes independent studies conducted by researchers and Preserve-coordinated efforts that target management needs. These studies have investigated diversity of phenomena including disease, invasive species, cultural surveys, and plant physiology. The Preserve may be best known for the intensive work on Sudden Oak Death conducted since the disease was first found in California in 1995. For more information about on-going and past research:

Osborn Active ResearchOsborn PublicationsOsborn DataOsborn Projects


Management issues at our preserves are representative of regional land management issues, and create opportunities for collaborative efforts with researchers, students, agencies and organizations. As a State University, we bring unique resources to these collaborations, including involvement of our faculty and students, use of the best available science and information, and dedication to adaptive approaches that inform future management decisions. As much as possible, our management initiatives are undertaken as demonstration projects that can be shared with students, landowners, managers, and policymakers to highlight successful techniques that conserve natural processes in our region.

Management at the Osborn Preserve is focused on invasive species control, particularly in grassland habitats, and watershed management. See Osborn Projects for more details.