Introducing Halo Ranch: Part of a resilient future for San Francisco Estuary

The San Francisco Estuary is one of the world’s truly unique tidal marsh systems. It’s also one of the most endangered, compromised by habitat loss from past development and threatened by the risk of future sea level rise.

California is fortunate to have strong and committed visions for restoring the marsh. Those efforts have given RES clear targets in siting, designing, and constructing the Halo Ranch complex, a unique site in the Petaluma River Baylands, just southeast of the City of Petaluma.

Halo Ranch is both a wetlands mitigation bank and an adjoining custom turnkey mitigation opportunity for protecting threatened tidal marsh species. The site occupies a unique position in San Pablo Bay, and RES’ restoration plan checks many boxes that leverage that unique location to accomplish state and regional goals for marsh restoration:

• It aligns with the State Water Resources Control Board requirements for siting mitigation banks in accordance with watershed plans.
• It is a priority area identified by, and following the restoration guidelines of, the US Fish and Wildlife Service’s Recovery Plan for Tidal Marsh Ecosystems of Northern and Central California.
• The restoration plan RES developed in coordination with the Interagency Review Team reflects a deep historical study and restoration principles informed by the San Francisco Estuary Institute’s Petaluma Valley Historical Hydrology and Ecology Study.
• Sea level rise and flooding models predict the site is not prone to complete inundation and can help form refugial high-tide habitat for the wildlife corridor. RES is re-establishing the wetland and tidal marsh areas accordingly.

Historically, Halo Ranch was a complex of seasonally wet meadows, streams, and riparian habitats situated just upslope of the Petaluma River. The seasonally wet meadows and riparian areas transitioned to a tidal marsh abutting the Petaluma River. Over time, farmlands replaced the wetlands and riparian habitat, while levee construction severed the hydrological connection to the Petaluma River and San Francisco Estuary.

Conservation efforts created a foothold in the adjoining land west of the river – the Petaluma Marsh preserve. This became a key factor in the site selection criteria for Halo Ranch. Re-establishing the seasonally wet meadow, stream, riparian habitat, tidal marsh, and sloughs and connecting them to tidal marsh habitat already under protection expands the wildlife corridor in an optimal way.

The restoration of Halo Ranch will help create the conditions for a continuous, thriving wildlife habitat supporting recovery plans for the salt marsh harvest mouse, Ridgway’s rail, salmonids, longfin smelt, and other denizens of the unique San Francisco Estuary.