Habitats in the Santa Cruz Mountains Region, California

Introduction:

Natural habitats are vital to animals, plants, and ecosystem functions important to society. These habitats that contain their own individual microcosm are just a minute’s drive away from each other. The San Francisco Bay Area and Santa Cruz Mountains Region contain many unique habitats that support a range of ecosystems. From the foothills of the mountains at Windy Hill Open Space preserve to the marshes of Ravenswood, the habitats exhibit a range of water availability, plant density/variety, and seasonal patterns important to animal behavior. Due to this variability, each habitat is uniquely sensitive to climate changes. It is therefore important to understand how each functions today and how each could change in the future. 

Site Description:

The Santa Cruz Mountains run northwest-southeast within the San Francisco Peninsula in central California, USA. The area includes elevations ranging from sea level to 2,500 feet above sea level, with the Pacific Ocean to the west and San Francisco Bay to the east. The terrain in the area is a combination of flat land near the ocean and San Francisco Bay, bumpy land in between the SF Bay and the Santa Cruz Mountains, and there is a steep landscape leading up to the highest elevations of the Santa Cruz Mountains.

The Bay Area has a Mediterranean climate, with the winter seasons being towards the end/beginning of the year and the summer seasons being towards the middle of the year. Being in a Mediterranean climate means that rain follows this seasonal pattern, with rain mostly occurring from around November to April. The rest of the year is in a dry season. Due to the Ocean being in the west, the temperature is usually stable and temperate. However, the temperature still follows a seasonal pattern with higher temperatures in the summer months and colder temperatures in the winter months. I started my studies of the habitats in the Bay Area in July of 2022, the transition between spring and summer. This marks the end of the rainy season and the beginning of the warm, dry season. 

The Bay Area is known for its high biodiversity, with many plant and animal species found only in central California. The biodiversity in the Bay Area varies greatly depending on the area depending on elevation, slope, distance from water, and other factors. For example, the foothills of the Santa Cruz Mountains are a mix of open grasslands and dense foliage with creeks and ponds scattered around the area, and the marshlands have a changing habitat with the high and low tides. 

Figure 1: Map of the eastern (bay-side) Santa Cruz Mountains surrounding Palo Alto. The black lines show the locations of the Windy Hill, Pearson-Arastradero, and Ravenswood Open Spaces. 

Figure 2: Map of the Pearson-Arastradero Grassland in the foothills of Santa Cruz Mountains. Studied Area circled in black.

Figure 3: Tributaries of Corte Madera Creek and Corte Madera Creek are circled in black. They are in the foothills of the Santa Cruz Mountains. Sausal Pond is also circled in the top right of the image.

Figure 4: The Ravenswood Open Space Preserve at the San Francisco Bay shoreline in East Palo Alto. The black circled area shows the habitat I examined. 

Science Questions:

What makes a good science question?

• Testable
• Broad enough to be interesting and informative
• Not “yes or no” questions
• Repeatable 
• Relevant

This was the “rubric” that I used when trying to make these questions.

What are the habitat characteristics of Sausal Pond, Corte Madera Creek, the Ravenswood tidal marsh, and Pearson-Arastradero grassland? 

• Sausal Pond
  • One of the first locations that I studied is Sausal Pond. Sausal Pond is in the foothills of the Santa Cruz Mountains within the Windy Hill Open Space Preserve. Sausal Pond is an instream pond because it is fed by and drains into a Sausal Creek. Basic observations of the pond include very dense foliage surrounding the pond, with cattails growing in the water, coast live oaks and other deciduous trees growing around the pond’s perimeter, and some grass and reeds growing along the shore of the pond. Sausal Pond, as a habitat, provides a lot of shade with the foliage that keeps the pond and shoreline cool and can be used as an area of refuge from predators. The pond also serves as a stable water supply for animals to drink from as well as a habitat for small critters and plants to live in. 

• What controls the water budget of Sausal Pond?
  • Understanding what controls Sausal Pond’s water budget is critical to understanding its sensitivity to climate changes. To do this, I made a crude equation using some of the likely contributors to Sausal Pond’s water budget.

Water Budget Equation:

G_in + S.F_in + R = E.T + SF_out + G_out

G_in = groundwater flow in, S.F_in = surface flow in(e.g: streams), R = rain, E.T = evapotranspiration (evaporation + transpiration), S.F_out = surface flow out,  G_out = groundwater flow out.

• Corte Madera Creek
  • The Corte Madera Creek was the second location that I studied. It is also in the foothills of the Santa Cruz mountains, but at a lower elevation than Sausal Pond. It is a tributary creek that is fed by other tributaries and it eventually flows east into the San Francisquito Creek and eventually into the San Francisco Bay. The creek lies at the bottom of a valley incised by the creek’s water over time. The surrounding area in the creek has a lot of shade, is moist/humid, has a cool temperature, and is home to an abundance of insects. The Corte Madera Creek provides a noticeably different habitat than Sausal Pond, although there is overlap in species because of their proximity.